Chapter 7 External Forced ConvectionFlow Across Cylinders And Spheres 7-35CFor the laminar flow, the heat transfer coefficient will be the highest at the stagnation point which corresponds to θ≈°0 . In turbulent flow, on the other hand, it will be highest when θis between . 90°°and 12013-36C Turbulence moves the fluid separation point further back on the rear of the body, reducing the size of the wake, and thus the magnitude of the pressure drag (which is the dominant mode of drag). As a result, the drag coefficient suddenly drops. In general, turbulence increases the drag coefficient for flat surfaces, but the drag coefficient usually remains constant at high Reynolds numbers when the flow is turbulent. 13-37CFriction drag is due to the shear stress at the surface whereas the pressure drag is due to the pressure differential between the front and back sides of the body when a wake is formed in the rear.
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This note was uploaded on 01/22/2012 for the course PHY 4803 taught by Professor Dr.danielarenas during the Fall '10 term at UNF.