Mixing shocks in two-phase flow

Abstract

In gas-liquid flows a certain sudden change of the flow structure may occur, which can be described as a transition from ‘jet flow’ to ‘froth flow’ accompanied by energy dissipation and pressure build-up. Upstream of this phenomenon the gas is the continuous phase; downstream the liquid is the continuous phase. The phenomenon, which has been called ‘mixing shock’, shows some similarity and also some differences with the plane shock wave in gasdynamics. In the first part of this paper the mixing shock is treated as a one-dimensional macroscopic process. With the aid of the laws of conservation of mass, momentum and energy, expressions are obtained for the pressure and entropy change across the mixing process. In addition the stability of the mixing shock in a cylindrical flow channel is treated. Next, a theory that explains the gas entrainment mechanism in the mixing shock is proposed. As an experimental tool a water-air ejector with the water as a driving medium was used. The experiments confirm the macroscopic and the microscopic theory. In the last section of this paper theoretical and experimental evidence is combined to construct a model of the processes that play a role in the shock.

Fundamentals of Multiphase Flow

“…This transition has been called a mixing shock (Witte 1969) and typically occurs when a droplet flow with significant relative motion transitions to a bubbly flow with negligible relative motion. Witte (1969) has analyzed these mixing shocks and obtains expressions for the compression ratio across the mixing shock as a function of the upstream slip and Euler number.…”

New Regenerative Cycle for Vapor Compression Refrigeration

“…Among others, Witte [4] investigated the efficiency of a propulsion device based on injection of compressed air bubbles in the throat section of a nozzle and observed the pressure jump associated with the supersonic flow. Indeed, this was further confirmed by both computer modeling and laboratory experiments.…”

“…With using a P-h diagram we can find the specific volume for both the motive stream in the point 8, V 8 , and the suction stream in the point 3, V 3, as well as the same for their mixing in the point 4, V 4 . In the case of two-phase flows, the cross-section area of the ejector mixing section per unit total ejector flow rate, a m , can be determined by equation…”

“…Our approach was justified by the fact that very limited information exists about any experiments conducted, and even if presented, the available literature does not show specific conditions under which those experiments were carried [1], [3], [4]. Most comprehensible description is shown in [1], where the author refers to experiments performed by others on the mixture of air and aqueous solution of glycerin.…”

Efficiency of liquid-jet high-pressure booster compressors

“…Their efficiency was comparatively low, since in short chambers and divergent channels typical of the one-phase apparatuses the two-phase operating process could be hardly arranged. Then the need for complete disintegration of liquid jets into droplets was established [1,2].…”