INVESTIGATION OF TURBULENCE BEHAVIOR IN WATERHAMMER

摘要

Understanding the turbulence behavior in unsteady (transient) flow in pipes is essential for modeling energy dissipation in waterhammer problems, modeling transient-related water-quality problem such as intrusion and verifying the assumptions involved in existing unsteady wall friction models. Laboratory studies of the turbulence response to waterhammer waves are not available and would be very difficult to conduct due to the high frequency of transient waves. This paper conducts numerical experiments on the response of turbulence to waterhammer waves, where a k - ε model is used. The pressure head traces produced by the present mathematical model are found to be in good agreement with three published laboratory experiments. This implies that, at least for the three experiments considered here, the turbulence response is well represented by the k - ε model. Therefore, the spatial and temporal variation of eddy-viscosity, turbulent kinetic energy and turbulent dissipation in these three cases are investigated in details. These results are used to shed some light on the validity of frozen turbulence, quasi-steady and quasi-laminar hypotheses, which are often adopted in modeling energy dissipation in waterhammer problems.