(a) A streamlined high-speed train is 100 m long, 2.5 m wide and has sides 2.5...

 

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(a) A streamlined high-speed train is 100 m long, 2.5 m wide and has sides 2.5 m high. The train moves at 200 km/hr through air with density 1.23 kg/m and dynamic viscosity 1.77x10$ Pa-s. The total drag on the two sides and the top can be assumed to be equal to the skin friction drag on one side of a flat plate that is 100 m long and 7.5 m wide (i.e., pressure drag can be neglected). (i) Estimate how far the laminar boundary layer is likely to extend from the leading edge. (ii) Calculate the drag force and the power required to overcome the skin friction. (iii) The power required to overcome the drag is now reduced to 100 kW. Assuming that air density and dynamic viscosity are not changed, estimate what the train speed would be in this case. (b) Using a sketch, define "flow separation" and identify the general conditions for this phenomenon to occur. Explain in your own words the key features of flow separation on a curved smooth surface and what effects sharp corners have on flow separation. (a) A streamlined high-speed train is 100 m long, 2.5 m wide and has sides 2.5 m high. The train moves at 200 km/hr through air with density 1.23 kg/m and dynamic viscosity 1.77x10$ Pa-s. The total drag on the two sides and the top can be assumed to be equal to the skin friction drag on one side of a flat plate that is 100 m long and 7.5 m wide (i.e., pressure drag can be neglected). (i) Estimate how far the laminar boundary layer is likely to extend from the leading edge. (ii) Calculate the drag force and the power required to overcome the skin friction. (iii) The power required to overcome the drag is now reduced to 100 kW. Assuming that air density and dynamic viscosity are not changed, estimate what the train speed would be in this case. (b) Using a sketch, define "flow separation" and identify the general conditions for this phenomenon to occur. Explain in your own words the key features of flow separation on a curved smooth surface and what effects sharp corners have on flow separation.