Drag and power-loss in rowing due to velocity fluctuations

The flow motions in the turbulent boundary layer between water and a rowing boat initiate a turbulent skin friction. Reducing this skin friction results in better rowing performances. A Taylor-Couette (TC) facility was used to verify the power losses due to velocity fluctuations P_V′ in relation to the total power, as a function of...

Lifetime of turbulent patch in Taylor Couette setup

In linearly stable shear flows like pipe and plane Couette flows, the transition from the laminar to the turbulent regime occurs abruptly. To better understand this transition, the time evolution of turbulent patches, created by controlled finite amplitude perturbations, have been studied in the literature. These studies mostly focused on pipe flows...

Lifetime of turbulent patch in Taylor Couette setup

In linearly stable shear ?ows like pipe and plane Couette ?ows, the transition from the laminar to the turbulent regime occurs abruptly. To better understand this transition, the time evolution of turbulent patches, created by controlled ?nite amplitude perturbations, have been studied in the literature. These studies mostly focused on pipe ?ows...

Experimental study of surface modification in a fully turbulent Taylor-Couette flow

Friction measurements were performed in a Taylor-Couette setup. Drag reduction was obtained with a riblet surface and indicated a drag reduction for a wide range of shear Reynolds numbers, with a maximum of 5.3% at Re_s=47000 (s+=14). Tomographic PIV verified that the friction coefficients are strongly related to the flow regimes and structures....

Experimental study of surface modification in a fully turbulent Taylor-Couette flow

Friction measurements were performed in a Taylor-Couette setup. Drag reduction was obtained with a riblet surface and indicated a drag reduction for a wide range of shear Reynolds numbers, with a maximum of 5.3% at Re_s=47000 (s+=14). Tomographic PIV verified that the friction coefficients are strongly related to the flow regimes and structures....

Riblet drag reduction and the effect of bulk fluid rotation in a fully turbulent Taylor-Couette flow

Low drag surfaces are often desired in many industries with applications in open and closed channel flows, such as ship hulls and pipe flows. Drag reduction is a phenomenon that can have substantial energy savings, resulting in ecological and economical benefits. We use a Taylor-Couette facility as experimental instrument to measure the drag...

PIV measurements of waves and turbulence in stratified horizontal twophase pipe flow

The technique for obtaining detailed velocity fields in a wavy liquid layer in stratified air/water pipe flow is described in this paper. By combining Particle Image Velocimetry (PIV) with an interface detection technique, the velocity field is resolved in the whole liquid layer. Furthermore, since the shape of the interface is resolved at each...

Experimental study on developed air cavities under a horizontal flat plate

Drag reduction by surface treatment in turbulent Taylor-Couette flow

We use a Taylor-Couette facility to study the drag reducing effects of commercial surface products at high shear Reynolds numbers (Res) under perfect couter-rotating conditions (riwi=rowo). The correlation between torque contribution of the von Karman flow and shear Reynolds number is investigated. At this moment no significant drag changes are...

Dispersion of bubbles in fully developed channel flow

Dispersion and preferential concentration of small, low Stokes number bubbles in horizontal turbulent channel flow is studied by DNS and experiments. A DNS of turbulent channel flow at Re = 360 with Lagrangian tracking of one-way coupled bubbles (d < n, St = 1.3×10?3) shows that equilibrium bubble concentration profiles can be described by a...

Particle Entrainment in Spherical-Cap Wakes

In this work we study the preferential concentration of small particles in the turbulent wake behind a spherical-cap object. We present a model predicting the mean particle concentration in the near-wake as a function of the characteristic Stokes number of the problem, the turbulence level and the Froude number. We compare the model with our...