Flows through plane sudden-expansions

A calculation method has been developed and used to represent flows downstr eam of plane symmetric expansions with dimensions and velocities encompassi ng laminar and turbulent flows. Except for very low Reynolds numbers, the f lows are time-dependent and asymmetric and the calculated results are appra ised first in relation to published measurements of laminar flows and then to new measurements obtained at a Reynolds number of 26500. The time-depend ent laminar simulations indicate that the critical Reynolds numbers are pre dicted with excellent accuracy for different expansion ratios and the detai ls of the asymmetric velocity profiles are in good agreement with experimen tal measurements. The laminar flow calculations also show that increasing t he thickness of the separating boundary layer leads to longer regions of se paration and no dominant frequency for Reynolds numbers up to those at whic h the third separation region was observed. The turbulent flow simulations made use of the k-epsilon turbulence model and provided a satisfactory repr esentation of measurements, except in regions close to the wall and within the recirculation regions. Also, the longer reattachment length was underes timated. Limitations are discussed in relation to these and higher-order as sumptions. Copyright (C) 2000 John Wiley & Sons, Ltd.