2021 Volume 14 Issue 2 Pages 43-48
State estimation of transient response flow in pneumatic pipelines is important for system design and phenomenon analysis. The purpose of this study is to investigate a one-dimensional numerical method by using a high-order finite upwind difference scheme that can calculate the transient response in a straight circular tube with turbulent transitions. In order to calculate such a flow by using a one-dimensional numerical model, the source term needs to be represented accurately. We propose an appropriate representation of the source term in the form of a switch between laminar and turbulent models with unsteady losses, depending on the critical Reynolds number. To validate the model, transient response experiments were conducted in a single closed-end circular tube with an inner diameter of 28 mm and a length of 4 m, up to an initial pressure difference of 7 kPa, and the closed-end pressure was measured. Comparison with experimental data showed that the transient response flow including turbulent transition can be calculated accurately by considering the pipe wall roughness and setting the critical Reynolds number between 12000 and 14000.