Fluid volume in fluent vs experiment

otubaba · December 11, 2013, 13:07

I am working on a flow around an airfoil simulation in fluent. Also I'll be performing an experiment on the same airfoil in a subsonic wind tunnel. My question is... For better comparison of both results, is it necessary for the fluid volume around my airfoil in fluent be the same as that in the working section of the wind tunnel?

Zaktatir · December 11, 2013, 14:35

The finite-volume method (FVM) is a method for representing and evaluating partial differential equations in the form of algebraic equations.

This is similar to the finite difference method or finite element method, values are calculated at discrete places on a meshed geometry.

In the finite volume method, volume integrals in a partial differential equation that contain a divergence term are converted to surface integrals, using the Gauss theorem. Then these integrals are translated to sums over face middle points to calculcate the convection terms. You need the gradient of the our variable on these faces to calculate the second order terms.

Experiment is reality and you do need no volumes. I thought you are kidding with that question or do i misunderstand you

otubaba · December 12, 2013, 11:20

Thanks Zaktatir. But I think you probably misunderstood me. I am actually concern about the far wall boundary and its effect on the result. In reality/experiment the working section of the wind tunnel is often fixed but in fluent, the boundary around the airfoil can be moved far away reducing its effect on airfoil.

Zaktatir · December 12, 2013, 12:47

I would suggest to look into the wing tutorial with pressure far field

flotus1 · December 12, 2013, 13:14

When you want to compare the results from simulation and experiment, it can be a good idea to model part of the wind tunnel in fluent unless you have a "perfect" wind tunnel that provides a completely uniform flow field with clearly defined turbulent quantities or you want to neglect the effect of the wind tunnel confinement.

December 11, 2013, 13:07	Fluid volume in fluent vs experiment	#1
otubaba New Member Join Date: Oct 2012 Posts: 9 Rep Power: 13	I am working on a flow around an airfoil simulation in fluent. Also I'll be performing an experiment on the same airfoil in a subsonic wind tunnel. My question is... For better comparison of both results, is it necessary for the fluid volume around my airfoil in fluent be the same as that in the working section of the wind tunnel?

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December 11, 2013, 14:35		#2
Zaktatir Senior Member Join Date: Jan 2010 Location: Germany Posts: 268 Rep Power: 17	The finite-volume method (FVM) is a method for representing and evaluating partial differential equations in the form of algebraic equations. This is similar to the finite difference method or finite element method, values are calculated at discrete places on a meshed geometry. In the finite volume method, volume integrals in a partial differential equation that contain a divergence term are converted to surface integrals, using the Gauss theorem. Then these integrals are translated to sums over face middle points to calculcate the convection terms. You need the gradient of the our variable on these faces to calculate the second order terms. Experiment is reality and you do need no volumes. I thought you are kidding with that question or do i misunderstand you

December 12, 2013, 11:20		#3
otubaba New Member Join Date: Oct 2012 Posts: 9 Rep Power: 13	Thanks Zaktatir. But I think you probably misunderstood me. I am actually concern about the far wall boundary and its effect on the result. In reality/experiment the working section of the wind tunnel is often fixed but in fluent, the boundary around the airfoil can be moved far away reducing its effect on airfoil.

December 12, 2013, 12:47		#4
Zaktatir Senior Member Join Date: Jan 2010 Location: Germany Posts: 268 Rep Power: 17	I would suggest to look into the wing tutorial with pressure far field

December 12, 2013, 13:14		#5
flotus1 Super Moderator Alex Join Date: Jun 2012 Location: Germany Posts: 3,399 Rep Power: 46	When you want to compare the results from simulation and experiment, it can be a good idea to model part of the wind tunnel in fluent unless you have a "perfect" wind tunnel that provides a completely uniform flow field with clearly defined turbulent quantities or you want to neglect the effect of the wind tunnel confinement.