The application of multilevel multi-integration to the calculation of the elastic deformation int... more The application of multilevel multi-integration to the calculation of the elastic deformation integrals and the use of an alternative relaxation process in the multilevel solution of the governing equations have resulted in an algorithm solving the EHL line contact problem in O(n ln n) operations, also for highly loaded situations. The reduction in computing time thus obtained was used to solve the problem using large numbers of nodal points and to study the pressure spike. The presented algorithm will enable fast and accurate solution of surface roughness and transient problems.
We discretise convective and diffusive operators such that their spectral properties are preserve... more We discretise convective and diffusive operators such that their spectral properties are preserved, i.e. convection ↔ skew-symmetric; diffusion ↔ symmetric, positive definite. Such a symmetry-preserving discretisation is used to perform a direct numerical simulation of a fully developed turbulent flow in a channel, where a matrix of cubes is mounted at one wall of the channel. The Reynolds number (based on the channel width and the mean bulk velocity) is equal to Re=13,000. The computed mean velocity profiles and Reynolds stresses agree well with the available experimental data.
This poster shows how HPCN can be used as a path-#nding toolfor turbulence research. The parallel... more This poster shows how HPCN can be used as a path-#nding toolfor turbulence research. The parallelization of direct numerical simulationof turbulent#ow using the data-parallel model and Fortran 95 constructs istreated, both on a shared memory and a distributed memory computer.
Flows around bluff bodies, a circular cylinder for instance, are difficult to simulate accurately... more Flows around bluff bodies, a circular cylinder for instance, are difficult to simulate accurately with a RANS method. To improve this type of simulations, LES models are considered in this paper. The idea behind these models is to minimize the subgrid dissipation. The models are based on the invariants of the rate of strain tensor. Also the governing equations are discretized such that less artificial dissipation is added. To proposed LES models are compared to an ILES model. The ILES model introduces artificial dissipation originating from the discretization of the governing equations. The comparison is performed using MARIN’s in-house CFD solver ReFRESCO. A flow around a circular cylinder with Re = 3, 900 is considered here to evaluate the LES models. The (I)LES models clearly perform better than no model. The differences between the turbulence models, however, were small.
This article deals with a numerical method for solving the unsteady, incompressible Navier–Stokes... more This article deals with a numerical method for solving the unsteady, incompressible Navier–Stokes equations in domains with arbitrarily-shaped boundaries, where the boundary is represented using the Cartesian grid approach. We introduce a novel cut-cell discretization which preserves the spectral properties of convection and diffusion. Here, convection is discretized by a skew-symmetric operator and diffusion is approximated by a symmetric, positive-definite coefficient matrix. Such a symmetrypreserving discretization conserves the kinetic energy (if the dissipation is turned off) and is stable on any grid. The method is successfully tested for an incompressible, unsteady flow around a circular cylinder at Re = 100. To cite this article: R. Verstap
We propose to discretize the convective and diffusive operators in the (incom- pressible) Navier-... more We propose to discretize the convective and diffusive operators in the (incom- pressible) Navier-Stokes equations in such a manner that their symmetries are preserved. The resulting spatial discretization inherits all symmetry-related conservation and stability properties from the continuous formulation. In particularly, a symmetry-preserving discretization is unconditionally stable, and conserves the energy in the absense of viscous dissipation. In this paper, a fourth-order, symmetry-preserving discretization method is described and tested successfully for direct numerical simulation of turbulent channel flow.
The application of multilevel multi-integration to the calculation of the elastic deformation int... more The application of multilevel multi-integration to the calculation of the elastic deformation integrals and the use of an alternative relaxation process in the multilevel solution of the governing equations have resulted in an algorithm solving the EHL line contact problem in O(n ln n) operations, also for highly loaded situations. The reduction in computing time thus obtained was used to solve the problem using large numbers of nodal points and to study the pressure spike. The presented algorithm will enable fast and accurate solution of surface roughness and transient problems.
We discretise convective and diffusive operators such that their spectral properties are preserve... more We discretise convective and diffusive operators such that their spectral properties are preserved, i.e. convection ↔ skew-symmetric; diffusion ↔ symmetric, positive definite. Such a symmetry-preserving discretisation is used to perform a direct numerical simulation of a fully developed turbulent flow in a channel, where a matrix of cubes is mounted at one wall of the channel. The Reynolds number (based on the channel width and the mean bulk velocity) is equal to Re=13,000. The computed mean velocity profiles and Reynolds stresses agree well with the available experimental data.
This poster shows how HPCN can be used as a path-#nding toolfor turbulence research. The parallel... more This poster shows how HPCN can be used as a path-#nding toolfor turbulence research. The parallelization of direct numerical simulationof turbulent#ow using the data-parallel model and Fortran 95 constructs istreated, both on a shared memory and a distributed memory computer.
Flows around bluff bodies, a circular cylinder for instance, are difficult to simulate accurately... more Flows around bluff bodies, a circular cylinder for instance, are difficult to simulate accurately with a RANS method. To improve this type of simulations, LES models are considered in this paper. The idea behind these models is to minimize the subgrid dissipation. The models are based on the invariants of the rate of strain tensor. Also the governing equations are discretized such that less artificial dissipation is added. To proposed LES models are compared to an ILES model. The ILES model introduces artificial dissipation originating from the discretization of the governing equations. The comparison is performed using MARIN’s in-house CFD solver ReFRESCO. A flow around a circular cylinder with Re = 3, 900 is considered here to evaluate the LES models. The (I)LES models clearly perform better than no model. The differences between the turbulence models, however, were small.
This article deals with a numerical method for solving the unsteady, incompressible Navier–Stokes... more This article deals with a numerical method for solving the unsteady, incompressible Navier–Stokes equations in domains with arbitrarily-shaped boundaries, where the boundary is represented using the Cartesian grid approach. We introduce a novel cut-cell discretization which preserves the spectral properties of convection and diffusion. Here, convection is discretized by a skew-symmetric operator and diffusion is approximated by a symmetric, positive-definite coefficient matrix. Such a symmetrypreserving discretization conserves the kinetic energy (if the dissipation is turned off) and is stable on any grid. The method is successfully tested for an incompressible, unsteady flow around a circular cylinder at Re = 100. To cite this article: R. Verstap
We propose to discretize the convective and diffusive operators in the (incom- pressible) Navier-... more We propose to discretize the convective and diffusive operators in the (incom- pressible) Navier-Stokes equations in such a manner that their symmetries are preserved. The resulting spatial discretization inherits all symmetry-related conservation and stability properties from the continuous formulation. In particularly, a symmetry-preserving discretization is unconditionally stable, and conserves the energy in the absense of viscous dissipation. In this paper, a fourth-order, symmetry-preserving discretization method is described and tested successfully for direct numerical simulation of turbulent channel flow.
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Papers by Roel Verstappen