How to calculate the strength/energy of vortex in Joules

Agad15 · November 2, 2015, 07:42

I would like to evaluate the strength of vortex in lid driven cavity flow. i am simulating the cases in Fluent. Although stream function (m^2/s)indicates the strength of vortex, I want to know vortex strength in Joules. How is it possible?

fluid23 · November 2, 2015, 16:50

You can differentiate your stream function to get your velocity field (http://web.mit.edu/16.unified/www/FA...ctures/f12.pdf) which is then integrated around a closed loop to get your vortex strength (http://web.mit.edu/16.unified/www/SP..._Notes/f18.pdf).

For lid driven cavity flow, you will probably not get a constant circulation moving radially inward and will probably have to integrate or average several radial locations to get a global result. (unless I am totally wrong about that, but i doubt it.)

fluid23 · November 2, 2015, 17:01

Also, unless I misunderstand your question I don't believe you can convert a circulation (vortex strength) to joules. Joule is a measurement of energy, circulation is not a measurement of energy. Dimensional analysis of the joule (kg-m^2/s^2) gives (M^1)(L^2)(T^-2) while circulation (m^2/s) gives (L^2/T^-1). Therefore you cannot convert between the two units...

November 2, 2015, 07:42	How to calculate the strength/energy of vortex in Joules	#1
Agad15 New Member Anvesh Join Date: Jan 2014 Posts: 25 Rep Power: 12	I would like to evaluate the strength of vortex in lid driven cavity flow. i am simulating the cases in Fluent. Although stream function (m^2/s)indicates the strength of vortex, I want to know vortex strength in Joules. How is it possible?

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November 2, 2015, 16:50		#2
fluid23 Senior Member Matt Join Date: Aug 2014 Posts: 947 Rep Power: 18	You can differentiate your stream function to get your velocity field (http://web.mit.edu/16.unified/www/FA...ctures/f12.pdf) which is then integrated around a closed loop to get your vortex strength (http://web.mit.edu/16.unified/www/SP..._Notes/f18.pdf). For lid driven cavity flow, you will probably not get a constant circulation moving radially inward and will probably have to integrate or average several radial locations to get a global result. (unless I am totally wrong about that, but i doubt it.)

November 2, 2015, 17:01		#3
fluid23 Senior Member Matt Join Date: Aug 2014 Posts: 947 Rep Power: 18	Also, unless I misunderstand your question I don't believe you can convert a circulation (vortex strength) to joules. Joule is a measurement of energy, circulation is not a measurement of energy. Dimensional analysis of the joule (kg-m^2/s^2) gives (M^1)(L^2)(T^-2) while circulation (m^2/s) gives (L^2/T^-1). Therefore you cannot convert between the two units...