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August 29, 2005, 05:39 
lift & drag coefficient on airfoil

#1 
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dear sirs how can i calculate the lift & drag coefficient on airfoil surface for 2d incompressible case, for fluent post processing i can calculate and draw only cp(pressure coefficient), what about lift & drag coefficient ?? thanks in advance for your early replay


August 29, 2005, 06:26 
Re: lift & drag coefficient on airfoil

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You can monitor lift & drag coefficients while your solution iterates by going to Solve>Monitors>Forces. In fact, if in your final results you want the lift & drag coefficient, then you should monitor them to ensure convergence.
Once you have a final solution you can get forces and moments from Report>Forces. It will print the force (or moment) in your units and in coefficient terms. Make sure you've defined your reference values at Report>Reference values. A sticking point is that "length" is the reference length used in the moment coefficient (Cm = 1/2*Rho*V^2*Aref*Lref) while "depth" is the length of your model in the z direction. If you set "depth" to 1, then it's a per unit length setup. Hope this helps, and good luck, Jason 

October 23, 2009, 01:59 
dear sir..

#3 
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vivit
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Can you tell me?? What is the Basic Calculation of FLUENT on Computing Lift Coef In Modelling 2D??
thanks 

October 23, 2009, 18:38 

#4 
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teguh hady
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Hy vivit apriliyanti!!
My problem is same as yours!! I think that 2d airfoil don't have A!!! So if A equal to 0 then Cl will be infinite!!! But when we run FLUNT 2D we'll see VOLUME after check our grid!!! the value of volume is not zero!! I think the value of Cl is based on that volume!! hope it helps!! teguhtf 

December 7, 2009, 07:25 
hello mister

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vivit
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wahat is grid independensi in FLUENT? please you explain,thnks


December 16, 2009, 08:22 
Basic Computation Of 2D

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teguh hady
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Sorry, for waiting. After searching in some books, I've opinion that For solving Cl & Cd in 2D. There is assumption that the value of A is 1. you can read this on Anderson Computational Fluid Mechanics And Heat Transfer.
Hope it helps teguhtf
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Now Or Never!!! 

December 16, 2009, 11:14 

#7  
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JT.Q
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Quote:
2、in force report panal, you can set the force vector to obtain cd and cl respectively.set x=1 and y=0,you will get cd,if x is the velocity direction.set y=1 and x=0, you will get cl. 

December 17, 2009, 09:30 

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March 31, 2015, 19:02 

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Quote:
I am simulating the flow over a 2 element airfoil which is to say that there is a main wing and a flap. I want all coefficients to be scaled to a unit chord. I am unsure whether FLUENT uses the real length of the airfoil or the reference length. I calculate both the lift and drag coefficient on the main, flap and both. However only the main wing and flap combined chord is 1m. I am not quite clear from your explanation what whether FLUENT is assuming a unit chord for all calculations of CL and CD regardless of actual size or if it assumes the actual size. Depth is the z direction or the span of the wing and the length is used for moment how do I define a unit chord? is it in the area value? Thanks in advance for the help. 

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