GRID CONVERGENCE INDEX ESTMATION OF LARGE EDDY SIMULATION FOR TURBULENT HEAT TRANSFER FLOW USING NEK5000

Abstract

Large eddy simulation is performed in heat transfer of turbulent flow with NEK5000 code based on spectral element method to study uncertainty quantification by Grid Convergence Index. Two geometries are investigated including simple geometrical configurations, pipe flow, and more complex geometrical configurations, rod bundle flow. The turbulent pipe flow with heat transfer is considered with Reynolds number Re = 19,000 and Prandtl number Pr = 0.71. Three meshes (fine, medium, and coarse) with the fixed interpolation polynomial order, 8 and three orders (4th, 6th, and 8th) of interpolation polynomial with the fine mesh are examined. The effects of different grid and interpolation polynomial order are studied to highlight the effectiveness of high order spectral element. The Grid Convergence Index using two modified versions from original Roache’s GCI method are estimated based on simulation results. Two modified versions include the modification of Roache’s GCI method described in the ASME V&V 20-2009 guideline and the simplified least square method version GCI. Though GCI estimation, it was found that the accuracy of the SLS – GCI method is better than that by Mod. – ASME. The rod bundle simulation takes the advantage of the symmetries of the domain that can be divided into twelve homologous sections. The rod is chosen with the case of P/D = 1.24 with Reynold number Re = 10,000 and Prandtl number Pr = 1.0. Three meshes (fine, medium, and coarse) with the fixed interpolation polynomial order of 7th order are examined to study quantify the uncertainty by GCI estimation with SLS – GCI method.