Abstract:The control of two-dimensional flows around the square back Ahmed body is achieved using porous devices added on some parts of the body. The square back Ahmed body is considered either in an open domain or on top of a road. The modelling of the flow in different media is performed by means of the penalisation method. A good choice of the location of the porous interfaces yields a significant improvement of the aerodynamic quantities, specially for the square back body.
“…Besides, the two-dimensional patterns of vortex shedding from a bluff body have the same qualitative features of the fully developed turbulent phase-averaged results [24]. It may be noted that the previous studies reported on this topic [10][11][12][13] considered certain discrete values of Re in the transitional and turbulent range, and restricted to a two-dimensional analysis. In the turbulent range of Reynolds number, the Darcy-Brinkman model becomes questionable due to the inertial fluctuation of the velocity field in the porous zone.…”
SUMMARYA numerical study on the laminar vortex shedding and wake flow due to a porous-wrapped solid circular cylinder has been made in this paper. The cylinder is horizontally placed, and is subjected to a uniform cross flow. The aim is to control the vortex shedding and drag force through a thin porous wrapper around a solid cylinder. The flow field is investigated for a wide range of Reynolds number in the laminar regime. The flow in the porous zone is governed by the Darcy-Brinkman-Forchheimer extended model and the Navier-Stokes equations in the fluid region. A control volume approach is adopted for computation of the governing equations along with a second-order upwind scheme, which is used to discretize the convective terms inside the fluid region. The inclusion of a thin porous wrapper produces a significant reduction in drag and damps the oscillation compared with a solid cylinder. Dependence of Strouhal number and drag coefficient on porous layer thickness at different Reynolds number is analyzed. The dependence of Strouhal number and drag on the permeability of the medium is also examined.
“…Besides, the two-dimensional patterns of vortex shedding from a bluff body have the same qualitative features of the fully developed turbulent phase-averaged results [24]. It may be noted that the previous studies reported on this topic [10][11][12][13] considered certain discrete values of Re in the transitional and turbulent range, and restricted to a two-dimensional analysis. In the turbulent range of Reynolds number, the Darcy-Brinkman model becomes questionable due to the inertial fluctuation of the velocity field in the porous zone.…”
SUMMARYA numerical study on the laminar vortex shedding and wake flow due to a porous-wrapped solid circular cylinder has been made in this paper. The cylinder is horizontally placed, and is subjected to a uniform cross flow. The aim is to control the vortex shedding and drag force through a thin porous wrapper around a solid cylinder. The flow field is investigated for a wide range of Reynolds number in the laminar regime. The flow in the porous zone is governed by the Darcy-Brinkman-Forchheimer extended model and the Navier-Stokes equations in the fluid region. A control volume approach is adopted for computation of the governing equations along with a second-order upwind scheme, which is used to discretize the convective terms inside the fluid region. The inclusion of a thin porous wrapper produces a significant reduction in drag and damps the oscillation compared with a solid cylinder. Dependence of Strouhal number and drag coefficient on porous layer thickness at different Reynolds number is analyzed. The dependence of Strouhal number and drag on the permeability of the medium is also examined.
“…2) with a 1920 Â 640 cells uniform mesh and X = (0, 12) Â (0, 6) Â (0, 4) in three dimensions with a 768 Â 384 Â 256 cells uniform mesh. The grid convergence for the same geometry has been studied in [6] and the grid 960 Â 320 corresponds already to the finest grid required. The velocity vector is U = (u, w) in two dimensions and U = (u, v,w) in three-dimensions.…”
Section: Modelling and Numerical Simulationmentioning
confidence: 99%
“…A control using porous layers is widely studied in [6] for the square back Ahmed body on top of a road. The main difference with the previous study is the distance between the body and the road that is equal to H in [6] and to 0.6H here as in the original benchmark [2].…”
Section: Passive Control Using Porous Layersmentioning
confidence: 99%
“…In a recent work Bruneau et al [6] introduced a passive control technique using a porous slice implemented on some parts of the two-dimensional square back Ahmed body in a free domain or on top of a road, reducing global quantities such as the drag coefficient, the enstrophy or the C Lrms of the flow. This new passive approach seems very promising as significant gains were obtained with a good choice of the layers location.…”
“…Indeed, in the car industry the most important aerodynamic parameter is the drag coefficient C D . A large number of simulations,with different porous layer locations,were performed to verify how far this passive control technique can contribute to the drag reduction [11]. In the following,only the most significant results are presented starting with the square back geometry.…”
Section: Control Of the Drag Coefficient Of Ground Vehiclesmentioning
The whole flow over a solid body covered by a porous layer is presented. The three main models used in the literature to compute efficiently the fluid flow are given: the reduction of the porous layer to a boundary condition, the coupling of Darcy equation with Navier-Stokes equations and the Brinkman-Navier-Stokes equations or the penalisation method. Numerical simulations on Cartesian grids using the latest model give easily accurate solutions of the flow around solid bodies with or without porous layers. Adding appropriate porous devices to the solid bodies, an efficient passive control of the two-dimensional incompressible flow is achieved. A strong regularisation of the flow is observed and a significant reduction of the vortex induced vibrations or the drag coefficient is obtained.
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