Role of Inflow Turbulence and Surrounding Buildings on Large Eddy Simulations of Urban Wind Energy

Giulio Vita,Simone Salvadori,Syeda Anam Hashmi,Charalampos Baniotopoulos,Hassan Hemida

doi:10.3390/en13195208

Abstract

Predicting flow patterns that develop on the roof of high-rise buildings is critical for the development of urban wind energy. In particular, the performance and reliability of devices largely depends on the positioning strategy, a major unresolved challenge. This work aims at investigating the effect of variations in the turbulent inflow and the geometric model on the flow patterns that develop on the roof of tall buildings in the realistic configuration of the University of Birmingham’s campus in the United Kingdom (UK). Results confirm that the accuracy of Large Eddy Simulation (LES) predictions is only marginally affected by differences in the inflow mean wind speed and turbulence intensity, provided that turbulence is not absent. The effect of the presence of surrounding buildings is also investigated and found to be marginal to the results if the inflow is turbulent. The integral length scale is the parameter most affected by the turbulence characteristics of the inflow, while gustiness is only marginally influenced. This work will contribute to LES applications on the urban wind resource and their computational setup simplification.

Highlights

Urban wind energy (UWE) is a branch of wind energy which has shown poor success, questioning the sensibility of harvesting wind in the urban environment, and hampering the public image of the whole wind energy sector [1]
The majority of studies on urban wind energy focus on the parametrization of the shape of high-rise buildings aimed at maximizing mean wind speed and minimizing turbulence, often without addressing the validation of results or attempting to deepen the knowledge on how turbulence is generated from the building or how turbulent coherent structures interact with obstacles [2,6,7]
While coarsening the mesh is not recommended in literature [6,27], research has started pushing the boundaries of coarse Large Eddy Simulations (LES) to increase its practicality

Summary

Introduction

Urban wind energy (UWE) is a branch of wind energy which has shown poor success, questioning the sensibility of harvesting wind in the urban environment, and hampering the public image of the whole wind energy sector [1]. Key to a good positioning strategy is through predicting flows in the urban environment [2,3]. Simulations tailored to assess the wind energy resource have only been conducted in a handful of studies, all reviewed in a recent significant paper [4]. Of the studies focusing on the wind energy resource, only 18% deals with a realistic urban setup, and 10% is conducted using Large Eddy Simulations (LES) [4], a numerical technique able to solve the inertial scales of turbulent flows. Navier-Stokes (RANS) models to predict wind conditions found in urban areas [4]. Only a single study has modelled urban winds for wind energy harvesting purposes using LES over a non-uniform array of cubes [5]. The majority of studies on urban wind energy focus on the parametrization of the shape of high-rise buildings aimed at maximizing mean wind speed and minimizing turbulence, often without addressing the validation of results or attempting to deepen the knowledge on how turbulence is generated from the building or how turbulent coherent structures interact with obstacles [2,6,7]

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Conclusion