I have created a 2D geometry of a simple shape (like a vehicle) using ANSYS design modeller and created a 2D mesh using workbench mesher.
After importing and solving in fluent, i got a converged solution and i can get the pressure and velocity contours as shown in fig 1 and 2.
I am interested in knowing the coefficient of drag. I do know i can create a drag monitor and i can print the drag coefficient values in the console.
Problem is, what value should i specify in area, depth and length in "reference values" ?
As we know, drag coefficient Cd=(2Fd)/(rho*u*u*A)
where, A is the frontal area of the car. (refer fig.3)
If the car geometry is 2d, the frontal area shouldn't be Zero?
Is it possible to determine drag force or drag coefficient in 2D?
There are several methods
using pressure distribution around objet profile (for pressure coefficient)
Pressure and speed distribution at enter and exit section of a wind tunnel using conservation of motion quantity
Équilibrium of forces thanks to force measurement. (not appliable in your case)
Answers are available on RG. See below
Consider 1 meter for profile width. Force is proportional to width.
You can use 'Paths' to integrate F from pressure. If an isotropic pressure is all you have, you don't need to integrate on the upper and lower 'surfaces'. You can use one path for each of the contributing sides; only add the components along x to find drag.
You'll be very far from realistic results here, but the 2d assumption in itself starts to become quite good if the object depth is larger than ~30 times the height of the object along y.
Thanks a lot to prof. Antoine and prof. Concli.
If the real width (along z axis) of the car is 1.5 m, I have to multiply the force along x direction with 1.5 to get the actual drag force, right?
I use Ansys workbench mesher to generate mesh and Fluent as solver. Is it possible to specify the thickness of 2D element as 1.5m anywhere in mesh or in Fluent in order to get the actual drag force directly?
If the 2D approximation remains valid, you can multiply force/meter by width.
You should consider that airflow cannot be really in 2D for short objects. Compare ball and cylinder Cx coefficients to have an idea of the approximation.
Size of the windtunnel that you modelize seems too small not to influence airflow around object. It could be interesting to enhance length of the studied area in front of object and beside it, to see influence of environment on the results you look for.
https://www.google.fr/url?sa=t&source=web&rct=j&url=http://www.users.miamioh.edu/sommerad/NSF%2520Files/comparison_with_experiments.pdf&ved=0ahUKEwjT1IjT0-TUAhXGthoKHS6QBvIQFghyMA4&usg=AFQjCNGs1hL0N1A29RegO-OP2-K2Yl7AuQ
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