This study investigated the properties of long bubbles penetrating viscoelastic fluids in a suddenly contracting and expanding tube. Injection gas flow is controlled by a mass flow controller (MFC). Some of dimensionless parameters, such as the capillary number (Ca), the Reynolds number (Re), the fractional ratio (m), and the Weissenberg number (Wi), are discussed herein. The experimental results showed that bubble velocity, Ca, and Wi increase as shear viscosity increases under a constant gas flow by MFC. However, as shear viscosity increases, bubble diameter decreases, andmincreases. When gas flow is 200 mL/min and shear viscosity increases, the bubble front is sharper in the contraction tube, and the bubble front shape is blunter in the sudden expansion tube. When gas flow is 600 mL/min and shear viscosity increases, the bubble front is blunter in the contraction tube and exhibits a torch shape in the sudden expansion tube.

This paper studies the behavior of second grade viscoelastic fluid past a cavity in a horizontal channel. The effects of Reynolds number, fluid elasticity and the aspect ratio of the cavity on the flow field are simulated numerically. The equations are converted into the vorticity and stream function equations. The solution is obtained by the finite difference method.The behavior of viscoelastic fluids is quite different from the Newtonian fluid, due to the effects of fluid elasticity. Only one flow pattern appears when the Newtonian fluid past the cavity. However, three kinds of flow patterns appear while the viscoelastic fluids past the cavity by increasing Reynolds number from 20 to 300. The flow field is affected by the fluid elasticity as well as the aspect ratio of the cavity. The transitional flow pattern appears at lower Reynolds number as the higher elasticity fluid past the cavity with larger aspect ratio.

A steady-state boundary layer flow analysis of a non-Newtonian magnetic fluid over a shrinking sheet was studied. The boundary layer thickness and the velocity distribution in the layer were studied under the conditions of a uniform magnetic field normal to the shrinking sheet and/or a vertical uniform mass suction across the sheet. The similarity transformation method was used to transform the governing partial differential equations to ordinary differential equations. The shooting method with Newton's algorithm and Runge-Kutta integration method were used to obtain the solutions of the equations. The results showed that the variation of the flow velocity profiles in the boundary layer was significant, the thickness of the boundary layer was thinner, and the skin friction coefficient was bigger for either shear thinning or shear thickening magnetic fluids under the conditions of a stronger magnetic field or a larger mass suction effect.

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