Turbulent Bubbly Channel Flow Investigated by Ultrasound Velocity Profiler

Abstract

Ultrasound velocity profiler (UVP) is applied to measurements of a horizontal turbulent bubbly channel flow to ascertain the mechanism of bubble-induced frictional drag reduction. Typical parameter regimes of the target flow are Re number of 0.6-6.0 x10 4 , void fraction of 0-3%, and bubble diameter of 10-50mm.Since the UVP system only outputs velocity profiles on an ultrasound beam inside a liquid phase, a signal processing method for raw velocity data is proposed and used to detect the bubble interface. A conditional averaged liquid phase velocity profile that excludes gas phase data, has shown for the first time the structure of a turbulent boundary layer altered by large buoyant bubbles sliding along the channel wall.

Relation between oil–water flow and extraction performance in liquid–liquid countercurrent centrifugal extractors with Taylor vortices

“…Researchers have applied the UVP method to clarify the flow of single-phase structures of not only water flows, but also magnetic flows [17][18][19]. There has also been research on two-phase flow mea-surement using UVP, but most studies have examined bubbly flows [20][21][22][23][24][25], and there are few measurement studies on oil-water multiphase flows [26]. Although UVP measurements are applicable in many cases, certain difficulties and problems with this method are yet to be overcome.…”

Ultrasonic detection of moving interfaces in gas–liquid two-phase flow

“…The second technique involves using the Doppler information from the reflected wave. This technique exploits the phenomenon that, during reflection, ultrasound pulses can generate a local standing wave in the vicinity of the interface [11]. Because the standing wave produces no Doppler shift frequency regardless of the flow velocity, the interface position can be detected from the low Doppler velocity layer.…”

Numerical Prediction of a Large Bubble Behavior in Wall Turbulent Flow

“…Recently, the above-mentioned two methodologies have the same issue on a decrease of drag reduction performance from downstream because of the large bubble. Meanwhile, Murai et al [6] [7] reported the drag reduction mechanism for these bubbles (10-50mm) and motivated a turning point in the drag reduction of the large bubble, as a new material for drag reduction. In addition, The advantage is that supplying a large bubble is much easier than generating a high flow rate of microbubbles or stabilizing air films with a wide area.…”