The direct numerical simulation (DNS) data of a turbulent, reacting boundary layer is used to study the turbulence-chemistry interaction and the scaling of the temperature fluctuations. We find that there is a feedback between the turbulence and the chemical reactions. Temperature fluctuations increase the reaction rates. Endothermic reactions reduce the magnitude of the temperature fluctuation...

The interference and proximity effects on the dynamic response of prismatic bluff bodies are investigated in a series of wind tunnel tests. The results show that the presence of a single, or a pair of upstream prisms of the same size can increase the interaction factor. The effects are more pronounced in a boundary layer flow with a lower level of turbulence, especially near the reduced velocit...

A new formulation for eddy diffusivity is derived from Taylor’s statistical theory on turbulence and from a generalized turbulent spectral equation for energy in the inertial subrange. The latter aspect is taken into account for considering the intermittency phenomenon within turbulence model. The approach is used for a stable atmospheric boundary layer parameterization. r 2005 Elsevier B.V. Al...

Observations are presented to show that in an adverse pressure gradient boundary layer, beneath free-stream turbulence, the interaction between Klebanoff streaks and naturally arising instability waves leads to helical disturbances which break down to form turbulent spots. This occurs under low to moderate levels, 1%–2%, of free-stream turbulence. At high levels of free-stream turbulence, conve...

Some aspects of transition induced by freestream turbulence can be understood in terms of the continuous spectrum of the Orr-Sommerfeld and Squire equations. Instead of discrete mode (Tollmien-Schlichting wave) precursors, transition can be studied, starting from continuous mode precursors. An examination of mode shapes leads to a theory of how freestream disturbances penetrate the boundary lay...

Experimental findings show that transition from laminar to turbulent flow may occur also if the exponentially growing perturbations, eigensolutions to the linearised disturbance equations, are damped. An alternative non-modal growth mechanism has been recently identified, also based on the linear approximation. This consists of the transient growth of streamwise elongated disturbances, with reg...

w data, valuable contributions have been made to the physical understanding of turbulence over an unprecedented range of Reynolds numbers. The shear stress measurements were made at the unique SLTEST (Surface Layer Turbulence and Environmental Science Test facility) site on the great salt lakes of Utah, pictured in figure 1. Winds over the site are known to remain strong and consistent for exte...

b. Quantify the temporal variation of turbulent stresses, turbulence production, dissipation and spectra in relation to the oceanographic parameters that represent the local environment, such as waves, currents, vertical density gradient, internal waves and the nature of the water-sediment interface. The conclusions will quantify the relative importance of different mechanisms that control the ...

We want to look at the dynamics of the coherent vortex structures which are generated at the bottom of sea waves by 1) the instability of the laminar boundary layer and the development of turbulence, 2) the nonlinear interaction of the oscillatory boundary layer with a wavy bed of small amplitude and with a sloping bottom and 3) the separation of the boundary layer at the crests of 2-D ripples ...

When a boundary layer starts to develop spatially over a flat plate, only disturbances of sufficiently large amplitude survive and trigger turbulence subcritically. Direct numerical simulation of the Blasius boundary-layer flow is carried out to track the dynamics in the region of phase space separating transitional from relaminarizing trajectories. In this intermediate regime, the correspondin...