Learning Forum

[feriko95]

Hi. I am doing a 2way fsi simulation in ansys fluent and transient structural about 2.5D membrane airfoil. z coordinate has only 1 element, and deflections in x and y axis just important. the picture attached.

[peteroznewman]

nWhy must the membrane have a chord-wise pre-stress of 300 kPa?nI could understand if the wing had an internal pressure that inflates the wing to help it keep its shape. That makes sense.n

[feriko95]

nthis membrane prestressed to maintain a tensile state and to reduce deflections under applied loadings.nI found a paper (attached) that set a pre-stress (pre strain) by introducing an initial elongation(had two membrane, upper and lower membrane, defined moveable trailing edge), mentioned in part 2.1 of the papernbut in my case because of my geometry cant define this method i dont know how to apply that. by convert strain to stress found that should define 300Kpa pre stress for the purpose.n

[peteroznewman]

nIn the paper, they describe the simple method of fixing the front solid body and applying a force on the rear solid body to tension the membrane between them as shown by the straight gray lines between the solid bodies. You can do the same. Don't fix the rigid body on the trailing edge. Use a Displacement to move it back until you get the desired level of stress in the membrane.n

[feriko95]

@peteroznewman nnDear peter, I mentioned that paper just to describe the similar subject, that paper simulated double membrane airfoil ( at top and bottom), but my problem as shown as in the first comment is a single membrane airfoil that only has a membrane at top and looks like this:nsimply put, there is membrane (supposed a very thin beam) that its end constrained like attached photo, it must have a pre-stress in X- axis, because of the purposes that i mentioned at previous comments. how to apply thisn

[peteroznewman]

nUse the same method for a single membrane. The leading edge has a pinned support: X = 0, Y = 0. The trailing edge can have a Displacement BC with Y = 0 and X = some small amount that stretches the membrane to create the required stress. n