Hachiro Hamaguchi

Analysis of the impact force by a transient liquid slug flowing out of a horizontal pipe

Abstract An abrupt increase in the gas flow rate in a horizontal gas-liquid two-phase stratified or wavy flow induces a transient slug flow. When this transient liquid slug flows out of a pipe, it applies a large impact force by its impingement on a structure located outside the pipe. The shape of this impact force-time curve is characterized by such quantities as initial impact force, maximum force, acting period of force and total momentum. The influences of each volumetric flux of two phases and of the pipe diameter on the impact force-time curves and the dynamic behavior of the transient liquid slug are experimentally studied and theoretically analyzed on the basis of Dukler-Hubbards model by applying equations of the integral balance of mass and momentum to the transient liquid slug. The calculated results agree well with the experimental results of the dynamic behavior of the transient liquid slug and of the impact force.

Velocity of a Large Bubble Rising in an Inclined Rectangular Channel

Velocity of a large single bubble rising in a stationary liquid in an inclined rectangular channel was measured using silicone oil having a kinematic viscosity of 1000mm2 /s. The size of cross section of the test channel was 5mm × (5–40)mm, i.e., the aspect ratio was from 1 to 8. Experiments were carried out changing the aspect ratio of cross section of the channel, the inclination angle and “posture angle”, where the “posture angle” is an angel by which the channel is rotated around the channel axis. Movement of a large bubble in an inclined circular tube is determined by the inclination angle. On the other hand, it is shown that movement of a large bubble in an inclined channel is influenced also by the posture angle beside the inclination angel, i.e., the posture angle is an important parameter in an inclined rectangular channel. Relations among the rising velocity, the inclination angle, the posture angle and the aspect ratio were obtained by the experiments.Copyright

Development of converter to change gas-liquid two-phase slug flow to bubbly flow in a vertical tube.

The mechanical and/or the thermal fatigue fracture of pipelines due to the pulsating characteristics of slug flow will be prevented if slug flow is changed to bubbly flow. Then kinds of flow pattern converters were developed and tested in a vertical tube of 30.3 mm I.D. This paper reports that the converter composed of five stages of porous plates is useful. The sintered porous plates of spherical particles made acrylonitrile-butadiene-styrene resin and bronze are selected from 76 kinds of porous plates.

Flow Characteristics of a Large Bubble in a Horizontal Channel

The flow characteristics of a large bubble penetrating into stationary liquid in a horizontal channel with rectangular cross-section have been studied. The velocity and the shape of the large bubble and the velocity profile of the liquid around the nose of the large bubble were measured for the channels with the length of 2.6m and the height of 22. 5, 32. 5, 42. 5 and 53mm. Their characteristics were analysed theoretically by the potential flow theory. The experimental results of the shape of the large bubble can be expressed by one curve in the dimensionless coordinates, and the measured velocity profile of the liquid in each channel show the same characteristics in the dimensionless form. These experimental results agree with the theoretical results. And so, it is clear that the potential flow theory is useful for this problem.