Assuming SMOOTH FLAT PLATE behavior (Ue= constant, no roughness), calculate the

Question

Assuming SMOOTH FLAT PLATE behavior (Ue= constant, no roughness), calculate the boundary layer thickness and skin friction coefficient for the boundary layer developing on an airfoil with a chord of 5 ft. Air properties should be taken as sea level standard values, and the air speed 70 knots. Show graphs of Cf
and overall thickness ("delta") vs. X/C. On each graph, show results for (1) ALL
TURBULENT, and (2) ALL LAMINAR. Use the equations provided in your lab manual for flat plate boundary layers. Also give the TOTAL drag on the flat plate (one side) for each case. DISCUSSION: What is the smallest size of roughness is would significantly increase the total drag on the plate with TURBULENT flow?

Explanation / Answer

Fluid drag comes in several forms, the most basic of which are pressure drag and friction drag. Pressure or form drag is the drag associated with the energy required to move fluid out from in front of an object in the flow, and then back in place behind the object. Much of the drag associated with walking through water is pressure drag, as the water directly in front of a body must be moved out and around the body before the body can move forward. The magnitude of pressure drag can be reduced by creating streamlined shapes. Friction or viscous drag is caused by the interactions between the fluid and a surface parallel to the flow, as well as the attraction between molecules of the fluid. Friction drag is similar to the motion of a deck of cards sliding across a table. The frictional interactions between the table and the bottom card, as well as between each successive card, mimic the viscous interactions between molecules of fluid. Moving away from the surface of an object in a fluid flow, each fluid layer has higher velocity until a layer is reached where the fluid has velocity equal to the mean flow. Fluids of higher viscosity

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