ORCID Profile
0000-0002-1261-6035
Current Organisation
University of New South Wales
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Acoustics and Noise Control (excl. Architectural Acoustics) | Mechanical Engineering | Turbulent Flows | Aerospace Engineering | Composite and Hybrid Materials | Dynamics, Vibration and Vibration Control | Ship and Platform Hydrodynamics | Interdisciplinary Engineering Not Elsewhere Classified | Hypersonic Propulsion and Hypersonic Aerodynamics | Numerical Modelling and Mechanical Characterisation | Maritime Engineering | Mechanical Engineering | Maritime Engineering not elsewhere classified | Aerospace Engineering Not Elsewhere Classified | Aerospace Engineering not elsewhere classified |
Management of Noise and Vibration from Transport Activities | Navy | Wind Energy | Expanding Knowledge in Engineering | Air transport | Wind | Air Safety | Space Transport | Aerospace equipment
Publisher: American Institute of Aeronautics and Astronautics
Date: 18-05-2019
DOI: 10.2514/6.2019-2717
Publisher: American Institute of Aeronautics and Astronautics
Date: 18-05-2019
DOI: 10.2514/6.2019-2718
Publisher: ASME International
Date: 09-03-2020
DOI: 10.1115/1.4046166
Abstract: Measurements of the wall pressure fluctuations near a wing-plate junction were made for wings with three different aspect ratios (AR) of 0.2, 0.5, and 1.0 at several angles of attack. The chord-based Reynolds number for each wing was 274,000. The results show that the wall pressure fluctuations are a function of wing AR for cases where AR≤ 1.0. For each wing, the pressure fluctuations are highest upstream of the wing leading-edge due to three-dimensional flow separation wings with AR = 1.0 and 0.5 show comparable levels, while those with AR = 0.2 show lower fluctuation levels over a wide frequency range. Downstream of the leading-edge, the pressure fluctuations decay rapidly on both sides of the wing until the maximum thickness location after which little variation is observed. The pressure fluctuations downstream of the leading-edge on the suction-side were observed to be comparable for AR = 0.2 and 0.5, while those for AR = 1.0 were higher in magnitude. On the pressure-side, the pressure fluctuations near the leading-edge are a weak function of AR however, those further downstream remain independent of AR. The pressure fluctuations aft of the wing on the suction-side are more coherent for lower ARs and show higher convection velocity, possibly due to an interaction between the tip and the junction flows for lower ARs.
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 05-2016
DOI: 10.2514/1.J054493
Publisher: Elsevier BV
Date: 02-2020
Publisher: Oxford University Press (OUP)
Date: 2023
Publisher: Elsevier BV
Date: 05-2012
Publisher: American Institute of Aeronautics and Astronautics
Date: 13-06-2014
DOI: 10.2514/6.2014-3290
Publisher: Elsevier BV
Date: 06-2021
Publisher: Elsevier BV
Date: 12-2014
Publisher: Elsevier BV
Date: 07-2011
Publisher: Elsevier BV
Date: 06-2020
Publisher: Cambridge University Press (CUP)
Date: 04-06-2020
DOI: 10.1017/S1049023X20000734
Abstract: Anthrax is a potential biological weapon and can be used in an air-borne or mail attack, such as in the attack in the United States in 2001. Planning for such an event requires the best available science. Since large-scale experiments are not feasible, mathematical modelling is a crucial tool to inform planning. The aim of this study is to systematically review and evaluate the approaches to mathematical modelling of inhalational anthrax attack to support public health decision making and response. A systematic review of inhalational anthrax attack models was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria. The models were reviewed based on a set of defined criteria, including the inclusion of atmospheric dispersion component and capacity for real-time decision support. Of 13 mathematical modelling studies of human inhalational anthrax attacks, there were six studies that took atmospheric dispersion of anthrax spores into account. Further, only two modelling studies had potential utility for real-time decision support, and only one model was validated using real data. The limited modelling studies available use widely varying methods, assumptions, and data. Estimation of attack size using different models may be quite different, and is likely to be under-estimated by models which do not consider weather conditions. Validation with available data is crucial and may improve models. Further, there is a need for both complex models that can provide accurate atmospheric dispersion modelling, as well as for simpler modelling tools that provide real-time decision support for epidemic response.
Publisher: Springer Singapore
Date: 15-05-2018
Publisher: Elsevier BV
Date: 04-2016
Publisher: American Institute of Aeronautics and Astronautics
Date: 09-01-2012
DOI: 10.2514/6.2012-255
Publisher: American Institute of Aeronautics and Astronautics
Date: 13-06-2014
DOI: 10.2514/6.2014-2917
Publisher: American Institute of Aeronautics and Astronautics
Date: 05-06-2011
DOI: 10.2514/6.2011-2732
Publisher: Elsevier BV
Date: 04-2022
Publisher: American Institute of Aeronautics and Astronautics
Date: 13-06-2014
DOI: 10.2514/6.2014-3287
Publisher: Elsevier BV
Date: 04-2017
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 02-2013
DOI: 10.2514/1.J051378
Publisher: Elsevier BV
Date: 07-2009
Publisher: Elsevier BV
Date: 06-2020
Publisher: American Institute of Aeronautics and Astronautics
Date: 24-06-2018
DOI: 10.2514/6.2018-3936
Publisher: IOP Publishing
Date: 06-09-2021
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 2007
DOI: 10.2514/1.23160
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 11-2009
DOI: 10.2514/1.43716
Publisher: Elsevier BV
Date: 10-2020
Publisher: Elsevier BV
Date: 12-2014
Publisher: Springer Science and Business Media LLC
Date: 21-07-2015
Publisher: Acoustical Society of America (ASA)
Date: 09-2019
DOI: 10.1121/1.5126693
Abstract: This paper is concerned with the influence of the incoming wall boundary layer thickness on the noise produced by a square finite wall-mounted cylinder in cross-flow. Acoustic and near wake velocity measurements have been taken in an anechoic wind tunnel for a cylinder in two different near-zero-pressure gradient turbulent boundary layers with thicknesses of 130% and 370% of the cylinder width, W. The cylinders have an aspect ratio of 0.29≤L/W≤22.9 (where L is the cylinder span) and were examined at a Reynolds number, based on width, of ReW = 1.4 × 104. The results presented in this paper demonstrate that increasing the height of the boundary layer delays the production of acoustic tones to higher aspect ratios. The height of the boundary layer changes the balance between upwash and downwash across the cylinder span, resulting in a delayed onset of the shedding regimes and correspondingly, the production of acoustic tones.
Publisher: Elsevier BV
Date: 06-2020
Publisher: Cambridge University Press (CUP)
Date: 26-10-2017
DOI: 10.1017/JFM.2017.682
Abstract: This paper presents the results of an experimental study that relates the flow structures in the wake of a square finite wall-mounted cylinder with the radiated noise. Acoustic and hot-wire measurements were taken in an anechoic wind tunnel. The cylinder was immersed in a near-zero-pressure gradient boundary layer whose thickness was 130 % of the cylinder width, $W$ . Aspect ratios were in the range $0.29\\leqslant L/W\\leqslant 22.9$ (where $L$ is the cylinder span), and the Reynolds number, based on width, was $1.4\\times 10^{4}$ . Four shedding regimes were identified, namely R0 ( $L/W $ ), RI ( $2 L/W $ ), RII ( $10 L/W $ ) and RIII ( $L/W $ ), with each shedding regime displaying an additional acoustic tone as the aspect ratio was increased. At low aspect ratios (R0 and RI), downwash dominated the wake, creating a highly three-dimensional shedding environment with maximum downwash at $L/W\\approx 7$ . Looping vortex structures were visualised using a phase eduction technique. The principal core of the loops generated the most noise perpendicular to the cylinder. For higher aspect ratios in RII and RIII, the main noise producing structures consisted of a series of inclined vortex filaments, where the angle of inclination varied between vortex cells.
Publisher: Elsevier BV
Date: 10-2015
Publisher: Elsevier BV
Date: 12-2010
Publisher: Acoustical Society of America (ASA)
Date: 09-2017
DOI: 10.1121/1.5003651
Abstract: Numerical simulations are used to investigate the noise generated by the passage of a rotor blade past a fixed object (the blade-passage effects), which was studied by simulating a three-bladed rotor that is supported by a vertical cylindrical tower. To isolate the blade-passage effects, no incoming wind was introduced in the simulation. The symmetric blade was set to zero pitch angle relative to the plane of rotation and two blade-tower distances were investigated. The sliding mesh method was used to simulate the rotation of the blades and Curle's acoustic analogy was used to predict the noise generated from the simulated flow data. Intense force fluctuations occur during the interaction on both the tower and the passing blade, and these are the primary sources of blade-passage noise. The contribution of the force fluctuations on the support tower to blade-passage noise, which previously had been ignored, was revealed to be more significant than that of the blades. The numerical model successfully predicts the noise spectra, which are validated by the very good agreement with experimental measurements. The simulations provide a framework to better understand blade–tower interaction noise in various applications.
Publisher: American Institute of Aeronautics and Astronautics
Date: 18-06-2015
DOI: 10.2514/6.2015-2831
Publisher: American Institute of Aeronautics and Astronautics
Date: 27-05-2016
DOI: 10.2514/6.2016-2760
Publisher: Elsevier BV
Date: 12-2018
Publisher: American Institute of Aeronautics and Astronautics
Date: 02-06-2017
DOI: 10.2514/6.2017-4183
Publisher: AIP Publishing
Date: 04-2018
DOI: 10.1063/1.5018877
Abstract: This paper presents a numerical study that focuses on the transient interaction between a reaction control jet and a hypersonic crossflow with a laminar boundary layer. The aim is to better understand the underlying physical mechanisms affecting the resulting surface pressure and control force. Implicit large-eddy simulations were performed with a round, sonic, perfect air jet issuing normal to a Mach 5 crossflow over a flat plate with a laminar boundary layer, at a jet-to-crossflow momentum ratio of 5.3 and a pressure ratio of 251. The pressure distribution induced on the flat plate is unsteady and is influenced by vortex structures that form around the jet. A horseshoe vortex structure forms upstream and consists of six vortices: two quasi-steady vortices and two co-rotating vortex pairs that periodically coalesce. Shear-layer vortices shed periodically and cause localised high pressure regions that convect downstream with constant velocity. A longitudinal counter-rotating vortex pair is present downstream of the jet and is formed from a series of trailing vortices which rotate about a common axis. Shear-layer vortex shedding causes periodic deformation of barrel and bow shocks. This changes the location of boundary layer separation which also affects the normal force on the plate.
Publisher: American Institute of Aeronautics and Astronautics
Date: 14-06-2019
DOI: 10.2514/6.2019-3438
Publisher: ASME International
Date: 31-05-2007
DOI: 10.1115/1.2771578
Abstract: A potential flow and viscous flow solver have been coupled to produce a robust computational tool useful for the design of low-speed wind tunnel contractions. After validation against published numerical and experimental wind tunnel data, the method is used to evaluate recently proposed contraction shapes from the literature. The results show that, on balance, a fifth-order polynomial provides a good design solution. Newly proposed shapes will either improve available flow area at the expense of contraction outlet flow uniformity or vice versa.
Publisher: Acoustical Society of America (ASA)
Date: 05-2017
DOI: 10.1121/1.4983295
Abstract: Trailing edge noise from stationary and rotating NACA 0012 airfoils is characterised and compared with a noise prediction based on the semi-empirical Brooks, Pope, and Marcolini (BPM) model. The NACA 0012 is symmetrical airfoil with no camber and 12% thickness to chord length ratio. Acoustic measurements were conducted in an anechoic wind tunnel using a stationary NACA 0012 airfoil at 0° pitch angle. Airfoil self-noise emissions from rotating NACA 0012 airfoils mounted at 0° and 10° pitch angles on a rotor-rig are studied in an anechoic room. The measurements were carried out using microphone arrays for noise localisation and magnitude estimation using beamforming post-processing. Results show good agreement between peak radiating trailing edge noise emissions of stationary and rotating NACA 0012 airfoils in terms of the Strouhal number. Furthermore, it is shown that noise predictions based on the BPM model considering only two dimensional flow effects, are in good agreement with measurements for rotating airfoils, at these particular conditions.
Publisher: AIP Publishing
Date: 03-2011
DOI: 10.1063/1.3563619
Abstract: Flows over a square cylinder of side length D with and without a splitter plate are numerically investigated at a Reynolds number of 150. The length of the splitter plate is varied systematically from L=0.5D to L=6D so the sensitivity of the flow structure to the inclusion of the splitter plate can be inspected. It is found that the splitter plate introduces a strong hydrodynamic interaction to the near wake of the cylinder and the length of the plate affects significantly the flow structure. The behavior of the flow can be grouped into three regimes. For short plate lengths (0≲L≲D), the free shear layers are convected further downstream before rolling up when the plate length is increased. For intermediate plate lengths (1.25D≲L≲4.75D), a secondary vortex is clearly visible around the trailing edge of the splitter plate and the shear layers begin to roll up closer to the trailing edge. For long plate lengths (L≳5D), a regime is observed in which the free shear layers reattach to the splitter plate. The study also proposes the minimum wake half-width as the length scale for a possible universal Strouhal number, which is found to be valid for 0≤L≤4D.
Publisher: Elsevier BV
Date: 08-2012
Publisher: Elsevier BV
Date: 2018
Publisher: Acoustical Society of America (ASA)
Date: 11-2018
DOI: 10.1121/1.5080462
Abstract: A two-step, hybrid procedure to calibrate the remote microphones is presented. The calibration obtained in this manner can be directly applied to the measured pressure spectrum without resorting to any modeling or assumptions about the shape of the calibration curve. To demonstrate an application of the methodology, measurements of wall pressure fluctuations underneath a zero pressure gradient turbulent boundary layer were made. The calibrated pressure spectrum is shown to be qualitatively and quantitatively consistent with previous experimental studies and an empirical model, indicating the accuracy of the hybrid calibration technique.
Publisher: Cambridge University Press (CUP)
Date: 14-07-2022
DOI: 10.1017/JFM.2022.517
Abstract: The supersonic wake of a circular cylinder in Mach 3 flow was studied through high-speed, focussing schlieren photography. The mean and unsteady behaviour of the separated shear layers, the reattachment process, the recompression wave and the early wake are analysed, and discussed in detail. The fluctuations in the wake are stronger and more coherent than those within the approaching shear layers and the recirculation region. The recompression of the shear layers energises the finer scales in the flow which leads to a departure from a $-$ 1 spectral roll-off observed in the schlieren spectra further upstream. The recompression wave exhibits low-frequency unsteadiness and a ripple-type motion which occurs as it is perturbed by shocklets radiating from the coherent structures in the wake. The wake consists of coherent disturbances with the same characteristic frequency as that for an incompressible flow over a cylinder however, this instability is suppressed as the wake accelerates, presumably due to increasing compressibility. The primary instability of the wake flow has a characteristic frequency nearly twice that of its incompressible counterpart and it is shown to be driven by the presence of aeroacoustic resonance in the wake. It is also shown that the resonance, which leads to the formation of broadband standing waves in the wake, is the result of an interaction between the wake instabilities and upstream propagating acoustic waves in the wake. The acoustic waves originate upstream of the reattachment region and are believed to be generated by the unsteady separation on the cylinder surface.
Publisher: Acoustical Society of America (ASA)
Date: 11-09-2013
DOI: 10.1121/1.4819185
Abstract: This letter investigates the use of multiple line arrays (LAs) in a Time-Reversal Mirror for localizing and characterizing multipole aeroacoustic sources in a uniform subsonic mean flow using a numerical Time-Reversal (TR) method. Regardless of the original source characteristics, accuracy of predicting the source location can be significantly improved using at least two LAs. Furthermore, it is impossible to determine the source characteristics using a single LA, rather a minimum of two are required to establish either the monopole or dipole source nature, while four LAs (fully surrounding the source) are required for characterizing a lateral quadrupole source.
Publisher: Elsevier BV
Date: 04-2019
Publisher: Elsevier BV
Date: 12-2017
Publisher: Oxford University Press (OUP)
Date: 27-08-2020
DOI: 10.1093/CID/CIAA1241
Abstract: Choral singing has become a major risk during the coronavirus disease 2019 (COVID-19) pandemic due to high infection rates. Our visualization and velocimetry results reveal that the majority of droplets expelled during singing follow the ambient airflow pattern. These results point toward the possibility of COVID-19 spread by small airborne droplets during singing.
Publisher: ASA
Date: 2013
DOI: 10.1121/1.4800456
Publisher: Elsevier BV
Date: 07-2017
Publisher: Elsevier BV
Date: 05-2016
Publisher: American Institute of Aeronautics and Astronautics
Date: 05-06-2011
DOI: 10.2514/6.2011-2720
Publisher: Elsevier BV
Date: 10-2023
Publisher: American Institute of Aeronautics and Astronautics
Date: 05-06-2011
DOI: 10.2514/6.2011-2782
Publisher: Elsevier BV
Date: 10-2018
Publisher: Elsevier BV
Date: 02-2022
Publisher: American Institute of Aeronautics and Astronautics
Date: 05-06-2011
DOI: 10.2514/6.2011-2785
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 09-2020
DOI: 10.2514/1.J059586
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 03-2007
DOI: 10.2514/1.24739
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 10-2013
DOI: 10.2514/1.J052391
Publisher: SAGE Publications
Date: 02-2013
DOI: 10.1260/0309-524X.37.1.97
Abstract: Current literature concerning the perception, annoyance and emission of low-frequency noise from wind turbines are reviewed. Wind turbine noise has been shown to be annoying to people with annoyance related to noise load. Other factors, such as those related to visual, economic and psychological effects, were also shown to affect a person's annoyance of wind turbine noise. Published infrasound (noise at frequencies less than 20 Hz) measurements show that levels at typical residential set-back distances are too low to be directly audible, but may be perceived via window rattling. On the other hand, low-frequency noise levels, in the frequency range of 20–200 Hz may exceed audibility thresholds and it is postulated they may be correlated with annoyance. A review of general low-frequency noise annoyance studies is presented and highlights the similarities of many wind turbine noise complaints with those due to low-frequency noise. The paper concludes with a suggestion to develop a new methodology that can simultaneously acquire annoyance and noise data at the time a person believes they are annoyed by wind turbine noise.
Publisher: Acoustical Society of America (ASA)
Date: 11-07-2014
DOI: 10.1121/1.4885485
Abstract: The response of the boundary layer over an airfoil with cavity to external acoustic forcing, across a sweep of frequencies, was measured. The boundary layer downstream of the cavity trailing edge was found to respond strongly and selectively at the natural airfoil tonal frequencies. This is considered to be due to enhanced feedback. However, the shear layer upstream of the cavity trailing edge did not respond at these frequencies. These findings confirm that an aeroacoustic feedback loop exists between the airfoil trailing edge and a location near the cavity trailing edge.
Publisher: American Institute of Aeronautics and Astronautics
Date: 27-05-2016
DOI: 10.2514/6.2016-2739
Publisher: Elsevier BV
Date: 05-2016
Publisher: Elsevier BV
Date: 03-2021
Publisher: IOP Publishing
Date: 23-08-2023
Abstract: Over 20 years ago a report commissioned by the European Commission identified air quality in schools as a public health priority. Despite this concern, little action was taken in the following two decades. Over the last two years as classrooms were increasingly recognised as hotspots for the transmission of SARS-CoV-2, renewed interest and resources have been made available in response to this issue. Questions remain, however, over how best to achieve safer classroom air. Our analysis assessed a range of in situ interventions to remove particulate matter (PM 2.5 ) and carbon dioxide from inside a populated classroom. Our approach used saline spray and volunteers’ exhalations as our source of PM 2.5 and carbon dioxide to explore the ability of high efficiency particulate air (HEPA) filters, natural ventilation and a recirculating A/C unit to remove these air pollutants which collectively provided a novel set of data. For a total window opening of 1.86 m 2 for a 181.7 m 3 classroom with a HEPA filter with a 703m 3 /hr clean air delivery rate, our results confirmed that outdoor air was needed to purge the room to reduce carbon dioxide levels that otherwise rose to ppm in 12 min. Cross and natural ventilation reduced levels of PM 2.5 and carbon dioxide very effectively—in under 5 and 10 min respectively during low levels of outside PM 2.5 . We conclude that natural ventilation supplemented with the use of HEPA filters is the most effective way to reliably improve indoor air quality year-round, balancing the need to have easy to enact approaches to reduce the buildup of PM 2.5 , airborne viruses and carbon dioxide. These results highlight an important knowledge gap. Without having localised real-time outdoor air pollution sensing, evidence-based decisions cannot be made about how often, and for how long, windows can safely remain open to purge classrooms in times of poor quality outdoor air.
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 10-2013
DOI: 10.2514/1.J052436
Publisher: Elsevier BV
Date: 04-2015
Publisher: Springer Berlin Heidelberg
Date: 18-12-2016
Publisher: Springer International Publishing
Date: 26-05-2018
Publisher: Springer Berlin Heidelberg
Date: 18-12-2016
Publisher: American Institute of Aeronautics and Astronautics
Date: 08-06-2020
DOI: 10.2514/6.2020-3039
Publisher: MDPI AG
Date: 27-12-2019
DOI: 10.3390/V12010033
Abstract: Two distinct phenomena of airborne transmission of variola virus (smallpox) were described in the pre-eradication era—direct respiratory transmission, and a unique phenomenon of transmission over greater distances, referred to as “aerial convection”. We conducted an analysis of data obtained from a systematic review following the PRISMA criteria, on the long-distance transmission of smallpox. Of 8179 studies screened, 22 studies of 17 outbreaks were identified—12 had conclusive evidence of aerial convection and five had partially conclusive evidence. Aerial convection was first documented in 1881 in England, when smallpox incidence had waned substantially following mass vaccination, making unusual transmissions noticeable. National policy at the time stipulated spatial separation of smallpox hospitals from other buildings and communities. The evidence supports the transmission of smallpox through aerial convection at distances ranging from 0.5 to 1 mile, and one instance of 15 km related to bioweapons testing. Other explanations are also possible, such as missed chains of transmission, fomites or secondary aerosolization from contaminated material such as bedding. The window of observation of aerial convection was within the 100 years prior to eradication. Aerial convection appears unique to the variola virus and is not considered in current hospital infection control protocols. Understanding potential aerial convection of variola should be an important consideration in planning for smallpox treatment facilities and protecting potential contacts and surrounding communities.
Publisher: American Society of Civil Engineers (ASCE)
Date: 09-2021
Publisher: Elsevier BV
Date: 06-2016
Publisher: Elsevier BV
Date: 2022
Publisher: Springer Science and Business Media LLC
Date: 15-02-2018
Publisher: American Society of Civil Engineers (ASCE)
Date: 11-2021
Publisher: Elsevier BV
Date: 04-2020
Publisher: American Institute of Aeronautics and Astronautics
Date: 05-06-2011
DOI: 10.2514/6.2011-2779
Publisher: AIP Publishing
Date: 10-2018
DOI: 10.1063/1.5048544
Abstract: This paper presents a numerical study on the flow structures developed when a pulsed reaction control jet is operated in a hypersonic crossflow with a laminar boundary layer. Understanding these flow structures is important to the design of reaction control jets and scramjet fuel injectors. Implicit large-eddy simulations were performed with a round, sonic, perfect air jet issuing normal to a Mach 5 crossflow over a flat plate, at a jet-to-crossflow momentum ratio of 5.3 and a pressure ratio of 251, and with square-wave pulsing at Strouhal numbers of 1/6 to 1/3, based on jet diameter and free-stream velocity. Pulsing the jet allows the shock structure to partially collapse when the jet is off. This shock collapse affects the shedding frequency of shear-layer vortices, the formation of shear-layers downstream of the jet outlet, and the formation of longitudinal counter-rotating vortices. The lead shocks formed at jet start-up allow deeper penetration by increasing the effective jet-to-crossflow momentum ratio near the jet outlet and by preventing interaction between hairpin vortices. Normalised penetration was increased by a maximum of 68% compared with the steady jet. Pulsing also provides a higher jet interaction force per unit mass flow rate compared with a steady jet, with a 52% increase recorded at a 33% duty cycle. Temporal and spatial variations of surface pressure are important for reaction control applications and have been quantified. Pressure distribution depends strongly on duty cycle, and higher interaction force per unit mass flow rate was observed in cases with low duty cycle.
Publisher: American Institute of Aeronautics and Astronautics
Date: 18-06-2015
DOI: 10.2514/6.2015-3143
Publisher: American Institute of Aeronautics and Astronautics
Date: 05-06-2011
DOI: 10.2514/6.2011-2813
Publisher: American Institute of Aeronautics and Astronautics
Date: 13-06-2014
DOI: 10.2514/6.2014-2316
Publisher: Elsevier BV
Date: 03-2014
Publisher: BMJ
Date: 24-07-2020
Publisher: Elsevier BV
Date: 03-2019
Publisher: Acoustical Society of America (ASA)
Date: 05-08-2014
DOI: 10.1121/1.4890204
Abstract: This letter presents the Point-Time-Reversal-Sponge-Layer (PTRSL) technique to enhance the focal-resolution of aeroacoustic Time-Reversal (TR). A PTRSL is implemented on a square domain centered at the predicted source location and is based on d ing the radial components of the incoming and outgoing fluxes propagating toward and away from the source, respectively. A PTRSL is shown to overcome the conventional half-wavelength diffraction-limit its implementation significantly reduces the focal spot size to one-fifth of a wavelength for a monopole source. Furthermore, PTRSL reduces the focal spots of a dipole source to three-tenths of a wavelength, as compared to three-fifths without its implementation.
Publisher: AIP
Date: 2011
DOI: 10.1063/1.3657023
Publisher: Acoustical Society of America (ASA)
Date: 02-2016
DOI: 10.1121/1.4941564
Abstract: This paper presents an experimental application of the aeroacoustic time-reversal (TR) source localization technique for studying flow-induced noise problems and compares the TR results with those obtained using conventional beamforming (CB). Experiments were conducted in an anechoic wind tunnel for the benchmark test-case of a full-span circular cylinder located in subsonic cross-flow wherein the far-field acoustic pressure was s led using two line arrays (LAs) of microphones located above and below the cylinder. The source map obtained using the signals recorded at the two LAs without modeling the reflective surfaces of the contraction-outlet and cylinder during TR simulations revealed the lift-dipole nature of aeroacoustic source generated at the Aeolian tone however, it indicates an error of 3/20 of Aeolian tone wavelength in the predicted location. Modeling the reflective contraction-outlet during TR was shown to improve the focal-resolution of the source and reduce side-lobe levels, especially in the low-frequency range. The experimental TR results were shown to be comparable to (a) the simulation results of an idealized dipole at the cylinder location in wind-tunnel flow and (b) that obtained by monopole and dipole CB, thereby demonstrating the suitability of TR method as a diagnostic tool to analyze flow-induced noise generation mechanism.
Publisher: Acoustical Society of America (ASA)
Date: 06-2018
DOI: 10.1121/1.5040981
Abstract: This paper is concerned with the influence of camber on the noise of a wall-mounted finite airfoil with natural boundary layer transition. Tonal noise measurements taken in an aeroacoustic wind tunnel are presented for airfoils with aspect ratio of 2, NACAxx12 profile and camber between 0 and 6% at 40% chord. The results show camber is an important parameter that determines the operating conditions for which acoustic tone generation occurs and the number and intensity of the tones produced. Airfoils with 0%–2% camber have an acoustic signature that is dominated by a high litude primary tone, whereas the spectra of airfoils with higher camber of 4%–6% feature a more pronounced side tone structure. Tonal noise production does not collapse with lift coefficient, demonstrating that the local flow conditions influence the noise source. Tonal noise production is explained in terms of changes to mean flow topology, namely the location of flow separation, which is linked to tonal noise generation. Scaling of airfoil tonal noise is found to vary with angle of attack and pressure gradient. Empirical scaling laws for the primary tone frequency dependence on velocity are also derived for the cambered airfoils.
Publisher: Acoustical Society of America (ASA)
Date: 28-03-2011
DOI: 10.1121/1.3565472
Abstract: This letter presents an experimental study on the tonal noise generated by a sharp-edged flat plate at low-to-moderate Reynolds number. Flow and far-field noise data reveal that, in this particular case, the tonal noise appears to be governed by vortex shedding processes. Also related to the existence of the tonal noise is a region of separated flow slightly upstream of the trailing edge. Hydrodynamic fluctuations at selected vortex shedding frequencies are strongly lified by the inflectional mean velocity profile in the separated shear layer. The lified hydrodynamic fluctuations are diffracted by the trailing edge, producing strong tonal noise.
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 07-2012
DOI: 10.2514/1.J051578
Publisher: Acoustical Society of America (ASA)
Date: 04-2018
DOI: 10.1121/1.5031113
Abstract: A simulation technique to analyse flow-induced noise problems that combines computational fluid dynamics (CFD), the boundary element method (BEM) and an aeroacoustic time-reversal (TR) source localisation method is presented. Hydrodynamic data are obtained from a high-fidelity CFD simulation of flow past a body and aeroacoustic sources are extracted based on Lighthill's acoustic analogy. The incident pressure field on the body due to the aeroacoustic sources is combined with a BEM representation of the body to obtain the spectrum of the direct, scattered and total acoustic pressure fields at far-field microphone locations. The microphone data are then used as input for the time-reversal simulations which are implemented by numerically solving two-dimensional linearized Euler equations. Decomposing the far-field pressure enables the TR simulation of the direct, scattered and total acoustic fields to be performed separately which yields the location and nature of the corresponding aeroacoustic sources. To demonstrate the hybrid CFD−BEM−TR technique, the sound generated by a cylinder in low Mach number cross-flow is considered. The nature of the aeroacoustic sources at the vortex shedding frequency and its second harmonic for the direct, scattered and total fields are identified.
Publisher: RWTH Aachen University
Date: 2019
Publisher: American Institute of Aeronautics and Astronautics
Date: 02-06-2017
DOI: 10.2514/6.2017-3719
Publisher: American Institute of Aeronautics and Astronautics
Date: 02-06-2017
DOI: 10.2514/6.2017-3718
Publisher: AIP Publishing
Date: 11-2021
DOI: 10.1063/5.0067609
Abstract: Respiratory infections transmit through droplets and aerosols generated by the infected in idual during respiratory emissions. It is essential to study the flow dynamics of these emissions to develop strategies for mitigating the risk of infection. In particular, the dynamics of droplets expelled during violent exhalations such as sneezing is crucial, but has received little attention to date. Here, for the first time, we present the results of droplet dynamics of 35 sneezes, obtained from four volunteers, using particle tracking velocimetry experiments. Our results reveal a mean droplet velocity of 2–5.4 m/s across the different subjects. These values are significantly lower than what is usually assumed in the studies simulating or replicating sneezes. Furthermore, the large variation in droplet speeds, flow direction, spread angle, and head movement is also quantified. These findings will enable the refinement of models and simulations of sneezes toward improving infection control guidelines.
Publisher: American Institute of Aeronautics and Astronautics
Date: 24-06-0014
DOI: 10.2514/6.2018-3296
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 03-2010
DOI: 10.2514/1.45657
Publisher: Elsevier BV
Date: 02-2016
Publisher: Polish Academy of Sciences Chancellery
Date: 26-07-2019
Publisher: American Institute of Aeronautics and Astronautics
Date: 02-06-2017
DOI: 10.2514/6.2017-3172
Publisher: Cambridge University Press (CUP)
Date: 04-09-2023
DOI: 10.1017/JFM.2023.630
Publisher: Cambridge University Press (CUP)
Date: 26-07-2019
DOI: 10.1017/JFM.2019.522
Abstract: This paper presents a combined experimental and large-eddy simulation study to characterise the effect of aspect ratio on the near-wake structure of a square finite wall-mounted cylinder (FWMC). The cylinder aspect ratios (span $L$ to width $W$ ) investigated in the experiments were $1.4\\leqslant L/W\\leqslant 21.4$ and the oncoming boundary-layer thicknesses were $1.3W$ and $0.9W$ at a Reynolds number based on cylinder width of $1.4\\times 10^{4}$ and $1.1\\times 10^{4}$ , respectively. In complementary simulations, the cylinder aspect ratios investigated were 1.4, 4.3, 10 and 18.6. The cylinder wake structure was visualised in three-dimensional space using a vortex core detection method and decomposed to its oscillation modes using the spectral proper orthogonal decomposition (SPOD) technique. A parametric diagram is proposed to predict whether the time-averaged wake structure is a dipole or a quadrupole pattern, based on oncoming boundary-layer height and aspect ratio. Cellular shedding occurs when the aspect ratio is high with up to three shedding cells occurring across the span for aspect ratios $L/W $ . Each of these cells sheds at a distinct frequency, as evidenced by the spectral content of the surface pressure measured on the side face and the near-wake velocity. Amplitude modulation is also observed in the vortex shedding, which explains the litude modulation of the acoustic pressure emitted by square FWMCs. SPOD is shown to be a viable method to identify the occurrence of cellular shedding in the wake.
Publisher: Elsevier BV
Date: 2015
Publisher: American Institute of Aeronautics and Astronautics
Date: 18-05-2019
DOI: 10.2514/6.2019-2663
Publisher: Elsevier BV
Date: 11-2014
Publisher: Cambridge University Press (CUP)
Date: 10-05-2016
DOI: 10.1017/AER.2016.39
Abstract: The flow and noise created by sawtooth trailing-edge serrations has been studied experimentally at a low Reynolds number. Experiments have been performed on a flat-plate model with an elliptical leading edge and an asymmetrically bevelled trailing edge at Reynolds numbers of Re c = 1 × 10 5 –1.3 × 10 5 , based on chord. Wide serrations with a wavelength (λ s ) to litude (2 h ) ratio of λ s / h = 0.6 were found to reduce the overall sound pressure level by up to 11dB. In contrast, narrower serrations with λ s / h = 0.2 produce tonal noise and increase the overall noise level by up to 4dB. Intense vortices across the span of the trailing edge with narrow serrations are shown to be the source of tonal noise. Wide serrations reduce turbulent velocity fluctuations at low frequencies which explains the lower radiated noise. The narrow serrations that produce low Reynolds number tonal noise were shown previously to be effective at higher Reynolds numbers (Re c 2 × 10 5 ), demonstrating that care is needed to fully understand the flow field over serrations for all intended operating conditions.
Publisher: Elsevier BV
Date: 06-2019
Publisher: Elsevier BV
Date: 11-2019
Publisher: Elsevier BV
Date: 11-2020
Publisher: American Institute of Aeronautics and Astronautics
Date: 04-06-2012
DOI: 10.2514/6.2012-2060
Publisher: American Institute of Aeronautics and Astronautics
Date: 04-06-2012
DOI: 10.2514/6.2012-2181
Publisher: Acoustical Society of America (ASA)
Date: 05-2011
DOI: 10.1121/1.3569698
Abstract: This paper presents experimental data concerning the flow and noise generated by a sharp-edged flat plate at low-to-moderate Reynolds number (Reynolds number based on chord of 2.0 × 105 to 5.0 × 105). The data are used to evaluate a variety of semi-empirical trailing edge noise prediction methods. All were found to under-predict noise at lower frequencies. Examination of the velocity spectra in the near wake reveals that there are energetic velocity fluctuations at low frequency about the trailing edge. A semi-empirical model of the surface pressure spectrum is derived for predicting the trailing edge noise at low-to-moderate Reynolds number.
Publisher: Elsevier BV
Date: 08-2012
Publisher: American Institute of Aeronautics and Astronautics
Date: 04-06-2012
DOI: 10.2514/6.2012-2186
Publisher: American Institute of Aeronautics and Astronautics
Date: 02-06-2017
DOI: 10.2514/6.2017-4036
Publisher: Springer Nature Singapore
Date: 2022
Publisher: Mary Ann Liebert Inc
Date: 02-2023
DOI: 10.1089/HS.2022.0100
Publisher: American Institute of Aeronautics and Astronautics
Date: 27-05-2016
DOI: 10.2514/6.2016-3002
Publisher: Elsevier BV
Date: 10-2023
Publisher: Elsevier BV
Date: 11-2019
Publisher: American Institute of Aeronautics and Astronautics
Date: 24-06-2018
DOI: 10.2514/6.2018-3796
Publisher: American Institute of Aeronautics and Astronautics
Date: 18-05-2019
DOI: 10.2514/6.2019-2435
Publisher: American Society of Civil Engineers (ASCE)
Date: 09-2021
Publisher: American Institute of Aeronautics and Astronautics
Date: 24-06-2018
DOI: 10.2514/6.2018-3792
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 02-2009
DOI: 10.2514/1.40503
Publisher: Springer Science and Business Media LLC
Date: 18-07-2020
Start Date: 05-2016
End Date: 05-2019
Amount: $318,470.00
Funder: Australian Research Council
View Funded ActivityStart Date: 06-2011
End Date: 12-2014
Amount: $420,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2010
End Date: 12-2013
Amount: $280,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2022
End Date: 12-2024
Amount: $480,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2012
End Date: 12-2016
Amount: $320,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2020
End Date: 02-2024
Amount: $490,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2017
End Date: 12-2019
Amount: $393,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2013
End Date: 04-2018
Amount: $440,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 04-2018
End Date: 10-2019
Amount: $680,320.00
Funder: Australian Research Council
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