Irrotational Flows and Viscosity

alibaig1991 · October 1, 2015, 10:08

Can an irrotational flow be viscous? If not why?

Alex C. · October 1, 2015, 10:33

Any good fluid mechanic textbook will guide you through this question.

Basically, if the flow is irrotational, the velocity field can be written as the gradient of a scalar function (velocity potential). By tensor algebra, you can show that the Laplacian of a gradient is zero everywhere, therefore the viscous term in the momentum equation vanishes in such case.

alibaig1991 · October 1, 2015, 11:02

So, we can say that all irrotational flows are inviscous?

October 1, 2015, 10:08	Irrotational Flows and Viscosity	#1
alibaig1991 New Member abcd efgh ijkl Join Date: Oct 2015 Posts: 26 Rep Power: 11	Can an irrotational flow be viscous? If not why?

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October 1, 2015, 10:33		#2
Alex C. Member Join Date: Jul 2013 Posts: 56 Rep Power: 13	Any good fluid mechanic textbook will guide you through this question. Basically, if the flow is irrotational, the velocity field can be written as the gradient of a scalar function (velocity potential). By tensor algebra, you can show that the Laplacian of a gradient is zero everywhere, therefore the viscous term in the momentum equation vanishes in such case.

October 1, 2015, 11:02		#3
alibaig1991 New Member abcd efgh ijkl Join Date: Oct 2015 Posts: 26 Rep Power: 11	So, we can say that all irrotational flows are inviscous?