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EXPERIMENTAL AND NUMERICAL INVESTIGATION OF BUBBLE AUGMENTED WATERJET PROPULSION

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Journal of Hydrodynamics 2012年第5期24卷 635-647页

作者： CHOI Jin-Keun SINGH Sowmitra HSIAO Chao-Tsung CHAHINE Georges L dynaflow INC. JessupMarylandUSA

This contribution presents experimental and numerical investigations of the concept jet propulsion augmentation using bubble injection. A half-3D （D-shaped cylindrical configuration to enable optimal visualizations） divergent-convergent nozzle was designed, built, and used for extensive experiments under different air injection conditions and thrust measurement schemes. The design, optimization, and analysis were conducted using numerical simulations. The more advanced model was based on a two-way coupling between an Eulerian description of the flow field and a Lagrangian tracking of the injected bubbles using our Surface Averaged Pressure （SAP） model. The numerical results compare very favorably with nozzle experiments and both experiments and simulations validation the thrust augmentation concept. For a properly designed nozzle and air injection system, air injection produces net thrust augmentation, which increases with the rate of bubble injection. Doubling of thrust was measured for a 50% air injection rate. This beneficial effect remains at 50% after account for liquid pump additional work to overcome increased pressure by air injection.

关键词： waterjet propulsion bubble dynamics multi-phase flow

MODELING MICROBUBBLE DYNAMICS IN BIOMEDICAL APPLICATIONS

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Journal of Hydrodynamics 2012年第2期24卷 169-183页

作者： CHAHINE Georges L. HSIAO Chao-Tsung dynaflow Inc.JessupMaryland 20794USA

Controlling microbubble dynamics to produce desirable biomedical outcomes when and where necessary and avoid deleterious effects requires advanced knowledge, which can be achieved only through a combination of experimental and numerical/ analytical techniques. The present communication presents a multi-physics approach to study the dynamics combining viscous- inviscid effects, liquid and structure dynamics, and multi bubble interaction. While complex numerical tools are developed and used, the study aims at identifying the key parameters influencing the dynamics, which need to be included in simpler models.

关键词： microbubble biological contrast agents thick shell ultrasound

NUMERICAL SIMULATION OF BUBBLE FLOW INTERACTIONS

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Journal of Hydrodynamics 2009年第3期21卷 316-332页

作者： CHAHINE Georges L. dynaflow INC. 10621-J Iron Bridge RoadJessup

Bubble flow interaction can be important in many practical engineering applications. For instance, cavitation is a problem of interaction between nuclei and local pressure field variations including turbulent oscillations and large scale pressure variations. Various types of behaviours fundamentally depend on the relative sizes of the nuclei and the length scales of the pressure variations as well as the relative importance of bubble natural periods of oscillation and the characteristic time of the field pressure variations. Similarly, bubbles can significantly affect the performance of lifting devices or propulsors. We present here some fundamental numerical studies of bubble dynamics and deformation, then a practical method using a multi-bubble Surface Averaged Pressure （DF-Multi-SAP ） to simulate cavitation inception and scaling, and connect this with more precise 3-D simulations. This same method is then extended to the study of two-way coupling between a viscous compressible flow and a bubble population in the flow field.

关键词： cavitation bubble flow interaction numerical simulation

ACOUSTIC MEASUREMENTS BUBBLES IN BIOLOGICAL TIESSURE

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Journal of Hydrodynamics 2009年第1期21卷 47-64页

作者： CHAHINE Georges L. TANGUAY Michel LORAINE Greg dynaflow INC. 10621-J Iron Bridge Road Jessup Maryland 20794 USA

An acoustic based instrument, the ABS Acoustic Bubble Spectrometer@@（ABS）, was investigated for the detection and quantification of bubbles in biological media. These include viscoelastic media （blood）, materials of varying density （bone in tissue）, non-homogenous distribution of bubbles （intravenous bubbly flow）, and bubbles migrating in tissue （decompression sickness, DCS）. The performance of the ABS was demonstrated in a series of laboratory experiments. Validation of the code was performed using a viscoelastic polymer solution, Polyox, in which the bubble size distribution and void fraction were determined by ABS measurements and with image analysis of high speed videos. These tests showed that the accuracy of the ABS was not significantly affected by viscoelasticity for bubbles smaller than 200 microns. The ABS detection and measurement of non-homogenous bubble distributions was demonstrated using a bubbly flow through a simulated vein surrounded by tissue. The scatter of acoustic signals due to bones in the acoustic pathway was also investigated. These in-vitro experiments were done using meat （beef） as a tissue simulant. Decompression experiments were done using beef meat which was held underwater at high pressure （9.9 atm） then rapidly decompressed. Bubble size distributions and void fraction calculations in these experiments were then validated using image analysis of high speed video. In addition, preliminary experiments were performed with the US Navy Medical Research Center, demonstrating the utility of the modified ABS system in detecting the evolution of bubbles in swine undergoing decompression sickness （DCS）. These results indicate that the ABS may be used to detect and quantify the evolution of bubbles in-vivo and aid in the monitoring of DCS.

关键词： ABS Acoustic Bubble Spectrometer@@ (ABS) biological tissue decompression sickness (DCS)