SAE 10W-30 oil with viscosity 1 x 10-4 lbf s/ft2 is used as a lubricant between two parts of a machine that slide past one another with a velocity difference of 4 ft/s. What spacing, in inches, is required if you don't want a shear stress of more than 2 lbf/ft2?

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Q1) By using dimensional analysis concept, express the wall shear stress for the pipe flow which is depending likely on the distance from the beginning of the pipe, pipe diameter, pipe wall roughness, fluid velocity, density and viscosity?

A Pitot-static probe was used to measure the velocity distribution in a water tunnel. The two pressure lines from the probe were connected to a U-tube manometer which uses a liquid of specific gravity 1.7. The maximum velocity expected in the water tunnel was 2.3 m/s. Your job was to select an appropriate U-tube from a manufacturer which supplies manometers of different heights. The cost increases significantly with manometer height. Which of these should you purchase?