Flapping fin thrust in FLUENT

jinks · July 5, 2012, 16:58

hey, I am simulating an oscillating/flapping fin in FLUENT. I plotted the cd vs the flow time and if the time averaged Cd comes out negative then it amount to a net THRUST rite? I need to know if this is the best way of calculating thrust. Also i should tell you, that for this oscillating fin, the average drag is coming out positive, contradictory to our hypothesis. Some one please help me with this.

Thank you.

meangreen · July 5, 2012, 17:30

It depends what surface you are defining your drag. (also on how you are defining your force) Think about it, it is going to be positive for one surface/phase and negative for the other. As air flows over a fin there will be a negative drag force for the air (the air is decelerating as it drags across the fin) but positive for the fin (the equal and opposite drag force from the air is implemented onto the fin).

cgpa4 · July 19, 2013, 19:34

I want to plot the curve for Cd vs flow time for a flow past cylinder. I tried by going to surface. But its not working. Please help me on it.

Mohammad

July 5, 2012, 16:58	Flapping fin thrust in FLUENT	#1
jinks New Member Ajinkya Desai Join Date: Jun 2012 Posts: 6 Rep Power: 13	hey, I am simulating an oscillating/flapping fin in FLUENT. I plotted the cd vs the flow time and if the time averaged Cd comes out negative then it amount to a net THRUST rite? I need to know if this is the best way of calculating thrust. Also i should tell you, that for this oscillating fin, the average drag is coming out positive, contradictory to our hypothesis. Some one please help me with this. Thank you.

July 19, 2013, 19:34	Cd vs Flow time	#3
cgpa4 New Member Mohammad Ashraf Hossain Join Date: Sep 2012 Posts: 7 Rep Power: 13	I want to plot the curve for Cd vs flow time for a flow past cylinder. I tried by going to surface. But its not working. Please help me on it. Mohammad

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July 5, 2012, 17:30		#2
meangreen Member Casey Join Date: Jun 2009 Posts: 98 Rep Power: 16	It depends what surface you are defining your drag. (also on how you are defining your force) Think about it, it is going to be positive for one surface/phase and negative for the other. As air flows over a fin there will be a negative drag force for the air (the air is decelerating as it drags across the fin) but positive for the fin (the equal and opposite drag force from the air is implemented onto the fin).