ORCID Profile
0000-0002-7053-4353
Current Organisation
Curtin University
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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)
Interdisciplinary Engineering | Marine Engineering | Turbulent Flows | Mechanical Engineering | Fluidisation and Fluid Mechanics | Mechanical Engineering | Fluid Physics | Mechanical engineering | Classical Physics | Respiratory Diseases | Biomechanical Engineering | Biomedical Engineering | Biomechanical Engineering | Optical And Photonic Systems | Educational Technology and Computing | Energy generation conversion and storage (excl. chemical and electrical) | Geophysical Fluid Dynamics | Fluid-structure interaction and aeroacoustics | Curriculum and Pedagogy | Dynamics, Vibration and Vibration Control | Chemical Engineering not elsewhere classified | Computational Fluid Dynamics | Heat and Mass Transfer Operations | Science, Technology and Engineering Curriculum and Pedagogy | Calculus of variations mathematical aspects of systems theory and control theory | Fluid Physics
ANZSRC Socio-Economic Objective (SEO)
Expanding Knowledge in Engineering | Transport | Air transport | Expanding Knowledge in the Physical Sciences | Pipeline Transport | Primary Mining and Extraction of Mineral Resources not elsewhere classified | Diagnostic methods | Coastal water transport | International sea transport | Basic Metal Products (incl. Smelting, Rolling, Drawing and Extruding) not elsewhere classified | Physical sciences | Teaching and Instruction Technologies | Learner and Learning Processes | Energy not elsewhere classified | Expanding Knowledge in the Environmental Sciences | Sheet Metal Products | Respiratory system and diseases (incl. asthma) | Expanding Knowledge in the Biological Sciences |
Related Links
Publications
Design and Validation of an Instrument to Measure Students’ Interactions and Satisfaction in Undergraduate Chemistry Laboratory Classes
Publisher: Springer Science and Business Media LLC
Date: 09-05-2020
Wave excitation on a flexible surface in the presence of a uniform mean flow
Publisher: ASMEDC
Date: 2002
Abstract: The excitation of neutrally stable waves in a system comprising uniform flow over a flexible wall is studied. Linear theory and numerical simulation are used. A feature of wave excitation in such systems is that distinct litude ratios exist when more than one wave is present. An litude-ratio equation is first derived for the two waves excited directly by oscillatory excitation applied to a spatially homogeneous plate-spring flexible wall. There after, a second litude-ratio equation is derived for waves on a wall with spatially varying foundation-spring stiffness coefficient. In this case, waves beyond a region of changing flexibility are continuously excited by waves propagating through the region of change. Both energyflux and WKB methods are used to derive the final litude-ratio equation. It is shown, inter alia, that the waves upstream and downstream of the region of slowly changing wall properties are well-described by the dispersion equation based upon local wall properties. Finally, the case of waves incident upon a region of rapidly changing wall properties is simulated and discussed.
The stability of a flexible cantilever in viscous channel flow
Publisher: Elsevier BV
Date: 05-2017
On the Aerodynamic Loading and Deformation of Convertible Car Roofs
Publisher: SAE International
Date: 05-03-2001
DOI: 10.4271/2001-01-1269
A study of the hydroelastic stability of a compliant panel using numerical methods
Publisher: Emerald
Date: 06-1992
DOI: 10.1108/EB017510
Abstract: A numerical method is developed which can simulate the interaction between a finite compliant panel and an unsteady potential flow. A boundary‐element technique yields the flow solution whilst finite‐differences are used to solve the wall dynamics these are then coupled to generate a fully interactive wall/flow system. Thus, the evolution of any wall disturbance can be followed. Parallel computing is appropriately employed and a stability investigation of a realistic compliant panel is carried out. Three‐dimensional flexural waves are found below a critical flow speed whilst beyond this threshold, essentially two‐dimensional unstable ergence waves are found. The form of ergence shows good agreement with that seen in experimental studies. The versatility of this new method will permit the investigation of a wide variety of single‐ and multi‐panel configurations subject to different forms of excitation.
Stochastic stabilization of slender beams in space: Modeling and boundary control
Publisher: Elsevier BV
Date: 05-2018
Instability of a cantilevered flexible plate in viscous channel flow
Publisher: Elsevier BV
Date: 10-2005
The nonlinear hydroelastic behaviour of flexible walls
Publisher: Elsevier BV
Date: 10-1997
Reduction of Mixing in Jet-Fed Water Storage Tanks
Publisher: American Society of Civil Engineers (ASCE)
Date: 2004
The interaction of Blasius boundary-layer flow with a compliant panel: global, local and transient analyses
Publisher: Cambridge University Press (CUP)
Date: 22-08-2017
DOI: 10.1017/JFM.2017.453
Abstract: We study the fluid–structure interaction (FSI) of a compliant panel with developing Blasius boundary-layer flow. The linearised Navier–Stokes equations in velocity–vorticity form are solved using a Helmholtz decomposition coupled with the dynamics of a plate-spring compliant panel couched in finite-difference form. The FSI system is written as an eigenvalue problem and the various flow- and wall-based instabilities are analysed. It is shown that global temporal instability can occur through the interaction of travelling wave flutter (TWF) with a structural mode or as a resonance between Tollmien–Schlichting wave (TSW) instability and discrete structural modes of the compliant panel. The former is independent of compliant panel length and upstream inflow disturbances while the specific behaviour arising from the latter phenomenon is dependent upon the frequency of a disturbance introduced upstream of the compliant panel. The inclusion of axial displacements in the wall model does not lead to any further global instabilities. The dependence of instability-onset Reynolds numbers with structural stiffness and d ing for the global modes is quantified. It is also shown that the TWF-based global instability is stabilised as the boundary layer progresses downstream while the TSW-based global instability exhibits discrete resonance-type behaviour as Reynolds number increases. At sufficiently high Reynolds numbers, a globally unstable ergence instability is identified when the wavelength of its wall-based mode is longer than that of the least stable TSW mode. Finally, a non-modal analysis reveals a high level of transient growth when the flow interacts with a compliant panel which has structural properties capable of reducing TSW growth but which is prone to global instability through wall-based modes.
Motions of a cantilevered flexible plate in viscous channel flow driven by a constant pressure drop
Publisher: Wiley
Date: 28-01-2009
DOI: 10.1002/CNM.1225
Numerical simulation of pharyngeal airflow applied to obstructive sleep apnea: effect of the nasal cavity in anatomically accurate airway models
Publisher: Springer Science and Business Media LLC
Date: 10-2015
DOI: 10.1007/S11517-015-1399-Z
Abstract: Repetitive brief episodes of soft-tissue collapse within the upper airway during sleep characterize obstructive sleep apnea (OSA), an extremely common and disabling disorder. Failure to maintain the patency of the upper airway is caused by the combination of sleep-related loss of compensatory dilator muscle activity and aerodynamic forces promoting closure. The prediction of soft-tissue movement in patient-specific airway 3D mechanical models is emerging as a useful contribution to clinical understanding and decision making. Such modeling requires reliable estimations of the pharyngeal wall pressure forces. While nasal obstruction has been recognized as a risk factor for OSA, the need to include the nasal cavity in upper-airway models for OSA studies requires consideration, as it is most often omitted because of its complex shape. A quantitative analysis of the flow conditions generated by the nasal cavity and the sinuses during inspiration upstream of the pharynx is presented. Results show that adequate velocity boundary conditions and simple artificial extensions of the flow domain can reproduce the essential effects of the nasal cavity on the pharyngeal flow field. Therefore, the overall complexity and computational cost of accurate flow predictions can be reduced.
On the direct determination of the eigenmodes of finite flow-structure systems
Publisher: The Royal Society
Date: 14-10-2009
Abstract: A new method for directly determining the eigenmodes of finite flow–structure systems is presented using the classical problem of the interaction of a uniform incompressible flow with a flexible panel, held at both ends, as an exemplar. The method is a hybrid of theoretical analysis and computational modelling. This method is contrasted with Galerkin and travelling-wave methods, which are most often used to study the hydroelasticity of such systems. The new method does not require an a priori approximation of perturbations via a finite sum of modes. Instead, the coupled equations for the wall–flow system are used to derive a single matrix equation for the system that is a second-order differential equation for the panel-displacement variable. This is achieved in this exemplar by applying a combination of boundary-element and finite-element methods to the discretized system. Standard state-space methods are then used to extract the eigenmodes of the system directly. We present the results for the stability of the case of an unsupported flexible plate, elucidating its ergence and flutter characteristics, and the effect of energy dissipation in the structure. We then present the results for the case of a spring-backed flexible plate, showing that its motion is dominated by travelling waves. Finally, we illustrate the versatility of the approach by extracting the stability diagrams and modes for a panel with spatially varying properties and a panel with non-standard boundary conditions. In doing so, we show how spatial inhomogeneity can modify the energy exchanges between flow and structure, thereby introducing a single-mode flutter instability at pre- ergence flow speeds.
Inverse optimal control of evolution systems and its application to extensible and shearable slender beams
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 03-2019
Developing an understanding of undergraduate student interactions in chemistry laboratories
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8RP00104A
Abstract: Laboratories play a crucial role in the undergraduate science curriculum and the effectiveness of learning in laboratories is influenced by learners’ interactions with other students, the instructors, and the equipment used. In this study, a pre-lab survey was used to collect information about students’ expectations of interactions in chemistry laboratories and how they can be ranked according to their importance. Post-lab surveys were used to capture students’ perspectives about the frequency of interactions that existed in laboratory sessions they had completed. Direct observations of some laboratories were also conducted principally to validate students’ self-reported interactions. The data were also sorted by three levels of student achievement in order to relate students’ expectations of the importance of different interactions (pre-lab survey) and their self-reported frequency of interactions (post-lab survey) with their laboratory grades. Results from the pre-lab survey showed that student–instructor interactions were anticipated to be the most important ahead of conducting the laboratory activity, whereas results from the post-lab surveys showed that the most frequent interactions occurred between students. Students’ self-reports (post-lab survey) and the direct observations agreed well suggesting that the post-lab survey is a robust tool for capturing the frequencies of student interactions in this and future studies. The results also showed that students gaining high grades both anticipated the importance of, and then engaged more frequently in, two-way communications with both students and instructors whereas students with lower grades placed a relatively higher reliance upon passive interactions such as the pre-lab briefing, the laboratory manual and internet sources. Finally, recommendations are offered to curriculum designers, instructors and students based on the overall findings of the study.
Student perceptions of instruction sheets in face-to-face and remotely-operated engineering laboratory learning
Publisher: Informa UK Limited
Date: 27-08-2019
Flutter of structurally inhomogeneous cantilevers in laminar channel flow
Publisher: Elsevier BV
Date: 10-2019
Flow-induced deformations of a compliant insert in channel flow: From small to large amplitudes
Publisher: American Society of Mechanical Engineers
Date: 12-08-2012
Abstract: In this paper we consider a fluid-conveying channel with a compliant insert undergoing large litude flow-induced deformations. The objective is to assess the suitability of an open source finite element library oomph-lib for modelling this system. The fundamental system is relevant to a host of applications in both engineered (e.g. flexible-pipes, membrane filters, and general aero-/hydro-elasticity) and biomechanical (e.g. blood flow, airway flow) systems. The structural model uses a geometrically nonlinear formulation of the solid mechanics. Viscous flow is modelled at Reynolds numbers producing unsteady laminar flow. We present a brief summary of previous component validations with oomph-lib. We then focus on the unsteady-state FSI validation by comparing with published results, obtained using different computational schemes. This is done for both small- litude and large- litude wall deformations. Finally, we look at some preliminary energetics analysis of the flexible wall. The validations demonstrate the suitability and versatility of oomph-lib as a modelling and predictive tool. The flexible wall energetics validation show the possibility of understanding system stability through analysis of the flexible wall and fluid energetics.
A combined boundary integral and vortex method for the numerical study of three-dimensional fluid flow systems
Publisher: Informa UK Limited
Date: 07-2012
Impact of Online Preparation Modules on Students Engagement and Interactions in Face-to-Face Fluid Mechanics Laboratories
Publisher: The University of Sydney Library
Date: 29-08-2023
DOI: 10.30722/IJISME.31.02.002
Abstract: The transformation of laboratory activities to better embed the development of essential personal attributes and the attainment of specific learning outcomes in the engineering curriculum has been supported by the integration of online preparation modules. Beyond the widely demonstrated effectiveness of multimedia pre-laboratory activities in strengthening students’ engagement and preparedness for the execution of experimental tasks, this study also focuses on the effect of these online modules on student-student and student-instructor interactions in face-to-face fluid mechanics laboratories. Survey data show that students with a mid-level of academic performance were more likely to adopt the new resources but that most students perceived them as a valuable complement to, or replacement for, the traditional instruction sheet. While students’ self-assurance in conducting the laboratory tasks and appreciation of the instructor’s support appear unaffected by the completion of the modules, observations suggest these modules can strengthen students’ autonomy and engagement within their group during the conduct of the laboratory activities. Indeed, the introduction of the modules appears to facilitate a transition of the instructor’s role from directing the laboratory to guiding students in peer-learning.
An alternative approach to student assessment for engineering–laboratory learning
Publisher: Informa UK Limited
Date: 03-07-2017
Large-amplitude oscillations of a finite-thickness cantilevered flexible plate in viscous channel flow
Publisher: ASMEDC
Date: 2010
DOI: 10.1115/FEDSM-ICNMM2010-30438
Abstract: The broad aim of the present work is to elucidate mechanisms of obstructive breathing disorders (snoring, sleep apnea) in which flow-induced instabilities of the soft palate feature. We use the well-established analogue system model wherein a two-dimensional flexible plate (soft palate) is mounted downstream of a rigid surface that separates upper and lower plane channel (oral and nasal tracts) flows that interact with the plate motion and then combine into a single plane channel (pharynx) flow. For this system, we take the next step towards biomechanical realism by modeling finite- litude motions of the flexible plate and incorporating finite thickness in its structure. The structural model makes use of a geometrically nonlinear formulation of the solid mechanics. Viscous flow is modeled at Reynolds numbers giving unsteady laminar flow. The fully-coupled fluid-structure interaction (FSI) model is developed using the open-source finite-element library oomph–lib. We first show the effects of finite litude and finite thickness on the in-vacuo modes of the plate through a validation study of the structural mechanics. Thereafter, we use the FSI model to illustrate both stable and unstable motions of the plate. Overall, this paper demonstrates the versatility of the new modeling approach and its suitability for characterizing the dependence of the plate’s stability on the system parameters.
A numerical simulation of the interaction of a compliant wall and inviscid flow
Publisher: Cambridge University Press (CUP)
Date: 1992
Convective heat transfer from a vertically-mounted vibrating heated plate
Publisher: Springer Berlin Heidelberg
Date: 18-12-2016
Near-wall anisotropy under round and planar jet impingement
Publisher: Springer Berlin Heidelberg
Date: 18-12-2016
A new method for determining the eigenmodes of finite flow-structure systems
Publisher: ASMEDC
Date: 2006
DOI: 10.1115/PVP2006-ICPVT-11-93940
Abstract: A new method for directly determining the eigenmodes of finite flow-structure systems is presented, using the classical problem of the interaction of a uniform flow with a flexible panel, held at both ends, as an exemplar. The method is a hybrid of theoretical analysis and computational modelling. This new approach is contrasted with the standard Galerkin method that is most often used to study the hydro-elasticity of finite systems. Unlike the Galerkin method, the new method does not require an a priori approximation of perturbations via a finite sum of modes. Instead, the coupled equations for the wall-flow system are cast, using computational methods that, in this exemplar, combine boundary-element and finite-element methods, to yield a single matrix equation for the system that is a second-order differential equation for the panel-displacement variable. Standard state-space methods are then used to extract the eigenmodes of the system directly. We present definitive results for the stability of the case of an unsupported flexible plate, elucidating its ergence and flutter characteristics, and the effect of energy dissipation in the structure. Finally, we present some results for the case of a spring-backed flexible plate that illustrate the complicated dynamics of this type of wall these dynamics would be poorly modelled by a traditional Galerkin method.
Optimization of viscoelastic compliant walls for transition delay
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 02-1994
DOI: 10.2514/3.11980
Asymptotic stability and transient growth in pulsatile Poiseuille flow through a compliant channel
Publisher: Cambridge University Press (CUP)
Date: 05-05-2017
DOI: 10.1017/JFM.2017.163
Abstract: The time-asymptotic linear stability of pulsatile flow in a channel with compliant walls is studied together with the evaluation of modal transient growth within the pulsation period of the basic flow as well as non-modal transient growth. Both one (vertical-displacement) and two (vertical and axial) degrees-of-freedom compliant-wall models are implemented. Two approaches are developed to study the dynamics of the coupled fluid–structure system, the first being a Floquet analysis in which disturbances are decomposed into a product of exponential growth and a sum of harmonics, while the second is a time-stepping technique for the evolution of the fundamental solution (monodromy) matrix. A parametric study of stability in the non-dimensional parameter space, principally defined by Reynolds number ( $Re$ ), Womersley number ( $Wo$ ) and litude of the applied pressure modulation ( $\\unicode[STIX]{x1D6EC}$ ), is then conducted for compliant walls of fixed geometric and material properties. The flow through a rigid channel is shown to be destabilized by pulsation for low $Wo$ , stabilized due to Stokes-layer effects at intermediate $Wo$ , while the critical $Re$ approaches the steady Poiseuille-flow result at high $Wo$ , and that these effects are made more pronounced by increasing $\\unicode[STIX]{x1D6EC}$ . Wall flexibility is shown to be stabilizing throughout the $Wo$ range but, for the relatively stiff wall used, is more effective at high $Wo$ . Axial displacements are shown to have negligible effect on the results based upon only vertical deformation of the compliant wall. The effect of structural d ing in the compliant-wall dynamics is destabilizing, thereby suggesting that the dominant inflectional (Rayleigh) instability is of the Class A (negative-energy) type. It is shown that very high levels of modal transient growth can occur at low $Wo$ , and this mechanism could therefore be more important than asymptotic lification in causing transition to turbulent flow for two-dimensional disturbances. Wall flexibility is shown to ameliorate mildly this phenomenon. As $Wo$ is increased, modal transient growth becomes progressively less important and the non-modal mechanism can cause similar levels of transient growth. We also show that oblique waves having non-zero transverse wavenumbers are stable to higher values of critical $Re$ than their two-dimensional counterparts. Finally, we identify an additional instability branch at high $Re$ that corresponds to wall-based travelling-wave flutter. We show that this is stabilized by the inclusion of structural d ing, thereby confirming that it is of the Class B (positive-energy) instability type.
Instability of a cantilevered flexible plate in viscous channel flow driven by constant pressure drop
Publisher: ASMEDC
Date: 2006
DOI: 10.1115/PVP2006-ICPVT-11-93943
Abstract: A new approach for studying the stability of a cantilevered flexible plate positioned within a 2-D viscous channel flow is presented as a representation of the human upper airway. Previous work has used constant inlet velocity conditions, an unrealistic assumption when modelling inhalation. Here we model a constant pressure drop that reflects inspiratory effort. Positioning of the flexible plate within the channel can also be varied. The constant pressure drop is imposed for each time step by computing appropriate inlet velocities. The Navier-Stokes equations are solved using an explicit finite-element method written specifically for the channel geometry within which the fully coupled plate moves. The motion of the plate, driven by the pressure field, is modelled using classical thin-plate mechanics with the addition of a shear-stress induced tension term. The investigation focuses on the motion of the flexible plate (soft palate) as one of the contributors to airway blockage during sleep. It is found that the tension induced by the fluid shear-stress can be significant when the plate is sufficiently flexible. We also demonstrate that imposing constant inlet velocity generates over-predictions of energy transfer between flow and flexible plate. Finally, we show that offsetting the flexible plate within the channel leads to changes in oscillation frequency and significant change to its energy interaction with the fluid flow.
Stability of a spring-mounted cantilevered flexible plate in a uniform flow
Publisher: Springer Berlin Heidelberg
Date: 13-11-2014
The effect of localised stiffening on the stability of a flexible panel in uniform flow
Publisher: Springer Berlin Heidelberg
Date: 13-11-2014
Reynolds averaged and large eddy computations of flow and heat transfer under round jet impingement
Publisher: American Society of Mechanical Engineers
Date: 03-08-2014
Abstract: The fluid dynamics and heat transfer characteristics of a turbulent round jet are modelled numerically using Reynolds-Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES). Meshes with varying degrees of coarseness, with both radial and axial refinements are investigated. Discretization is carried out using the finite volume method. The jet configurations are chosen to enable validation against well-established experimental jet-impingement heat-transfer studies, particularly that of Cooper et al. [1]. The Reynolds number studied is 23000. The height of discharge from the impingement wall is fixed at twice the jet diameter. The work critically examines the effect of Reynolds number, standoff distance and helps to ascertain the relative merits of various turbulence models, by comparing turbulent statistics and the Nusselt number distributions. The present work is carried out as a preliminary validation, in a wider study intended to determine the thermofluidic behaviour of jets impinging upon an oscillating surface.
Eigen-analysis of an inviscid channel flow with a finite flexible plate in one wall
Publisher: Springer Berlin Heidelberg
Date: 13-11-2014
Effect of the velopharynx on intraluminal pressures in reconstructed pharynges derived from individuals with and without sleep apnea
Publisher: Elsevier BV
Date: 09-2013
DOI: 10.1016/J.JBIOMECH.2013.07.007
Abstract: The most collapsible part of the upper airway in the majority of in iduals is the velopharynx which is the segment positioned behind the soft palate. As such it is an important morphological region for consideration in elucidating the pathogenesis of obstructive sleep apnea (OSA). This study compared steady flow properties during inspiration in the pharynges of nine male subjects with OSA and nine body-mass index (BMI)- and age-matched control male subjects without OSA. The k-ωSST turbulence model was used to simulate the flow field in subject-specific pharyngeal geometric models reconstructed from anatomical optical coherence tomography (aOCT) data. While analysis of the geometry of reconstructed pharynges revealed narrowing at velopharyngeal level in subjects with OSA, it was not possible to clearly distinguish them from subjects without OSA on the basis of pharyngeal size and shape alone. By contrast, flow simulations demonstrated that pressure fields within the narrowed airway segments were sensitive to small differences in geometry and could lead to significantly different intraluminal pressure characteristics between subjects. The ratio between velopharyngeal and total pharyngeal pressure drops emerged as a relevant flow-based criterion by which subjects with OSA could be differentiated from those without.
Progress on the Use of Compliant Walls for Laminar-Flow Control
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 05-2001
DOI: 10.2514/2.2790
Power output of spring-mounted lifting plates in a cross flow
Publisher: Springer Singapore
Date: 15-05-2019
Effect of Structural Stiffness on the Stability of Pulsatile Poiseuille Flow Through a Compliant Channel
Publisher: Springer Singapore
Date: 15-05-2018
A predictive capability for the aerodynamic deformation of convertible car roofs
Publisher: SAGE Publications
Date: 07-06-2010
DOI: 10.1243/09544070JAUTO1408
Abstract: The flow-induced deformation of a membrane in a flow is studied using experimental and computational approaches in a configuration that represents the effect of the aerodynamic load on a convertible car roof. The computational method couples a commercial computational fluid dynamics code with an in-house structural code to predict membrane deformation. A converged statically deformed state, within 1 per cent difference in the displacement variable, is reached after three iterations between the fluid and structural codes. The predictions of membrane deformation are shown to agree well with the experimental results. The key outcome is the demonstration of a methodology that will be useful in the engineering design of convertible car roofs.
Boundary stabilization of extensible and unshearable marine risers with large in-plane deflection
Publisher: Elsevier BV
Date: 03-2017
Modelling of a cantilevered flexible plate undergoing large-amplitude oscillations due to a high reynolds-number axial flow
Publisher: Springer Berlin Heidelberg
Date: 18-12-2016
Pressure Wave Propagation in Fluid-Filled Co-Axial Elastic Tubes Part 2: Mechanisms for the Pathogenesis of Syringomyelia
Publisher: ASME International
Date: 12-2003
DOI: 10.1115/1.1634281
Abstract: Our aim in this paper is to use a simple theoretical model of the intraspinal cerebrospinal-fluid system to investigate mechanisms proposed for the pathogenesis of syringomyelia. The model is based on an inviscid theory for the propagation of pressure waves in co-axial, fluid-filled, elastic tubes. According to this model, the leading edge of a pressure pulse tends to steepen and form an elastic jump, as it propagates up the intraspinal cerebrospinal-fluid system. We show that when an elastic jump is incident on a stenosis of the spinal subarachnoid space, it reflects to form a transient, localized region of high pressure within the spinal cord that for a cough-induced pulse is estimated to be 50 to 70 mm Hg or more above the normal level in the spinal subarachnoid space. We propose this as a new mechanism whereby pressure pulses created by coughing or sneezing can generate syrinxes. We also use the same analysis to investigate Williams’ suck mechanism. Our results do not support his concept, nor, in cases where the stenosis is severe, the differential-pressure-propagation mechanism recently proposed by Greitz et al. Our analysis does provide some support for the piston mechanism recently proposed by Oldfield et al. and Heiss et al. For instance, it shows clearly how the spinal cord is compressed by the formation of elastic jumps over part of the cardiac cycle. What appears to be absent for this piston mechanism is any means whereby the elastic jumps can be focused (e.g., by reflecting from a stenosis) to form a transient, localized region of high pressure within the spinal cord. Thus it would seem to offer a mechanism for syrinx progression, but not for its formation.
Application of a multi-objective genetic algorithm in a stabilisation strategy for flexible panels in a mean flow
Publisher: Springer Berlin Heidelberg
Date: 18-12-2016
The hydroelastic stability of three-dimensional disturbances of a finite compliant wall
Publisher: Elsevier BV
Date: 08-1993
Support services for higher degree research students: A survey of three Australian universities
Publisher: Informa UK Limited
Date: 26-10-2016
On the Difference between the Hydroelastic Instability of Infinite and Very Long Compliant Panels
Publisher: Elsevier BV
Date: 05-1993
The nonlinear oscillations of a flexible surface comprising one wall of an inviscid channel flow
Publisher: Springer Berlin Heidelberg
Date: 18-12-2016
Global Stability Analysis of Blasius Boundary-Layer Flow over a Compliant Panel Accounting for Axial and Vertical Displacements
Publisher: Springer Berlin Heidelberg
Date: 18-12-2015
Power output of spring-mounted lifting plates in axial flow
Publisher: Springer Berlin Heidelberg
Date: 18-12-2016
Pressure Wave Propagation in Fluid-Filled Co-Axial Elastic Tubes Part 1: Basic Theory
Publisher: ASME International
Date: 12-2003
DOI: 10.1115/1.1634280
Abstract: Our work is motivated by ideas about the pathogenesis of syringomyelia. This is a serious disease characterized by the appearance of longitudinal cavities within the spinal cord. Its causes are unknown, but pressure propagation is probably implicated. We have developed an inviscid theory for the propagation of pressure waves in co-axial, fluid-filled, elastic tubes. This is intended as a simple model of the intraspinal cerebrospinal-fluid system. Our approach is based on the classic theory for the propagation of longitudinal waves in single, fluid-filled, elastic tubes. We show that for small- litude waves the governing equations reduce to the classic wave equation. The wave speed is found to be a strong function of the ratio of the tubes’ cross-sectional areas. It is found that the leading edge of a transmural pressure pulse tends to generate compressive waves with converging wave fronts. Consequently, the leading edge of the presure pulse steepens to form a shock-like elastic jump. A weakly nonlinear theory is developed for such an elastic jump.
Stability of a cantilevered flexible plate with non-uniform thickness in viscous channel flow
Publisher: Springer Berlin Heidelberg
Date: 18-12-2016
Particle Image Velocimetry and Infrared Thermography of Turbulent Jet Impingement on an Oscillating Surface
Publisher: Elsevier BV
Date: 11-2018
Excitation and evolution of waves on an inhomogeneous flexible wall in a mean flow
Publisher: Elsevier BV
Date: 09-2003
Stability of Blasius Boundary-Layer Flow Interacting With a Compliant Panel
Publisher: American Society of Mechanical Engineers
Date: 20-07-2014
Abstract: We develop a model to study the fluid-structure interaction (FSI) of a compliant panel with a Blasius boundary-layer flow. We carry out a two-dimensional global linear stability analysis modeling the flow using a combination of vortex and source boundary-element sheets on a computational grid while the dynamics of a plate-spring compliant wall are represented in finite-difference form. The system is then couched as an eigenvalue problem and the eigenvalues of the various flow- and wall-based instabilities are analyzed for two distinct sets of system parameters. Key findings are that coalescence — or resonance — of a structural eigenmode with either the most unstable flow-based Tollmien-Schlichting Wave (TSW) or wall-based travelling-wave flutter (TWF) modes can occur. This renders the convective nature of these instabilities to become global for a finite compliant wall, a phenomenon that has not hitherto been reported in the literature.
Syringomyelia and the Fluid-Structure Interactions of a Cerebrospinal Waveguide
Publisher: American Society of Mechanical Engineers
Date: 20-07-2014
Abstract: In the disease syringomyelia, fluid-filled cavities, called syrinxes, form in the spinal cord. The expansion of these pathological pressure vessels compresses the surrounding nerve fibers and blood supply, which is associated with neurological damage. We investigate the spinal wave-propagation characteristics, principally to serve as a reference for more anatomically-detailed models. The spinal cord is modeled as an elastic cylinder, which becomes an annulus containing inviscid fluid when a syrinx is included. This is surrounded by an annulus of inviscid fluid, representing the cerebrospinal fluid occupying the subarachnoid space, with an outer rigid boundary approximating the dura mater. The axisymmetric harmonic motion is solved as an eigenvalue problem. We present dispersion diagrams and describe the physical mechanism of each wave mode. We identify potentially damaging syrinx fluid motions and tissue stress concentrations from the eigenvectors. Finally, we determine the dependence of each wave mode on syrinx radius and cord tissue compressibility.
The excitation of waves on a flexible panel in a uniform flow
Publisher: The Royal Society
Date: 15-12-1998
Perceptions of the relative importance of student interactions for the attainment of engineering laboratory-learning outcomes
Publisher: Informa UK Limited
Date: 02-07-2020
Optimal swimming modes of a homo-sapien performing butterfly-stroke kick
Publisher: ASMEDC
Date: 2006
DOI: 10.1115/PVP2006-ICPVT-11-93938
Abstract: This paper outlines the development and application of a computational method that finds the most efficient two-dimensional swimming mode of a human performing fully submerged butterfly-stroke kick at high Reynolds number. The optimal solution of this non-linear problem is found using a Genetic Algorithm (GA) search method where possible solutions compete in a ‘survival of the fittest’ scheme to ‘breed’ the optimal solution. The swimming is modelled using Discrete Vortex Method (DVM) and Boundary Element Method (BEM) computational techniques. The BEM solves for the inviscid flow field around the two-dimensional body while the shedding of vorticies from joints where the curvature is high (ie. knee, waist and ankle joints) generate the vortex structures necessary for propulsion. The motion of the limbs is characterised by a displacement function which includes the possibility for simple harmonic or non-harmonic motion with a ‘rest’ period in the kick. The finite number of joints means that a finite length parameter set can be developed which characterises the motion of the swimming body. This parameter set is fed into the GA to perform the optimisation based on a scoring function. In this case, the scoring function is simply the distance that the body swims in a set amount of time. The objective of the GA is to maximise this score for a set kicking frequency. This method opens a wider possibility for optimisation of a variety of systems that involve fluid-structure interactions, particulary the possibility of optimisation in the non-linear regime of prescribed motion coupled with compliant surfaces (such as rubbery flippers) that could further increase efficiency.
Global instabilities and transient growth in Blasius boundary-layer flow over a compliant panel
Publisher: Springer Science and Business Media LLC
Date: 05-2015
Fluid–structure interaction of a two-dimensional membrane in a flow with a pressure gradient with application to convertible car roofs
Publisher: Elsevier BV
Date: 02-2010
Hydroelastic stability of flexible panel: Eigen-analysis and time-domain response
Publisher: ASMEDC
Date: 2010
DOI: 10.1115/FEDSM-ICNMM2010-30057
Abstract: A state-space model, based upon computational modeling, is used to investigate the hydroelastic stability of a finite flexible panel interacting with a uniform flow. A merit of this approach is that it allows the fluid-structure system eigenmodes to be found readily when structural inhomogeneity is included or a source of external excitation is present. The system studied herein is two-dimensional although the concepts presented can be readily extended to three dimensions. Two problems are considered. In the first, we solve the initial-value, boundary-value, problem to show how the system response evolves from a source of localized excitation. This problem is deceptively complex and has evidenced some very unusual behaviour as demonstrated by theoretical studies based on the assumption of an infinitely long flexible panel. Our contribution herein is to formulate and illustrate the use of a hybrid of theoretical and computational models that includes the effects of finiteness. In the second problem we solve the boundary-value problem to determine the long-time response and investigate the effects of adding localized structural inhomogeneity on the linear stability of a flexible panel. It is well known that a simple flexible plate first loses its stability to ergence that is replaced by modal-coalescence flutter at higher speeds. Our contribution is to show how the introduction of localized structural inhomogeneity can be used to modify the ergence-onset and flutter-onset critical flow speeds.
Boundary layer instability over compliant walls: Comparison between theory and experiment
Publisher: AIP Publishing
Date: 10-1995
DOI: 10.1063/1.868748
Abstract: Theoretical studies have shown that compliant walls are able to attenuate the Tollmien–Schlichting waves that lead to conventional two-dimensional boundary-layer transition. This phenomenon was demonstrated in towing-tank tests conducted by Gaster et al. The results of these experiments also featured a different and very dramatic form of boundary-layer breakdown. We contend that this type of breakdown was due to a hydroelastic mode of instability, namely traveling-wave flutter. In this paper we model the two-layer viscoelastic compliant wall of Gaster et al. and its interaction with the boundary-layer flow using the asymptotic theory of Carpenter and Gajjar en-type calculations are carried out for the traveling-wave flutter. Excellent agreement is found between the stability characteristics of the TWF mode and the measurements of the new form of breakdown found in the experiments thus a complete understanding of the physical features found in the experiments is now available. Such understanding is essential for progress to be made in the technological development of compliant panels for transition delay.
Non-linear spring-mounted flexible plates in axial flow
Publisher: Springer Singapore
Date: 15-05-2019
Fluid–structure interactions in a cylindrical layered wave guide with application in the spinal column to syringomyelia
Publisher: Elsevier BV
Date: 04-2017
A Three Dimensional Imaging-Based Framework for Planning Maxillomandibular Advancement Surgery for the Treatment of Obstructive Sleep Apnoea
Publisher: IEEE
Date: 12-2013
DOI: 10.1109/WCSE.2013.55
Measurement, Reconstruction, and Flow-Field Computation of the Human Pharynx With Application to Sleep Apnea
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 10-2010
In-silico study of the nasal cavity’s influence on the pharyngeal wall pressure in anatomically-correct airway models of patients with obstructive sleep apnea
Publisher: Springer International Publishing
Date: 2014
Large-eddy simulations of a turbulent jet impinging on a vibrating heated wall
Publisher: Elsevier BV
Date: 06-2017
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