Publications Details
A grid refinement study of two-dimensional transient flow over a backward-facing step using a spectral-element method
The two-dimensional transient flow over a backward-facing step is numerically simulated using the spectral-element computational fluid dynamics code NEKTON. The simulated geometry corresponds to that of Kaiktsis et al. (1991) and Armaly et al. (1983), and flow is examined at Reynolds numbers of 500 and 800. A systematic grid refinement study is performed by varying both the element size and the order of the polynomial representation within the elements. For both values of the Reynolds number, it is observed that low-resolution cases exhibit sustained chaotic temporal behavior but that high-resolution cases evolve toward asymptotically steady flow by a monotonic decay of the transient. The resolution required to obtain asymptotically steady behavior is seen to increase with Reynolds number. These results suggest that the recently reported transition to chaotic flow at Reynolds numbers around 700 is an artifact of inadequate spatial resolution. The cause of resolution-dependent temporal behavior of spectral-element methods is explored.