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Old Oct 5th 2014, 10:25 AM   #1
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A plate held in fluid flow

If I am hanging a square plate using a thread in a fluid flow what will be the force acting on the plate? will it be drag force it self?

In drag force, there is a cross section area, but the cross section area of plate is negligible. So is it drag force itself or is there some other equation? Assume the plate to be rough.

Will the same force be acting on the thread too?
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Old Oct 5th 2014, 10:57 AM   #2
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Drag... skin, form and wave!

Some consider drag has three aspects.
1) skin drag - your plate has a "rough" surface.
2) form drag - square versus rounded corners of your plate
3) wave drag is principally an air/water-interface event. Oil tanker bows are designs to reduce wave drag.

This is all I have on drag...

http://www.thermospokenhere.com/wp/0...rag_force.html

Good Luck TSH
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Old Oct 5th 2014, 10:11 PM   #3
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Thank you.
But my case is a plate held parallel to flow. so the flow is not directly hitting the face of plate.

Now will the form drag be there? I can neglect wave drag.

What will be the equation for skin drag then.
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Old Oct 6th 2014, 01:28 AM   #4
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I found this reference:

http://me.lsu.edu/~meniki/me3842/Notes/Drag&Lift.pdf

which states for a flat plate parallel to the flow under laminar flow conditions (not turbulent) skin drag coefficient is Cd=1.328/sqrt(Re_L), where Re_L is the Reynolds number based on the length of the plate:

Re_L = vL/nu, wher nu= the dynamic viscosity of the fluid.

Given this Cd the area to be used in the drag formula is the surface area of the plate, not its leading edge area. Hope this helps.
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