dear sirs how can i calculate the lift & drag coefficient on airfoil surface for 2-d 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

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

[vivit apriliyanti]

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

[teguhtf]

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

[vivit apriliyanti]

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

[teguhtf]

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

[jiangtao167]

Originally Posted by n. natik
;123784

dear sirs how can i calculate the lift & drag coefficient on airfoil surface for 2-d 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

1、for a 2d case,take x-y plan for example, the length in z direction is 1, so A=L(m)*1=L(m)
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.

[aescarbi]

Originally Posted by vivit apriliyanti

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

Grid independence means that your solution does not change appreciately when you refine your mesh.

[Exkalabur22]

Originally Posted by Jason
;123785

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

Hello

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.