Search Results

You are looking at 1 - 4 of 4 items for :

  • Author or Editor: D. S. Henn x
  • Journal of the Atmospheric Sciences x
  • Refine by Access: All Content x
Clear All Modify Search
R. I. Sykes and D. S. Henn

Abstract

Numerical calculations of two-dimensional convection between flat plates at high Rayleigh numbers are presented. They do not show the large cell aspect ratios observed by Rothermel and Agee in their numerical calculations at high Rayleigh numbers. The present results appear to be insensitive to grid resolution, the conventional test of numerical accuracy, large amplitude random perturbations and the numerical representation of the diffusion term. We therefore suggest that the mechanism observed by Rothermel and Agee, which produces increasingly larger aspect ratio cells with increasing Rayleigh number, is strongly influenced by the numerical method used to solve the equations.

Full access
R. I. Sykes and D. S. Henn

Abstract

No abstract available.

Full access
R. I. Sykes and D. S. Henn

Abstract

A series of large-eddy simulators of free and sheared convective flow between moving flat plates is presented. Results for free convection are compared with laboratory data. The ratio of friction velocity to the convective velocity sale,u */w *,is identified as an important parameter in sheared convective flow determining the formation of longitudinal rolls. Rolls are found for u */w * ≥ 0.35, with aspect ratio decreasing as this parameter increases. It is shown that, in this regime, two-dimensional simulations with a proper choice of roll orientation and turbulence length-scale can produce correct velocity variances and roll aspect ratio.

Full access
R. I. Sykes, W. S. Lewellen, and D. S. Henn

Abstract

Two-dimensional numerical computations of the developing boundary layer with a positive surface heat flux are presented. The model incorporates moisture phase-change effects; we are particularly interested in the cloud-street formation. The results show that cloud streets with large aspect ratios of about 10 can develop under certain conditions, and cloud top entrainment is identified as a crucial feature. Runs without phase change indicate roll merging to a certain extent, but do not product aspect ratios greater than 4.

Full access