Lattice Boltzmann simulation of the ERCOFTAC pump impeller

Abstract

The analysis of unsteady flows is becoming more and more important in the field of hydraulic turbomachinery applications, both for stable and especially for unstable operating conditions and other transient phenomena. Unsteady Reynolds-averaged Navier-Stokes (RANS) methods for incompressible flows, implemented via finite volume or finite element approaches, reach their limit in both accuracy and acceptable computational time. The accuracy mainly suffers due to the strong dependence of the solution on turbulence model variants. Furthermore, incompressibility of the flow and the linked implicit pressure equation makes large eddy simulations (LES) of Navier-Stokes-based methods for such flows prohibitively expensive. An alternative to Navier-Stokes fluid solvers are methods based on the solution of the discrete Boltzmann equation, so-called Lattice Boltzmann Methods (LBM). The purpose of this work is to present first results of an ongoing project involving the simulation of unsteady hydraulic turbomachines at high Reynolds numbers. For this purpose, the ERCOFTAC pump impeller was selected as a test case. Results obtained with the current implementation of the in-house code suggest, that the present methodology could provide a viable alternative for the analysis of unsteady flow phenomena in hydromachines.