Jets are ubiquitous in astronomy. It has been conjectured that the existence of jets is intimately connected with the spin of the central object and the viscous angular momentum transport of the inner disk. Bipolar jet-like structures propelled by the viscous torque on a spinning central object are also known in a completely different context, namely the flow in the laboratory of a viscoelastic...

We report results from high Prandtl number turbulent thermal convection experiments. The viscous boundary layer and the Reynolds number are measured in four different fluids over wide ranges of the Prandtl number Pr and the Rayleigh number Ra, all in a single convection cell of unity aspect ratio. We find that the normalized viscous layer thickness may be represented as delta(v)/L=0.65Pr(0.24)R...

The channel flow subjected to a wind stress at the free surface and an oscillating pressure gradient is investigated using large-eddy simulations. The orientation of the surface stress is parallel with the oscillating pressure gradient and a purely pulsating mean flow develops. The Reynolds number is typically Re!=10 and the Keulegan–Carpenter number—the ratio between the oscillation period and...

Discontinuous Galerkin methods, originally developed in the advective case, have been successively extended to advection–diffusion problems, and are now used in very diverse applications. We here consider the numerical solution of the compressible Reynolds-averaged Navier–Stokes and k–x turbulence model equations by means of DG space discretization and implicit time integration. Detailed descri...

In probability density function (PDF) methods of turbulent flows, the joint PDF of several flow variables is computed by numerically integrating a system of stochastic differential equations for Lagrangian particles. A set of parallel algorithms is proposed to provide an efficient solution of the PDF transport equation modeling the joint PDF of turbulent velocity, frequency and concentration of...

We present the Langevin rigid approach, a technique for animating the dynamics of immersed rigid bodies in viscous incompressible fluid in real-time. We use generalized Kirchhoff equations to ensure forces and torques from the surrounding fluid that create realistic motion of immersed rigid bodies. We call our method the Langevin rigid approach because the generalized Langevin equations are app...

The flow of a viscous fluid in a plane channel is simulated numerically following the DNS approach, and using a computational code for the numerical integration of the Navier-Stokes equations implemented on a hybrid CPU/GPU computing architecture (for the meaning of symbols and acronyms used, one can refer to the Nomenclature). Three turbulent-flow databases, each representing the turbulent sta...

We study liquid-liquid dispersions in a turbulent Taylor–Couette flow, produced between two counterrotating coaxial cylinders. In pure Water and in counterrotation, Reynolds numbers up to 1.4× 10 are reached. The liquids we use are a low-viscous Oil and pure Water or a Sodium Iodide solution with a refractive index matched to that of Oil, in order to get transparent dispersions. We first charac...

A systematic study of large-scale velocity structures in turbulent thermal convection is carried out in three different aspect-ratio cells filled with water. Laser Doppler velocimetry is used to measure the velocity profiles and statistics over varying Rayleigh numbers Ra and at various spatial positions across the whole convection cell. Large velocity fluctuations are found both in the central...

An oscillating, weakly ionized surface plasma has been investigated for use in turbulent boundary layer viscous drag reduction. The study was based on reports showing that mechanical spanwise oscillations of a wall can reduce viscous drag due to a turbulent boundary layer by up to 40%. It was hypothesized that the plasma induced body force in high electric field gradients of a surface plasma al...