Amplification of magnetic field due to kinematic turbulent dynamo action is studied in the regime of small magnetic Prandtl numbers. Such a regime is relevant for planets and stars interiors, as well as for liquid-metal laboratory experiments. A comprehensive analysis based on the Kazantsev-Kraichnan model is reported, which establishes the dynamo threshold and the dynamo growth rates for varyi...

The present article focuses on the evaluation of a first-moment closure model applicable to film cooling flow and heat transfer computations. The present first-moment closure model consists of a higher level of turbulent heat flux modeling in which two additional transport equations for temperature variance kθ and its dissipation rate εθ are ...

In high speed engines, thorough turbulent mixing of fuel and air is required to obtain high performance and high efficiency. Thus, the ability to predict turbulent mixing is crucial in obtaining accurate numerical simulation of an engine and its performance. Current state of the art in CFD simulation is to assume both turbulent Prandtl number and Schmidt numbers to be constants. However, since ...

Scaling relationships are proposed for the turbulent katabatic flow of a stably stratified fluid down a homogeneously cooled planar slope—the turbulent analogue of a Prandtl-type slope flow. The Theorem predicts that such flows are controlled by three nondimensional parameters: the slope angle, the Prandtl number, and a Reynolds number defined in terms of the surface thermal forcing (surface bu...

a = mean speed of sound, R T 1=2 aw = mean speed of sound at the wall, RTw 1=2 C = turbulent viscosity parameter, T= Lk cp = specific heat at constant pressure, R= 1 ; 1004:5 J= kg K cv = specific heat at constant volume, R= 1 ; 717:5 J= kg K f = uniform body force, w=h h = half channel height hw = wall length scale, h=Re i = turbulence intensity, 2k=3 = U1 k = turbulent kinetic energy, uiui=2 ...

Aims. We study the dependence of turbulent transport coefficients, such as α effect and turbulent magnetic diffusivity, on shear and magnetic Reynolds number in the presence of helical forcing. Methods. We use three-dimensional direct numerical simulations with periodic boundary conditions and measure turbulent transport coefficients using the kinematic test field method. In all cases the magne...

The Ra and Pr number scaling of the Nusselt number Nu, the Reynolds number Re, the temperature fluctuations, and the kinetic and thermal dissipation rates is studied for snumericald homogeneous Rayleigh–Bénard turbulence, i.e., Rayleigh–Bénard turbulence with periodic boundary conditions in all directions and a volume forcing of the temperature field by a mean gradient. This system serves as mo...

The progress in our understanding of several aspects of turbulent Rayleigh-Bénard convection is reviewed. The focus is on the question of how the Nusselt number and the Reynolds number depend on the Rayleigh number Ra and the Prandtl number Pr, and on how the thicknesses of the thermal and the kinetic boundary layers scale with Ra and Pr. Non-Oberbeck-Boussinesq effects and the dynamics of the ...