Sensitivity of inflow boundary conditions on downstream wind and turbulence profiles through building obstacles using a CFD approach

Abstract

This study investigates the sensitivity on inflow turbulence profiles for predicting the downstream wind velocity and turbulent kinetic energy profiles within the street arrays of urban environments. Computational fluid dynamics (CFD) techniques, and the realizable k–ε turbulence model are used to model the wind environment and the CFD model is validated by wind tunnel measurement. The results show that turbulence is internally generated by the upwind building obstacles. The shape and magnitude of downwind velocity and turbulence profiles are not greatly affected by different input turbulence profiles deviating from the baseline turbulence profile (within an envelope of ±50%) as the flow advances from the upstream to downstream regions within the building arrays. Various profiles of turbulent kinetic energy magnitude (within an envelope of ±50%) and with the same velocity profile are input as inlet boundary conditions to three different geometric settings, and also to an actual urban setting. Turbulent kinetic energy and wind speed ratios are obtained at different locations within the computational domain, and used as indicators for comparison and investigation. The study finds that even with a significant deviation (50%) in magnitude from the inflow turbulent kinetic energy profile, there is less than 15% difference in the wind speed and turbulent kinetic energy in the downwind region of the urban area.