Kojiro Nozawa

Large eddy simulation of the flow around a low-rise building immersed in a rough-wall turbulent boundary layer

Abstract The objective of this paper is to validate the large eddy simulation (LES) technique for predicting a flow around an obstacle under the condition that a turbulent flow is approaching the obstacle. The turbulent inflow data were generated for both a smooth surface and rough surfaces by the method we had proposed. A half-height cube was immersed in the turbulent boundary layers with several types of vertical velocity profile. With regard to the pressure distributions on the surface of the half-height cube, the computed time-averaged and rms values are in good agreement with previous experimental ones. However, the peak pressure coefficients are underestimated, especially compared to full-scale data.

Numerical prediction of wind loading on buildings and structures : Activities of AIJ cooperative project on CFD

This study presents the activities of the Architectural Institute of Japan (AIJ) concerning the Computational Fluid Dynamics (CFD) for a numerical prediction of wind loading on buildings and structures. In the AIJ project, the flows and the pressures around a low-rise building (breadth : depth : height = 1 : 1 : 0.5) have been computed by 10 members of the working group, who mainly employed the κ-e model or the large eddy simulation for turbulent flows. Here, on the basis of the results of the AIJ project, future subjects for further development of the CFD technique are discussed. Also we present how to find the way to realize the practical use of the CFD technique on prediction of wind loading.

Les of Flow Past a Square Cylinder Using Embedded Meshes

This paper presents the result of a large-eddy simulation of the complicated turbulent flow past a square cylinder. The technique of embedded meshes is employed for the computation of turbulent flows with various scales. We also apply the 3rd-order upwind scheme (Kawamura et al., 1984) to the convective terms to avoid numerical instability.

Large Eddy Simulation of a Turbulent Boundary Layer Flow over Urban-Like Roughness

In this study, Large Eddy Simulation of a boundary layer flow over large-scale roughness was performed targeting the experiments conducted by Cheng and Castro (2). In order to duplicate the experimental conditions, the quasi-periodic boundary method for rough-wall boundary flows was applied to the inlet boundary conditions. The characteristics of the turbulent boundary layer flows over urban-like roughness (with a roughness area density of 25% and a boundary layer height ratio δ/h around 7) are different from the common homogenous with δ/h larger than 50. The spatial variation of vertical profiles of mean and fluctuation velocities are studied in detail and compared to the experimental data. We focus on the influence on the spatial variations of turbulence structure deduced by large-scale roughness.