The Dynamics of Multi-phase Flow in Collimated Jets.
Miller AL; Kugel RW; Savanick GA
Proc 5th Am Water Jet Conf 1989 Aug; :179-189
The dynamics and thermal characteristics of a small-diameter, high- speed waterjet expanding into a larger diameter open-ended pipe were studied by the U.S. Bureau of Mines. The void created as the jet expands into the larger pipe are filled by vaporization or by entrainment of backflowing air from the pipe exit. The resulting mixture exits the larger pipe as a well-dispersed multiphase fluid. Observation of the vaporization-dispersion phenomena through glass pipes indicated three distinct flow regions: (1) jet breakup, (2) collimation, and (3) backflow. Massflow distribution measurements in region 2 suggest a system of well-dispersed droplets. Pressure and temperature measurements in the first two regions are consistent with vaporization equilibrium values and show little variation. A computer simulation of evaporation rate was used to verify that vaporization equilibrium is reached in a fraction of the residence time of the fluid in the pipe. Surface conductivity measurements indicate the absence of a water film on the inner pipe walls up to region 3, where a significant increase in surface conductivity occurs. The boundary between regions 2 and 3 is marked by a considerable discontinuity in pressure and temperature. These observations will be used to develop a model to determine flow losses and momentum transfer in the multiphase flow.
Proc. 5th Am. Water Jet Conf., August 29-31, 1989, PP. 179-189