When a uniform flow enters a pipe or a duct, thin boundary layers along pipe walls start developing. These boundary layers grow as the flow propagates downstream, and eventually they coalesce at the pipe centerline. Beyond this point where this coalescence occurs, flow characteristics such as velocity, wall shear stress, etc., no longer vary with axial distance. Such a flow is called a fully developed flow, and the distance from the pipe entrance to this location is called the entrance length. In many industrial internal flow situations, such as air flow through a car exhaust system or oil flow through a pipeline, it is critical to identify the state of the fluid flow, i.e., whether it is still developing or fully developed, in order to simulate/identify proper working conditions for other downstream components.
In this homework, you will learn how to set up an axisymmetric turbulent pipe flow problem in Ansys Fluent. You will identify the entrance length from the simulation and compare it with theoretical calculations.
Download the Mesh file required for setting up the simulation and associated Case & Data files here. Follow the instructions below to set up this simulation in Ansys Fluent starting with the Mesh file. In case you face any issues setting up or running the simulation, refer to the corresponding initial and final Case and Data files.
Let’s now take a look at how the entrance length obtained from simulations compares with the theoretical calculations.