ORCID Profile
0000-0003-2308-799X
Current Organisation
University of Adelaide
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Mechanical Engineering | Water Resources Engineering | Civil Engineering | Mechanical Engineering | Infrastructure Engineering and Asset Management | Dynamics, Vibration and Vibration Control | Solid Mechanics | Acoustics and Noise Control (excl. Architectural Acoustics) | Renewable Power and Energy Systems Engineering (excl. Solar Cells) | Palaeontology (incl. Palynology) | Control Systems, Robotics and Automation | Water resources engineering | Electrical Engineering | Interdisciplinary Engineering | Composite and Hybrid Materials | Biomechanical Engineering | Biomedical Engineering | Biomechanical Engineering | Structural Engineering | Aerospace Engineering | Electrical and Electronic Engineering | Aerodynamics (excl. Hypersonic Aerodynamics) | Nanomaterials | Civil engineering | Theoretical and Applied Mechanics | Fluidisation and Fluid Mechanics | Aerospace Structures | Ocean Engineering | Marine Engineering | Infrastructure engineering and asset management
ANZSRC Socio-Economic Objective (SEO)
Expanding Knowledge in Engineering | Wave Energy | Computer hardware and electronic equipment not elsewhere classified | Other | Management of Noise and Vibration from Transport Activities | Navy | Air transport | Aerospace equipment | Rail Safety | Air Safety | Ecosystem Assessment and Management of Coastal and Estuarine Environments | Metals (e.g. Composites, Coatings, Bonding) | Water Services and Utilities | Energy Conservation and Efficiency in Transport | Expanding Knowledge in the Physical Sciences | Scientific Instruments | Public health not elsewhere classified | Expanding Knowledge in the Agricultural and Veterinary Sciences |
Related Links
Publications
Surface Strain Measurements Using a 3D Scanning Laser Vibrometer
Publisher: Springer Science and Business Media LLC
Date: 06-10-2011
On the dynamics of the Furuta pendulum
Publisher: Hindawi Limited
Date: 2011
DOI: 10.1155/2011/528341
Abstract: The Furuta pendulum, or rotational inverted pendulum, is a system found in many control labs. It provides a compact yet impressive platform for control demonstrations and draws the attention of the control community as a platform for the development of nonlinear control laws. Despite the popularity of the platform, there are very few papers which employ the correct dynamics and only one that derives the full system dynamics. In this paper, the full dynamics of the Furuta pendulum are derived using two methods: a Lagrangian formulation and an iterative Newton-Euler formulation. Approximations are made to the full dynamics which converge to the more commonly presented expressions. The system dynamics are then linearised using a Jacobian. To illustrate the influence the commonly neglected inertia terms have on the system dynamics, a brief ex le is offered.
Real-time FPGA control of a hexapod robot for 6-DOF biomechanical testing
Publisher: IEEE
Date: 11-2011
Errors in the measurement of acoustic energy density in one-dimensional sound fields
Publisher: Elsevier BV
Date: 10-2000
A multipole array magnetic spring
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 10-2005
Axial Force Between a Thick Coil and a Cylindrical Permanent Magnet: Optimizing the Geometry of an Electromagnetic Actuator
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2012
Sound propagation through elevated, heated jets in cooler cross-flow: An experimental study
Publisher: Acoustical Society of America (ASA)
Date: 07-2021
DOI: 10.1121/10.0005489
Abstract: Sound propagation through hot exhaust plumes with cooler cross-winds is present in many real world systems. One particular ex le is the sound propagation from exhaust stacks attached to open cycle gas turbine power stations. The research presented in this paper investigates the sound propagation from a reduced-scale exhaust stack, with a cross-flow from experiments conducted in a wind tunnel. Experimental measurements of the flow and temperature fields provide insight into the complex sound radiation characteristics. Results from the acoustic measurements show the change in the sound directivity arising from the inclusion of the hot exhaust plume, leading to non-axisymmetric sound directivity and a concentration of sound downwind of the exhaust stack outlet. In certain cross-flow conditions, the hot exhaust plume can increase the sound observed downwind by up to 11 dB when compared to the scenario of sound propagation from an exhaust stack in the absence of a heated jet or cross-flow. This paper describes the acoustic directivity at various radial distances from the exhaust stack, acoustic frequencies, jet temperatures, and cross-flow free-stream velocity. The results from this paper emphasise the importance of taking into consideration the hot exhaust plume with cooler cross-flow when estimating sound levels downwind of the stack.
Attenuation of turbulence by the passive control of sweep events in a turbulent boundary layer using micro-cavities
Publisher: AIP Publishing
Date: 11-2017
DOI: 10.1063/1.4995466
Abstract: Cavity arrays have been previously identified to disrupt the sweep events and consequently the bursting cycle in the boundary layer by capturing the structures responsible for the Reynolds stresses. In the present study, the sensitivity of a flushed-surface cavity array in reducing the turbulent energy production has been investigated. Two plates of varying thicknesses and four different backing cavity volumes were considered, at three different Reynolds numbers. The volume of the backing cavity was shown to be the most important characteristic in determining the attenuation of streamwise velocity fluctuations within the logarithmic region of the turbulent boundary layer. However, the results also demonstrated that the orifice length of the cavity array had negligible effect in modifying the reduction of the turbulent energy by the cavity array in this investigation. The results show that the maximum reduction in turbulence generation achieved for this study occurs when the backing volume is 3.1 × 106 times greater than the viscous length scale at Reθ = 3771. The reduction in turbulence intensity, sweep intensity, and energy spectrum were shown to be 5.6%, 6.3%, and 13.4%, respectively. By decreasing the cavity volume to zero, no change in the turbulent boundary layer turbulence statistics was found. The results suggest a larger reduction in turbulence intensity, sweep intensity, and energy spectrum that can be achieved with a larger backing volume.
Performance assessment of an insect-inspired target tracking model in background clutter
Publisher: IEEE
Date: 12-2014
Optimization of the Magnetic Field Produced by Frustum Permanent Magnets for Single Magnet and Planar Halbach Array Configurations
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2021
Longitudinal flight dynamics modelling and control of scramspace I
Publisher: American Institute of Aeronautics and Astronautics
Date: 09-01-2012
DOI: 10.2514/6.2012-255
Active control of transformer noise by using power line signal as reference
Publisher: IEEE
Date: 06-2013
Bio-inspired feature extraction and enhancement of targets moving against visual clutter during closed loop pursuit
Publisher: IEEE
Date: 09-2013
Expression for the estimation of time-averaged acoustic energy density using the two-microphone method (L)
Publisher: Acoustical Society of America (ASA)
Date: 05-2003
DOI: 10.1121/1.1567273
Abstract: Acoustic energy density has been shown to exhibit lower spatial variance in reactive sound fields compared to the acoustic potential energy estimate offered by microphones, making it a very useful measure of the acoustic energy within an enclosure. Previously, frequency domain time-averaged energy density estimates have come about by estimating the pressure average and particle velocity between two closely spaced microphones using either analog or digital electronics. A frequency domain expression can be obtained by adding the weighted sum of the auto-spectral densities of both the pressure and particle velocity magnitude. The purpose of this letter is to derive an expression for the time-averaged acoustic energy density in the frequency domain using the auto- and cross-spectral densities between the two closely spaced microphones. The resulting expression is validated numerically.
A Kalman filter approach to virtual sensing for active noise control
Publisher: Elsevier BV
Date: 02-2008
Parameters for Optimizing the Forces Between Linear Multipole Magnet Arrays
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2010
Stochastic analysis of the nonlinear dynamics of oscillating water columns: A frequency domain approach
Publisher: Elsevier BV
Date: 10-2023
Errors arising from three-dimensional energy density sensing in one-dimensional sound fields
Publisher: Elsevier BV
Date: 09-2000
The true potential of nonlinear stiffness for point absorbing wave energy converters
Publisher: Elsevier BV
Date: 02-2022
Adjoint nonlinear active noise control algorithm for virtual microphone
Publisher: Elsevier BV
Date: 02-2012
Multichannel FSLMS algorithm based active headrest
Publisher: IEEE
Date: 09-2013
Active Structural-Acoustic Control of a Rocket Fairing Using Proof-Mass Actuators
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 03-2001
DOI: 10.2514/2.3673
Comment on “A Virtual Sensing Method for Tonal ANVC Systems” [C. M. Tran and S. C. Southward, 2002, J. Dyn. Syst., Meas., Control 124(1), 35–40]
Publisher: ASME International
Date: 15-03-2007
DOI: 10.1115/1.2745885
Abstract: In a paper by Tran and Southward (2002, J. Dyn. Syst., Meas., Control, 124(1), pp. 35–40), a virtual sensing method for tonal active noise and vibration control systems is proposed. The aim of the proposed method is to obtain accurate estimates of the virtual outputs of the dynamic system under consideration. For this purpose, a hybrid adaptive feedforward observer is designed based on an observable state-space representation of the dynamic system. In this paper, it is shown that if the number of physical sensors used in the proposed method is less than the state-space system order, the observer can converge to infinitely many solutions for which the state reconstruction errors are not equal to zero. Since accurate state estimates are required to obtain accurate estimates of the virtual sensor outputs, the suggested hybrid adaptive feedforward observer is only suitable for rejecting nonstationary disturbances at the physical sensor outputs, and not for virtual sensing purposes.
A Biologically Inspired Facilitation Mechanism Enhances the Detection and Pursuit of Targets of Varying Contrast
Publisher: IEEE
Date: 11-2014
A multiple-sensor method for control of structural vibration with spatial objectives
Publisher: Elsevier BV
Date: 09-2006
Understanding of the flow behaviour on a Helmholtz resonator excited by grazing flow
Publisher: Informa UK Limited
Date: 28-05-2014
A comparison of filter design structures for multi-channel acoustic communication systems
Publisher: Acoustical Society of America (ASA)
Date: 2008
DOI: 10.1121/1.2804940
Abstract: The application of inverse filter designs as a means of providing improved communication performance in acoustic environments is investigated. Tikhonov regularized inverse filters of channel transfer functions calculated in the frequency domain are used as a means of obtaining multi-channel filters. Three classifications of inverse filter structures have been considered using time-domain simulations. The performance of Tikhonov regularized inverse filters designed according to each of these classifications is compared with each other and against a filter design developed by Stojanovic [Stojanovic, M. (2005). “Retrofocusing techniques for high rate acoustic communications,” J. Acoust. Soc. Am. 117, 1173–1185]. It is shown that the filter design developed by Stojanovic requires less regularization and outperforms the Tikhonov regularized inverse filter designs when communicating over a single channel. While the filter developed by Stojanovic is designed to use multiple transmitters to transmit to a single receiver, the filter was implemented in a multi-channel system and proposed to have a focusing similar to that obtained using time-reversal. It was found that for the scenario used in the simulation, the Tikhonov regularized inverse design for full multi-channel inversion achieved better focusing than the design by Stojanovic, where simulation results show 20dB less cross-talk at the expense of around 2dB loss in signal strength.
Maximizing the Force Between Two Cuboid Magnets
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2010
An investigation into the sensory application of DBD plasma actuators for pressure measurement
Publisher: Elsevier BV
Date: 11-2011
Adaptive velocity-based six degree of freedom load control for real-time unconstrained biomechanical testing
Publisher: Elsevier BV
Date: 09-2014
DOI: 10.1016/J.JBIOMECH.2014.06.023
Abstract: Robotic biomechanics is a powerful tool for further developing our understanding of biological joints, tissues and their repair. Both velocity-based and hybrid force control methods have been applied to biomechanics but the complex and non-linear properties of joints have limited these to slow or stepwise loading, which may not capture the real-time behaviour of joints. This paper presents a novel force control scheme combining stiffness and velocity based methods aimed at achieving six degree of freedom unconstrained force control at physiological loading rates.
Performance comparison of the floating and fully submerged quasi-point absorber wave energy converters
Publisher: Elsevier BV
Date: 08-2017
Pipe crack early warning for burst prevention by permanent acoustic noise level monitoring in smart water networks
Publisher: Informa UK Limited
Date: 20-10-2020
Steady-state sound propagation through hot exhaust jets in cooler cross-flow: A computational study
Publisher: Acoustical Society of America (ASA)
Date: 07-2023
DOI: 10.1121/10.0020069
Abstract: An analysis has been carried out to investigate the sound radiation through a heated jet in cooler cross-flow, which is representative of many industrial exhaust systems, using a hybrid steady-state computational fluid dynamics and computational acoustic model. The mean flow and temperature fields are modelled using steady-state computational fluid dynamics, with the turbulence modelled using Reynolds Averaged Navier-Stokes equations. The corresponding mean flow and temperature fields are used in the computational sound propagation model using linearised acoustic wave equation with mean flow based on a scalar flow potential. The results obtained from the computational simulations show that the flow significantly changes the sound propagation path and that the sound levels downstream of the duct outlet are higher than expected from using an acoustic monopole radiation pattern. The dominant mechanism affecting the propagation of sound is the refraction arising from the plume's temperature and velocity gradients. The sound propagation is highly dependent on the proximity from the duct outlet, normalised wavenumber, temperature and the jet to cross-flow mean velocity ratio. This computational study builds upon previous experimental work to analyse the fluid-acoustic interaction for heated jets in cooler cross-flow to understand the complex radiation pattern that leads to higher-than-expected sound levels downstream of the duct outlet.
Mechanism of sweep event attenuation using micro-cavities in a turbulent boundary layer
Publisher: AIP Publishing
Date: 05-2018
DOI: 10.1063/1.5026130
Abstract: Cavity arrays have been identified as a potential passive device to disrupt and capture sweep events, which are responsible for the excess Reynolds stresses in the boundary layer. In the present study, the mechanism of the attenuation of captured sweep events has been analyzed, as well as the non-linear relationship between the volume of the backing cavity and the reduction in sweep intensity. The influence of cavity array on the turbulent boundary layer has been analyzed, with a total of six different backing cavity arrangements with varying volumes. Three of the backing cavities have been used to determine the non-linear relationship between the effectiveness of the cavity array in reducing sweep intensity and the volume of the backing cavity. The other three have been used to determine the mechanism by which the arrays manipulate the captured sweep events. The pre-multiplied energy spectra of multiple velocity histories were significantly reduced, by up to 12.5%, in the low and mid-range wavelength values (λx+& ), which is associated with the coherent structures. The results show that the maximum reduction in sweep intensity of approximately 7% may be obtained when Reθ = 3771. It has been demonstrated that the non-linear relationship between sweep event intensity reduction and cavity volume has reached an upper limit in this investigation. Results from this study have revealed that the cavity array weakens the sweep intensity of the captured sweep events by d ing the energy of the events through the friction losses in the cavity array and also in the large volume of the backing cavity.
Feedback control of structurally radiated sound into enclosed spaces using structural sensing
Publisher: Acoustical Society of America (ASA)
Date: 11-1999
DOI: 10.1121/1.428132
Abstract: A technique is developed that addresses sensor and actuator placement and feedback control of structural/acoustic problems that can be described as a flexible structure surrounding an acoustic cavity. Specifically, this work is directed at the space launch vehicle problem, where it is assumed that it is not possible to obtain, in advance of a required control output, a coherent measurement of the disturbance or to directly measure the quantity to be controlled. These assumptions necessitate the use of structural sensing to predict the sound pressure in the cavity and of feedback control to reduce the radiated sound. A method for selecting sensor and actuator positions based on a transformation of the problem into radiation modes is covered as well as an optimal feedback control approach which allows the control of radiated pressure into a defined subvolume of the cavity using only structural actuators and sensors. Finally, an ex le problem is completed which draws on all of the theoretical development to suppress radiated sound within a subvolume.
Modal analysis of a submerged spherical point absorber with asymmetric mass distribution
Publisher: Elsevier BV
Date: 2019
Discrete implementation of biologically inspired image processing for target detection
Publisher: IEEE
Date: 12-2011
Nonlinear hydrodynamics analysis of a submerged spherical point absorber with asymmetric mass distribution
Publisher: Elsevier BV
Date: 03-2020
A computationally efficient frequency-domain filtered-X LMS algorithm for virtual microphone
Publisher: Elsevier BV
Date: 05-2013
Nonlinear active noise control for headrest using virtual microphone control
Publisher: Elsevier BV
Date: 04-2013
Vibration of snowboard decks
Publisher: Elsevier BV
Date: 06-2010
A discussion of wind turbine interaction and stall contributions to wind farm noise
Publisher: Elsevier BV
Date: 04-2014
Active noise control in a pure tone diffuse sound field using virtual sensing
Publisher: Acoustical Society of America (ASA)
Date: 06-2009
DOI: 10.1121/1.3123404
Abstract: Local active noise control systems generate a zone of quiet at the physical error sensor using one or more secondary sources to cancel acoustic pressure and its spatial derivatives at the sensor location. The resulting zone of quiet is generally limited in size and as such, placement of the error sensor at the location of desired attenuation is required, which is often inconvenient. Virtual acoustic sensors overcome this by projecting the zone of quiet away from the physical sensor to a remote location. The work described here investigates the effectiveness of using virtual sensors in a pure tone diffuse sound field. Stochastically optimal virtual microphones and virtual energy density sensors are developed for use in diffuse sound fields. Analytical expressions for the controlled sound field generated with a number of control strategies are presented. These expressions allow the optimal control performance to be predicted. Results of numerical simulations and experimental measurements made in a reverberation chamber are also presented and compared.
On using Helmholtz-type resonance to reduce the size of dual-purpose offshore oscillating water column wave energy converters
Publisher: AIP Publishing
Date: 09-2023
DOI: 10.1063/5.0165334
Nonlinear stiffness enhancement of submerged wave energy device in high fidelity model
Publisher: Elsevier BV
Date: 06-2022
Active control of structural sound radiation using a spatial control method with multiple structural sensors
Publisher: IEEE
Date: 2005
Nonlinear dynamics of a floating offshore wind turbine platform via statistical quadratization — Mooring, wave and current interaction
Publisher: Elsevier BV
Date: 09-2021
Local facilitation improves success in closed loop simulations of insect small target pursuit
Publisher: Frontiers Media SA
Date: 2013
Self-noise and directivity of simple airfoils during stall: an experimental comparison
Publisher: Elsevier BV
Date: 12-2017
Coherenceogram for leak detection in water pipes
Publisher: Elsevier BV
Date: 07-2022
Harnessing hydro-kinetic energy from wake-induced vibration using virtual mass spring damper system
Publisher: Elsevier BV
Date: 11-2015
Control of a cylindrical PVTOL vehicle: Global non-linear velocity tracking control considering aerodynamics
Publisher: Informa UK Limited
Date: 10-2007
Mechanism of control of the near-wall turbulence using a micro-cavity array
Publisher: AIP Publishing
Date: 07-2021
DOI: 10.1063/5.0051375
Abstract: Coherent structures in a turbulent boundary layer have been shown to have an influence on the skin-friction drag acting on surfaces beneath the boundary layer. The use of micro-cavities on a flat surface has recently shown the potential to passively control a turbulent boundary layer by attenuating the sweep events. Previous experiments have determined the design parameters of the cavity array for the optimal boundary-layer control by reducing the sweep events. However, investigating the flow physics behind the interaction of the boundary-layer flow with the cavities is challenging. High near-wall velocity gradients and very small scales and sizes of the cavity holes limit the experiments from investigating the flow characteristics very close to the wall and inside the holes. Therefore, in the present work, direct numerical simulations have been utilized to model the boundary layer flow over a flat surface with a micro-cavity array in order to understand the flow interactions. Detection of coherent structures in the boundary layer shows a reduction in the number of events over the cavity array. Reynolds stresses have been analyzed to determine the effect of micro-cavities. The reduction in the Reynolds shear stress results in a lower skin-friction drag. The flow fluctuations through the holes in the streamwise sequence have been found to be highly correlated using cross correlation. These flow fluctuations interact with the boundary layer to suppress the coherent structures. Overall, the use of the micro-cavity array has resulted in a reduced wall shear stress and approximately 5.6% lower local skin-friction drag.
Active control of energy density in a one-dimensional waveguide: A cautionary note (L)
Publisher: Acoustical Society of America (ASA)
Date: 31-05-2005
DOI: 10.1121/1.1920213
Abstract: Acoustic energy density has been shown to be a highly effective cost function for active noise control systems. Many researchers have used the sound field in a one-dimensional waveguide to trial their control strategies before moving onto more realistic three-dimensional sound fields. This letter aims to shed some light on the observations made in the early papers on one-dimensional energy density control and also shows that some of the analysis was incorrect and the conclusions reached may be flawed.
A review, supported by experimental results, of voltage, charge and capacitor insertion method for driving piezoelectric actuators
Publisher: Elsevier BV
Date: 10-2010
An Alternative Nonlinear Control Law for the Global Stabilization of the PVTOL Vehicle
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2007
Analysis of the turbulent boundary layer in the vicinity of a self-excited cylindrical Helmholtz resonator
Publisher: Informa UK Limited
Date: 08-04-2015
Active noise control in a free field with virtual sensors
Publisher: Acoustical Society of America (ASA)
Date: 2001
DOI: 10.1121/1.1326950
Abstract: The zone of local control around a “virtual energy density sensor” is compared with that offered by an actual energy density sensor, a single microphone, and a virtual microphone. Intended as an introduction to the concept of forward difference prediction and a precursor to evaluating the virtual sensor control algorithms in d ed enclosures, this paper investigates an idealized scenario of a single primary sound source in a free-field environment. An analytical model is used to predict the performance of the virtual error sensors and compare their control performance with their physical counterparts. The model is then experimentally validated. The model shows that in general the virtual energy density sensor outperforms the actual energy density sensor, the actual microphone, and the virtual microphone in terms of centering a practically sized zone of local control around an observer who is remotely located from any physical sensors. However, in practice, the virtual sensor algorithms are shown to be sensitive (by varying degrees) to short wavelength spatial pressure variations of the primary and secondary sound fields.
A Review of Virtual Sensing Algorithms for Active Noise Control
Publisher: MDPI AG
Date: 03-11-2008
DOI: 10.3390/A1020069
A sensitivity study on the effect of mass distribution of a single-tether spherical point absorber
Publisher: Elsevier BV
Date: 10-2019
A Simplified Force Equation for Coaxial Cylindrical Magnets and Thin Coils
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2011
Active preload control of a redundantly actuated Stewart platform for backlash prevention
Publisher: Elsevier BV
Date: 04-2015
Detection of Delamination Damage in a Composite Laminate Beam Utilising the Principle of Strain Compatibility
Publisher: Trans Tech Publications, Ltd.
Date: 10-2009
DOI: 10.4028/WWW.SCIENTIFIC.NET/KEM.417-418.269
Abstract: This paper presents an experimental investigation of a new method for damage detection based on the most fundamental concept in continuum mechanics: strain compatibility. Compliance with this principle implies a deformed material is free from discontinuities, which are indicative of many types of structural damage. Therefore the principle of strain compatibility, in its ability to identify discontinuities, is very promising as a new foundation for future research into non-destructive evaluation and structural health monitoring technologies. The proposed method has many advantages compared to existing damage detection techniques, such as its invariance to material properties, type and intensity of loading, and the geometry of the structure. In this paper, a proposed formulation of the strain compatibility equation for beam structures, which is invariant to loading intensity, is presented. An experimental investigation of the proposed algorithm was conducted on a delaminated cantilever beam, utilising a PSV-3D scanning laser vibrometer. The experiment demonstrated that the strain compatibility technique can accurately locate delamination damage in composite beam structures.
Effect of a model predictive control on the design of a power take-off system for wave energy converters
Publisher: Elsevier BV
Date: 10-2021
A comprehensive, genus-level time-calibrated phylogeny of the tree flora of Mediterranean Europe and an assessment of its vulnerability
Publisher: Informa UK Limited
Date: 26-12-2019
Statistical errors in the estimation of time-averaged acoustic energy density using the two-microphone method
Publisher: Acoustical Society of America (ASA)
Date: 27-02-2004
DOI: 10.1121/1.1639334
Abstract: Time-averaged acoustic energy density can be estimated using the auto- and cross-spectral densities between two closely spaced microphones. In this paper, an analysis of the random errors that arise using two microphone measurements is undertaken. An expression for the normalized random error of the time-averaged acoustic energy density spectral density estimate is derived. This expression is verified numerically. The lower and upper bounds of the normalized random error are derived. It is shown that the normalized random error of the estimate is not a strong function of the sound field properties, and is chiefly dependent on the number of records averaged.
Virtual error sensing for active noise control in a one-dimensional waveguide: Performance prediction versus measurement (L)
Publisher: Acoustical Society of America (ASA)
Date: 2003
DOI: 10.1121/1.1523386
Abstract: Virtual error sensing is a novel active noise control technique, which is designed to produce a zone of attenuation remote from the physical error sensors. In this letter virtual sensing is investigated for tonal noise (both on and off resonance) in a long narrow duct. The performance of the virtual error sensors using real-time control is compared to the performance determined from an analytical model and the performance determined through the postprocessing of experimental data. Two ex les of control using postprocessed experimental transfer function data are presented the first relied on transfer functions measured using broadband noise and the second relied on transfer functions measured at discrete frequencies. The results highlight the significant errors encountered as a result of using broadband transfer functions in lightly d ed enclosures.
A nonlinear active noise control algorithm for virtual microphones controlling chaotic noise
Publisher: Acoustical Society of America (ASA)
Date: 08-2012
DOI: 10.1121/1.4731227
Abstract: In active noise control (ANC) systems, virtual microphones provide a means of projecting the zone of quiet away from the physical microphone to a remote location. To date, linear ANC algorithms, such as the filtered-x least mean square (FXLMS) algorithm, have been used with virtual sensing techniques. In this paper, a nonlinear ANC algorithm is developed for a virtual microphone by integrating the remote microphone technique with the filtered-s least mean square (FSLMS) algorithm. The proposed algorithm is evaluated experimentally in the cancellation of chaotic noise in a one-dimensional duct. The secondary paths evaluated experimentally exhibit non-minimum phase response and hence poor performance is obtained with the conventional FXLMS algorithm compared to the proposed FSLMS based algorithm. This is because the latter is capable of predicting the chaotic signal found in many physical processes responsible for noise. In addition, the proposed algorithm is shown to outperform the FXLMS based remote microphone technique under the causality constraint (when the propagation delay of the secondary path is greater than the primary path). A number of experimental results are presented in this paper to compare the performance of the FSLMS algorithm based virtual ANC algorithm with the FXLMS based virtual ANC algorithm.
Modelling of wind turbine wake using large eddy simulation
Publisher: Elsevier BV
Date: 2018
Acoustic-centric modal filter design for active noise control
Publisher: Elsevier BV
Date: 08-2004
Numerical study of flow and energy fields in thermoacoustic couples of non-zero thickness
Publisher: Elsevier BV
Date: 04-2009
A generalized approach to modal filtering for active noise control - Part II: Acoustic sensing
Publisher: No publisher found
Date: 2002
A novel digital charge-based displacement estimator for sensorless control of a grounded-load piezoelectric tube actuator
Publisher: Elsevier BV
Date: 08-2013
Active control of sound transmission using structural error sensing
Publisher: Acoustical Society of America (ASA)
Date: 11-1998
DOI: 10.1121/1.423872
Abstract: The active minimization of harmonic sound transmission into an arbitrarily shaped enclosure using error signals derived from structural vibration sensors is investigated numerically. It is shown that by considering the dynamics of the coupled system, it is possible to derive a set of “structural radiation” modes which are orthogonal with respect to the global potential energy of the coupled acoustic space and which can be sensed by structural vibration sensors. Minimization of the litudes of the “radiation modes” is thus guaranteed to minimize the interior acoustic potential energy. The coupled vibro-acoustic system under investigation is modelled using finite element analysis which allows systems with complex geometries to be investigated rather than limiting the analysis to simple analytically tractable systems. Issues regarding the practical implementation of sensing the orthonormal sets of structural radiation modes are discussed. Specific ex les relating to the minimization of the total acoustic potential energy within a longitudinally stiffened cylinder are given, comparing the performance offered using error sensing of the radiation modes on the structure against the more traditional error criteria namely, the discrete sensing of the structural kinetic energy on the boundary and the acoustic potential energy in the enclosed space.
Experimental investigation of a co-located wind and wave energy system in regular waves
Publisher: Elsevier BV
Date: 12-2023
Active noise control at a moving location in a modally dense three-dimensional sound field using virtual sensing
Publisher: Acoustical Society of America (ASA)
Date: 05-2008
DOI: 10.1121/1.2932809
Abstract: Local active noise control systems generate a zone of quiet at the physical error sensor using secondary sources to cancel the acoustic pressure at the sensor location. The resulting zone of quiet is generally limited in size and as such, placement of the physical error sensor at the location of desired attenuation is required, which is often inconvenient. Virtual acoustic sensors overcome this by projecting the zone of quiet away from the physical error sensor to a remote location. While virtual acoustic sensors have shown potential to improve the performance of local active noise control systems, it is, however, likely that the desired location of maximum attenuation is not spatially fixed. The work described here presents a virtual sensing method capable of tracking a desired location in a modally dense three-dimensional sound field. The developed algorithm has been experimentally verified in a three-dimensional enclosure and the experimental results are presented.
Modelling the three-dimensional vibration of composite archery arrows under free–free boundary conditions
Publisher: SAGE Publications
Date: 03-04-2012
Abstract: Archery performance has been shown to be dependent on the resonance frequencies and operational deflection shape of the arrows. This vibrational behaviour is influenced by the design and material of the arrow and the presence of damage in the arrow structure. In recent years arrow design has progressed to use lightweight and stiff composite materials. This paper investigates the vibration of composite archery arrows through a finite difference model based on Euler–Bernoulli theory, and a three-dimensional finite element modal analysis. Results from the numerical simulations are compared to experimental measurements using a Polytec scanning laser Doppler vibrometer (PSV-400). The experiments use an acoustically coupled vibration actuator to excite the composite arrow with free–free boundary conditions. Evaluation of the vibrational behaviour shows good agreement between the theoretical models and the experiments.
A new hybrid method for sensorless control of piezoelectric actuators
Publisher: Elsevier BV
Date: 05-2013
Molecular dynamics simulations of acoustic absorption by a carbon nanotube
Publisher: AIP Publishing
Date: 06-2018
DOI: 10.1063/1.5026528
Abstract: Acoustic absorption by a carbon nanotube (CNT) was studied using molecular dynamics (MD) simulations in a molecular domain containing a monatomic gas driven by a time-varying periodic force to simulate acoustic wave propagation. Attenuation of the sound wave and the characteristics of the sound field due to interactions with the CNT were studied by evaluating the behavior of various acoustic parameters and comparing the behavior with that of the domain without the CNT present. A standing wave model was developed for the CNT-containing system to predict sound attenuation by the CNT and the results were verified against estimates of attenuation using the thermodynamic concept of exergy. This study demonstrates acoustic absorption effects of a CNT in a thermostatted MD simulation, quantifies the acoustic losses induced by the CNT, and illustrates their effects on the CNT. Overall, a platform was developed for MD simulations that can model acoustic d ing induced by nanostructured materials such as CNTs, which can be used for further understanding of nanoscale acoustic loss mechanisms associated with molecular interactions between acoustic waves and nanomaterials.
A global non-linear control design for a PVTOL vehicle with aerodynamics
Publisher: IEEE
Date: 2005
Optimal virtual sensing for active noise control in a rigid-walled acoustic duct
Publisher: Acoustical Society of America (ASA)
Date: 11-2005
DOI: 10.1121/1.2047127
Abstract: The performance of local active noise control systems is generally limited by the small sizes of the zones of quiet created at the error sensors. This is often exacerbated by the fact that the error sensors cannot always be located close to an observer’s ears. Virtual sensing is a method that can move the zone of quiet away from the physical location of the transducers to a desired location, such as an observer’s ear. In this article, analytical expressions are derived for optimal virtual sensing in a rigid-walled acoustic duct with arbitrary termination conditions. The expressions are derived for tonal excitations, and are obtained by employing a traveling wave model of a rigid-walled acoustic duct. It is shown that the optimal solution for the virtual sensing microphone weights is independent of the source location and microphone locations. It is also shown that, theoretically, it is possible to obtain infinite reductions at the virtual location. The analytical expressions are compared with forward difference prediction techniques. The results demonstrate that the maximum attenuation, that theoretically can be obtained at the virtual location using forward difference prediction techniques, is expected to decrease for higher excitation frequencies and larger virtual distances.
Implementation and analysis of an innovative digital charge amplifier for hysteresis reduction in piezoelectric stack actuators
Publisher: AIP Publishing
Date: 04-2014
DOI: 10.1063/1.4871295
Abstract: Smart actuators are the key components in a variety of nanopositioning applications, such as scanning probe microscopes and atomic force microscopes. Piezoelectric actuators are the most common smart actuators due to their high resolution, low power consumption, and wide operating frequency but they suffer hysteresis which affects linearity. In this paper, an innovative digital charge lifier is presented to reduce hysteresis in piezoelectric stack actuators. Compared to traditional analog charge drives, experimental results show that the piezoelectric stack actuator driven by the digital charge lifier has less hysteresis. It is also shown that the voltage drop of the digital charge lifier is significantly less than the voltage drop of conventional analog charge lifiers.
Stiffness analysis and control of a stewart platform-based manipulator with decoupled sensor-actuator locations for ultrahigh accuracy positioning under large external loads
Publisher: ASME International
Date: 08-08-2014
DOI: 10.1115/1.4027945
Abstract: Robot frame compliance has a large negative effect on the global accuracy of the system when large external forces/torques are exerted. This phenomenon is particularly problematic in applications where the robot is required to achieve ultrahigh (micron level) accuracy under very large external loads, e.g., in biomechanical testing and high precision machining. To ensure the positioning accuracy of the robot in these applications, the authors proposed a novel Stewart platform-based manipulator with decoupled sensor–actuator locations. The unique mechanism has the sensor locations fully decoupled from the actuator locations for the purpose of passively compensating for the load frame compliance, as a result improving the effective stiffness of the manipulator in six degrees of freedom (6DOF). In this paper, the stiffness of the proposed manipulator is quantified via a simplified method, which combines both an analytical model (robot kinematics error model) and a numerical model [finite element analysis (FEA) model] in the analysis. This method can be used to design systems with specific stiffness requirements. In the control aspect, the noncollocated positions of the sensors and actuators lead to a suboptimal control structure, which is addressed in the paper using a simple Jacobian-based decoupling method under both kinematics- and dynamics-based control. Simulation results demonstrate that the proposed manipulator configuration has an effective stiffness that is increased by a factor of greater than 15 compared to a general design. Experimental results show that the Jacobian-based decoupling method effectively increases the dynamic tracking performance of the manipulator by 25% on average over a conventional method.
Linear-parameter-varying control of an improved three-degree-of-freedom aeroelastic model
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 03-2010
DOI: 10.2514/1.45657
Nonlinear active noise control with virtual sensing technique
Publisher: IEEE
Date: 12-2010
Adaptive identification of hysteresis and creep in piezoelectric stack actuators
Publisher: Springer Science and Business Media LLC
Date: 10-05-2009
Feasibility of feedback control of transmitted sound into a launch vehicle fairing using structural sensing and proof mass actuators
Publisher: American Institute of Aeronautics and Astronautics
Date: 12-04-1999
DOI: 10.2514/6.1999-1529
Active control of sound transmission through a structure into a coupled enclosure of arbitrary shape.
Publisher: Acoustical Society of America (ASA)
Date: 04-1996
DOI: 10.1121/1.415301
Abstract: A numerical procedure for assessing the performance of an active noise and vibration control system for a harmonically excited weakly coupled multimodal vibroacoustic system is presented. The structure and the contiguous acoustic space have been modeled separately with a commercially available finite element analysis package (ANSYS) and then combined using a modal coupling theory for weakly coupled systems. Numerical results are compared against experimental measurements for a finite longitudinally stiffened cylinder with an integral floor. Experimental based response matrices were measured and used to predict the system response. Modal analysis was applied in order to reduce the required effort in determining the response matrix. A design methodology for optimizing the physical control system is reviewed and several trends presented.
Theoretical design parameters for a quasi-zero stiffness magnetic spring for vibration isolation
Publisher: Elsevier BV
Date: 09-2009
A digital charge amplifier for hysteresis elimination in piezoelectric actuators
Publisher: IOP Publishing
Date: 06-06-2013
Active control experiments on a panel structure using a spatially weighted objective method with multiple sensors
Publisher: Elsevier BV
Date: 08-2008
Using frequency-weighted data fusion to improve the performance of a digital charge amplifier
Publisher: IEEE
Date: 05-2012
Exhaust stack silencer design using finite element analysis
Publisher: Institute of Noise Control Engineering (INCE)
Date: 2000
DOI: 10.3397/1.2827965
Design considerations for a three-tethered point absorber wave energy converter with nonlinear coupling between hydrodynamic modes
Publisher: Elsevier BV
Date: 06-2022
Active preload control of a redundantly actuated Stewart platform for backlash prevention
Publisher: IEEE
Date: 05-2013
Transducer sensitivity compensation using diagonal preconditioning for time reversal and Tikhonov inverse filtering in acoustic systems
Publisher: Acoustical Society of America (ASA)
Date: 2006
DOI: 10.1121/1.2139069
Abstract: Filters are commonly used in sound reproduction and communication systems as a means of compensating for the response of the electro-acoustic plant. Two commonly used filter designs in the field of acoustics are the time reversal filter and the Tikhonov inverse filter. In this paper the influence of transducer sensitivities on the performance of these filters is examined. It is shown that the sensitivity of the transducers can negatively affect the performance of the resulting filter. To compensate for the decrease in performance, diagonal preconditioning can be implemented in the system. It is shown that by using diagonal matrices, which minimize the condition number of the system, the loss in performance arising from unbalanced sensitivities is minimized. This paper proposes an algorithm to find such a set of diagonal matrices and results are presented showing the improvements in performance arising from the modified filter design.
Numerical simulation of optimal deconvolution in a shallow-water environment
Publisher: Acoustical Society of America (ASA)
Date: 07-2001
DOI: 10.1121/1.1379081
Abstract: A fast technique for deconvolving signals in a dispersive multipath shallow-water environment using inverse filters is compared with the more commonly used deconvolution technique of time reversal (also known as phase conjugation). The objective of such techniques is to improve the accuracy of sound transmission from a source array to some receiving space. Time reversal provides benefits in this regard but here the additional performance that can be gained from inverse filters is examined. Several strategies for obtaining a set of inverse filters are discussed, each aimed at improving the accuracy of the reconstruction of the desired time signals through inverse techniques. It will be shown that an “optimal” inversion (in the sense of achieving a flat system response in the frequency domain) does not necessarily achieve a realizable time domain filter. A fast field model (using OASES) of the Giglio Basin shallow-water test facility is used as the basis for evaluating the various focusing strategies for single receiver locations. It will be seen that inverse filter arrays provide enhanced temporal and spatial focusing when compared to time reversal arrays. In addition, inverse filtering allows multiple receivers to be used, thereby increasing bandwidth or improving redundancy.
The effect of arrangement of two circular cylinders on the maximum efficiency of Vortex-Induced Vibration power using a Scale-Adaptive Simulation model
Publisher: Elsevier BV
Date: 08-2014
Erratum: Theoretical design parameters for a quasi-zero stiffness magnetic spring for vibration isolation (Journal of Sound and Vibration 326 (2009) 12 (88-103))
Publisher: Elsevier BV
Date: 2011
Turbulence characteristics in the wake of a heliostat in an atmospheric boundary layer flow
Publisher: AIP Publishing
Date: 04-2020
DOI: 10.1063/5.0005594
Abstract: The mean and spectral characteristics of turbulence in the wake flow of a flat plate model resembling a heliostat in the atmospheric boundary layer flow are investigated in a wind tunnel experiment. Mean velocity and turbulence kinetic energy were characterized in the wake of a heliostat model at three elevation angles up to a distance of eight times the characteristic dimension of the heliostat panel. An increase in turbulence intensity and kinetic energy was found in the wake flow, reaching a peak at a distance equal to approximately twice the characteristic dimension of the heliostat panel. Furthermore, spectral and wavelet analysis of velocity fluctuations in the wake showed that the dominant mechanism in the immediate downstream of the plate was the breakdown of large inflow turbulence structures to smaller scales. In the end, the wake-induced turbulence patterns and wind loads in a heliostat field were discussed. It was found that compared to a heliostat at the front row, the heliostats positioned in high-density regions of a field were subjected to a higher turbulence intensity and, consequently, larger dynamic wind loading. The results show that it is necessary to consider the increased unsteady wind loads for the design of a heliostat in high-density regions of a field, where the gap between the rows is less than three-times the characteristic length of the heliostat panel.
Analytic Magnetic Fields and Semi-Analytic Forces and Torques Due to General Polyhedral Permanent Magnets
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2020
Properties of neuronal facilitation that improve target tracking in natural pursuit simulations
Publisher: The Royal Society
Date: 07-2015
Abstract: Although flying insects have limited visual acuity (approx. 1°) and relatively small brains, many species pursue tiny targets against cluttered backgrounds with high success. Our previous computational model, inspired by electrophysiological recordings from insect ‘small target motion detector’ (STMD) neurons, did not account for several key properties described from the biological system. These include the recent observations of response ‘facilitation’ (a slow build-up of response to targets that move on long, continuous trajectories) and ‘selective attention’, a competitive mechanism that selects one target from alternatives. Here, we present an elaborated STMD-inspired model, implemented in a closed loop target-tracking system that uses an active saccadic gaze fixation strategy inspired by insect pursuit. We test this system against heavily cluttered natural scenes. Inclusion of facilitation not only substantially improves success for even short-duration pursuits, but it also enhances the ability to ‘attend’ to one target in the presence of distracters. Our model predicts optimal facilitation parameters that are static in space and dynamic in time, changing with respect to the amount of background clutter and the intended purpose of the pursuit. Our results provide insights into insect neurophysiology and show the potential of this algorithm for implementation in artificial visual systems and robotic applications.
Structural radiation mode sensing for active control of sound radiation into enclosed spaces
Publisher: Acoustical Society of America (ASA)
Date: 12-1999
DOI: 10.1121/1.428225
Abstract: In the recent article by Cazzolato and Hansen [J. Acoust. Soc. Am. 104, 2878–2889 (1998)] it was shown that it is possible to derive for a structure some set of surface velocity distributions, referred to as radiation modes, which are orthogonal in terms of their contributions to the acoustic potential energy of a coupled cavity. The technique used an orthonormal decomposition to derive an expression for the radiation modes which was based on prior work for free-field sound radiation. It will be shown in the following letter that for the special case involving the calculation of global internal potential energy it is possible to use a simple approach which requires no orthonormal decomposition since the expression for the global potential energy is already in a form that can be easily diagonalized.
On the importance of nonlinear hydrodynamics and resonance frequencies on power production in multi-mode WECs
Publisher: Elsevier BV
Date: 12-2021
An optimal arrangement of mooring lines for the three-tether submerged point-absorbing wave energy converter
Publisher: Elsevier BV
Date: 08-2016
Numerical comparison of thermoacoustic couples with modified stack plate edges
Publisher: Elsevier BV
Date: 09-2008
Finite-length porous surfaces for control of a turbulent boundary layer
Publisher: AIP Publishing
Date: 04-2022
DOI: 10.1063/5.0084505
Abstract: This study investigates the potential of finite-length porous surfaces with a subsurface chamber for the control of the turbulent boundary layer. The effect of the subsurface chamber on the boundary layer is investigated by hot-wire anemometry measurements of the boundary layer response to different chamber configurations. Three different chamber configurations were investigated: a common cavity that connected the array of surface perforations, a locally reacting chamber with in idual cavities underneath each perforation, and chambers that connected the perforations in streamwise or spanwise flow directions. It was found that a common backing cavity and in idual cavities reduced the peak turbulence intensity, whereas the test case with streamwise or spanwise channels increased the turbulence intensity and strengthened large-scale turbulent structures within the boundary layer. While both common and in idual cavities were effective in reducing turbulence, the in idual cavities created a larger reduction in the pre-multiplied spectrum with an average of 80% at large scales compared to between 40% and 60% reduction at large scales for common cavities with different volumes. Hence, a short porous surface with in idual cavities underneath each perforation was found to be the most effective turbulence-reducing configuration among the investigated cases.
Frequency domain expressions for the estimation of time-averaged acoustic energy density
Publisher: Acoustical Society of America (ASA)
Date: 31-05-2005
DOI: 10.1121/1.1904505
Abstract: This paper builds on earlier work by the same authors to derive expressions for the time-averaged acoustic energy density in the frequency domain using the auto- and cross-spectral densities of multiple microphone elements. Expressions for the most common three-dimensional geometric arrangements are derived. Simplified expressions for use with two channel spectrum analysers are also presented.
An autonomous robot inspired by insect neurophysiology pursues moving features in natural environments
Publisher: IOP Publishing
Date: 13-07-2017
Abstract: Many computer vision and robotic applications require the implementation of robust and efficient target-tracking algorithms on a moving platform. However, deployment of a real-time system is challenging, even with the computational power of modern hardware. Lightweight and low-powered flying insects, such as dragonflies, track prey or conspecifics within cluttered natural environments, illustrating an efficient biological solution to the target-tracking problem. We used our recent recordings from 'small target motion detector' neurons in the dragonfly brain to inspire the development of a closed-loop target detection and tracking algorithm. This model exploits facilitation, a slow build-up of response to targets which move along long, continuous trajectories, as seen in our electrophysiological data. To test performance in real-world conditions, we implemented this model on a robotic platform that uses active pursuit strategies based on insect behaviour. Our robot performs robustly in closed-loop pursuit of targets, despite a range of challenging conditions used in our experiments low contrast targets, heavily cluttered environments and the presence of distracters. We show that the facilitation stage boosts responses to targets moving along continuous trajectories, improving contrast sensitivity and detection of small moving targets against textured backgrounds. Moreover, the temporal properties of facilitation play a useful role in handling vibration of the robotic platform. We also show that the adoption of feed-forward models which predict the sensory consequences of self-movement can significantly improve target detection during saccadic movements. Our results provide insight into the neuronal mechanisms that underlie biological target detection and selection (from a moving platform), as well as highlight the effectiveness of our bio-inspired algorithm in an artificial visual system.
Theoretical analysis of a non-contact spring with inclined permanent magnets for load-independent resonance frequency
Publisher: Elsevier BV
Date: 03-2012
An approximate backstepping control law for the global stabilisation of symmetric VTOL vehicles
Publisher: IEEE
Date: 02-2007
Deriving time-domain models of structural-acoustic radiation into free space
Publisher: Elsevier BV
Date: 09-2005
Leak Detection for Pipelines Using In-Pipe Optical Fiber Pressure Sensors and a Paired-IRF Technique
Publisher: American Society of Civil Engineers (ASCE)
Date: 10-2020
Vibration isolation using six degree-of-freedom quasi-zero stiffness magnetic levitation
Publisher: Elsevier BV
Date: 12-2015
Interaction of a flow-excited Helmholtz resonator with a grazing turbulent boundary layer
Publisher: Elsevier BV
Date: 10-2014
A moving zone of quiet for narrowband noise in a one-dimensional duct using virtual sensing
Publisher: Acoustical Society of America (ASA)
Date: 03-2007
DOI: 10.1121/1.2431583
Abstract: A frequent problem in active noise control is that the zone of quiet created at the error sensor tends to be very small. This means that the error sensor generally needs to be located close to an observer’s ear, which might not always be a convenient or feasible solution. Virtual sensing is a method that can move the zone of quiet away from the error sensor to a desired location that is spatially fixed. This method has been investigated previously, and has shown potential to improve the performance of an active noise control system. However, it is very likely that the desired location of the zone of quiet is not spatially fixed. An active noise control system incorporating a virtual sensing method thus has to be able to create a moving zone of quiet that tracks the observer’s ears. This paper presents a method for creating a moving zone of quiet based on the LMS virtual microphone technique. To illustrate the proposed method, it is implemented in an acoustic duct and narrowband control results are presented. These results show that a moving zone of quiet was effectively created inside the duct for narrowband noise.
Paired-IRF Method for Detecting Leaks in Pipe Networks
Publisher: American Society of Civil Engineers (ASCE)
Date: 05-2020
Effect of a rigid wall on the vortex induced vibration of two staggered circular cylinders
Publisher: AIP Publishing
Date: 05-2014
DOI: 10.1063/1.4879275
Abstract: Vortex Induced Vibrations (VIVs) play a key role in a wide range of engineering applications including the extraction of renewable energy. In this paper, numerical studies of the phenomenon of VIV were conducted to investigate the flow behaviour around two identical circular cylinders. The upstream cylinder was located in the vicinity of a rigid wall and downstream one was mounted on an elastic support with one degree of freedom. The Reynolds number based on the cylinder's diameter was kept constant at 8700, while the separation between the upstream cylinder and the wall was varied. The results show that this separation distance known as the gap ratio has a significant effect on the dynamic behaviour of the upstream and downstream cylinders. Accordingly, the interaction of shear layers between the upstream cylinder and the rigid wall has a strong influence on the vortex dynamics of both cylinders, in particular, when the upstream cylinder was mounted close to the wall. In this arrangement, a jet flow produced in the wake of the upstream cylinder significantly affects the vortex shedding frequency, and the lift and drag coefficients of both cylinders. This can alter the dynamic response of the downstream cylinder and theoretical efficiency of the VIV power.
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