I'm studying about the backward facing step flow, suddenly,
I'm wondering what is the result from backward facing step flow.
I mean, is there problem due to BFS???
I saw somthing like lower performance and problem in exhaustion system of cars
but I didn't find detailed information.
please, Let me know about bad effects of BFS
A backward facing step is a bad thing in fluid flow. It causes a large separation bubble to form which will in general reattach some way downstream. The flow field is very three dimansional and unsteady. There is an increase in drag if the inlet flow is laminar transition is likely to be caused and a turbulent exit boundary layer will form. The only thing worse than a BFS is a forward facing step. This is worse because it forms two separation bubbles, one before the step and one after. An alternative to the BFS is a smooth curving surface, but this is harder to predict because the location of separation becomes a function of the stresses in the incomming boundary layer and turbulence models are not reliable to predict this.
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