High-resolution large-eddy simulations of simplified urban flows

TL;DR

This study uses high-resolution large-eddy simulations to analyze turbulent flow around two obstacles in different regimes, revealing detailed flow structures and turbulence behaviors relevant for urban flow modeling.

Contribution

It provides detailed LES data on flow regimes around multiple obstacles, highlighting flow interactions and turbulence characteristics in simplified urban flow scenarios.

Findings

Turbulence activity varies significantly across flow regimes.

Strong interactions occur between obstacles in wake-interference regimes.

Flow around obstacles exhibits distinct regions of turbulence and separation.

Abstract

High-fidelity large-eddy simulations of the flow around two rectangular obstacles are carried out at a Reynolds number of 10,000 based on the free-stream velocity and the obstacle height. The incoming flow is a developed turbulent boundary layer. Mean-velocity components, turbulence fluctuations, and the terms of the turbulent-kinetic-energy budget are analyzed for three flow regimes: skimming flow, wake interference, and isolated roughness. Three regions are identified where the flow undergoes the most significant changes: the first obstacle's wake, the region in front of the second obstacle, and that around the second obstacle. In the skimming-flow case, turbulence activity in the cavity between the obstacles is limited and mainly occurs in a small region in front of the second obstacle. In the wake-interference case, there is a strong interaction between the free-stream flow that penetrates the cavity and the wake of the first obstacle. This interaction results in more intense turbulent fluctuations between the obstacles. In the isolated-roughness case, the wake of the first obstacle is in good agreement with that of an isolated obstacle. Separation bubbles with strong turbulent fluctuations appear around the second obstacle.