关键词: supersonic gas-droplet two-phase flow;interfacial momentum transfer;velocity slip; relaxation time;numerical simulation;laser Doppler velocimeter measurement

Abstract: Modelling and simulations are conducted on velocity slip and interfacial momentum transfer
for super-sonic two-phase (gas-droplet) flow in the transient section inside and outside a
Laval jet(L J). The initial velocity slipbetween gas and droplets causes an interfacial
momentum transfer flux as high as (2.0-5.0) × 104 Pa. The relaxationtime corresponding to
this transient process is in the range of 0.015-0.090 ms for the two-phase flow formed
insidethe LJ and less than 0.5 ms outside the LJ. It demonstrates the unique performance of
this system for application tofast chemical reactions using electrically active media with
a lifetime in the order of 1 ms. Through the simulationsof the transient processes with
initial Mach number Mg from 2.783 to 4.194 at different axial positions inside theLJ. it is
found that Mg has the strongest effect on the process. The momentum flux increases as the
Mach numberdecreases. Due to compression by the shock wave at the end of the L J, the flow
pattern becomes two dimensionaland viscous outside the LJ. Laser Doppler velocimeter (LDV)
measurements of droplet velocities outside the LJ arein reasonably good agreement with the
results of the simulation.

Key words: supersonic gas-droplet two-phase flow, interfacial momentum transfer, velocity slip, relaxation time, numerical simulation, laser Doppler velocimeter measurement