A NUMERICAL STUDY OF A THERMALLY STRATIFIED BOUNDARY-LAYER UNDER VARIOUS STABLE CONDITIONS

A direct numerical simulation of a stratified boundary layer under var ious stable conditions is made by a finite-difference method without a ny turbulence model. The numerical simulation is very successful, show ing variations of turbulent quantities due to thermal stratification. Namely, the intensities and fluxes of velocity and temperature fluctua tions are significantly suppressed with increasing stability similar t o the experimental results. Flow visualization of computational result s is very useful to understand changes in the flow structure under sta ble stratification. However, compared with experimental results, the d iscrepancies in turbulence structure in the lowest part of the boundar y layer (especially for z/delta < 0.2, delta is the boundary layer thi ckness) are observed.