Huailiang Wei

Bio: Huailiang Wei is an academic researcher from Clarkson University. The author has contributed to research in topics: Bubble & Buoyancy. The author has an hindex of 2, co-authored 2 publications receiving 24 citations.

Migration of a Pair of Bubbles under the Combined Action of Gravity and Thermocapillarity

Abstract: The migration of a pair of gas bubbles in an unbounded fluid subject to the combined action of gravity and a downward temperature gradient is considered in the quasistatic limit of negligible Reynolds and Peclet numbers. The solution for the case when the line-of-centers is oriented arbitrarily with respect to the gravity vector is constructed by superposing solutions of the axisymmetric and asymmetric problems. In the axisymmetric problem, it is found that a pair of unequal bubbles can reach a stable critical separation at which both bubbles move at the same velocity, if the smaller bubble is on top of the larger one; at an appropriate balance of the relative strengths of the gravitational and thermocapillary effects, such a pair of bubbles also can reach a motionless state. It is also shown that a downward moving bubble can cause a small bubble which is nearby to move upward, opposite to the direction in which the small bubble would move if isolated. Finally, flow structures, computed by a boundary-collocation method, are illustrated via streamlines in an appropriate symmetry plane in the laboratory frame of reference or in a reference frame traveling with one of the bubbles as appropriate.

Interactions between two bubbles under isothermal conditions and in a downward temperature gradient

Abstract: Results from experiments on the motion of a pair of air bubbles in a silicone oil under isothermal conditions as well as in a downward temperature gradient are reported. Three situations were investigated: motion driven by buoyancy, motion dominated by thermocapillarity, and motion when the gravitational force and the thermocapillary force on the larger bubble of the pair were comparable. The experimental results were found to be in good agreement with theoretical predictions from the method of reflections. When the gravitational force was slightly smaller than the thermocapillary force on the larger bubble in the pair, the larger bubble moved downward but the smaller bubble nearby was found to move upward. This counterintuitive behavior is actually consistent with expectation, and an explanation is given.

Pool Boiling Critical Heat Flux in Reduced Gravity

Abstract: An experimental investigation has been conducted to measure pool boiling critical heat fluxes in reduced gravity. A horizontal cylindrical cartridge heater immersed in water at reduced pressures during parabolic flights on NASA's KC-135 resulted in boiling on the heater surface. Visual observations and qualitative data trends indicate that the conventional Taylor-Helmholtz instability model still governs the critical heat flux mechanism over the range of gravitational accelerations of the current study, which range from 0.0005 < g/g o < 0.044. Using data from more than 40 individual tests, two semi-empirical correlations have been developed to account for the effect of thermocapillary flow, which tends to decrease the critical heat flux below the predictions of previous correlations

Experimental analysis of the heat transfer induced by thermocapillary convection around a bubble

Abstract: The surface tension driven flow in the liquid vicinity of gas bubbles on a heated wall and its contribution to the heat transfer are investigated experimentally in a configuration where surface tension force and buoyancy forces oppose one another. This liquid flow caused by the temperature gradient along the interface is called thermocapillary or thermal Marangoni convection. The studies were made with silicone oils of different viscosities so that a wide range of dimensionless numbers were encountered. The velocity fields are determined from the motion of carbon particles in the meridian plane of the bubble. The influence of the temperature gradient, the oil viscosity, and the bubble shape on the profiles along the interface and in the direction normal to the interface is analyzed. The temperature field is determined by holographic interferometry. For the axisymmetric problem, the interferograms are evaluated by solving the Abel-integral equation. From the isotherms, the temperature distribution along the bubble surface and in the liquid beneath the bubble is measured. To quantify the contribution of thermocapillarity to the heat transfer, the heat flux transferred by thermocapillarity is measured. A heat exchange law giving the increase in heat flux due to Marangoni convection in comparison to themore » conductive regime is proposed.« less

Miscible Fluids in Microgravity (MFMG): A Zero-Upmass Investigation on the International Space Station

Abstract: Miscible Fluids in Microgravity (MFMG) was a zero-upmass investigation performed on the International Space Station. The goal of MFMG was to determine if interfacial phenomena seen with immiscible fluids could be seen with miscible fluids. The experiments had to be performed with existing materials on the ISS. Honey and water were chosen as the fluids, and urine collection syringes were used as the vessels in which the experiments were performed. In March 2004 (Increment 8) Dr. Michael Foale performed four experiments under isothermal conditions to determine: If a stream of honey injected into water would exhibit the Rayleigh-Tomotika instability and break into small drops. If an aspherical drop of water in honey would spontaneously assume a spherical shape. The experiments were performed successfully. During Increment 9, Mike Fincke performed two runs in which a stream of honey was injected into water while the syringe was attached to the surface of the Commercial Generic Bioprocessing Apparatus (CGBA) at approximately 31° C. No change in the stream shape was observed. Two more runs were performed on Increments 10 and 11 but no additional phenomena were observed. No behavior beyond simple diffusion was observed. We performed simulations with the Navier-Stokes equations plus a Korteweg stress term. We estimated that the maximum possible value of the square gradient parameter was 10−12 N for the honey-water system.

Buoyancy-driven interactions of viscous drops with deforming interfaces

Abstract: Experiments were conducted on the interactions of two different-sized deformable drops moving due to gravity in an immiscible viscous fluid at low Reynolds number. As the drops come close to each other, several interactions are possible: (i) separation of the drops, (ii) capture of the smaller drop behind the larger drop, (iii) breakup of the smaller drop into two or more drops, and (iv) pass-through of one drop through the other, with possible cycle interaction or leap-frogging. The interactions depend on several system parameters, including the drop-to-medium viscosity ratio, the radius ratio of the two drops, the initial horizontal offset of the two drops at large vertical separation, and the gravitational Bond number (which represents the ratio of buoyant forces to interfacial tension forces for the larger drop and describes how much the drops will deform). Experimental analysis was conducted by videotaping trajectories of glycerol–water drops of various compositions falling in castor oil. The results show good agreement with available theoretical results, both for interaction maps and individual trajectories. The results also provide data beyond the present limitations of theoretical algorithms and reveal the new pass-through phenomenon.