Hele-Shaw flow

About: Hele-Shaw flow is a research topic. Over the lifetime, 5451 publications have been published within this topic receiving 151320 citations.

Mathematical Modeling of the Flow of Four Fluids in a Packed Bed.

Abstract: Macroscopic flow phenomena play important roles not only for improving productivity and energy efficiency but also for achieving the stable operation in metallurgical and chemical reactors. This review paper deals with flow phenomena of four fluids which are single-phase or multi-phase flow of gas, fine particles, liquid and packed particles. In some previous researches on the multi-phase flow, fundamental equations were derived for a continuous fluid phase and dispersed phases with different types of modeling. However, in this paper, continuous flow was assumed for each phase in the derivation of the equation of motion for obtaining the numerical solution. The model has been applied to the simulation of not only four phase flows but also one to three phase flows. Typical examples for application will be described for several processes.

Low Reynolds number flow through nozzle-diffuser elements in valveless micropumps

Abstract: Flow characteristics of low Reynolds number laminar flow through gradually expanding conical and planar diffusers were investigated. Such diffusers are used in valveless micropumps to effect flow rectification and thus lead to pumping action in one preferential direction. Four different types of diffuser flows are considered: fully developed and thin inlet boundary layer flows through conical and planar diffusers. The results from the numerical analysis have been quantified in terms of pressure loss coefficient. The variation of pressure loss coefficient with diffuser angle is presented for Reynolds numbers of 200, 500 and 1000. The pressure loss coefficients have been used to calculate the diffuser efficiency for two different types of nozzle-diffuser elements. The general trend of variation of pressure loss coefficient with diffuser angle was found to be similar to that for high Reynolds number turbulent flow. However, unlike at high Reynolds numbers, pressure loss coefficients at low Reynolds numbers vary significantly with Reynolds number. It was also observed that trends of variation in the pressure loss coefficient with Reynolds number are different for small and large diffuser angles. Also, at low Reynolds numbers, the pressure loss coefficients for a thin inlet boundary layer are not always smaller than those for fully developed inlet boundary layer, in contrast to the behavior for high Reynolds number flows. Contrary to past claims, flow rectification is shown to be indeed possible for laminar flows. The two different types of nozzle-diffuser elements considered led to pumping action in opposite directions. Further, it was observed that flow rectification properties of both kinds of nozzle-diffuser elements improved with increasing Reynolds number.

Observations on the elastic instability in cone-and-plate and parallel-plate flows of a polyisobutylene Boger fluid

Abstract: Experimental measurements of the shear stress and normal stresses in the viscometric flow of a well-characterized polyisobutylene/polybutene solution between a cone-and-plate and between parallel plates show the onset of an “anti-thixotropic” flow transition, which results in a time-dependent, apparent shear-thickening of the viscosity and first normal stress difference. Measurements of the critical conditions for the onset of the flow transition, made by systematically varying the plate separation in the parallel-plate geometry, demonstrate that this rotational instability is a function of the angular velocity in the flow and initially grows exponentially in time, in agreement with theoretical predictions for an Oldroyd-B model. However, experiments show that the disturbance which causes this flow transition is nonaxisymmetric, over-stable in time and subcritical in γ. Spectral analysis also shows that the nonlinear flow which ultimately develops is temporally aperiodic. These features of the flow transition do not agree with the existing theoretical analysis. The experimentally constructed flow-stability diagram shows that, for a given fluid, the instability occurs at a critical Deborah number which is insensitive to the specific geometrical parameters, temperature, and shear-rate of the flow. This interpretation of the elastic instability clarifies recent measurements of the flow stability for the Ml viscoelastic test fluid.

Numerical Study of the Flow Around a Bus-Shaped Body

Abstract: Flow around a simplified bus is analyzed using large-eddy simulation. At the Reynolds number of 0.21 × 10 6 , based on the model height and the incoming velocity. the flow produces features and aerodynamic forces relevant for the higher (interesting in engineering) Reynolds number. A detailed survey of both instantaneous and time-averaged flows is made and a comparison with previous knowledge on similar flows is presented. Besides the coherent structures observed in experimental and previous numerical studies, new smaller-scale structures were registered here. The mechanisms of formation of flow structures are explained and the difference between instantaneous and time-averaged flow features found in the experimental observations is confirmed. Aerodynamic forces are computed and their time history is used to reveal the characteristic frequencies of the flow motion around the body