Experimental investigation on friction characteristics of pulsating flow in a pipe with different shapes

Abstract

The present experimental study investigated the flow resistance of pulsating turbulent pipe flow. The effect of frictional losses is determined for the different diameters of the pipes, pulsation frequency, and amplitude and compared with steady flow. Further, the influence of wave patterns (sinusoidal, square, and triangular) on flow resistance is examined. The flow resistance obtained for pulsating flow in terms of dimensionless frequency parameter ( √𝜔́ ) does not show any effects with the pipe diameters. The results show that the flow resistance decreases with the Reynolds number for both steady and pulsating flow. It is experimentally demonstrated that the flow resistance of pulsating flows is greater than that of steady flow in the same range of Reynolds number. Further, for a given pulsation amplitude, the enhancement in friction factor increases with an increase in pulsation frequency. It is attributed that pulsation increases fluid-particle interaction between the fluid layers and with the surface and gives rise to friction. The pulsation amplitude represents the fluid location acceleration, increasing the amplitude, the transverse interaction between the fluid layers increases and exhibiting more frictional resistance. The flow resistance in the accelerating zone increases and decreases in the decelerating zone of the pulsating flow. The decelerating zone's flow resistance is higher than the steady flow for the same Reynolds number. It indicates that the flow resistance is highly dependent on the transverse interaction of the fluid layers rather than the velocity.