Project ForgeThe arrangement shown in the figure measures the velocity V of a gas of density 1 kg/m³ flowing through a pipe. The acceleration due to gravity is 9.81 m/s². If the manometric fluid is water (density 1000 kg/m³) and the velocity V is 20 m/s, the differential head h (in mm) between the two arms of the manometer is __________.
Explanation
This is a Pitot-type device: the dynamic pressure of the gas is balanced by the manometric water column, ρgas·V²/2 ≈ ρwater·g·h (the gas column's own weight is negligible against water's). h = ρgas·V²/(2·ρwater·g) = (1×20²)/(2×1000×9.81) = 400/19620 ≈ 0.0204 m ≈ 20.4 mm.
Source: GATE ME 2017 Session 2 (ME-2) (2017)
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