Local similarity profiles from direct numerical simulation

In the present analysis a continuous turbulent stably stratified channel flow is studied with a direct numerical simulation model and with a simple similarity model. With DNS, the flow is simulated without the need of a specific turbulence closure model, whereas the local similarity model is based on a simple parameterization of turbulence. A relatively low Reynolds flow is simulated and both models explicitly account for molecular flux contributions. The flow configuration is identical to a study by Nieuwstadt. In spite of their different nature, both models give comparable results on the evolution of the mean and the flux profiles. Inspired by this the DNS results were used to calculate flux-profile relationships. The dimensionless gradients of wind and temperature from our DNS show strong evidence for log-linear behaviour close to the traditional Phi_m,h = 1+ 5 z/Lambda over the range of analysi(0