Simulation of transient flow in micro-hydraulic pipe system

Abstract

This paper presents the modelling and simulation of transient flow in micro-hydraulic pipe systems. Liquid stream energy dissipation occurs mainly as a result of friction losses. Theoretical considerations of water hammer resulting from rapid valve closing, supported by experimental verification, were undertaken. The experimental system incorporated a straight two-meters long section of a steel pipe with an internal diameter of 4·10−3 m. An attempt was made to determine the degree of conformity of the transient flow model (previously verified in conventional pipes) to the experimental results obtained for small-internal-diameter pipes. Shear stress on the pipe wall was modelled using first a simplified quasi-steady approach and then an effective modified unsteady friction model. The pressure waveforms at the valve (at the downstream end of the pipe) were obtained for initial flow velocity, v01 = 2.39 m/s and v02 = 1.14 m/s, respectively. Experimental studies were carried out in the region of laminar flows with Reynolds numbers below 100.