Stability of the Structure in Multicomponent Flows

Citation

Kytömaa, Harri Kaarlo (1987) Stability of the Structure in Multicomponent Flows. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/VNYA-FE49. https://resolver.caltech.edu/CaltechETD:etd-03262007-142052

Abstract

Friction pressure drop measurements were made in vertical bubbly and particulate flows, and friction factors up to two orders of magnitude higher than pure liquid values were obtained. The two-phase friction multiplier for air-water flows was shown to attain values up to 15 times higher than the predictions given by the Lockhart and Martinelli correlations (1949). These findings exemplify the lack of detailed understanding of multi-component flow phenomena. The lack of understanding of the flow kinematics and the small amount of information available on the topic has been primarily due to the primitive stage of development of flow measuring instrumentation.

A shielded, temperature compensated and non-intrusive Impedance Volume Fraction Meter (IVFM) was built and shown to have good spatial and temporal resolution. The dynamic calibration of the device demonstrated that the volume fraction measuring device could also be used to measure both the dispersed medium velocity and concentration. This device enabled us to carry out measurements of small and large amplitude kinematic stability and wave propagation in two-component and three-component flows. The velocities of small amplitude kinematic waves in both air-water and solids-water flows were measured using a cross-correlation technique and these were shown to be non-dispersive. The persistence of flow structure was quantified using the coherence of the IVFM noise at two locations. The structure in solids-water flows was found to be more persistent than in air-water flows, and the most coherent wave length was measured to be of the order of .5 m, or five pipe diameters in both flows. The statistical properties in the inherent noise in the IVFM output was shown to contain valuable information on two- and three-component flow quantities and regime.

In this thesis, we show that much can be learned about the complex nature of multi-component flows with adequate instrumentation, and we emphasize the need for further development of critical flow measuring techniques for use not only in fundamental investigations but also in the monitoring and control of practical multiphase flow processes.

Thesis Files