Steven Frankel | Technion Israel Institute of Technology (original) (raw)

Papers by Steven Frankel

Research paper thumbnail of Accuracy Assessment of RANS Predictions of Active Flow Control for Hydrofoil Cavitation

Processes

In this work, we numerically investigate the cavitating flow on the scaled-down 2D model of guide... more In this work, we numerically investigate the cavitating flow on the scaled-down 2D model of guided vanes. Furthermore, the effects of wall injection on both the cavitation and on the hydrodynamic performance of the guided vane are studied. The numerical simulations are performed using OpenFOAM v1906. We used a 2D k- ω SST model for modeling the turbulence in the present set of simulations. We studied the flow for two angles of attack, viz. 3 ∘ and 9 ∘ . For the 3 ∘ angle of attack, the present numerical work is in good agreement with the previous experimental work, but for the larger angle of attack, because of flow separation, the present simulations do not capture the flow correctly.

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Research paper thumbnail of High-Order Implicit-Explicit Multi-block Time-stepping Method for Hyperbolic PDEs

52nd Aerospace Sciences Meeting, 2014

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Research paper thumbnail of A Study of Coupled Turbulent Mixing, Soot Chemistry, and Radiation Effects Using the Linear Eddy Model

Combustion and Flame, 1998

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Research paper thumbnail of Study of Spectral Noise Emissions from Standard Turbulent Nonpremixed Flames

Aiaa Journal, 2004

The occurrence of oscillating combustion and combustion instability has led to resurgence of inte... more The occurrence of oscillating combustion and combustion instability has led to resurgence of interest in causes, mechanisms, suppression, and control of flame noise. Nonpremixed flame noise is low frequency and difficult to control using conventional acoustic liner and so ...

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Research paper thumbnail of Numerical simulation of turbulence transition and sound radiation for flow through a rigid glottal model

Journal of The Acoustical Society of America, 2007

Large eddy simulation (LES)-based computational aeroacoustics techniques were applied to a static... more Large eddy simulation (LES)-based computational aeroacoustics techniques were applied to a static model of the human glottis, idealized here as a planar channel with an orifice, to study flow-acoustic interactions related to speech. Rigid models of both converging and diverging glottal passages, each featuring a 20 deg included angle and a minimal glottal diameter of 0.04 cm, with an imposed transglottal pressure of 15 cm H2O, were studied. The Favre-filtered compressible Navier-Stokes equations were integrated for this low-Mach-number flow using an additive semi-implicit Runge-Kutta method and a high-order compact finite-difference scheme with characteristic-based nonreflecting boundary conditions and a multiblock approach. Flow asymmetries related to the Coanda effect and transition to turbulence, as well as the far-field sound, were captured. Acoustic-analogy-based far-field sound predictions were compared with direct simulations and showed that dipole sources, arising from unsteady flow forces exerted on the glottal walls, are primarily responsible for the tonal sound observed in the divergent glottis case.

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Research paper thumbnail of Stochastic Inlet Conditions for Large-Eddy Simulation of a Fully Turbulent Jet

Aiaa Journal, 2003

RefDoc Bienvenue - Welcome. Refdoc est un service / is powered by. ...

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Research paper thumbnail of Effects of Spatial Filtering on Sound Radiation from a Subsonic Axisymmetric Jet

Aiaa Journal, 2000

ABSTRACT

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Research paper thumbnail of Experimental verification of the quasi-steady approximation for aerodynamic sound generation by pulsating jets in tubes

Journal of The Acoustical Society of America, 2002

Voice production involves sound generation by a confined jet flow through an orifice (the glottis... more Voice production involves sound generation by a confined jet flow through an orifice (the glottis) with a time-varying area. Predictive models of speech production are usually based on the so-called quasi-steady approximation. The flow rate through the time-varying orifice is assumed to be the same as a sequence of steady flows through stationary orifices for wall geometries and flow boundary conditions that instantaneously match those of the dynamic, nonstationary problem. Either the flow rate or the pressure drop can then be used to calculate the radiated sound using conventional acoustic radiation models. The quasi-steady approximation allows complex unsteady flows to be modeled as steady flows, which is more cost effective. It has been verified for pulsating open jet flows. The quasi-steady approximation, however, has not yet been rigorously validated for the full range of flows encountered in voice production. To further investigate the range of validity of the quasi-steady approximation for voice production applications, a dynamic mechanical model of the larynx was designed and built. The model dimensions approximated those of human vocal folds. Airflow was supplied by a pressurized, quiet air storage facility and modulated by a driven rubber orifice. The acoustic pressure of waves radiated upstream and downstream of the orifice was measured, along with the orifice area and other time-averaged flow variables. Calculated and measured radiated acoustic pressures were compared. A good agreement was obtained over a range of operating frequencies, flow rates, and orifice shapes, confirming the validity of the quasi-steady approximation for a class of relevant pulsating jet flows.

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Research paper thumbnail of Computational aeroacoustics of phonation, Part I: Computational methods and sound generation mechanisms

Journal of The Acoustical Society of America, 2002

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Research paper thumbnail of Broadband sound generation by confined turbulent jets

Journal of The Acoustical Society of America, 2002

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Research paper thumbnail of Aerodynamic transfer of energy to the vocal folds

Journal of The Acoustical Society of America, 2005

The aerodynamic transfer of energy from glottal airflow to vocal fold tissue during phonation was... more The aerodynamic transfer of energy from glottal airflow to vocal fold tissue during phonation was explored using complementary synthetic and numerical vocal fold models. The synthetic model was fabricated using a flexible polyurethane rubber compound. The model size, shape, and material properties were generally similar to corresponding human vocal fold characteristics. Regular, self-sustained oscillations were achieved at a frequency of approximately 120 Hz. The onset pressure was approximately 1.2 kPa. A corresponding two-dimensional finite element model was developed using geometry definitions and material properties based on the synthetic model. The finite element model upstream and downstream pressure boundary conditions were based on experimental values acquired using the synthetic model. An analysis of the fully coupled fluid and solid numerical domains included flow separation and unsteady effects. The numerical results provided detailed flow data that was used to investigate aerodynamic energy transfer mechanisms. The results support the hypothesis that a cyclic variation of the orifice profile from a convergent to a divergent shape leads to a temporal asymmetry in the average wall pressure, which is the key factor for the achievement of self-sustained vocal fold oscillations. me rica.

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Research paper thumbnail of Sound generation by steady flow through glottis-shaped orifices

Journal of The Acoustical Society of America, 2004

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Research paper thumbnail of Computational aeroacoustics of phonation, Part II: Effects of flow parameters and ventricular folds

Journal of The Acoustical Society of America, 2002

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Research paper thumbnail of Modeling transition to turbulence in eccentric stenotic flows

Journal of Biomechanical Engineering-transactions of The Asme, 2008

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Research paper thumbnail of Numerical Modeling of Pulsatile Turbulent Flow in Stenotic Vessels

Journal of Biomechanical Engineering-transactions of The Asme, 2003

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Research paper thumbnail of Direct numerical simulation of stenotic flows, Part 1: Steady flow

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Research paper thumbnail of Direct numerical simulation of stenotic flows. Part 1. Steady flow

Journal of Fluid Mechanics, 2007

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Research paper thumbnail of Direct numerical simulation of stenotic flows. Part 2. Pulsatile flow

Journal of Fluid Mechanics, 2007

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Research paper thumbnail of Performance of a 3Bladed Propeller Pump to Provide Cavopulmonary Assist in the Failing Fontan Circulation

Annals of Thoracic Surgery, 2008

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Research paper thumbnail of Mechanical Cavopulmonary Assist for the Univentricular Fontan Circulation Using a Novel Folding Propeller Blood Pump

Asaio Journal, 2007

A blood pump specifically designed to operate in the unique anatomic and physiologic conditions o... more A blood pump specifically designed to operate in the unique anatomic and physiologic conditions of a cavopulmonary connection has never been developed. Mechanical augmentation of cavopulmonary blood flow in a univentricular circulation would reduce systemic venous pressure, increase preload to the single ventricle, and temporarily reproduce a scenario analogous to the normal two-ventricle circulation. We hypothesize that a folding propeller blood pump would function optimally in this cavopulmonary circulation. The hydraulic performance of a two-bladed propeller prototype was characterized in an experimental flow loop using a blood analog fluid for 0.5-3.5 lpm at rotational speeds of 3,600-4,000 rpm. We also created five distinctive blood pump designs and evaluated their hydraulic performance using computational fluid dynamics (CFD). The two-bladed prototype performed well over the design range of 0.5-3.5 lpm, producing physiologic pressure rises of 5-18 mm Hg. Building upon this proof-of-concept testing, the CFD analysis of the five numerical models predicted a physiologic pressure range of 5-40 mm Hg over 0.5-4 lpm for rotational speeds of 3,000-7,000 rpm. These preliminary propeller designs and the two-bladed prototype achieved the expected hydraulic performance. Optimization of these configurations will reduce fluid stress levels, remove regions of recirculation, and improve the hydraulic performance of the folding propeller. This propeller design produces the physiologic pressures and flows that are in the ideal range to mechanically support the cavopulmonary circulation and represents an exciting new therapeutic option for the support of a univentricular Fontan circulation.

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Research paper thumbnail of Accuracy Assessment of RANS Predictions of Active Flow Control for Hydrofoil Cavitation

Processes

In this work, we numerically investigate the cavitating flow on the scaled-down 2D model of guide... more In this work, we numerically investigate the cavitating flow on the scaled-down 2D model of guided vanes. Furthermore, the effects of wall injection on both the cavitation and on the hydrodynamic performance of the guided vane are studied. The numerical simulations are performed using OpenFOAM v1906. We used a 2D k- ω SST model for modeling the turbulence in the present set of simulations. We studied the flow for two angles of attack, viz. 3 ∘ and 9 ∘ . For the 3 ∘ angle of attack, the present numerical work is in good agreement with the previous experimental work, but for the larger angle of attack, because of flow separation, the present simulations do not capture the flow correctly.

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Research paper thumbnail of High-Order Implicit-Explicit Multi-block Time-stepping Method for Hyperbolic PDEs

52nd Aerospace Sciences Meeting, 2014

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A Study of Coupled Turbulent Mixing, Soot Chemistry, and Radiation Effects Using the Linear Eddy Model

Combustion and Flame, 1998

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Study of Spectral Noise Emissions from Standard Turbulent Nonpremixed Flames

Aiaa Journal, 2004

The occurrence of oscillating combustion and combustion instability has led to resurgence of inte... more The occurrence of oscillating combustion and combustion instability has led to resurgence of interest in causes, mechanisms, suppression, and control of flame noise. Nonpremixed flame noise is low frequency and difficult to control using conventional acoustic liner and so ...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Numerical simulation of turbulence transition and sound radiation for flow through a rigid glottal model

Journal of The Acoustical Society of America, 2007

Large eddy simulation (LES)-based computational aeroacoustics techniques were applied to a static... more Large eddy simulation (LES)-based computational aeroacoustics techniques were applied to a static model of the human glottis, idealized here as a planar channel with an orifice, to study flow-acoustic interactions related to speech. Rigid models of both converging and diverging glottal passages, each featuring a 20 deg included angle and a minimal glottal diameter of 0.04 cm, with an imposed transglottal pressure of 15 cm H2O, were studied. The Favre-filtered compressible Navier-Stokes equations were integrated for this low-Mach-number flow using an additive semi-implicit Runge-Kutta method and a high-order compact finite-difference scheme with characteristic-based nonreflecting boundary conditions and a multiblock approach. Flow asymmetries related to the Coanda effect and transition to turbulence, as well as the far-field sound, were captured. Acoustic-analogy-based far-field sound predictions were compared with direct simulations and showed that dipole sources, arising from unsteady flow forces exerted on the glottal walls, are primarily responsible for the tonal sound observed in the divergent glottis case.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Stochastic Inlet Conditions for Large-Eddy Simulation of a Fully Turbulent Jet

Aiaa Journal, 2003

RefDoc Bienvenue - Welcome. Refdoc est un service / is powered by. ...

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Research paper thumbnail of Effects of Spatial Filtering on Sound Radiation from a Subsonic Axisymmetric Jet

Aiaa Journal, 2000

ABSTRACT

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Experimental verification of the quasi-steady approximation for aerodynamic sound generation by pulsating jets in tubes

Journal of The Acoustical Society of America, 2002

Voice production involves sound generation by a confined jet flow through an orifice (the glottis... more Voice production involves sound generation by a confined jet flow through an orifice (the glottis) with a time-varying area. Predictive models of speech production are usually based on the so-called quasi-steady approximation. The flow rate through the time-varying orifice is assumed to be the same as a sequence of steady flows through stationary orifices for wall geometries and flow boundary conditions that instantaneously match those of the dynamic, nonstationary problem. Either the flow rate or the pressure drop can then be used to calculate the radiated sound using conventional acoustic radiation models. The quasi-steady approximation allows complex unsteady flows to be modeled as steady flows, which is more cost effective. It has been verified for pulsating open jet flows. The quasi-steady approximation, however, has not yet been rigorously validated for the full range of flows encountered in voice production. To further investigate the range of validity of the quasi-steady approximation for voice production applications, a dynamic mechanical model of the larynx was designed and built. The model dimensions approximated those of human vocal folds. Airflow was supplied by a pressurized, quiet air storage facility and modulated by a driven rubber orifice. The acoustic pressure of waves radiated upstream and downstream of the orifice was measured, along with the orifice area and other time-averaged flow variables. Calculated and measured radiated acoustic pressures were compared. A good agreement was obtained over a range of operating frequencies, flow rates, and orifice shapes, confirming the validity of the quasi-steady approximation for a class of relevant pulsating jet flows.

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Research paper thumbnail of Computational aeroacoustics of phonation, Part I: Computational methods and sound generation mechanisms

Journal of The Acoustical Society of America, 2002

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Broadband sound generation by confined turbulent jets

Journal of The Acoustical Society of America, 2002

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Aerodynamic transfer of energy to the vocal folds

Journal of The Acoustical Society of America, 2005

The aerodynamic transfer of energy from glottal airflow to vocal fold tissue during phonation was... more The aerodynamic transfer of energy from glottal airflow to vocal fold tissue during phonation was explored using complementary synthetic and numerical vocal fold models. The synthetic model was fabricated using a flexible polyurethane rubber compound. The model size, shape, and material properties were generally similar to corresponding human vocal fold characteristics. Regular, self-sustained oscillations were achieved at a frequency of approximately 120 Hz. The onset pressure was approximately 1.2 kPa. A corresponding two-dimensional finite element model was developed using geometry definitions and material properties based on the synthetic model. The finite element model upstream and downstream pressure boundary conditions were based on experimental values acquired using the synthetic model. An analysis of the fully coupled fluid and solid numerical domains included flow separation and unsteady effects. The numerical results provided detailed flow data that was used to investigate aerodynamic energy transfer mechanisms. The results support the hypothesis that a cyclic variation of the orifice profile from a convergent to a divergent shape leads to a temporal asymmetry in the average wall pressure, which is the key factor for the achievement of self-sustained vocal fold oscillations. me rica.

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Research paper thumbnail of Sound generation by steady flow through glottis-shaped orifices

Journal of The Acoustical Society of America, 2004

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Research paper thumbnail of Computational aeroacoustics of phonation, Part II: Effects of flow parameters and ventricular folds

Journal of The Acoustical Society of America, 2002

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Modeling transition to turbulence in eccentric stenotic flows

Journal of Biomechanical Engineering-transactions of The Asme, 2008

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Numerical Modeling of Pulsatile Turbulent Flow in Stenotic Vessels

Journal of Biomechanical Engineering-transactions of The Asme, 2003

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Direct numerical simulation of stenotic flows, Part 1: Steady flow

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Direct numerical simulation of stenotic flows. Part 1. Steady flow

Journal of Fluid Mechanics, 2007

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Research paper thumbnail of Direct numerical simulation of stenotic flows. Part 2. Pulsatile flow

Journal of Fluid Mechanics, 2007

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Research paper thumbnail of Performance of a 3Bladed Propeller Pump to Provide Cavopulmonary Assist in the Failing Fontan Circulation

Annals of Thoracic Surgery, 2008

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Mechanical Cavopulmonary Assist for the Univentricular Fontan Circulation Using a Novel Folding Propeller Blood Pump

Asaio Journal, 2007

A blood pump specifically designed to operate in the unique anatomic and physiologic conditions o... more A blood pump specifically designed to operate in the unique anatomic and physiologic conditions of a cavopulmonary connection has never been developed. Mechanical augmentation of cavopulmonary blood flow in a univentricular circulation would reduce systemic venous pressure, increase preload to the single ventricle, and temporarily reproduce a scenario analogous to the normal two-ventricle circulation. We hypothesize that a folding propeller blood pump would function optimally in this cavopulmonary circulation. The hydraulic performance of a two-bladed propeller prototype was characterized in an experimental flow loop using a blood analog fluid for 0.5-3.5 lpm at rotational speeds of 3,600-4,000 rpm. We also created five distinctive blood pump designs and evaluated their hydraulic performance using computational fluid dynamics (CFD). The two-bladed prototype performed well over the design range of 0.5-3.5 lpm, producing physiologic pressure rises of 5-18 mm Hg. Building upon this proof-of-concept testing, the CFD analysis of the five numerical models predicted a physiologic pressure range of 5-40 mm Hg over 0.5-4 lpm for rotational speeds of 3,000-7,000 rpm. These preliminary propeller designs and the two-bladed prototype achieved the expected hydraulic performance. Optimization of these configurations will reduce fluid stress levels, remove regions of recirculation, and improve the hydraulic performance of the folding propeller. This propeller design produces the physiologic pressures and flows that are in the ideal range to mechanically support the cavopulmonary circulation and represents an exciting new therapeutic option for the support of a univentricular Fontan circulation.

Bookmarks Related papers MentionsView impact