Mechanism of pressure oscillation in Taylor-Couette-Poiseuille flow with abruptly contracting and expanding annular gap

摘要

This study numerically investigates the effects of an abruptly contracting and expanding annular gap on the propagation of Taylor vortices in Taylor-Couette-Poiseuille flow. The results show that the pressure drop between the inlet and the outlet exhibits oscillations with low frequency and large amplitude. The nondimensional amplitude of oscillating pressure increases linearly with an increase in the rotating Reynolds number, whereas the nondimensional oscillating frequency remains nearly invariant with varying rotating and axial Reynolds numbers. Owing to the alternate action of counter-rotating Taylor vortex pairs in front of the block, local flow resistance periodically increases and decreases, resulting in the pressure drop oscillation. By analyzing the drift velocity and wavelength of the propagating Taylor vortex pair, a prediction model for the oscillating frequency is developed. Its results show that the nondimensional frequency is proportional to the blockage ratio. With an increase in the latter, the oscillating amplitude nonmonotonically changes as a result of the tunneling phenomenon, whereby the anticlockwise rotating Taylor roller is punctured by axial flow. Based on the above mechanism of pressure oscillation, the structure of a vortex breaker is proposed that can effectively reduce the oscillation in pressure.