Physics Help Forum A plate held in fluid flow

 Thermodynamics and Fluid Mechanics Thermodynamics and Fluid Mechanics Physics Help Forum

 Oct 5th 2014, 10:25 AM #1 Junior Member   Join Date: Oct 2014 Posts: 2 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?
 Oct 5th 2014, 10:57 AM #2 Senior Member   Join Date: Jun 2010 Location: NC Posts: 419 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
 Oct 5th 2014, 10:11 PM #3 Junior Member   Join Date: Oct 2014 Posts: 2 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.
 Oct 6th 2014, 01:28 AM #4 Physics Team     Join Date: Jun 2010 Location: Morristown, NJ USA Posts: 2,354 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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