Abstract
Abstract. This paper describes MicroHH 1.0, a new and open-source (www.microhh.org) computational fluid dynamics code for the simulation of turbulent flows in the atmosphere. It is primarily made for direct numerical simulation but also supports large-eddy simulation (LES). The paper covers the description of the governing equations, their numerical implementation, and the parameterizations included in the code. Furthermore, the paper presents the validation of the dynamical core in the form of convergence and conservation tests, and comparison of simulations of channel flows and slope flows against well-established test cases. The full numerical model, including the associated parameterizations for LES, has been tested for a set of cases under stable and unstable conditions, under the Boussinesq and anelastic approximations, and with dry and moist convection under stationary and time-varying boundary conditions. The paper presents performance tests showing good scaling from 256 to 32 768 processes. The graphical processing unit (GPU)-enabled version of the code can reach a speedup of more than an order of magnitude for simulations that fit in the memory of a single GPU.
Highlights
1 Introduction In this paper, we present a description of MicroHH 1.0, a new computational fluid dynamics code for the simulation of turbulent flows in doubly periodic domains, with a focus on those in the atmosphere
MicroHH is designed for the direct numerical simulation (DNS) technique and supports the large-eddy simulation (LES) technique
The implementation of a dynamical core that is fully fourth order in space, which is very beneficial for DNS, but to retain the option to switch to second-order accuracy for LES, required a new code design
Summary
We present a description of MicroHH 1.0, a new computational fluid dynamics code for the simulation of turbulent flows in doubly periodic domains, with a focus on those in the atmosphere. The simulation algorithms have been designed and are written from scratch with the goal to create a fast and highly parallel code that is able to run on machines with more than 10 000 cores. It is a key requirement for the code to be able to perform DNS at very high Reynolds numbers or to conduct LES at very fine grids (grid spacing less than 1 m), or in domains that approach the synoptic scales (beyond 1000 km). There is a short description of where to get MicroHH, and where to find its tutorials and a selection of visualizations (see code availability section)
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