Study on Time-Average Friction Characteristics of Low Flow Rate Single-Phase Flow in a Rectangular Channel in Rolling Motion

Studies of time-average friction characteristics of low flow rate single-phase flow in a rectangular channel under rolling motion condition were carried out.The test fluid is deionized water and the equivalent diameter of the rectangular channel is 5.39 mm,the range of the Reynolds number is 800-20000 and the amplitude of the flow rate exceeds ±30%.Two methods were employed to calculate the time-average friction coefficient and the results showed that the time-average friction coefficients obtained by the two methods are different in laminar flow.Different methods represent different physical meanings.When the time-average friction coefficient is calculated by integrating the instantaneous friction coefficient which is acquired by Darcy equation in a period,this time-average value represents time-average viscous dissipation.On the other hand,when the time-average coefficient is computed by Darcy equation which employs time-average pressure drop and velocity,this time-average friction coefficient represents time-average pressure drop.