Effects of turbulence on the mean pressure field in the separated-reattaching flow above a low-rise building

Abstract

The effects of upstream turbulence in the atmospheric boundary layer flow on the mean surface pressure distribution within the separated flow above a typical low-rise building roof are investigated experimentally. Time-averaged Navier-Stokes equations are used to evaluate the pressure gradients from planar particle image velocimetry data. The pressure fields are reconstructed by integrating the pressure gradients using an analytic interpolation approach. This reconstruction approach is validated by successfully matching the reconstructed pressure to Bernoulli's equation along a streamline far from the body and with pressure measurements on the surface of the body. Through this process, the mean pressure field can be directly explained from the mean velocity and turbulence fields near the roof. For high turbulence intensity levels, the maximum suction coefficient on the roof surface was found to be increased. Such increased magnitudes are directly related to the reduced size of mean separation bubble in higher turbulence, more rapid variation of the velocity magnitude near the leading edge, and enhanced variation of the turbulence stresses. On the other hand, a higher rate of surface pressure recovery is found in the leeward portion of the separation bubble, which is mainly due to the more rapid variation of the turbulence stresses.