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The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Sun, 19 May 2024 10:26:38 GMT2024-05-19T10:26:38ZFree-Surface Effects on Two-Dimensional Hydrofoils by RANS-VOF Simulations
http://hdl.handle.net/10985/23321
Free-Surface Effects on Two-Dimensional Hydrofoils by RANS-VOF Simulations
PERNOD, Laetitia; SACHER, Matthieu; WACKERS, Jeroen; AUGIER, Benoit; BOT, Patrick
Foiling yachts and crafts are both very sensitive to the flying height in terms of stability and performance, raising the scientific issue of the influence of the free-surface when the foil is at low submergence. This work presents numerical simulations of a 2D hydrofoil section NACA0012 at 5° angle of attack in the vicinity of the free-surface, for different values of the submergence depth, for a chord-based Froude number of 0.571 and a Reynolds number of 159,000. Unsteady-Reynolds Averaged Navier-Stokes (URANS) equations are solved with a mixture model to capture the free surface (Volume Of Fluid method), and using an automatic grid refinement. Verification of the numerical model and validation with data from the literature are presented. Deformation of the free surface and alteration of the hydrodynamic forces compared to the deep immersion case are observed for a submergence depth-to-chord ratio ℎ/c lower than 2. The foil drag increases up to more than three times the infinite-depth value at ℎ/c≈0.5. The lift force slightly increases until ℎ/c around 1, and then decreases sharply. For ℎ/c < 0.5, the pressure field around the foil is totally modified and the lift is swapped to downward. The study highlights the importance of considering the effect of finite submergence to compute foils’ hydrodynamic forces, for example to be used in Velocity Prediction Programs (VPP) of foiling crafts.
Fri, 27 Jan 2023 00:00:00 GMThttp://hdl.handle.net/10985/233212023-01-27T00:00:00ZPERNOD, LaetitiaSACHER, MatthieuWACKERS, JeroenAUGIER, BenoitBOT, PatrickFoiling yachts and crafts are both very sensitive to the flying height in terms of stability and performance, raising the scientific issue of the influence of the free-surface when the foil is at low submergence. This work presents numerical simulations of a 2D hydrofoil section NACA0012 at 5° angle of attack in the vicinity of the free-surface, for different values of the submergence depth, for a chord-based Froude number of 0.571 and a Reynolds number of 159,000. Unsteady-Reynolds Averaged Navier-Stokes (URANS) equations are solved with a mixture model to capture the free surface (Volume Of Fluid method), and using an automatic grid refinement. Verification of the numerical model and validation with data from the literature are presented. Deformation of the free surface and alteration of the hydrodynamic forces compared to the deep immersion case are observed for a submergence depth-to-chord ratio ℎ/c lower than 2. The foil drag increases up to more than three times the infinite-depth value at ℎ/c≈0.5. The lift force slightly increases until ℎ/c around 1, and then decreases sharply. For ℎ/c < 0.5, the pressure field around the foil is totally modified and the lift is swapped to downward. The study highlights the importance of considering the effect of finite submergence to compute foils’ hydrodynamic forces, for example to be used in Velocity Prediction Programs (VPP) of foiling crafts.Boundary Element Method Analysis of 3D Effects and Free-Surface Proximity on Hydrofoil Lift and Drag Coefficients in Varied Operating Conditions
http://hdl.handle.net/10985/24641
Boundary Element Method Analysis of 3D Effects and Free-Surface Proximity on Hydrofoil Lift and Drag Coefficients in Varied Operating Conditions
NICOLAS, Hugo; PERALI, Paolo; SACHER, Matthieu; BOT, Patrick
The use of hydrofoils to enhance ship performance raises the scientific issue of free-surface proximity, which is important to consider during the design stage, to feed velocity prediction programs, for instance. Typically, the flow over a shallowly submerged hydrofoil is characterized by the Froude number, the submergence depth-to-chord ratio, the angle of attack, and geometric parameters of the lifting surface. Among these parameters, the present paper investigates the influence of the wing aspect ratio on the lift and drag coefficients of hydrofoils operating near a free surface. For this purpose, rectangular wings with an H105 profile at 2° angle of attack and aspect ratios ranging from 4 to 20 are systematically analyzed using a 3D boundary element method. The free surface is modeled using a linearized Neumann-Kelvin boundary condition. Chord-based Froude numbers of 0.5, 1.1, and 6.3 are studied. The submersion depth is swept between 0.1 and 30 times the foil chord length. The evolution of the normalized lift and drag coefficients with respect to the foil submersion and the aspect ratio is discussed in detail. Flow velocity is shown to play a significant role in the evolution of the lift and drag coefficients with submersion depth, close to the free surface, for all the aspect ratios. Its influence gets reduced by moving away from the free surface. The critical submersion depth, where the free-surface effects cease, is found to increase with higher flow velocity and aspect ratio. Furthermore, both positive and negative correlations between the force coefficients and the aspect ratio are identified, depending on the operating conditions. It is found that when the proximity to the free surface either enhances or impairs a force coefficient relative to its value in unbounded flow, increasing the aspect ratio amplifies this effect. Overall, this study confirms the effectiveness of steady boundary element methods for simulating the flow around hydrofoil wings in the vicinity of a free surface and contributes to further understanding the influence of geometric parameters on hydrofoil performance.
Mon, 04 Dec 2023 00:00:00 GMThttp://hdl.handle.net/10985/246412023-12-04T00:00:00ZNICOLAS, HugoPERALI, PaoloSACHER, MatthieuBOT, PatrickThe use of hydrofoils to enhance ship performance raises the scientific issue of free-surface proximity, which is important to consider during the design stage, to feed velocity prediction programs, for instance. Typically, the flow over a shallowly submerged hydrofoil is characterized by the Froude number, the submergence depth-to-chord ratio, the angle of attack, and geometric parameters of the lifting surface. Among these parameters, the present paper investigates the influence of the wing aspect ratio on the lift and drag coefficients of hydrofoils operating near a free surface. For this purpose, rectangular wings with an H105 profile at 2° angle of attack and aspect ratios ranging from 4 to 20 are systematically analyzed using a 3D boundary element method. The free surface is modeled using a linearized Neumann-Kelvin boundary condition. Chord-based Froude numbers of 0.5, 1.1, and 6.3 are studied. The submersion depth is swept between 0.1 and 30 times the foil chord length. The evolution of the normalized lift and drag coefficients with respect to the foil submersion and the aspect ratio is discussed in detail. Flow velocity is shown to play a significant role in the evolution of the lift and drag coefficients with submersion depth, close to the free surface, for all the aspect ratios. Its influence gets reduced by moving away from the free surface. The critical submersion depth, where the free-surface effects cease, is found to increase with higher flow velocity and aspect ratio. Furthermore, both positive and negative correlations between the force coefficients and the aspect ratio are identified, depending on the operating conditions. It is found that when the proximity to the free surface either enhances or impairs a force coefficient relative to its value in unbounded flow, increasing the aspect ratio amplifies this effect. Overall, this study confirms the effectiveness of steady boundary element methods for simulating the flow around hydrofoil wings in the vicinity of a free surface and contributes to further understanding the influence of geometric parameters on hydrofoil performance.Upwind sail aerodynamics : A RANS numerical investigation validated with wind tunnel pressure measurements
http://hdl.handle.net/10985/8685
Upwind sail aerodynamics : A RANS numerical investigation validated with wind tunnel pressure measurements
BOT, Patrick
The aerodynamics of a sailing yacht with different sail trims are presented, derived from simulations performed using Computational Fluid Dynamics. A Reynolds-averaged Navier-Stokes approach was used to model sixteen sail trims first tested in a wind tunnel, where thepressure distributions on the sails were measured. An original approach was employed byusing two successive simulations: the first one on a large domain to model the blockage due to the wind tunnel walls and the sails model, and a second one on a smaller domain to model the flow around the sails model. A verification and validation of the computed aerodynamic forces and pressure distributions was performed. The computed pressure distribution is shown to agree well with the measured pressures. The sail surface pressure was correlated with the increase of turbulent viscosity in the laminar separation bubble, the flow reattachment and the trailing edge separation. The drive force distribution on both sails showed that the fore part of the genoa (fore sail) provides the majority of the drive force and that the effect of the aft sail is mostly to produce an upwash effect on the genoa. An aerodynamic model based on potential flow theory and a viscous correction is proposed. This model, with one free parameter to be determined, is shown to fit the results better than the usual form drag and induced drag only, even if no friction drag is explicitly considered.
A novel method similar to marching technique was used to model wind tunnel tests. ► Sail trim criteria based on their interactive effect are identified. ► Areas of separated flow were characterised. ► Local flow field was correlated with sail surface pressures. ► An aerodynamic model based on potential flow with viscous correction is proposed.
Sun, 01 Jan 2012 00:00:00 GMThttp://hdl.handle.net/10985/86852012-01-01T00:00:00ZBOT, PatrickThe aerodynamics of a sailing yacht with different sail trims are presented, derived from simulations performed using Computational Fluid Dynamics. A Reynolds-averaged Navier-Stokes approach was used to model sixteen sail trims first tested in a wind tunnel, where thepressure distributions on the sails were measured. An original approach was employed byusing two successive simulations: the first one on a large domain to model the blockage due to the wind tunnel walls and the sails model, and a second one on a smaller domain to model the flow around the sails model. A verification and validation of the computed aerodynamic forces and pressure distributions was performed. The computed pressure distribution is shown to agree well with the measured pressures. The sail surface pressure was correlated with the increase of turbulent viscosity in the laminar separation bubble, the flow reattachment and the trailing edge separation. The drive force distribution on both sails showed that the fore part of the genoa (fore sail) provides the majority of the drive force and that the effect of the aft sail is mostly to produce an upwash effect on the genoa. An aerodynamic model based on potential flow theory and a viscous correction is proposed. This model, with one free parameter to be determined, is shown to fit the results better than the usual form drag and induced drag only, even if no friction drag is explicitly considered.CHARACTERIZATION OF A FLOW SEPARATION SENSOR ON A HYDROFOIL: THE HYDRO E-TELLTALE
http://hdl.handle.net/10985/20171
CHARACTERIZATION OF A FLOW SEPARATION SENSOR ON A HYDROFOIL: THE HYDRO E-TELLTALE
ALAS, Rémi; VOISIN, Dimitri; SOULIER, Antoine; BRAUD, Caroline; MARCILLAT, Paul; PEZERIL, Baudoin; D'ARCO, François; BOT, Patrick
The performance of lifting bodies such as hydrofoils is determined by the flow state and particular attention should be paid to flow separation, as this greatly affects the generated lift and drag. Sailors are used to look at telltales (woolies) to trim their sails or steer their yacht. A French company developed an electronic telltale for sails based on a strain gauge activated by a silicon strand, with the appropriate signal processing to deliver the same information as a classical wool-made telltale, basically attached or separated flow. This new sensor proved useful when woolies are not visible or to deliver a signal to feed a control system, such as the autopilot for example. It was also applied to wind turbines to control the blade pitch. Mer Agitée is now developing an equivalent hydrodynamic e-Telltale to be used on hydrofoils and rudders to help trimming and controlling. The present work presents the investigation of a foil section fitted with this new sensor in a water tunnel, combining force and PIV measurements with the sensor signal, on a wide range of angle of attack. Results show that the hydro e-Telltale enables detecting the flow separation and anticipate stall, and possibly allows for detecting the boundary layer transition to turbulence. The feedback from this new sensor could be used for example in a control loop to make an “Anti-Stall System” on a rudder or a foil.
Fri, 01 Jan 2021 00:00:00 GMThttp://hdl.handle.net/10985/201712021-01-01T00:00:00ZALAS, RémiVOISIN, DimitriSOULIER, AntoineBRAUD, CarolineMARCILLAT, PaulPEZERIL, BaudoinD'ARCO, FrançoisBOT, PatrickThe performance of lifting bodies such as hydrofoils is determined by the flow state and particular attention should be paid to flow separation, as this greatly affects the generated lift and drag. Sailors are used to look at telltales (woolies) to trim their sails or steer their yacht. A French company developed an electronic telltale for sails based on a strain gauge activated by a silicon strand, with the appropriate signal processing to deliver the same information as a classical wool-made telltale, basically attached or separated flow. This new sensor proved useful when woolies are not visible or to deliver a signal to feed a control system, such as the autopilot for example. It was also applied to wind turbines to control the blade pitch. Mer Agitée is now developing an equivalent hydrodynamic e-Telltale to be used on hydrofoils and rudders to help trimming and controlling. The present work presents the investigation of a foil section fitted with this new sensor in a water tunnel, combining force and PIV measurements with the sensor signal, on a wide range of angle of attack. Results show that the hydro e-Telltale enables detecting the flow separation and anticipate stall, and possibly allows for detecting the boundary layer transition to turbulence. The feedback from this new sensor could be used for example in a control loop to make an “Anti-Stall System” on a rudder or a foil.A New Sensor to Characterize Flow Separation on a Hydrofoil
http://hdl.handle.net/10985/21858
A New Sensor to Characterize Flow Separation on a Hydrofoil
VOISIN, Dimitri; SOULIER, Antoine; BOT, Patrick
The performance of lifting bodies such as hydrofoils is determined by the flow state and particular attention should be paid to flow separation, as this greatly affects the generated lift and drag. Sailors are used to look at telltales (woolies) to trim their sails or steer their yacht. A French company developed an electronic telltale for sails based on a strain gauge activated by a silicon strand, with the appropriate signal processing to deliver the same information as a classical wool-made telltale, basically attached or separated flow. This new sensor proved useful when woolies are not visible or to deliver a signal to feed a control system, such as the autopilot for example. It was also applied to wind turbines to control the blade pitch. Mer Agit\'ee is now developing an equivalent hydrodynamic e-Telltale to be used on hydrofoils and rudders to help trimming and controlling. The present work presents the investigation of a foil section fitted with this new sensor in a water tunnel, combining force and PIV measurements with the sensor signal, on a wide range of angle of attack. Results show that the hydro e-Telltale enables detecting the flow separation and anticipate stall, and possibly allows for detecting the boundary layer transition to turbulence. In many cases of fluid flow over a lifting body, it is interesting to get some real-time feedback from the flow in order to help optimizing performance and controlling the system. The feedback from this new sensor could be used in a closed-loop controlling system, for example feeding a reduced-order model of the flow around the foil.
Fri, 01 Jan 2021 00:00:00 GMThttp://hdl.handle.net/10985/218582021-01-01T00:00:00ZVOISIN, DimitriSOULIER, AntoineBOT, PatrickThe performance of lifting bodies such as hydrofoils is determined by the flow state and particular attention should be paid to flow separation, as this greatly affects the generated lift and drag. Sailors are used to look at telltales (woolies) to trim their sails or steer their yacht. A French company developed an electronic telltale for sails based on a strain gauge activated by a silicon strand, with the appropriate signal processing to deliver the same information as a classical wool-made telltale, basically attached or separated flow. This new sensor proved useful when woolies are not visible or to deliver a signal to feed a control system, such as the autopilot for example. It was also applied to wind turbines to control the blade pitch. Mer Agit\'ee is now developing an equivalent hydrodynamic e-Telltale to be used on hydrofoils and rudders to help trimming and controlling. The present work presents the investigation of a foil section fitted with this new sensor in a water tunnel, combining force and PIV measurements with the sensor signal, on a wide range of angle of attack. Results show that the hydro e-Telltale enables detecting the flow separation and anticipate stall, and possibly allows for detecting the boundary layer transition to turbulence. In many cases of fluid flow over a lifting body, it is interesting to get some real-time feedback from the flow in order to help optimizing performance and controlling the system. The feedback from this new sensor could be used in a closed-loop controlling system, for example feeding a reduced-order model of the flow around the foil.Vortex Induced Vibration Analysis of a Cantilevered Hydrofoil by Laser Vibrometry and TR-PIV
http://hdl.handle.net/10985/21859
Vortex Induced Vibration Analysis of a Cantilevered Hydrofoil by Laser Vibrometry and TR-PIV
LEROY, Laure; BOT, Patrick
The structural response of a steel cantilevered hydrofoil is analyzed through an experiment carried out in a hydrodynamic tunnel for Reynolds numbers ranging from 2 105 to 8:25 105. The hydrofoil is set at a 17 angle to the flow direction, in order to maximize the hydrodynamic forcing issued from the vortex shedding, thus enhancing fluid structure interactions. The structural response is measured through the vibration velocity using a laser Doppler vibrometer. The flow dynamics are analyzed through Time Resolved-Particle Image Velocimetry (TR-PIV) and Proper Orthogonal Decomposition. An interaction between the vortex shedding phenomenon and the modal response of the structure is observed. A decrease of the modal frequencies occurs
for Reynolds numbers above 4 105. The modal frequencies are found to decrease towards the vortex shedding frequency as the velocity increases resulting in resonance flow velocities much lower than the ones predicted in a non coupling hypothesis. The experimental results presented in this paper will help to develop fluid-structure interaction models and simulations in naval
applications.
Fri, 01 May 2020 00:00:00 GMThttp://hdl.handle.net/10985/218592020-05-01T00:00:00ZLEROY, LaureBOT, PatrickThe structural response of a steel cantilevered hydrofoil is analyzed through an experiment carried out in a hydrodynamic tunnel for Reynolds numbers ranging from 2 105 to 8:25 105. The hydrofoil is set at a 17 angle to the flow direction, in order to maximize the hydrodynamic forcing issued from the vortex shedding, thus enhancing fluid structure interactions. The structural response is measured through the vibration velocity using a laser Doppler vibrometer. The flow dynamics are analyzed through Time Resolved-Particle Image Velocimetry (TR-PIV) and Proper Orthogonal Decomposition. An interaction between the vortex shedding phenomenon and the modal response of the structure is observed. A decrease of the modal frequencies occurs
for Reynolds numbers above 4 105. The modal frequencies are found to decrease towards the vortex shedding frequency as the velocity increases resulting in resonance flow velocities much lower than the ones predicted in a non coupling hypothesis. The experimental results presented in this paper will help to develop fluid-structure interaction models and simulations in naval
applications.Experimental Study of the Flow in a Compact Heat Exchanger Channel with Embossed-type Vortex Generators
http://hdl.handle.net/10985/9495
Experimental Study of the Flow in a Compact Heat Exchanger Channel with Embossed-type Vortex Generators
DUPONT, Frédéric; BOT, Patrick; GABILLET, Céline
The isothermal flow in a model channel of plate-fin heat exchanger with periodically arranged embossed-like vortex generators is investigated. Velocity measurements are performed by LDA in the transitional regime (Reynolds number from 1000 up to 5000). Strong longitudinal vortices are observed downstream of each vortex generator. The vortex roll-up process is highlighted by the evolution of the velocity vector field in the cross section of the flow. The modifications of the vortex characteristics after successively encountered generators are investigated. This work shows most of the flow features which are known to produce heat transfer enhancement, and shows that these smooth shaped vortex generators are very promising for enhanced heat exchangers.
Wed, 01 Jan 2003 00:00:00 GMThttp://hdl.handle.net/10985/94952003-01-01T00:00:00ZDUPONT, FrédéricBOT, PatrickGABILLET, CélineThe isothermal flow in a model channel of plate-fin heat exchanger with periodically arranged embossed-like vortex generators is investigated. Velocity measurements are performed by LDA in the transitional regime (Reynolds number from 1000 up to 5000). Strong longitudinal vortices are observed downstream of each vortex generator. The vortex roll-up process is highlighted by the evolution of the velocity vector field in the cross section of the flow. The modifications of the vortex characteristics after successively encountered generators are investigated. This work shows most of the flow features which are known to produce heat transfer enhancement, and shows that these smooth shaped vortex generators are very promising for enhanced heat exchangers.Nonlinear disturbance evolution in a two-dimensional boundary layer along an elastic plate and induced radiated sound
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 GMThttp://hdl.handle.net/10985/89342010-01-01T00:00:00ZGOBERT, Marie-LaureEHRENSTEIN, UweASTOLFI, Jacques AndreBOT, PatrickThe 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 assumptionsTurbulent flow around circular arcs
http://hdl.handle.net/10985/21577
Turbulent flow around circular arcs
SOUPPEZ, Jean-Baptiste R.G.; VIOLA, Ignazio Maria; BOT, Patrick
The flow around a circular arc is governed by the effect of the sharp leading edge and the arc’s curvature. There is a range of incidences where a leading-edge separation bubble (LESB) is formed on the convex side of the arc, and the reattached boundary layer separates further downstream. Akin to foils and cylinders, for increasing values of the Reynolds number, the boundary layer turns from laminar to turbulent resulting in a step change in the forces, here termed force crisis. This phenomenon is characterized experimentally for an arc with a camber-to-chord ratio of 0.22 and for a range of the Reynolds number from 53 530 to 218 000. Forces are measured both in a towing tank and in a water tunnel, and particle image velocimetry is undertaken in the water tunnel. In stark contrast to cylinders, where the force crisis is associated with the laminar-to-turbulent transition of the boundary layer, here, it is found to be associated with the suppressed relaminarization of the boundary layer. In fact, the LESB is always turbulent at the tested conditions, and relaminarization occurs up to a combination of critical angles of attack and critical Reynolds numbers. The critical angle of attack varies linearly with the Reynolds number. These results may contribute to the design of thin cambered wings, sails, and blades at a transitional Reynolds number such as the wings of micro aerial vehicles, swept wings in subsonic flight, turbomachinery blades, and the sails of autonomous sailing vessels
Sat, 01 Jan 2022 00:00:00 GMThttp://hdl.handle.net/10985/215772022-01-01T00:00:00ZSOUPPEZ, Jean-Baptiste R.G.VIOLA, Ignazio MariaBOT, PatrickThe flow around a circular arc is governed by the effect of the sharp leading edge and the arc’s curvature. There is a range of incidences where a leading-edge separation bubble (LESB) is formed on the convex side of the arc, and the reattached boundary layer separates further downstream. Akin to foils and cylinders, for increasing values of the Reynolds number, the boundary layer turns from laminar to turbulent resulting in a step change in the forces, here termed force crisis. This phenomenon is characterized experimentally for an arc with a camber-to-chord ratio of 0.22 and for a range of the Reynolds number from 53 530 to 218 000. Forces are measured both in a towing tank and in a water tunnel, and particle image velocimetry is undertaken in the water tunnel. In stark contrast to cylinders, where the force crisis is associated with the laminar-to-turbulent transition of the boundary layer, here, it is found to be associated with the suppressed relaminarization of the boundary layer. In fact, the LESB is always turbulent at the tested conditions, and relaminarization occurs up to a combination of critical angles of attack and critical Reynolds numbers. The critical angle of attack varies linearly with the Reynolds number. These results may contribute to the design of thin cambered wings, sails, and blades at a transitional Reynolds number such as the wings of micro aerial vehicles, swept wings in subsonic flight, turbomachinery blades, and the sails of autonomous sailing vesselsWind-tunnel pressure measurements on model-scale rigid downwind sails
http://hdl.handle.net/10985/14915
Wind-tunnel pressure measurements on model-scale rigid downwind sails
VIOLA, Ignazio Maria; FLAY, Richard G.J.; BRETT, Jean-Sébastien; BOT, Patrick
This paper describes an experiment that was carried out in the Twisted Flow Wind Tunnel at The University of Auckland to measure a detailed set of pressure distributions on a rigid 1/15th scale model of a modern asymmetric spinnaker. It was observed that the pressures varied considerably up the height of the spinnaker. The fine resolution of pressure taps allowed the extent of leading edge separation bubbles, pressure recovery region, and effect of sail curvature to be observed quite clearly. It was found that the shape of the pressure distributions could be understood in terms of conventional aerodynamic theory. The sail performed best at an apparent wind angle of about 55°, which is its design angle, and the effect of heel was more pronounced near the head than the foot.
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/10985/149152013-01-01T00:00:00ZVIOLA, Ignazio MariaFLAY, Richard G.J.BRETT, Jean-SébastienBOT, PatrickThis paper describes an experiment that was carried out in the Twisted Flow Wind Tunnel at The University of Auckland to measure a detailed set of pressure distributions on a rigid 1/15th scale model of a modern asymmetric spinnaker. It was observed that the pressures varied considerably up the height of the spinnaker. The fine resolution of pressure taps allowed the extent of leading edge separation bubbles, pressure recovery region, and effect of sail curvature to be observed quite clearly. It was found that the shape of the pressure distributions could be understood in terms of conventional aerodynamic theory. The sail performed best at an apparent wind angle of about 55°, which is its design angle, and the effect of heel was more pronounced near the head than the foot.