Nested Multi-scale System in the PALM Large-Eddy Simulation Model

Abstract

Large-Eddy Simulation (LES) of atmospheric boundary layer (ABL) is becoming an important research method for urban air-quality studies. Until very recently, it was impossible to include detailed structures, such as buildings in ABL LES. Nowadays, it is possible, but such LES is still limited to a relatively small areas because typically about 1 m resolution is required. However, for several reasons an ABL LES domain should cover a large area leading to huge computational task. A means to overcome this is to concentrate resolution to the primary area of interest by means of model nesting. The idea of nesting is to simultaneously run a series of two or more LES in domains with different sizes and resolutions. In this work, two-way nesting is implemented in the parallelized LES model PALM. The nesting system is tested for several test cases including a convective boundary layer with zero mean wind, several neutral boundary layers over both flat terrain and terrain with an array of obstacles.