A comparison of periodic boundary conditions for computing fully-developed square duct flow using LES

摘要

In this paper, two different types of periodic boundary conditions have been used to compute fully-developed square-duct flow using LES. A relatively new periodic condition based on a fixed mass flow rate is benchmarked against the more traditional constant pressure gradient-based periodic condition. In the mass-based condition, the mass flow is imposed directly at the periodic boundary and the pressure field emerges as part of the solution as opposed to traditional method, which involves imposing the pressure gradient as a constant volumetric source in the flow direction. The two different conditions were implemented into a three-dimensional, unstructured, parallel CFD code. The code solves the incompressible Navier-Stokes equations using second-order spatial discretization and a three-time-level method for time discretization. The code was parallelized using the PETSc framework with a single program multiple data (SPMD) message-passing model and is run on the SHARCnet distributed memory parallel computer network. Simulations for a Reynolds number 5810 showed first that results obtained using the two different boundary conditions were essentially the same and similar to previous published results of the same flow. The simulations also showed that the computed flow evolves more quickly using the mass-based condition and thus a statistically relevant result can be obtained in less time using the mass-based condition.