# Calculating drag coefficient from Fluent

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 March 11, 2000, 09:45 Calculating drag coefficient from Fluent #1 Richard Guest   Posts: n/a Can any one tell me how to calculate drag coefficient from Fluent on the 2-D airfoil. I have done this using wall force(from fluent display) taking X-direction normalforce + x-direction shear force divide by 0.5u*2 but i end up getting the wrong result. Could any one tell me if this is the right approach.

 March 28, 2000, 10:16 Re: Calculating drag coefficient from Fluent #2 Flav Guest   Posts: n/a Solve / Monitor / Surface / Drag Then chose the airfoil edges to compute the drag force from. To get a non-dimensional drag coefficient, set your airfoil parameters in the following section : Report / Reference values Set length, speed, rho etc. The reported Cd should be ok now. Good luck. Cheers, Flav mr.dargahi, sabin, metmet and 1 others like this.

 March 30, 2000, 00:24 Re: Calculating drag coefficient from Fluent #3 N. Jalaiah Guest   Posts: n/a Hi Richard, I also tried to plot the Cd profile for flow past a circular cylider case but the results are not coming correctly. I followed this way. Solve/Monitors/Force/Drag ... then I chosen the curve for Cd plot. I set the density, velocity, but not the length at Report / Reference values. I wonder whether length details are truly needed for calculating the Cd value. Bye, Jalaiah

 February 15, 2010, 10:12 #4 New Member   alessio Join Date: Nov 2009 Posts: 5 Rep Power: 7 Hi guys, i'm tring to calculate the drag force coefficient in a 3-d case and the fluid is behind a cylinder. the fluid is: density = 800 kg/m^3 dinamic viscosity = 0.005 kg/ms velocity = 8 m/s the cylinder is: diameter = 13 mm length = 300 mm stiffness modulus = 200000 MPa poisson coefficient = 0.3 to calculate the drag coefficient i push: solve/monitors/force/drag coefficient..... the direction of the vector of force is in parallel to the flow flowing i set the reference value: Area = 0.013*0.3 that is the product for diameter and the length of the cylinder, Length = 0.013 that is the diameter then i set other values: viscosity, velocity, density of fluid as i wrote upforward. i put 90 nodes around the circonference of the cylinder, and 25 along to the length of the cylinder. the algorytm used is LES, because this is a 3d case I used PISO and second order upwind for momentum... the Cd value is incresing but after 0.02 seconds it is still to 0.7. How can i do, please help me. Alessio Thank to all

July 7, 2011, 05:53
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Quote:
 Originally Posted by alessios123 ... I set the reference value: Area = 0.013*0.3 that is the product for diameter and the length of the cylinder, Length = 0.013 that is the diameter then i set other values: viscosity, velocity, density of fluid as i wrote upforward. i put 90 nodes around the circonference of the cylinder, and 25 along to the length of the cylinder. the algorytm used is LES, because this is a 3d case I used PISO and second order upwind for momentum... the Cd value is incresing but after 0.02 seconds it is still to 0.7. How can i do, please help me. Alessio Thank to all
Check the Area one more time, it seem an Area is incorrectly calculated

 August 27, 2011, 20:32 #6 Member   Tobino Join Date: Jan 2011 Location: Osaka,Japan Posts: 33 Rep Power: 6 Hi, I am using Fluent to calculated Force too, my model is a hull of ship. my results showed that the Viscous Force is ok but the Pressure Fore is not corrected. Anybody knows what is wrong? Tobino,

September 20, 2011, 09:11
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Quote:
 Originally Posted by tobino Hi, I am using Fluent to calculated Force too, my model is a hull of ship. my results showed that the Viscous Force is ok but the Pressure Fore is not corrected. Anybody knows what is wrong? Tobino,
what do you mean "the Pressure Forcee is not correct?"

 March 18, 2014, 02:07 Calculating forces #8 New Member   Aalisha Join Date: Jan 2014 Posts: 18 Rep Power: 3 Hello, I have created a 3-D model of a 3 blade tidal current turbine with the blade length 710 mm and blade width 162 mm. It is surrounded by a cylinder which will act as a rotor and finally by a brick acting as a stator. After exporting the mesh from gambit 2.2.30 to fluent 6.1, I want to calculate the drag and lift force on the walls of the blades. I have defined the units (angular velocity into rpm), grid interfaces, boundary conditions. However when I follow the command Solve>> Monitors>> Forces It shows an error saying " No data to plot". If anyone can explain this?

February 17, 2015, 08:45
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Jakub
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Quote:
 Originally Posted by aalisha It shows an error saying " No data to plot". If anyone can explain this?
It just means that you didn't start calculations, so there is nothing to show. After calculations begin, plot should appear.

September 21, 2015, 03:24
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N B Khan
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Quote:
 Originally Posted by Centurion2011 Check the Area one more time, it seem an Area is incorrectly calculated
Sir, if we change the reference area value, then we need to run the simulation again???

 September 21, 2015, 04:44 yeap #11 Member     Join Date: Jul 2011 Posts: 73 Blog Entries: 1 Rep Power: 10 It depends on what are you looking for?! If you are looking for Cd, based on results obtained for aerdynamic force,then these results might not be correct if reference are is not correct. __________________ I'M NOT A GYNECOLOGIST BUT I'LL TAKE A LOOK.

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