A boundary layer growth model for one-dimensional turbulent unsteady pipe friction

Abstract

Unsteady flow in pipe networks is efficiently modelled using a one-dimensional flow approximation. It is general practice in engineering to assume a quasi-steady state approximation of the friction for unsteady pipe flows. The result of this approximation is an under-estimation of the damping during fast transient events. To remedy this shortcoming, an unsteady friction model is often employed. Unsteady friction models for laminar flow can be theoretically determined and have been successfully used for many years. However, the same cannot be said for unsteady friction in turbulent flows. A number of empirical unsteady friction models have been formulated, but only perform well for certain unsteady transient event types. This paper presents a new unsteady friction model for turbulent flows based on the growth and destruction of the boundary layer during a transient event.