https://sam.ensam.eu:443 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Fri, 12 Jun 2026 12:00:36 GMT 2026-06-12T12:00:36Z http://hdl.handle.net/10985/8836 Analysis of added mass in cavitating flow BENAOUICHA, Mustapha; ASTOLFI, Jacques Andre The paper addresses a theoretical study of the added mass effect in cavitating flow.The cavitation is considered to induce a strong time–space variation of the fluid density at the interface between an inviscid fluid and a three-degree-of-freedom rigid section. The coupled problem is then simplified to a Laplace equation written for the pressure with a boundary condition at the fluid–structure interface depending on the acceleration, the velocity of the structure and on the rate of change of flow density. It is shown that contrary to the homogeneous flow, the added mass operator is not symmetrical and depends on the flow through fluid density variation. The added mass coefficients decrease as the cavitation increases which should induce an increase of the natural structural frequencies. The model shows also an added damping operator related to the rate of change of flow density. Added damping coefficients are found to be positive or negative according to the rate of change of the fluid density, indicating the possibility of instability development between flexible structures and unsteady cavitating flows. Sun, 01 Jan 2012 00:00:00 GMT http://hdl.handle.net/10985/8836 2012-01-01T00:00:00Z BENAOUICHA, Mustapha ASTOLFI, Jacques Andre The paper addresses a theoretical study of the added mass effect in cavitating flow.The cavitation is considered to induce a strong time–space variation of the fluid density at the interface between an inviscid fluid and a three-degree-of-freedom rigid section. The coupled problem is then simplified to a Laplace equation written for the pressure with a boundary condition at the fluid–structure interface depending on the acceleration, the velocity of the structure and on the rate of change of flow density. It is shown that contrary to the homogeneous flow, the added mass operator is not symmetrical and depends on the flow through fluid density variation. The added mass coefficients decrease as the cavitation increases which should induce an increase of the natural structural frequencies. The model shows also an added damping operator related to the rate of change of flow density. Added damping coefficients are found to be positive or negative according to the rate of change of the fluid density, indicating the possibility of instability development between flexible structures and unsteady cavitating flows. http://hdl.handle.net/10985/8992 Cavity induced vibration of flexible hydrofoils AKCABAY, Deniz Tolga; CHAE, Eun Jung; YOUNG, Yin Lu; DUCOIN, Antoine; ASTOLFI, Jacques Andre The objective of this work is to investigate the influence of cavity-induced vibrations on the dynamic response and stability of a NACA66 hydrofoil at 8° angle of attack at Re=750 000 via combined experimental measurements and numerical simulations. The rectangular, cantilevered hydrofoil is assumed to be rigid in the chordwise direction, while the spanwise bending and twisting deformations are represented using a two-degrees-of-freedom structural model. The multiphase flow is modeled with an incompressible, unsteady Reynolds Averaged Navier–Stokes solver with the k–ω Shear Stress Transport (SST) turbulence closure model, while the phase evolutions are modeled with a mass-transport equation based cavitation model. The numerical predictions are compared with experimental measurements across a range of cavitation numbers for a rigid and a flexible hydrofoil with the same undeformed geometries. The results showed that foil flexibility can lead to: (1) focusing – locking – of the frequency content of the vibrations to the nearest sub-harmonics of the foil׳s wetted natural frequencies, and (2) broadening of the frequency content of the vibrations in the unstable cavitation regime, where amplifications are observed in the sub-harmonics of the foil natural frequencies. Cavitation was also observed to cause frequency modulation, as the fluid density, and hence fluid induced (inertial, damping, and disturbing) forces fluctuated with unsteady cavitation. Wed, 01 Jan 2014 00:00:00 GMT http://hdl.handle.net/10985/8992 2014-01-01T00:00:00Z AKCABAY, Deniz Tolga CHAE, Eun Jung YOUNG, Yin Lu DUCOIN, Antoine ASTOLFI, Jacques Andre The objective of this work is to investigate the influence of cavity-induced vibrations on the dynamic response and stability of a NACA66 hydrofoil at 8° angle of attack at Re=750 000 via combined experimental measurements and numerical simulations. The rectangular, cantilevered hydrofoil is assumed to be rigid in the chordwise direction, while the spanwise bending and twisting deformations are represented using a two-degrees-of-freedom structural model. The multiphase flow is modeled with an incompressible, unsteady Reynolds Averaged Navier–Stokes solver with the k–ω Shear Stress Transport (SST) turbulence closure model, while the phase evolutions are modeled with a mass-transport equation based cavitation model. The numerical predictions are compared with experimental measurements across a range of cavitation numbers for a rigid and a flexible hydrofoil with the same undeformed geometries. The results showed that foil flexibility can lead to: (1) focusing – locking – of the frequency content of the vibrations to the nearest sub-harmonics of the foil׳s wetted natural frequencies, and (2) broadening of the frequency content of the vibrations in the unstable cavitation regime, where amplifications are observed in the sub-harmonics of the foil natural frequencies. Cavitation was also observed to cause frequency modulation, as the fluid density, and hence fluid induced (inertial, damping, and disturbing) forces fluctuated with unsteady cavitation. http://hdl.handle.net/10985/8837 Simulating variable pitch crossflow water turbines: A coupled unsteady ONERA-EDLIN model and streamtube model PAILLARD, Benoît; HAUVILLE, Frederic; ASTOLFI, Jacques Andre This article describes a new method for simulating unsteady hydrodynamics forces and moments on the blades of a crossflow ‘Darrieus’ turbine with active pitch variation. This method is based on the ONERAEDLIN dynamic stall model, coupled with a momentum streamtube model to take into account the turbine interference on the flow. Both models are presented, and compared separately with experimental results for a pitching airfoil for the ONERA-EDLIN model; and for Darrieus turbine for the momentum theory. The model coupling is then detailed and compared with experimental data taken from the open literature [1] The turbine has 2 straight blades with a NACA 0012 section operating in water at a mean chord Reynolds number of 4 104 for tip speed ratio l ¼ 2.5, 5 and 7.5. Good agreement was found for average l ¼ 5, and qualitative agreement could be obtained at low and high l, where dynamic stall effects and interference effects respectively are predominant. This is positive because l ¼ 5 is the closest value from the optimal power production point. Variable pitch is finally introduced in the model and several functions are tested in order to increase efficiency. A maximum increase of 53% on the power coefficient was found to occur with a sinusoidal law. 2012 Elsevier Ltd. All rights reserved. 1. Introduction Tidal turbines are currently the power source that shows the most advantages [2]. No land occupation like a dam, steady predictable power input and output unlike wind turbines, no waste or side effects like fossil or nuclear power plants. These devices can consist of a classic horizontal axis screw-like systems, or crossflow turbines which have many advantages in water [3], such as being independent of the tide direction. Variable pitch crossflow turbines enable a Darrieus system to improve its performance and decrease parasitic forces,mainly responsible for fatigue and systemfailure [4]. They have been studied at IRENAV since 2007 as the SHIVA project. This project of novel tidal turbines deals with three topics,which will be introduced here. Darrieus turbines have been studied extensively during the 70s and 80s, especially by SANDIA organization [5e8]. A reference publication on this topic can be found in [9]. Though almost no Darrieus turbine produced electrical power from wind since early 90s, a renewed interest arose from water turbines because most drawbacks which prevented this system from becoming Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10985/8837 2013-01-01T00:00:00Z PAILLARD, Benoît HAUVILLE, Frederic ASTOLFI, Jacques Andre This article describes a new method for simulating unsteady hydrodynamics forces and moments on the blades of a crossflow ‘Darrieus’ turbine with active pitch variation. This method is based on the ONERAEDLIN dynamic stall model, coupled with a momentum streamtube model to take into account the turbine interference on the flow. Both models are presented, and compared separately with experimental results for a pitching airfoil for the ONERA-EDLIN model; and for Darrieus turbine for the momentum theory. The model coupling is then detailed and compared with experimental data taken from the open literature [1] The turbine has 2 straight blades with a NACA 0012 section operating in water at a mean chord Reynolds number of 4 104 for tip speed ratio l ¼ 2.5, 5 and 7.5. Good agreement was found for average l ¼ 5, and qualitative agreement could be obtained at low and high l, where dynamic stall effects and interference effects respectively are predominant. This is positive because l ¼ 5 is the closest value from the optimal power production point. Variable pitch is finally introduced in the model and several functions are tested in order to increase efficiency. A maximum increase of 53% on the power coefficient was found to occur with a sinusoidal law. 2012 Elsevier Ltd. All rights reserved. 1. Introduction Tidal turbines are currently the power source that shows the most advantages [2]. No land occupation like a dam, steady predictable power input and output unlike wind turbines, no waste or side effects like fossil or nuclear power plants. These devices can consist of a classic horizontal axis screw-like systems, or crossflow turbines which have many advantages in water [3], such as being independent of the tide direction. Variable pitch crossflow turbines enable a Darrieus system to improve its performance and decrease parasitic forces,mainly responsible for fatigue and systemfailure [4]. They have been studied at IRENAV since 2007 as the SHIVA project. This project of novel tidal turbines deals with three topics,which will be introduced here. Darrieus turbines have been studied extensively during the 70s and 80s, especially by SANDIA organization [5e8]. A reference publication on this topic can be found in [9]. Though almost no Darrieus turbine produced electrical power from wind since early 90s, a renewed interest arose from water turbines because most drawbacks which prevented this system from becoming http://hdl.handle.net/10985/8934 Nonlinear disturbance evolution in a two-dimensional boundary layer along an elastic plate and induced radiated sound GOBERT, Marie-Laure; EHRENSTEIN, Uwe; ASTOLFI, Jacques Andre; BOT, Patrick The interaction between a boundary-layer flow and an elastic plate is addressed by direct numerical simulation, taking into account the full coupling between the fluid flow and the flexible wall. The convectively unstable flow state is harmonically forced and two-dimensional nonlinearly saturated wavelike disturbances are computed along archetype-plates with respect to stiffness and natural frequencies. In the aim of determining the low-Mach-number radiated sound for the system, the simulation data are used to solve the Lighthill’s equation in terms of a Green’s function in the wavenumber-frequency space. Different degrees of fluid-structure coupling are implemented in the radiated sound model and the resulting acoustic pressure levels are compared. The sound radiation levels are shown to be increased in the presence of flexible walls with however significant differences in the radiated pressure levels for different coupling assumptions Fri, 01 Jan 2010 00:00:00 GMT http://hdl.handle.net/10985/8934 2010-01-01T00:00:00Z GOBERT, Marie-Laure EHRENSTEIN, Uwe ASTOLFI, Jacques Andre BOT, Patrick The interaction between a boundary-layer flow and an elastic plate is addressed by direct numerical simulation, taking into account the full coupling between the fluid flow and the flexible wall. The convectively unstable flow state is harmonically forced and two-dimensional nonlinearly saturated wavelike disturbances are computed along archetype-plates with respect to stiffness and natural frequencies. In the aim of determining the low-Mach-number radiated sound for the system, the simulation data are used to solve the Lighthill’s equation in terms of a Green’s function in the wavenumber-frequency space. Different degrees of fluid-structure coupling are implemented in the radiated sound model and the resulting acoustic pressure levels are compared. The sound radiation levels are shown to be increased in the presence of flexible walls with however significant differences in the radiated pressure levels for different coupling assumptions http://hdl.handle.net/10985/9621 Modélisation couplée multiphysique d'une hydrolienne RIM-DRIVEN; A multi physical approach for the design of RIM‑DRIVEN Tidal Turbines DROUEN, Laurent; CHARPENTIER, Jean-Frederic; HAUVILLE, Frederic; ASTOLFI, Jacques Andre; SEMAIL, Eric; CLENET, Stephane Le travail présenté concerne le développement d’une méthodologie de conception de systèmes hydroliens innovants de type RIM‑DRIVEN pour la récupération de l’énergie des courants de marée. L’originalité d’un système RIM‑DRIVEN réside dans la structure même de l’hydrolienne, inspirée directement des nouveaux systèmes de propulsion navale, où le rotor et le stator sont placés en périphérie de l’hélice et protégés par une tuyère, l’entrefer étant immergé. Au sein d’une structure de type RIM‑DRIVEN les phénomènes électromécaniques, thermiques et hydrodynamique sont intimement couplés. Du fait du très fort couplage des phénomènes physiques au sein du système, cette méthodologie associe au sein d’un même environnement d’optimisation des modèles électromagnétiques et thermiques spécifiques de la génératrice avec des modèles hydrodynamique des performances de l’hélice et de l’écoulement dans l’entrefer. L’approche proposée est illustrée par une étude de cas qui concerne une machine de 10m de diamètre destinée à être implantée dans le Raz de Sein. Les modèles ont été validés par des résultats issus d’une campagne expérimentale sur un démonstrateur dédié.; This paper deals with the study of an unconventional design of marine tidal turbine where the electrical generator is located in the periphery of the blades and where the magnetic gap is underwater. This kind of solution called “RIM DRIVEN” structure allows increasing the compactness and the robustness of the system. Due to the strong interaction of the multi physical phenomena, an electromagnetic model and a thermal model of the PM generator are associated with a hydrodynamic model of the blades and of the water flow in the underwater air gap. These models are used in a global coupled design approach in order to optimize, under constraints, the global efficiency of the system. This approach is illustrated in a case study which deals with the design of a 10m diameter tidal turbine. Proposed coupled models are validated by comparison with experimental data from the tests of an academic low power demonstrator Thu, 01 Jan 2015 00:00:00 GMT http://hdl.handle.net/10985/9621 2015-01-01T00:00:00Z DROUEN, Laurent CHARPENTIER, Jean-Frederic HAUVILLE, Frederic ASTOLFI, Jacques Andre SEMAIL, Eric CLENET, Stephane Le travail présenté concerne le développement d’une méthodologie de conception de systèmes hydroliens innovants de type RIM‑DRIVEN pour la récupération de l’énergie des courants de marée. L’originalité d’un système RIM‑DRIVEN réside dans la structure même de l’hydrolienne, inspirée directement des nouveaux systèmes de propulsion navale, où le rotor et le stator sont placés en périphérie de l’hélice et protégés par une tuyère, l’entrefer étant immergé. Au sein d’une structure de type RIM‑DRIVEN les phénomènes électromécaniques, thermiques et hydrodynamique sont intimement couplés. Du fait du très fort couplage des phénomènes physiques au sein du système, cette méthodologie associe au sein d’un même environnement d’optimisation des modèles électromagnétiques et thermiques spécifiques de la génératrice avec des modèles hydrodynamique des performances de l’hélice et de l’écoulement dans l’entrefer. L’approche proposée est illustrée par une étude de cas qui concerne une machine de 10m de diamètre destinée à être implantée dans le Raz de Sein. Les modèles ont été validés par des résultats issus d’une campagne expérimentale sur un démonstrateur dédié. This paper deals with the study of an unconventional design of marine tidal turbine where the electrical generator is located in the periphery of the blades and where the magnetic gap is underwater. This kind of solution called “RIM DRIVEN” structure allows increasing the compactness and the robustness of the system. Due to the strong interaction of the multi physical phenomena, an electromagnetic model and a thermal model of the PM generator are associated with a hydrodynamic model of the blades and of the water flow in the underwater air gap. These models are used in a global coupled design approach in order to optimize, under constraints, the global efficiency of the system. This approach is illustrated in a case study which deals with the design of a 10m diameter tidal turbine. Proposed coupled models are validated by comparison with experimental data from the tests of an academic low power demonstrator http://hdl.handle.net/10985/8996 Effect of the laminar separation bubble induced transition on the hydrodynamic performance of a hydrofoil DELAFIN, Pierre-Luc; DENISET, François; ASTOLFI, Jacques Andre The present study deals with the effect of the laminar separation bubble (LSB) induced transition on the lift, drag and moment coefficients of a hydrofoil. A 2D numerical study, based on the SST γ –Reθ transition model of ANSYS-CFX⃝R , is conducted on a NACA66 hydrofoil. Angles of attack range from −4° to 14° and the chord-based Reynolds number is Re = 7.5 × 105. An experimental investigation is carried out in the French naval academy research institute’s hydrodynamic tunnel based on the measurements of lift, drag and moment. Experiments on a smooth, mirror finished, hydrofoil enable comparison with RANS calculations using the transition model. Experiments with a roughness added on the leading edge enable comparison with RANS calculations using the SST fully turbulent model. For angles of attack below 6°, the LSB triggered laminar to turbulent transition of the boundary layers of the suction and pressure sides is located near the trailing edge of the smooth NACA66. As the angle of attack reaches 6°, the LSB suddenly moves to the leading edge on the suction side while transition is located at the trailing edge on the pressure side. The smooth hydrofoil shows higher CL and CM and lower CD than the rough leading edge one from −4° to 6°. Both experiments lead to the same coefficients from 6° to 14°. The calculations show that both models are in good agreement with their corresponding experiments. Velocity profiles in the vicinity of the LSB at an angle of attack of 2° and pressure coefficients of the calculations using the transition model are compared with published experimental studies and show very good agreement. The SST γ –Reθ transition model proves to be a relevant, even essential, prediction tool for lifting bodies operating at a moderate Reynolds number. The authors thank the technical staff of IRENav for their contribution to the experimental set up. Wed, 01 Jan 2014 00:00:00 GMT http://hdl.handle.net/10985/8996 2014-01-01T00:00:00Z DELAFIN, Pierre-Luc DENISET, François ASTOLFI, Jacques Andre The present study deals with the effect of the laminar separation bubble (LSB) induced transition on the lift, drag and moment coefficients of a hydrofoil. A 2D numerical study, based on the SST γ –Reθ transition model of ANSYS-CFX⃝R , is conducted on a NACA66 hydrofoil. Angles of attack range from −4° to 14° and the chord-based Reynolds number is Re = 7.5 × 105. An experimental investigation is carried out in the French naval academy research institute’s hydrodynamic tunnel based on the measurements of lift, drag and moment. Experiments on a smooth, mirror finished, hydrofoil enable comparison with RANS calculations using the transition model. Experiments with a roughness added on the leading edge enable comparison with RANS calculations using the SST fully turbulent model. For angles of attack below 6°, the LSB triggered laminar to turbulent transition of the boundary layers of the suction and pressure sides is located near the trailing edge of the smooth NACA66. As the angle of attack reaches 6°, the LSB suddenly moves to the leading edge on the suction side while transition is located at the trailing edge on the pressure side. The smooth hydrofoil shows higher CL and CM and lower CD than the rough leading edge one from −4° to 6°. Both experiments lead to the same coefficients from 6° to 14°. The calculations show that both models are in good agreement with their corresponding experiments. Velocity profiles in the vicinity of the LSB at an angle of attack of 2° and pressure coefficients of the calculations using the transition model are compared with published experimental studies and show very good agreement. The SST γ –Reθ transition model proves to be a relevant, even essential, prediction tool for lifting bodies operating at a moderate Reynolds number. http://hdl.handle.net/10985/8905 An experimental study of boundary-layer transition induced vibrations on a hydrofoil DUCOIN, Antoine; ASTOLFI, Jacques Andre; GOBERT, Marie-Laure This paper aims at characterizing experimentally laminar to turbulent transition induced vibrations. Here, the transition is known to be triggered by a Laminar Separation Bubble that results from a laminar separation of the boundary-layer flow on a hydrofoil. In this study we consider two NACA66312 (Mod) laminar hydrofoils at low angles of incidence (mostly 2° and 4°) and Reynolds numbers ranging from Re=450 000 to 1 200 000, in order to get transitional regimes. The first hydrofoil, made of steel (E=2.1×1011 Pa), is referred to as the rigid hydrofoil, although it is seen to vibrate under the action of the LSB. To better understand the possible interaction between the flow and the foil vibrations, vibration measurements are repeated using a flexible hydrofoil (E=3×109 Pa) of same geometry (under zero loading) and in close configurations. The experiments are carried out at the French Naval Academy Research Institute (IRENav, France). Wall pressure and flow velocity measurements enable a characterization of the laminar separation bubble and the identification of a vortex shedding at a given frequency. It is hence shown that the boundary-layer transition induces important foil vibrations, whose characteristics in terms of frequency and amplitude depend on the vortex shedding frequency, and can be coupled with natural frequencies of the hydrofoils. Sun, 01 Jan 2012 00:00:00 GMT http://hdl.handle.net/10985/8905 2012-01-01T00:00:00Z DUCOIN, Antoine ASTOLFI, Jacques Andre GOBERT, Marie-Laure This paper aims at characterizing experimentally laminar to turbulent transition induced vibrations. Here, the transition is known to be triggered by a Laminar Separation Bubble that results from a laminar separation of the boundary-layer flow on a hydrofoil. In this study we consider two NACA66312 (Mod) laminar hydrofoils at low angles of incidence (mostly 2° and 4°) and Reynolds numbers ranging from Re=450 000 to 1 200 000, in order to get transitional regimes. The first hydrofoil, made of steel (E=2.1×1011 Pa), is referred to as the rigid hydrofoil, although it is seen to vibrate under the action of the LSB. To better understand the possible interaction between the flow and the foil vibrations, vibration measurements are repeated using a flexible hydrofoil (E=3×109 Pa) of same geometry (under zero loading) and in close configurations. The experiments are carried out at the French Naval Academy Research Institute (IRENav, France). Wall pressure and flow velocity measurements enable a characterization of the laminar separation bubble and the identification of a vortex shedding at a given frequency. It is hence shown that the boundary-layer transition induces important foil vibrations, whose characteristics in terms of frequency and amplitude depend on the vortex shedding frequency, and can be coupled with natural frequencies of the hydrofoils. http://hdl.handle.net/10985/10205 Computational and experimental investigation of flow over a transient pitching hydrofoil DUCOIN, Antoine; ASTOLFI, Jacques Andre; DENISET, François; SIGRIST, Jean-François The present study is developed within the framework of marine structure design operating in transient regimes. It deals with an experimental and numerical investigation of the time–space distribution of the wall-pressure field on a NACA66 hydrofoil undergoing a transient up-and-down pitching motion from 0 to 15 at four pitching velocities and a Reynolds number Re¼ 0.75 106. The experimental investigation is performed using an array of wall-pressure transducers located on the suction side and by means of time–frequency analysis and Empirical Modal Decomposition method. The numerical study is conducted for the same flow conditions. It is based on a 2D RANS code including mesh reconstruction and an ALE formulation in order to take into account the foil rotation and the tunnel walls. Due to the moderate Reynolds number, a laminar to turbulent transition model was also activated. For the operating flow conditions of the study, experimental and numerical flow analysis revealed that the flow experiences complex boundary layer events as leading-edge laminar separation bubble, laminar to turbulent transition, trailing-edge separation and flow detachment at stall. Although the flow is relatively complex, the calculated wall pressure shows a quite good agreement with the experiment provided that the mesh resolution and the temporal discretization are carefully selected depending on the pitching velocity. It is particularly shown that the general trend of the wall pressure (low frequency) is rather well predicted for the four pitching velocities with for instance a net inflection of the wall pressure when transition occurs. The inflection zone is reduced as the pitching velocity increases and tends to disappear for the highest pitching velocity. Conversely, high frequency wall-pressure fluctuations observed experimentally are not captured by the RANS model. Based on the good agreement with experiment, the model is then used to investigate the effects of the pitching velocity on boundary layer events and on hydrodynamic loadings. It is shown that increasing the pitching velocity tends to delay the laminar-to-turbulence transition and even to suppress it for the highest pitching velocity during the pitch-up motion. It induces also an increase of the stall angle (compared to quasi-static one) and an increase of the hysteresis effect during pitch-down motion resulting to a significant increase of the hydrodynamic loading. Thu, 01 Jan 2009 00:00:00 GMT http://hdl.handle.net/10985/10205 2009-01-01T00:00:00Z DUCOIN, Antoine ASTOLFI, Jacques Andre DENISET, François SIGRIST, Jean-François The present study is developed within the framework of marine structure design operating in transient regimes. It deals with an experimental and numerical investigation of the time–space distribution of the wall-pressure field on a NACA66 hydrofoil undergoing a transient up-and-down pitching motion from 0 to 15 at four pitching velocities and a Reynolds number Re¼ 0.75 106. The experimental investigation is performed using an array of wall-pressure transducers located on the suction side and by means of time–frequency analysis and Empirical Modal Decomposition method. The numerical study is conducted for the same flow conditions. It is based on a 2D RANS code including mesh reconstruction and an ALE formulation in order to take into account the foil rotation and the tunnel walls. Due to the moderate Reynolds number, a laminar to turbulent transition model was also activated. For the operating flow conditions of the study, experimental and numerical flow analysis revealed that the flow experiences complex boundary layer events as leading-edge laminar separation bubble, laminar to turbulent transition, trailing-edge separation and flow detachment at stall. Although the flow is relatively complex, the calculated wall pressure shows a quite good agreement with the experiment provided that the mesh resolution and the temporal discretization are carefully selected depending on the pitching velocity. It is particularly shown that the general trend of the wall pressure (low frequency) is rather well predicted for the four pitching velocities with for instance a net inflection of the wall pressure when transition occurs. The inflection zone is reduced as the pitching velocity increases and tends to disappear for the highest pitching velocity. Conversely, high frequency wall-pressure fluctuations observed experimentally are not captured by the RANS model. Based on the good agreement with experiment, the model is then used to investigate the effects of the pitching velocity on boundary layer events and on hydrodynamic loadings. It is shown that increasing the pitching velocity tends to delay the laminar-to-turbulence transition and even to suppress it for the highest pitching velocity during the pitch-up motion. It induces also an increase of the stall angle (compared to quasi-static one) and an increase of the hysteresis effect during pitch-down motion resulting to a significant increase of the hydrodynamic loading. http://hdl.handle.net/10985/8998 An experimental analysis of fluid structure interaction on a flexible hydrofoil in various flow regimes including cavitating flow DUCOIN, Antoine; ASTOLFI, Jacques Andre; SIGRIST, Jean-François The structural response of a rectangular cantilevered flexible hydrofoil submitted to various flow regimes is analyzed through an original experiment carried out in a hydrodynamic tunnel at a Reynolds number of 0.75 × 10 6 . The experiment considers static and transient regimes. The latter consists of transient pitching motions at low and fast pitching velocities. The experiments are also performed for cavitating flow. The structural response is analyzed through the measurement of the free foil tip section displacement using a high speed video camera and surface velocity vibrations using a laser doppler vibrometer. In non cavitating flows, it is shown that the structural response is linked to the hydrodynamic loading, which is governed by viscous effects such as laminar to turbulent transition induced by Laminar Separation Bubble (LSB), and stall. It is also observed that the foil elastic displacement depends strongly on the pitching velocity. Large overshoots and hysteresis effect are observed as the pitching velocity increases. Cavitation induces a large increase of the vibration level due to hydrodynamic loading unsteadiness and change of modal response for specific frequencies. The experimental results presented in this paper will help to develop high fidelity fluid–structure interaction models in naval applications. The authors gratefully acknowledge the technical staff of IRENav for its contribution to the experimental set up. Sun, 01 Jan 2012 00:00:00 GMT http://hdl.handle.net/10985/8998 2012-01-01T00:00:00Z DUCOIN, Antoine ASTOLFI, Jacques Andre SIGRIST, Jean-François The structural response of a rectangular cantilevered flexible hydrofoil submitted to various flow regimes is analyzed through an original experiment carried out in a hydrodynamic tunnel at a Reynolds number of 0.75 × 10 6 . The experiment considers static and transient regimes. The latter consists of transient pitching motions at low and fast pitching velocities. The experiments are also performed for cavitating flow. The structural response is analyzed through the measurement of the free foil tip section displacement using a high speed video camera and surface velocity vibrations using a laser doppler vibrometer. In non cavitating flows, it is shown that the structural response is linked to the hydrodynamic loading, which is governed by viscous effects such as laminar to turbulent transition induced by Laminar Separation Bubble (LSB), and stall. It is also observed that the foil elastic displacement depends strongly on the pitching velocity. Large overshoots and hysteresis effect are observed as the pitching velocity increases. Cavitation induces a large increase of the vibration level due to hydrodynamic loading unsteadiness and change of modal response for specific frequencies. The experimental results presented in this paper will help to develop high fidelity fluid–structure interaction models in naval applications. http://hdl.handle.net/10985/21837 Verification and validation for the cavitating flow around a NACA0015 hydrofoil PERALI, Paolo; HAUVILLE, Frederic; LEROYER, Alban; ASTOLFI, Jacques Andre; VISONNEAU, Michel When cavitation occurs around hydrofoils it is the cause of noise radiation, vibration and erosion. Consequently numerical cavitation models have been developped and tested over the last decades (Schnerr and Sauer [1]). However, recent works show that numerical predictions for cavitating flow might be very sensitive to the spatial resolution of the mesh and require dicretization errors estimations (Negrato et al. [2], Asnaghi et al. [3]). The experimental and numerical approches joined in this work are the first step of the validation of the ISIS-CFD code for cavitating flows with fluid-structure interaction. Although, only results for a rigid profile in cavitating conditions are presented in this work. The test case is a NACA0015 profile in the cavitation tunnel located at the french Naval Academy Research Institute. On the numerical side, the ISIS-CFD code is used to solve the unsteady Reynolds Averaged Navier Stokes Equations (uRANSE). The two phases mixture dynamics are solved thanks to an interface capturing method and the Sauer cavitation model. The test case is first adressed using a two-dimensional computational domain. A set of unstructured grids is generated using Hexpress to perform a grids and time steps convergence study and obtain uncertainty estimations for both wetted and cavitating flow conditions. Then, the same study is done for an extended three-dimensional geometry taking into account the lateral walls of the tunnel and the convergent section located upstream of the test section. Influences of the turbulence quantities at the inflow and the cavitation model parameters are also assessed. The numerical results are compared with experimental effort measurements, high-speed camera signals and PIV acquisitions provided by Lelong [4]. From the verification and validation analysis a three dimensional grid and a set of computational parameters are chosen for future calculations with fluid-structure interaction and cavitation. Tue, 01 Jan 2019 00:00:00 GMT http://hdl.handle.net/10985/21837 2019-01-01T00:00:00Z PERALI, Paolo HAUVILLE, Frederic LEROYER, Alban ASTOLFI, Jacques Andre VISONNEAU, Michel When cavitation occurs around hydrofoils it is the cause of noise radiation, vibration and erosion. Consequently numerical cavitation models have been developped and tested over the last decades (Schnerr and Sauer [1]). However, recent works show that numerical predictions for cavitating flow might be very sensitive to the spatial resolution of the mesh and require dicretization errors estimations (Negrato et al. [2], Asnaghi et al. [3]). The experimental and numerical approches joined in this work are the first step of the validation of the ISIS-CFD code for cavitating flows with fluid-structure interaction. Although, only results for a rigid profile in cavitating conditions are presented in this work. The test case is a NACA0015 profile in the cavitation tunnel located at the french Naval Academy Research Institute. On the numerical side, the ISIS-CFD code is used to solve the unsteady Reynolds Averaged Navier Stokes Equations (uRANSE). The two phases mixture dynamics are solved thanks to an interface capturing method and the Sauer cavitation model. The test case is first adressed using a two-dimensional computational domain. A set of unstructured grids is generated using Hexpress to perform a grids and time steps convergence study and obtain uncertainty estimations for both wetted and cavitating flow conditions. Then, the same study is done for an extended three-dimensional geometry taking into account the lateral walls of the tunnel and the convergent section located upstream of the test section. Influences of the turbulence quantities at the inflow and the cavitation model parameters are also assessed. The numerical results are compared with experimental effort measurements, high-speed camera signals and PIV acquisitions provided by Lelong [4]. From the verification and validation analysis a three dimensional grid and a set of computational parameters are chosen for future calculations with fluid-structure interaction and cavitation.