We report a new thermal boundary layer equation for turbulent Rayleigh-Bénard convection for Prandtl number Pr>1 that takes into account the effect of turbulent fluctuations. These fluctuations are neglected in existing equations, which are based on steady-state and laminar assumptions. Using this new equation, we derive analytically the mean temperature profiles in two limits: (a) Pr≳1 and (b)...

The transitional boundary layer flow over a flat plate is investigated. The boundary layer flow is known to develop unstable Tollmien-Schlichting waves above a critical value of the Reynolds number. However, it is also known that this transition can be observed for sub-critical Reynolds numbers. In that case the basin of attraction of the laminar state coexists with the sustained turbulence. In...

Flow visualization by the schlieren technique in the neighbourhood of a fully developed cavity on two axisymmetric headforms has shown the existence of laminar boundary-layer separation upstream of cavitation separation, and the distance between the two separations to be strongly dependent on Reynolds number. Based on present results, a semi-empirical method is developed to predict the position...

The prediction of the entropy generation rate in laminar shear layers is treated as steady, even in the presence of high levels of free stream turbulence. Here we highlight the deficiencies of this approach by quantifying the magnitude of entropy generation rate fluctuations in the laminar boundary layer subjected to free stream turbulence. We find fluctuation levels in excess of 100% in the ne...

To be applicable to complex aerodynamic flows at realistic Reynolds numbers, large eddy simulation (LES) must be combined with a model for the inner part of the boundary layer. Aerodynamic flows are, in general, very sensitive to the location of boundary layer transition. While traditional LES can predict the transition location and process accurately, existing wall-modeled LES approaches can n...