Urban Large-Eddy Simulation

The animation displays the development of turbulence structures induced by a densely built-up artificial island off the coast of Macau. Animation data were derived using the parallelized large-eddy simulation model PALM (http://palm.muk.uni-hannover.de/), simulating a neutrally stratified flow over Macau, with a mean flow from the southeast to the northwest and a 10-m wind of approximately 1m/s. The vertical direction of the model domain is stretched by a factor of 3 for better visualization. Turbulence structures and intensities are visualized by the rotation of the velocity vector (absolute values), with highest values in red and lowest values in white . Buildings are displayed in blue. The animation spans over 1 hour with a time-lapse factor of 43, and was created with the visualization software VAPOR (https://www.vapor.ucar.edu/). The total PALM model domain had a size of 768 x 256 x 96 grid points in streamwise, spanwise and vertical direction, with a uniform grid spacing of 8m in each direction . Above 400m the vertical grid spacing is successively stretched up to a maximum vertical grid spacing of 40m. Non-cyclic boundary conditions are used in streamwise direction and a turbulence recycling method is applied, in order to guarantee a fully turbulent inflow. In total, the simulation required 1 hour of CPU time using 128 cores on the Cray-XC30 of the North-German Supercomputing Alliance (https://www.hlrn.de/).