A CFD simulation approach for prediction of aerodynamic and acoustic characteristics of helicopte... more A CFD simulation approach for prediction of aerodynamic and acoustic characteristics of helicopter rotors is presented. The numerical method is based on a finite-volume discretization of Navier–Stokes equations using a higher-accuracy numerical scheme for unstructured hybrid meshes.
A new technique for devising new models of turbulent viscosity for unsteady quasi-periodic flows ... more A new technique for devising new models of turbulent viscosity for unsteady quasi-periodic flows is proposed in the report. The turbulent flow simulation strategy is based on two different flowfield decompositions, the Reynolds averaging, and the phase averaging. Properties of the mean flow are recovered on the base of the time-averaging of quasi-periodic solution of the Reynolds averaged Navier-Stokes equations. This yields an upper bound for the turbulent viscosity of the Organised Eddy Simulation model. The methods under study are verified on a typical test case, the flow around a square cylinder.
We review a few recent investigations concerning LES (Large Eddy Simulation), OES (Organised Eddy... more We review a few recent investigations concerning LES (Large Eddy Simulation), OES (Organised Eddy Simulation), and Statistical Modelling works with two-equation RANS models aiming at preparing short term improvement of industrial tools for a good representation of separated, unsteady flows, involving vortex shedding. A focus will be proposed on OES modelling and on the use of wall laws. Examples will concern vortex shedding behind cylinders and airfoils, dynamic stall of multi-body airfoil. This paper is dedicated to Pierre Perrier at the occasion of the NFD2000 symposium organised in his honour.
This report proposes a linearised Euler discretisation that will be compatibl- e with some existi... more This report proposes a linearised Euler discretisation that will be compatibl- e with some existing state of art in numerical methods for compressible flows on unstructured triangulations. The important property is the use of a stabilisation terms involving sixth-order derivatives. The main idea is to realize this programme by developing a scheme that enjoys superconvergence, i.e. a high convergence order when it is applied to a cartesian triangulation. We present a test case validating the theoretical order of accuracy and the so-called Tam test case, allowing some comparisons with two other typical numerical schemes for acoustics.
Lecture Notes in Computational Science and Engineering, 2019
The method for numerical simulation of flows over moving solid bodies of complex shapes on unstru... more The method for numerical simulation of flows over moving solid bodies of complex shapes on unstructured meshes is presented. The mathematical model is based on the compressible Navier-Stokes equations. The immersed boundary penalty method, namely the Brinkman penalization method, is used to mimic the influence of the solid on the flow. This method provides a possibility to operate in simply connected domains covering the streamlined bodies and, therefore, does not require a traditional “body-fitted” mesh. The relaxation source terms (i.e. penalty functions) are added to the governing equations, to provide the required boundary condition on the fluid-solid interface. The original level set technique of tracking the moving solid boundary over the computational domain is developed. The results of numerical simulation of flow over pitching and plunging airfoil demonstrate the efficiency of the method.
The paper presents an approach to numerical simulation of airframe noise on unstructured meshes a... more The paper presents an approach to numerical simulation of airframe noise on unstructured meshes and demonstrates its workability on the slat noise case. The numerical approach implements a possibility to treat smaller movable components of the considered configuration using the Brinkman penalization method, a variant of immersed boundary techniques, complete with the mesh deformation algorithms. The computations are carried out using the higher-accuracy lower-cost EBR scheme on unstructured meshes. The developed method is aimed to reduce the computational costs needed for a series of predictions in course of optimization. II. Mathematical model and numerical approach Mathematical model For the slat noise cases presented in the paper we use the recent modifications of hybrid DDES and IDDES models [1-3] for scale resolving simulation of turbulent flows. Generally, when computing the turbulent flow over a system of bodies, we assume that the main (parent) bodies are immovable in the absolute coordinate system and keep their shapes. The smaller bodies, or details, whose shape can be changeable and which can move with respect to the main bodies are simulated by the immersed boundary (IB) method. This approach allows us to operate in simply connected domains [4-5] which noticeably simplifies the treatment of moving bodies and varying geometries. For the considered slat-wing configuration, the wing presents the main body and the slat is a movable component of changeable shape. When using the IB method for the slat case, the governing equations system is solved both in the domain F external to the slat and in the domain S occupied by the slat. To implement the Dirichlet boundary conditions for
We describe a numerical scheme for hyperbolics well adapted to both aerodynamics and aeroacoustic... more We describe a numerical scheme for hyperbolics well adapted to both aerodynamics and aeroacoustics. The scheme is vertex centered, It applies with second order accuracy to unstructured tetrahedrizations and extends to higher order (up to sixth) on a certain type of cartesian meshes. Several basic aeroacoustic numerical experiments are presented.
We propose and experiment a reconstruction finite-volume scheme for vertex-centered unstructured ... more We propose and experiment a reconstruction finite-volume scheme for vertex-centered unstructured meshes. The reconstruction is quadratic and $P_2$-exact with respect to mean cell values. The quadrature formulas for fluxes are also exact for quadratic polynomial. The resulting scheme is third-order accurate. We evaluate its accuracy on advection test cases. We apply this method to the linearised Euler model and compare it to a superconvergent mixed-element-volume scheme.
The paper describes a supercomputer application in simulations of fluid-structure interaction pro... more The paper describes a supercomputer application in simulations of fluid-structure interaction problems. A compressible flow solver based on a high-accuracy scheme for unstructured hybrid meshes is considered. It combines an immersed boundary method with a dynamic mesh adaptation method in order to represent motion of solid objects in a turbulent flow. The use of immersed boundaries allows you to dynamically adapt the mesh resolution near moving solid surfaces without changing the mesh topology. Multilevel MPI + OpenMP parallelization of these components fits well with the architecture of modern cluster systems. The proposed implementation can engage thousands of CPU cores in one simulation efficiently. An example application is presented in which a high-speed turbulent flow around a cavity with a deflector is simulated.
The problem of shrouded rotor rotation is numerically solved basing on the Navier–Stokes equation... more The problem of shrouded rotor rotation is numerically solved basing on the Navier–Stokes equations in a noninertial coordinate system. The configuration considered is a model helicopter tail rotor.The calculations are performed using edge-based reconstruction (EBR) schemes on unstructured tetrahedral grids with the variables determined at gridpoints. The numerical results on the aerodynamic forces and the acoustic radiation intensity and direction in the far field are presented and analyzed.
Russian Journal of Numerical Analysis and Mathematical Modelling, 2014
ABSTRACT An original technology of stability analysis of an airfoil boundary layer is presented i... more ABSTRACT An original technology of stability analysis of an airfoil boundary layer is presented in this paper. The technology includes an extraction of the boundary layer from the results of laminar flow computations, the computation of neutral curves and increments of Tollmien-Schlichting waves, and the computation of the location of laminar-turbulent transition zone by the e N -method for a given set of freestream turbulence levels. To be specific, we consider the flow around the NACA23012 airfoil with zero angle of attack at moderate Reynolds numbers.
A CFD simulation approach for prediction of aerodynamic and acoustic characteristics of helicopte... more A CFD simulation approach for prediction of aerodynamic and acoustic characteristics of helicopter rotors is presented. The numerical method is based on a finite-volume discretization of Navier–Stokes equations using a higher-accuracy numerical scheme for unstructured hybrid meshes.
A new technique for devising new models of turbulent viscosity for unsteady quasi-periodic flows ... more A new technique for devising new models of turbulent viscosity for unsteady quasi-periodic flows is proposed in the report. The turbulent flow simulation strategy is based on two different flowfield decompositions, the Reynolds averaging, and the phase averaging. Properties of the mean flow are recovered on the base of the time-averaging of quasi-periodic solution of the Reynolds averaged Navier-Stokes equations. This yields an upper bound for the turbulent viscosity of the Organised Eddy Simulation model. The methods under study are verified on a typical test case, the flow around a square cylinder.
We review a few recent investigations concerning LES (Large Eddy Simulation), OES (Organised Eddy... more We review a few recent investigations concerning LES (Large Eddy Simulation), OES (Organised Eddy Simulation), and Statistical Modelling works with two-equation RANS models aiming at preparing short term improvement of industrial tools for a good representation of separated, unsteady flows, involving vortex shedding. A focus will be proposed on OES modelling and on the use of wall laws. Examples will concern vortex shedding behind cylinders and airfoils, dynamic stall of multi-body airfoil. This paper is dedicated to Pierre Perrier at the occasion of the NFD2000 symposium organised in his honour.
This report proposes a linearised Euler discretisation that will be compatibl- e with some existi... more This report proposes a linearised Euler discretisation that will be compatibl- e with some existing state of art in numerical methods for compressible flows on unstructured triangulations. The important property is the use of a stabilisation terms involving sixth-order derivatives. The main idea is to realize this programme by developing a scheme that enjoys superconvergence, i.e. a high convergence order when it is applied to a cartesian triangulation. We present a test case validating the theoretical order of accuracy and the so-called Tam test case, allowing some comparisons with two other typical numerical schemes for acoustics.
Lecture Notes in Computational Science and Engineering, 2019
The method for numerical simulation of flows over moving solid bodies of complex shapes on unstru... more The method for numerical simulation of flows over moving solid bodies of complex shapes on unstructured meshes is presented. The mathematical model is based on the compressible Navier-Stokes equations. The immersed boundary penalty method, namely the Brinkman penalization method, is used to mimic the influence of the solid on the flow. This method provides a possibility to operate in simply connected domains covering the streamlined bodies and, therefore, does not require a traditional “body-fitted” mesh. The relaxation source terms (i.e. penalty functions) are added to the governing equations, to provide the required boundary condition on the fluid-solid interface. The original level set technique of tracking the moving solid boundary over the computational domain is developed. The results of numerical simulation of flow over pitching and plunging airfoil demonstrate the efficiency of the method.
The paper presents an approach to numerical simulation of airframe noise on unstructured meshes a... more The paper presents an approach to numerical simulation of airframe noise on unstructured meshes and demonstrates its workability on the slat noise case. The numerical approach implements a possibility to treat smaller movable components of the considered configuration using the Brinkman penalization method, a variant of immersed boundary techniques, complete with the mesh deformation algorithms. The computations are carried out using the higher-accuracy lower-cost EBR scheme on unstructured meshes. The developed method is aimed to reduce the computational costs needed for a series of predictions in course of optimization. II. Mathematical model and numerical approach Mathematical model For the slat noise cases presented in the paper we use the recent modifications of hybrid DDES and IDDES models [1-3] for scale resolving simulation of turbulent flows. Generally, when computing the turbulent flow over a system of bodies, we assume that the main (parent) bodies are immovable in the absolute coordinate system and keep their shapes. The smaller bodies, or details, whose shape can be changeable and which can move with respect to the main bodies are simulated by the immersed boundary (IB) method. This approach allows us to operate in simply connected domains [4-5] which noticeably simplifies the treatment of moving bodies and varying geometries. For the considered slat-wing configuration, the wing presents the main body and the slat is a movable component of changeable shape. When using the IB method for the slat case, the governing equations system is solved both in the domain F external to the slat and in the domain S occupied by the slat. To implement the Dirichlet boundary conditions for
We describe a numerical scheme for hyperbolics well adapted to both aerodynamics and aeroacoustic... more We describe a numerical scheme for hyperbolics well adapted to both aerodynamics and aeroacoustics. The scheme is vertex centered, It applies with second order accuracy to unstructured tetrahedrizations and extends to higher order (up to sixth) on a certain type of cartesian meshes. Several basic aeroacoustic numerical experiments are presented.
We propose and experiment a reconstruction finite-volume scheme for vertex-centered unstructured ... more We propose and experiment a reconstruction finite-volume scheme for vertex-centered unstructured meshes. The reconstruction is quadratic and $P_2$-exact with respect to mean cell values. The quadrature formulas for fluxes are also exact for quadratic polynomial. The resulting scheme is third-order accurate. We evaluate its accuracy on advection test cases. We apply this method to the linearised Euler model and compare it to a superconvergent mixed-element-volume scheme.
The paper describes a supercomputer application in simulations of fluid-structure interaction pro... more The paper describes a supercomputer application in simulations of fluid-structure interaction problems. A compressible flow solver based on a high-accuracy scheme for unstructured hybrid meshes is considered. It combines an immersed boundary method with a dynamic mesh adaptation method in order to represent motion of solid objects in a turbulent flow. The use of immersed boundaries allows you to dynamically adapt the mesh resolution near moving solid surfaces without changing the mesh topology. Multilevel MPI + OpenMP parallelization of these components fits well with the architecture of modern cluster systems. The proposed implementation can engage thousands of CPU cores in one simulation efficiently. An example application is presented in which a high-speed turbulent flow around a cavity with a deflector is simulated.
The problem of shrouded rotor rotation is numerically solved basing on the Navier–Stokes equation... more The problem of shrouded rotor rotation is numerically solved basing on the Navier–Stokes equations in a noninertial coordinate system. The configuration considered is a model helicopter tail rotor.The calculations are performed using edge-based reconstruction (EBR) schemes on unstructured tetrahedral grids with the variables determined at gridpoints. The numerical results on the aerodynamic forces and the acoustic radiation intensity and direction in the far field are presented and analyzed.
Russian Journal of Numerical Analysis and Mathematical Modelling, 2014
ABSTRACT An original technology of stability analysis of an airfoil boundary layer is presented i... more ABSTRACT An original technology of stability analysis of an airfoil boundary layer is presented in this paper. The technology includes an extraction of the boundary layer from the results of laminar flow computations, the computation of neutral curves and increments of Tollmien-Schlichting waves, and the computation of the location of laminar-turbulent transition zone by the e N -method for a given set of freestream turbulence levels. To be specific, we consider the flow around the NACA23012 airfoil with zero angle of attack at moderate Reynolds numbers.
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