Large-Eddy Simulation of Heat Transfer Around a Square Cylinder Using Unstructured Grids

Abstract

This paper presents a method of large eddy simulation on unstructured grids designed to predict the wall heat transfer in typical aeronautical applications featuring turbulent flows and complex geometries. Two types of wall treatment are considered: a wall-function model using a full tetrahedral grid and a wall-resolved method computed on a hybrid tetrahedral-prismatic grid. These two approaches are tested against the square cylinder case at moderate Reynolds number (Re = 22 050) where many reference data are available for flow dynamics and heat transfer. Both predict accurately the unsteady flow around the cylinder and in its near-wake but only the wall-resolved approach reproduces the Nusselt number global value and its spatial distribution around the cylinder wall. This latter method is used to investigate the coupling between periodic vortex shedding and wall heat transfer using a phase-averaged analysis. Nomenclature CD = drag coefficient C f = algebraic friction coefficient Cp = pressure coefficient

Joint experimental and numerical study of the influence of flame holder temperature on the stabilization of a laminar methane flame on a cylinder

“…An unstructured hybrid mesh is used to accurately capture the conjugate heat transfer between the solid and the reactive flow [38,39] . Five layers of quad elements are used outside of the cylinder boundary (flow region) and ten are used inside (solid region).…”

Large Eddy Simulations of flow around a circular cylinder close to a flat seabed

“…A three-dimensional LES model is therefore utilized in the present study. LES were also used to simulate the flow around a square cylinder in the vicinity of a plane wall, at a comparable Re = 22000; [16] and [17] provided promising results and good comparison to the experimental research.…”

Large Eddy Simulation of Flow and Heat Transfer Around Two Square Cylinders in a Tandem Arrangement

“…The stretching ratio between the height of an inner layer to the adjacent outer layer has been set to 1:13, leading to a prism aspect ratio of Ax/Ah = 1.83 -2.45 in the outer layer. The proper height of the inner prism layer (Ah/D) has been determined by a mesh convergence study based on the global Nusselt number Nu for an isolated square cylinder compared to the experimental correlation of Igarashi [4], A previous study has shown that A h/D < 0.002 is required to match the empirical Nusselt number for a Reynolds number of Re = 22,050 [31]. Using this mesh con straint in the near-wall region and the mentioned sizes in other regions leads to a grid of 3 x 106 nodes (12 x 106 cells).…”

“…The parallel LES code [29][30][31] solves the full compressible Navier-Stokes equations using a cellvertex/finite element approximation and Taylor-Galerkin weighted residual central distribution scheme [32] on unstructured grids. This explicit scheme provides third-order accuracy on hybrid meshes and satisfies low-dissipation requirements of LES applications [33], The explicit time step At is imposed by the Courant-Friedrichs-Lewy number condition, CFL = ( ( t / + cjAr/Ax) = 0 .7 , where Ax is the size of the grid cell while U and c are the flow and sound local velocities, respectively.…”