Theoretical analysis of phase-lag in low frequency laminar pulsating flow

The phase-lag between pressure gradient and flow rate in laminar pulsating flow in circular pipes and parallel-plate channels are studied theoretically. It is found that the phase-lag between pressure gradient and flow rate in low frequency (f < 0.5 Hz) pulsating laminar flow exists both in circular pipes and parallel-plate channels. The phase-lag increases with the increase of pulsating frequency, radius of the pipe and the height of the channel, however, it decreases with increase of the fluid viscosity. In addition, the phase-lag is not related to the pulsating amplitude. The analytical results show that velocity radial distribution does not affected by the low frequency pulsation and the value of phase-lag depends on the ratio of the acceleration pressure drop to the total pressure drop.

► Theoretical models were established to analysis the phase-lag.
► The effect parameters on phase-lag were investigated.
► The reasons that induced the phase-lag were analyzed.