Races using kitefoil and windfoil surfboards have been in the Olympic Games for the first time in Paris 2024,signalling their relevance in sailing sports.However,the dynamics of these devices is yet not well understoo...Races using kitefoil and windfoil surfboards have been in the Olympic Games for the first time in Paris 2024,signalling their relevance in sailing sports.However,the dynamics of these devices is yet not well understood,in particular the influence on the hydrodynamic forces and moments of the distance of the foil to the free surface.Considering this,the present paper documents an experimental investigation in which forces and torque produced,under uniform flow,by a full-scale state-of-the-art hydrofoil(suitable both for kitesurf and windsurf)were measured.A range of velocities,angles of attack,and submergences were tested,leading to Froude numbers based on submergence with maximum values around five,a typical range in actual sailing conditions.From these tests,formulae for the hydrodynamic coefficients have been proposed.They can be used for developing Velocity Prediction Programs(VPP)for this kind of craft,a necessary tool to plan racing configurations and to analyze their racing performance.With the aim of making the experimental data useful for benchmarking numerical models and for future research on related topics such as foil ventilation and transition to turbulence,the specimen’s 3D file is provided as supplementary material to this paper.展开更多
Beaches along the eastern branch of the Giens double tombolo are subject to coastal erosion.Prediction of the behavior of the beach profile configuration in response to natural and anthropogenic changes using the conc...Beaches along the eastern branch of the Giens double tombolo are subject to coastal erosion.Prediction of the behavior of the beach profile configuration in response to natural and anthropogenic changes using the concept of equilibrium beach profile(EBP)could be useful in finding the most suitable measure to address the erosion problem.Field investigation data of 11 beaches along the eastern tombolo were supplied for this study,and a nonlinear fitting technique was applied to estimate the best parameter values of seven empirical formulations of the relevant EBP.All of the observed beach profiles could be described by a single function,but a single EBP was inadequate to represent all of the beach profiles observed.The variation found could be explained in terms of longshore variation of bathymetry,sediment size,and wave parameters.Analysis of the validity of the EBPs revealed that a representative EBP of each beach is governed by different equilibrium parameters.展开更多
In this article,we study the convergence of an IIPG(Incomplete Interior Penalty Galerkin)Discontinuous Galerkin numerical method for the Richards equation.The Richards equation is a degenerate parabolic nonlinear equa...In this article,we study the convergence of an IIPG(Incomplete Interior Penalty Galerkin)Discontinuous Galerkin numerical method for the Richards equation.The Richards equation is a degenerate parabolic nonlinear equation for modeling flows in porous media with variable saturation.The numerical solution of this equation is known to be difficult to calculate numerically,due to the abrupt displacement of the wetting front,mainly as a result of highly nonlinear hydraulic properties.As time scales are slow,implicit numerical methods are required,and the convergence of nonlinear solvers is very sensitive.We propose an original method to ensure convergence of the numerical solution to the exact Richards solution,using a technique of auto-calibration of the penalty parameters derived from the Galerkin Discontinuous method.The method is constructed using nonlinear 1D and 2D general elliptic problems.We show that the numerical solution converges toward the unique solution of the continuous problem under certain conditions on the penalty parameters.Then,we numerically demonstrate the efficiency and robustness of the method through test cases with analytical solutions,laboratory test cases,and large-scale simulations.展开更多
We propose a new section-averaged one-dimensional model for blood flows in deformable arteries.The model is derived from the three-dimensional Navier-Stokes equations,written in cylindrical coordinates,under the“thin...We propose a new section-averaged one-dimensional model for blood flows in deformable arteries.The model is derived from the three-dimensional Navier-Stokes equations,written in cylindrical coordinates,under the“thin-artery”assumption(similar to the“shallow-water”assumption for free surface models).The blood flow/artery interaction is taken into account through suitable boundary conditions.The obtained equations enter the scope of the nonlinear convection-diffusion problems.We show that the resulting model is energetically consistent.The proposed model extends most extant models by adding more scope,depending on an additional viscous term.We compare both models computationally based on an Incomplete Interior Penalty Galerkin(IIPG)method for the parabolic part,and on a Runge Kutta Discontinuous Galerkin(RKDG)method for the hyperbolic part.The time discretization explicit/implicit is based on the well-known Additive Runge-Kutta(ARK)method.Moreover,through a suitable change of variables,by construction,we show that the numerical scheme is well-balanced,i.e.,it preserves exactly still-steady state solutions.To end,we numerically investigate its efficiency through several test cases with a confrontation to an exact solution.展开更多
We propose a new two-dimensional blood flow reduced model taking into account of complex artery geometry as in the case of severe aneurysm.We derive the model from the three-dimensional Navier-Stokes equations written...We propose a new two-dimensional blood flow reduced model taking into account of complex artery geometry as in the case of severe aneurysm.We derive the model from the three-dimensional Navier-Stokes equations written in a curvilinear coordinate system under the thin-artery assumption,with boundary conditions including wall tissue deformation.We show that the model is energetically consistent with the full Navier-Stokes problem.This model,obtained via radial averaging,is,up to our knowledge,the first one.It has the advantage of being more accurate than the classical one-dimensional models and being solved in a reasonable time in comparison with the Navier-Stokes models.To this purpose,we use a Runge-Kutta Discontinuous Galerkin(RKDG)method to solve the two-dimensional problem.We end the paper with several numerical test cases to show the efficiency and robustness of the numerical model,and in particular,we show the limit of the one-dimensional models in the case of a severe aneurysm.展开更多
文摘Races using kitefoil and windfoil surfboards have been in the Olympic Games for the first time in Paris 2024,signalling their relevance in sailing sports.However,the dynamics of these devices is yet not well understood,in particular the influence on the hydrodynamic forces and moments of the distance of the foil to the free surface.Considering this,the present paper documents an experimental investigation in which forces and torque produced,under uniform flow,by a full-scale state-of-the-art hydrofoil(suitable both for kitesurf and windsurf)were measured.A range of velocities,angles of attack,and submergences were tested,leading to Froude numbers based on submergence with maximum values around five,a typical range in actual sailing conditions.From these tests,formulae for the hydrodynamic coefficients have been proposed.They can be used for developing Velocity Prediction Programs(VPP)for this kind of craft,a necessary tool to plan racing configurations and to analyze their racing performance.With the aim of making the experimental data useful for benchmarking numerical models and for future research on related topics such as foil ventilation and transition to turbulence,the specimen’s 3D file is provided as supplementary material to this paper.
基金financially supported by the 911 Project of Vietnam International Education Development,Ministry of Education and Training,Vietnam
文摘Beaches along the eastern branch of the Giens double tombolo are subject to coastal erosion.Prediction of the behavior of the beach profile configuration in response to natural and anthropogenic changes using the concept of equilibrium beach profile(EBP)could be useful in finding the most suitable measure to address the erosion problem.Field investigation data of 11 beaches along the eastern tombolo were supplied for this study,and a nonlinear fitting technique was applied to estimate the best parameter values of seven empirical formulations of the relevant EBP.All of the observed beach profiles could be described by a single function,but a single EBP was inadequate to represent all of the beach profiles observed.The variation found could be explained in terms of longshore variation of bathymetry,sediment size,and wave parameters.Analysis of the validity of the EBPs revealed that a representative EBP of each beach is governed by different equilibrium parameters.
基金supported by the ADEN-MED project(Adaptability to Extreme events and Natural risks-application to the Mediterranean and Djibouti),funded by the Region Sud Provence-Alpes-Cote d’Azur under the AAP MEDCLIMAT“Natural risks and food sovereignty”by France 2030 through the Priority Research Program and Equipment(PEPR)“Maths-Vives-Mathematics in Interactions”,targeted project HYDRAUMATH(ANR-23-EXMA-007),operated by ANR.
文摘In this article,we study the convergence of an IIPG(Incomplete Interior Penalty Galerkin)Discontinuous Galerkin numerical method for the Richards equation.The Richards equation is a degenerate parabolic nonlinear equation for modeling flows in porous media with variable saturation.The numerical solution of this equation is known to be difficult to calculate numerically,due to the abrupt displacement of the wetting front,mainly as a result of highly nonlinear hydraulic properties.As time scales are slow,implicit numerical methods are required,and the convergence of nonlinear solvers is very sensitive.We propose an original method to ensure convergence of the numerical solution to the exact Richards solution,using a technique of auto-calibration of the penalty parameters derived from the Galerkin Discontinuous method.The method is constructed using nonlinear 1D and 2D general elliptic problems.We show that the numerical solution converges toward the unique solution of the continuous problem under certain conditions on the penalty parameters.Then,we numerically demonstrate the efficiency and robustness of the method through test cases with analytical solutions,laboratory test cases,and large-scale simulations.
基金supported by the ADEN-MED project(Adaptability to Extreme Events and Natural Risks-Application to the Mediterranean and Djibouti)funded by the Région Sud Provence-Alpes-Côte d’Azur under the AAP MEDCLIMAT“Natural Risks and Food Sovereignty”.
文摘We propose a new section-averaged one-dimensional model for blood flows in deformable arteries.The model is derived from the three-dimensional Navier-Stokes equations,written in cylindrical coordinates,under the“thin-artery”assumption(similar to the“shallow-water”assumption for free surface models).The blood flow/artery interaction is taken into account through suitable boundary conditions.The obtained equations enter the scope of the nonlinear convection-diffusion problems.We show that the resulting model is energetically consistent.The proposed model extends most extant models by adding more scope,depending on an additional viscous term.We compare both models computationally based on an Incomplete Interior Penalty Galerkin(IIPG)method for the parabolic part,and on a Runge Kutta Discontinuous Galerkin(RKDG)method for the hyperbolic part.The time discretization explicit/implicit is based on the well-known Additive Runge-Kutta(ARK)method.Moreover,through a suitable change of variables,by construction,we show that the numerical scheme is well-balanced,i.e.,it preserves exactly still-steady state solutions.To end,we numerically investigate its efficiency through several test cases with a confrontation to an exact solution.
文摘We propose a new two-dimensional blood flow reduced model taking into account of complex artery geometry as in the case of severe aneurysm.We derive the model from the three-dimensional Navier-Stokes equations written in a curvilinear coordinate system under the thin-artery assumption,with boundary conditions including wall tissue deformation.We show that the model is energetically consistent with the full Navier-Stokes problem.This model,obtained via radial averaging,is,up to our knowledge,the first one.It has the advantage of being more accurate than the classical one-dimensional models and being solved in a reasonable time in comparison with the Navier-Stokes models.To this purpose,we use a Runge-Kutta Discontinuous Galerkin(RKDG)method to solve the two-dimensional problem.We end the paper with several numerical test cases to show the efficiency and robustness of the numerical model,and in particular,we show the limit of the one-dimensional models in the case of a severe aneurysm.
