Eldad Avital | Queen Mary, University of London (original) (raw)

Papers by Eldad Avital

Research paper thumbnail of Computational and Experimental Investigation of Supersonic Flow and their Controls

World Academy of Science, Engineering and Technology, International Journal of Mathematical, Computational, Physical, Electrical and Computer Engineering, Jan 22, 2013

Research paper thumbnail of Physically Derived Synthesis Model of an Aeolian Tone

Journal of The Audio Engineering Society, Sep 20, 2016

Research paper thumbnail of Experimental investigation of nonlinear properties of crackle and screech in supersonic jets

Journal of the Acoustical Society of America, Jun 1, 2017

Supersonic crackle, an irritable component of aircraft jet noise, was investigated using model sc... more Supersonic crackle, an irritable component of aircraft jet noise, was investigated using model scale measurements. Near-field results showed Gaussian distribution but far-field had high skewness and even higher in its derivative. Skewness, a measure of asymmetry in the waveform, was compared to screech arising from shock associated noise which was also high but in contrast to crackle its skewness derivative had dropped to a much smaller value than its waveform. Both crackle and screech are nonlinear but their nonlinear properties are entirely different. Crackle is quantified when its derivative skewness becomes larger than its waveform skewness which should exceed 0.3.

Research paper thumbnail of On the Determination of Density Profiles in Stratified Seas from Kinematical Patterns of Ship-Induced Internal Waves

Journal of Ship Research, Dec 1, 1994

The aim of this paper is to propose a method for determining the dispersion relation of a highly ... more The aim of this paper is to propose a method for determining the dispersion relation of a highly stratified medium from measured geometrical patterns of ship-generated internal waves. This is a first step towards devising a practical method for calculating the density distribution of a stratified fluid from the detectable free-surface kinematic signature of the induced internal wake, by using some optical or remote sensing means. We assume that the body which causes the wake moves with a constant velocity along a circular trajectory. By applying the constant-phase method, we derive an explicit solution for the wake crest lines. Then, for an infinitely large ship's turning radius (straight course), a closed-form expression for the dispersion relation versus wake geometry is obtained. A similar approximate form is also obtained for a circular course. Some numerical simulations are presented, and the applicability of the proposed method is demonstrated for several realistic thermocline distributions, measured in lakes and seas.

Research paper thumbnail of An implicit Eulerian–Lagrangian model for flow-net interaction using immersed boundary method in OpenFOAM

Ocean Engineering, Nov 1, 2022

Research paper thumbnail of Direct Numerical Simulation Of Particle Saltation In Turbulent Channel Flow

Research paper thumbnail of Numerical Simulation Of A Three Blade Marine Current Turbine

Research paper thumbnail of ACOUSTICS2008/2333 Nonlinear Propagation of Screech Noise

Research paper thumbnail of Dynamic large deformation analysis of a cantilever beam

Mathematics and Computers in Simulation, Aug 1, 2020

Research paper thumbnail of In-vitro investigation of the hemodynamic responses of the cerebral, coronary and renal circulations with a rotary blood pump installed in the descending aorta

Medical Engineering & Physics, Feb 1, 2017

This study investigates the hemodynamic responses of the cardiovascular system when a rotary bloo... more This study investigates the hemodynamic responses of the cardiovascular system when a rotary blood pump is operating in the descending aorta, with a focus on the cerebral, coronary and renal autoregulation, using our in-house cardiovascular emulator. Several improvements have been made from our previous studies. A novel coronary system was developed to replicate the native coronary perfusion. Three pinch valves actuated by stepper motors were used to simulate the regional autoregulation systems of the native cerebral, coronary and renal circulations. A rotary pump was installed in the descending aorta, in series with the heart, and the hemodynamic responses of the cardiovascular system were investigated with a focus on cerebral, coronary and renal circulation over a wide range of pump rotor speeds. Experiments were performed twice, once with the autoregulation systems active and once with the autoregulation systems inactive, to reflect that there will be some impairment of autoregulatory systems in a patient with heart failure. It was shown that by increasing the rotor speed to 3000 rpm, the cardiac output was improved from 2.9 to 4.1 L/min as a result of an afterload reduction induced by the pressure drop upstream of the pump. The magnitudes of changes in perfusion in the cerebral, coronary and renal circulations were recorded with regional autoregulation systems active and inactive.

Research paper thumbnail of Variation of dominant discharge along the riverbed based on numerical and deep-learning models: A case study in the Middle Huaihe River, China

Journal of Hydrology, Sep 1, 2022

Research paper thumbnail of Airborne Transmission of SARS-CoV-2: The Contrast between Indoors and Outdoors

Fluids, Feb 22, 2024

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Research paper thumbnail of Computational study of aerofoil's self-noise when subject to leading edge jet blowing flow control

28th AIAA/CEAS Aeroacoustics 2022 Conference, Jun 13, 2022

Research paper thumbnail of Computations of Nonlinear Propagation of Sound Emitted from High Speed Mixing Layers

arXiv (Cornell University), Feb 17, 2014

Non-linear sound propagation is investigated computationally by simulating compressible time-deve... more Non-linear sound propagation is investigated computationally by simulating compressible time-developing mixing layers using the Large Eddy Simulation (LES) approach and solving the viscous Burgers Equation. The mixing layers are of convective Mach numbers of 0.4, 0.8 and 1.2. The LES results agree qualitatively with known flow behavior. Mach waves are observed in the near sound field of the supersonic mixing layer computed by the LES. These waves show steepening typical to non-linear propagation. Further calculations using the Burgers equation support this finding, where the initial wave slope has a role in kicking them. No visible non-linear propagation effects were found for the subsonic mixing layers. The effects of geometrical spreading and viscosity are also considered.

Research paper thumbnail of Propagation of Pressure Waves in Compression System Prototype for Magnetized Target Fusion Reactor in General Fusion Inc

Research paper thumbnail of Effects of temperature ratio on the sound generation from an axisymmetric jet

Research paper thumbnail of Flow Seperation and Passive Flow Control on E387 Airfoil

The behavior of a MVG vane at three different design angles was simulated with LES on an Eppler e... more The behavior of a MVG vane at three different design angles was simulated with LES on an Eppler e387 airfoil that was suffering flow separation. The e387 airfoil was placed at an angle of attack of 12 degrees and at Reynolds number of 200,000 based on the chord length. Different parameters of the generated vortex from the MVG were analyzed to study the behavior of the vortex. The MVG vanes were found to suppress the separation, with the MVG vane placed at 18.5 being the most effective. It was found that turbulence has a strong effect on the instantaneous behavior of the flow field and the easiest measurable characteristic of the MVG’s effect on the flow separation was its effect on the wall shear stress. Recommendations for the optimum placement of the MVG and its zone of influence are discussed.

Research paper thumbnail of Direct numerical simulation on local scour around the cylinder induced by internal solitary waves propagating over a slope

Ocean Engineering, Mar 1, 2022

Research paper thumbnail of A computational model of ureteral peristalsis and an investigation into ureteral reflux

Biomedical Engineering Letters, Nov 18, 2017

The aim of this study is to create a computational model of the human ureteral system that accura... more The aim of this study is to create a computational model of the human ureteral system that accurately replicates the peristaltic movement of the ureter for a variety of physiological and pathological functions. The objectives of this research are met using our in-house fluid-structural dynamics code (CgLes-Ycode). A realistic peristaltic motion of the ureter is modelled using a novel piecewise linear force model. The urodynamic responses are investigated under two conditions of a healthy and a depressed contraction force. A ureteral pressure during the contraction shows a very good agreement with the corresponding clinical data. The results also show a dependency of the wall shear stresses on the contraction velocity. It confirms the presence of high shear stress at the proximal part of the ureter. Additionally, it is shown that an inefficient lumen contraction can increase the possibility of a continuous reflux during the propagation of peristalsis.

Research paper thumbnail of Influence of curvature distribution smoothing on the reduction of aerofoil self-noise

International Journal of Numerical Methods for Heat & Fluid Flow, Feb 2, 2023

Purpose-The paper aims to investigate the influence of smooth curvature distributions on the self... more Purpose-The paper aims to investigate the influence of smooth curvature distributions on the self-noise of a low Reynolds number aerofoil and to unveil the flow mechanisms in the phenomenon. Design/methodology/approach-The paper performed Large Eddy Simulation (LES) approach to investigate the unsteady aerodynamic performance of both the original aerofoil E387 and the redesigned aerofoil A7 in a time-dependent study of boundary layer characteristics at Reynolds number 100,000 and Angle of Attack 4-degree. The aerofoil A7 is redesigned from E387 by removing the irregularities in the surface curvature distributions and keeping a nearly identical geometry. Flow vorticity magnitude of both aerofoils, along with the spectra of the vertical fluctuating velocity component and noise level, are analysed to demonstrate the bubble flapping process near the trailing edge and the vortex shedding phenomenon. Findings-The paper provides quantitative insights about how the flapping process of the laminar separation bubble within the boundary layer near the trailing edge affects the aerofoil self-noise. It is found that the aerofoil A7 with smooth curvature distributions presents a 10% smaller laminar separation bubble compared to the aerofoil E387 at Reynolds number 100,000 and Angle of Attack 4-degree. The LES results also suggests that curvature distribution smoothing leads to a 6.5% reduction in overall broadband noise level. Originality/value-This paper fulfils an identified need to reveal the unknown flow structure and the boundary layer characteristics that resulted in the self-noise reduction phenomenon yielded by curvature distribution smoothing.

Research paper thumbnail of Computational and Experimental Investigation of Supersonic Flow and their Controls

World Academy of Science, Engineering and Technology, International Journal of Mathematical, Computational, Physical, Electrical and Computer Engineering, Jan 22, 2013

Research paper thumbnail of Physically Derived Synthesis Model of an Aeolian Tone

Journal of The Audio Engineering Society, Sep 20, 2016

Research paper thumbnail of Experimental investigation of nonlinear properties of crackle and screech in supersonic jets

Journal of the Acoustical Society of America, Jun 1, 2017

Supersonic crackle, an irritable component of aircraft jet noise, was investigated using model sc... more Supersonic crackle, an irritable component of aircraft jet noise, was investigated using model scale measurements. Near-field results showed Gaussian distribution but far-field had high skewness and even higher in its derivative. Skewness, a measure of asymmetry in the waveform, was compared to screech arising from shock associated noise which was also high but in contrast to crackle its skewness derivative had dropped to a much smaller value than its waveform. Both crackle and screech are nonlinear but their nonlinear properties are entirely different. Crackle is quantified when its derivative skewness becomes larger than its waveform skewness which should exceed 0.3.

Research paper thumbnail of On the Determination of Density Profiles in Stratified Seas from Kinematical Patterns of Ship-Induced Internal Waves

Journal of Ship Research, Dec 1, 1994

The aim of this paper is to propose a method for determining the dispersion relation of a highly ... more The aim of this paper is to propose a method for determining the dispersion relation of a highly stratified medium from measured geometrical patterns of ship-generated internal waves. This is a first step towards devising a practical method for calculating the density distribution of a stratified fluid from the detectable free-surface kinematic signature of the induced internal wake, by using some optical or remote sensing means. We assume that the body which causes the wake moves with a constant velocity along a circular trajectory. By applying the constant-phase method, we derive an explicit solution for the wake crest lines. Then, for an infinitely large ship's turning radius (straight course), a closed-form expression for the dispersion relation versus wake geometry is obtained. A similar approximate form is also obtained for a circular course. Some numerical simulations are presented, and the applicability of the proposed method is demonstrated for several realistic thermocline distributions, measured in lakes and seas.

Research paper thumbnail of An implicit Eulerian–Lagrangian model for flow-net interaction using immersed boundary method in OpenFOAM

Ocean Engineering, Nov 1, 2022

Research paper thumbnail of Direct Numerical Simulation Of Particle Saltation In Turbulent Channel Flow

Research paper thumbnail of Numerical Simulation Of A Three Blade Marine Current Turbine

Research paper thumbnail of ACOUSTICS2008/2333 Nonlinear Propagation of Screech Noise

Research paper thumbnail of Dynamic large deformation analysis of a cantilever beam

Mathematics and Computers in Simulation, Aug 1, 2020

Research paper thumbnail of In-vitro investigation of the hemodynamic responses of the cerebral, coronary and renal circulations with a rotary blood pump installed in the descending aorta

Medical Engineering & Physics, Feb 1, 2017

This study investigates the hemodynamic responses of the cardiovascular system when a rotary bloo... more This study investigates the hemodynamic responses of the cardiovascular system when a rotary blood pump is operating in the descending aorta, with a focus on the cerebral, coronary and renal autoregulation, using our in-house cardiovascular emulator. Several improvements have been made from our previous studies. A novel coronary system was developed to replicate the native coronary perfusion. Three pinch valves actuated by stepper motors were used to simulate the regional autoregulation systems of the native cerebral, coronary and renal circulations. A rotary pump was installed in the descending aorta, in series with the heart, and the hemodynamic responses of the cardiovascular system were investigated with a focus on cerebral, coronary and renal circulation over a wide range of pump rotor speeds. Experiments were performed twice, once with the autoregulation systems active and once with the autoregulation systems inactive, to reflect that there will be some impairment of autoregulatory systems in a patient with heart failure. It was shown that by increasing the rotor speed to 3000 rpm, the cardiac output was improved from 2.9 to 4.1 L/min as a result of an afterload reduction induced by the pressure drop upstream of the pump. The magnitudes of changes in perfusion in the cerebral, coronary and renal circulations were recorded with regional autoregulation systems active and inactive.

Research paper thumbnail of Variation of dominant discharge along the riverbed based on numerical and deep-learning models: A case study in the Middle Huaihe River, China

Journal of Hydrology, Sep 1, 2022

Research paper thumbnail of Airborne Transmission of SARS-CoV-2: The Contrast between Indoors and Outdoors

Fluids, Feb 22, 2024

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Research paper thumbnail of Computational study of aerofoil's self-noise when subject to leading edge jet blowing flow control

28th AIAA/CEAS Aeroacoustics 2022 Conference, Jun 13, 2022

Research paper thumbnail of Computations of Nonlinear Propagation of Sound Emitted from High Speed Mixing Layers

arXiv (Cornell University), Feb 17, 2014

Non-linear sound propagation is investigated computationally by simulating compressible time-deve... more Non-linear sound propagation is investigated computationally by simulating compressible time-developing mixing layers using the Large Eddy Simulation (LES) approach and solving the viscous Burgers Equation. The mixing layers are of convective Mach numbers of 0.4, 0.8 and 1.2. The LES results agree qualitatively with known flow behavior. Mach waves are observed in the near sound field of the supersonic mixing layer computed by the LES. These waves show steepening typical to non-linear propagation. Further calculations using the Burgers equation support this finding, where the initial wave slope has a role in kicking them. No visible non-linear propagation effects were found for the subsonic mixing layers. The effects of geometrical spreading and viscosity are also considered.

Research paper thumbnail of Propagation of Pressure Waves in Compression System Prototype for Magnetized Target Fusion Reactor in General Fusion Inc

Research paper thumbnail of Effects of temperature ratio on the sound generation from an axisymmetric jet

Research paper thumbnail of Flow Seperation and Passive Flow Control on E387 Airfoil

The behavior of a MVG vane at three different design angles was simulated with LES on an Eppler e... more The behavior of a MVG vane at three different design angles was simulated with LES on an Eppler e387 airfoil that was suffering flow separation. The e387 airfoil was placed at an angle of attack of 12 degrees and at Reynolds number of 200,000 based on the chord length. Different parameters of the generated vortex from the MVG were analyzed to study the behavior of the vortex. The MVG vanes were found to suppress the separation, with the MVG vane placed at 18.5 being the most effective. It was found that turbulence has a strong effect on the instantaneous behavior of the flow field and the easiest measurable characteristic of the MVG’s effect on the flow separation was its effect on the wall shear stress. Recommendations for the optimum placement of the MVG and its zone of influence are discussed.

Research paper thumbnail of Direct numerical simulation on local scour around the cylinder induced by internal solitary waves propagating over a slope

Ocean Engineering, Mar 1, 2022

Research paper thumbnail of A computational model of ureteral peristalsis and an investigation into ureteral reflux

Biomedical Engineering Letters, Nov 18, 2017

The aim of this study is to create a computational model of the human ureteral system that accura... more The aim of this study is to create a computational model of the human ureteral system that accurately replicates the peristaltic movement of the ureter for a variety of physiological and pathological functions. The objectives of this research are met using our in-house fluid-structural dynamics code (CgLes-Ycode). A realistic peristaltic motion of the ureter is modelled using a novel piecewise linear force model. The urodynamic responses are investigated under two conditions of a healthy and a depressed contraction force. A ureteral pressure during the contraction shows a very good agreement with the corresponding clinical data. The results also show a dependency of the wall shear stresses on the contraction velocity. It confirms the presence of high shear stress at the proximal part of the ureter. Additionally, it is shown that an inefficient lumen contraction can increase the possibility of a continuous reflux during the propagation of peristalsis.

Research paper thumbnail of Influence of curvature distribution smoothing on the reduction of aerofoil self-noise

International Journal of Numerical Methods for Heat & Fluid Flow, Feb 2, 2023

Purpose-The paper aims to investigate the influence of smooth curvature distributions on the self... more Purpose-The paper aims to investigate the influence of smooth curvature distributions on the self-noise of a low Reynolds number aerofoil and to unveil the flow mechanisms in the phenomenon. Design/methodology/approach-The paper performed Large Eddy Simulation (LES) approach to investigate the unsteady aerodynamic performance of both the original aerofoil E387 and the redesigned aerofoil A7 in a time-dependent study of boundary layer characteristics at Reynolds number 100,000 and Angle of Attack 4-degree. The aerofoil A7 is redesigned from E387 by removing the irregularities in the surface curvature distributions and keeping a nearly identical geometry. Flow vorticity magnitude of both aerofoils, along with the spectra of the vertical fluctuating velocity component and noise level, are analysed to demonstrate the bubble flapping process near the trailing edge and the vortex shedding phenomenon. Findings-The paper provides quantitative insights about how the flapping process of the laminar separation bubble within the boundary layer near the trailing edge affects the aerofoil self-noise. It is found that the aerofoil A7 with smooth curvature distributions presents a 10% smaller laminar separation bubble compared to the aerofoil E387 at Reynolds number 100,000 and Angle of Attack 4-degree. The LES results also suggests that curvature distribution smoothing leads to a 6.5% reduction in overall broadband noise level. Originality/value-This paper fulfils an identified need to reveal the unknown flow structure and the boundary layer characteristics that resulted in the self-noise reduction phenomenon yielded by curvature distribution smoothing.