実在都市における中立大気境界層内の乱流組織構造

Abstract

Turbulence coherent structures over an actual urban area, Kyoto, under a neutrally stratified condition is investigated by conducting large-eddy simulations(LESs). To validate the LES, we compare LES results with observational data at Ujigawa Open Laboratory included in the computational region. The vertical profiles of mean velocity and the streamwise velocity power spectra in the LES are qualitatively consistent with the observations. The instantaneous velocity field in the horizontal plane shows that low and high momentum regions elongated in the streamwise direction exits over an actual urban area. In addition, the field indicates low and high momentum regions with ejection and sweep, respectively. Conditionally averaged velocity field shows counter-rotating vortex pair. The instantaneous spanwise velocity component field in the vertical plane also indicates the vortex pair. These characteristics are similar to results from turbulent flows both over block arrays and over a smooth surface.