Velocity drop over backward facing step

warlocklw · February 9, 2012, 10:52

Velocity will drop over step height at backward facing step. However, the drop rate differ if the inlet velocity changed, that is Reynolds Number changed.

Can someone explain why the velocity drop more gradual if Re increase, while low Re will have sharper velocity drop rate? Thanks in advanced.

ghorrocks · February 9, 2012, 17:06

Have you looked at the flow fields? I think you will find as you increase Re number over this range the separation gets more pronounced, meaning that the velocity slow down and pressure recovery associated with the flow over the step gets spread over a longer distance.

warlocklw · February 9, 2012, 22:24

Yes, the recirculation zone size increase with Re. Thanks for your explanation.

February 9, 2012, 10:52	Velocity drop over backward facing step	#1
warlocklw New Member Join Date: Nov 2011 Posts: 24 Rep Power: 15	Velocity will drop over step height at backward facing step. However, the drop rate differ if the inlet velocity changed, that is Reynolds Number changed. Can someone explain why the velocity drop more gradual if Re increase, while low Re will have sharper velocity drop rate? Thanks in advanced.

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February 9, 2012, 17:06		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	Have you looked at the flow fields? I think you will find as you increase Re number over this range the separation gets more pronounced, meaning that the velocity slow down and pressure recovery associated with the flow over the step gets spread over a longer distance.

February 9, 2012, 22:24		#3
warlocklw New Member Join Date: Nov 2011 Posts: 24 Rep Power: 15	Yes, the recirculation zone size increase with Re. Thanks for your explanation.