Unformatted text preview: Midterm Practice Exam 1 for MAE355 Problem 1 a. Give the definitions of the lift, drag, and moment coefficients CL, CD, and CM in mathematical expressions and name the variables used in these definitions. b. What are the advantages of using these dimensionless coefficients rather than the lift, drag, and moment themselves? c. What is the unit for kinematic viscosity in SI units? Problem 2 a. What are the similarity parameters for inviscid flows? b. What are the similarity parameters for incompressible, inviscid flows? Problem 3 Consider two different flows over geometrically similar airfoil shapes, one airfoil being twice the size of the other. The flow over the smaller airfoil has freestream properties given by T= 200K, =1.23 kg/m3, and V= 100 m/s. The flow over the large airfoil is described by T= 800K, =1.739 kg/m3, and V= 200 m/s. Assume that both and a are proportional to T1/2. Are the two flows dynamically similar? Problem 4 A flatplate airfoil has a Cp distribution as shown in the sketch on the left. As seen in the sketch, the upper surface Cp is constant at 1.0 from the leading edge to x = 0.25. From the quarterchord location, the upper surface Cp varies linearly from 1.0 to 0.0 at the trailing edge. The lowersurface Cp varies linearly from +1.0 at the leading edge to 0.0 at the trailing edge. The skin friction coefficient Cf is zero on both surfaces of the plate. If the is 10 deg, determine Cn, Ca, Cl, Cd, and Cmc/4. Note that you need to find Cmc/4, and one way to determine this is from CmLE and Cl. Problem 5 Consider the following Couette flow between two parallel flat plates at a distance h apart, where the lower plate is stationnary and the upper plate moves with a velocity U. See accompanying sketch. All flow properties are assumed to be constant along the x direction. The velocity field between two plates is given by Vx=Uy/h, and Vy=0. i. determine the line integral C Vds for the contour OABCO (shown in the sketch), when going in the counterclockwise direction. ii. determine the vorticity in the flow field, where = curl V. iii. determine the volume flux C VdA at the inlet flow OC. ...
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This note was uploaded on 09/17/2009 for the course MAE 355 taught by Professor Luo during the Fall '09 term at N.C. State.
- Fall '09