Performance of instantaneous acceleration models of unsteady skin friction in practical applications

Abstract

This paper presents results of the authors’ previous investigations into the behaviour of the Brunone instantaneous acceleration unsteady friction model for slow and rapid transients in simple reservoir-pipeline-valve systems including a laboratory apparatus and a hydroelectric power plant. These results have been previously presented at IAHR WG Meetings in Brno, Czech republic (1999) and Trondheim, Norway (2001). The Brunone model is simple and gives reasonable match between the computed and measured results, at least, for valve closure cases. The model produces sufficient damping with a slight phase shift of the pressure pulses. The results obtained by the quasi-steady friction model agree well with measured results for slow transients; however, this model produces insufficient damping of the pressure pulses for rapid transients. The valve closure time and the corresponding length of the pipeline control the effect of unsteadiness on attenuation, shape and timing of the pressure pulses. There is a strong need to test unsteady friction models for other flow conditions (e.g., valve openings). Results of measurements are available upon request.