Effect of rolling motion on single-phase laminar flow resistance of forced circulation with different pump head

Effects of rolling motion on single-phase laminar flow resistance during forced circulation with different pump heads were investigated. Purified water was used as the working fluid and the flow rate ranged from 0.04 to 0.16 m3/h. Different pump heads were obtained by a variable speed electromotor, by which the flow rate was controlled combining with a regulating valve. The experimental results indicate that the influence of rolling motion on transient flow rate and frictional resistance largely depends on the pump head. The flow rate in rolling motion oscillates periodically with its amplitude decreasing rapidly as the pump head increases, and finally, tends to be steady as the pump head further increases to a high level. The system flow resistance curve and pump performance curve are employed to analyze the characteristics of flow oscillation. When the pump supplies a low head, the frictional pressure drop fluctuates asynchronously with the flow rate and could not be predicted by conventional correlations. While the pump supplies a high head, the frictional pressure drop does not fluctuate and could be predicted by conventional correlations. Effects of rolling motion on single-phase laminar flow resistance are clarified by analyzing the velocity distribution. In spite of the above mentioned effects, rolling motion has no influence on time-averaged flow resistance regardless of the pump head.

► Effects of rolling motion on single-phase flow behavior depend on the pump head.
► Pump performance curve and system curve are employed to analyze flow fluctuation.
► The fluctuation amplitude of flow rate decreases as the pump head increases.
► Transient frictional resistances representing different pump heads are compared.
► Rolling has no influence on frictional resistance if the pump head is sufficiently high.