What is an adverse pressure gradient, and where does it occur on an airfoil (Show that on an airfoil using a free hand sketch)? b) Why do golf balls have dimples? Hint: Support your answer by a sketch

Question A3 a) With the help of sketches briefly describe the main differences between laminar and turbulent boundary layers in relation to friction drag and flow separation. A tug boat is pulling a log raft (Figure QA3) on the surface of a lake at a constant speed of Uboat = 5m/s. The log raft can be modelled as a flat plate (L=20m and W = 5.0m). u ug U boat 8 U Tug Boat rope boat Air Water L -X Log Raft Figure QA3 Assume the boundary layer forming on both sides (air side and water side) of the log raft is two-dimensional and laminar with a second order velocity distribution: W b) By using the Momentum Integral Equation find an expression for the wall shear stress in terms of Reynolds number and then estimate the tensile stress acting on the rope assuming the rope has a circular cross section with a diameter of 15 mm) and the power required to pull it. c) What would be the tensile stress on the rope if we assume the boundary layers on the log raft were turbulent? You may assume:…