A new large-eddy simulation model for simulating air flow and warm clouds above highly complex terrain. Part I: The dry model |
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| Authors: | Daniel Reinert Volkmar Wirth Joachim Eichhorn Walter-Georg Panhans |
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| Institution: | (1) Institute for Atmospheric Physics, Johannes Gutenberg-University Mainz, Becherweg 21, 55099 Mainz, Germany |
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| Abstract: | This paper presents the dry version of a new large-eddy simulation (LES) model, which is designed to simulate air flow and
clouds above highly complex terrain. The model is three-dimensional and nonhydrostatic, and the governing equations are sound
filtered by use of the anelastic approximation. A fractional step method is applied to solve the equations on a staggered
Cartesian grid. Arbitrarily steep and complex orography can be accounted for through the method of viscous topography. The
dynamical model core is validated by comparing the results for a spreading density current against a benchmark solution. The
model accuracy is further assessed through the simulation of turbulent flow across a quasi two-dimensional ridge. The results
are compared with wind-tunnel data. The method of viscous topography is not restricted to moderately sloped terrain. Compared
to models using curvilinear grids, it allows this model to be applied to a much wider range of flows. This is illustrated
through the simulation of an atmospheric boundary-layer flow over a surface mounted cube. The results show that the dry model
version is able to accurately represent the complex flow in the vicinity of three-dimensional obstacles. It is concluded that
the method of viscous topography was successfully implemented into a micrometeorological LES model. As will be shown in Part
II, this allows the detailed study of clouds in highly complex terrain. |
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| Keywords: | Complex orography Inflow turbulence Large-eddy simulation Turbulent flow |
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