Multiphase Flow

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Multiphase flow is a generalization of the modeling where more than two phases are co-exists among the liquid, gas, solid phase. Analysis of multiphase flow can be applied widely including turbo machinery, air/space vehicle, etc. ASDL is conducting research on incompressible/compressible 2 phase flow(gas-liquid mixture) analysis.

 

Cavitation is the formation of gas bubbles of a flowing liquid in a region where the pressure of the liquid falls below its vapor pressure as Figure 1. This phenomena can be observed in rotating machinery such as liquid rocket engine or underwater vehicles. Generally, cavitation bubble affects fluid machinery adversely such as choking at nozzle, cyclic stress on rotating pump inducer, etc. In Figure 1, numerical result shows VOF contour and streamline on quarter caliber ogive body in water.

 

 

Fig. 1 (left)Cavitation around submerged body (right) VOF contour and mesh for water cavitation)

 

Generally, cavitation in cryogenic fluids generates substantial thermal effects and steep variations in fluid properties, which in turn alter the cavity characteristics. Understanding and quantifying these thermal effects are important for the design of liquid rocket turbo machinery systems that pump liquid hydrogen and liquid oxygen. Figure 2 is simulation results which shows isosurface of vapor volume fraction at 0.4 and contour on blade suction surface of inducer.

 

 

Fig. 2 Isosurface of vapor volume fraction (at 0.4) and contour on blade surface : water(left), hydrogen(right)

 

Analytical analysis of 2 phase flow can be applied to complex flow physics such as underwater explosion or Liquid-shock/gas-bubble interaction. Figure 3 is numerical results of underwater explosion which shows interaction between the ocean surface and the underwater blast wave. Figure 4 is numerical results of interaction problem between a liquid shock and a cylindrical air bubble. When the liquid shock hits the gas bubble, it is reflected as a rarefaction wave, whereas the transmitted wave is still a shock. When the transmitted shock arrives at the gas-liquid phase interface, a blast wave is generated at the right end of the gas bubble.

 

 

Fig. 3 Numerical schileren and y-directional velocity contour of underwater explosion problem

 

 

Fig. 4 Numerical results of liquid-shock/gas-bubble interaction : Pressure contour(left), numerical schileren(right)