Assessing the Horizontal Homogeneity of the Atmospheric Boundary Layer (HHABL) Profile Using Different CFD Software

Islam Abohela,Elsa Aristodemou,Abas Hadawey,Raveendran Sundararajan

doi:10.3390/atmos11101138

Abstract

One of the main factors affecting the reliability of computational fluid dynamics (CFD) simulations for the urban environment is the Horizontal Homogeneity of the Atmospheric Boundary Layer (HHABL) profile—meaning the vertical profiles of the mean streamwise velocity, the turbulent kinetic energy, and dissipation rate are maintained throughout the streamwise direction of the computational domain. This paper investigates the preservation of the HHABL profile using three different commercial CFD codes—the ANSYS Fluent, the ANSYS CFD, and the Siemens STAR-CCM+ software. Three different cases were considered, identified by their different inlet conditions for the inlet velocity, turbulent kinetic energy, and dissipation rate profiles. Simulations were carried out using the RANS k-ε turbulence model. Slight variations in the eddy viscosity models, as well as in the wall boundary conditions, were identified in the different software, with the standard wall function with roughness being implemented in the Fluent applications, the scalable wall function with roughness in the CFX applications, and the blended wall function option in the STAR-CCM+ simulations. There was a slight difference in the meshing approach in the three different software, with a prism-layer option in the STAR-CCM+ software, which allowed a finer mesh near the wall/ground boundary. The results show all three software are able to preserve the horizontal homogeneity of the ABL—less than 0.5% difference between the software—indicating very similar degrees of accuracy.

Highlights

This work is part of a research project aiming to study the optimum mounting locations of roof-mounted wind turbines on isolated buildings using computational fluid dynamics (CFD), with the implementation of existing commercial CFD software
This paper aims to investigate the horizontal homogeneity of the Homogeneity of the Atmospheric Boundary Layer (HHABL) profile using three commercial CFD
The work presented in this paper looks at a detailed analysis of the HHABL profile through the variations of three parameters, namely the streamwise velocity (u), the turbulent kinetic energy (TKE), and the turbulent dissipation rate (TDR), through an empty domain

Summary

Introduction

This work is part of a research project aiming to study the optimum mounting locations of roof-mounted wind turbines on isolated buildings using computational fluid dynamics (CFD), with the implementation of existing commercial CFD software. It is crucial/important to investigate how different commercial software respond to the HHABL profile challenge. Numerical simulation methods, including computational fluid dynamics (CFD), is one of the primary assessment tools for urban physics [1]. CFD simulation can be used as a tool for informed decision-making in urban design applications [8]. CFD simulations are embedded with errors and uncertainties linked with the numerical diffusion due Atmosphere 2020, 11, 1138; doi:10.3390/atmos11101138 www.mdpi.com/journal/atmosphere

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