Problem 4: A venturi meter is measuring the flow of water; it has a main diameter of 3.5 cm tapering down to a throat diameter of 1.0 cm. If the pressure difference is measured to be 18 mm Hg, what is the speed of water entering the venturi throat?

Solution

Given

Main diameter = 3.5 cm = 0.035 m = d_{1} (say) Cross-sectional area of main diameter = Density of water = ρ = 1000 kg/m^{3}

Throat diameter = 1.0 cm = 0.01 m = d_{2} (say)
Cross-sectional area of the throat diameter =
Pressure difference = 18 mm-Hg = 18 × 133 = 2394 pascals

Required

Velocity of water

Formula

Solution

Knowing the pressure difference and areas of cross-sections, put values in the formula to find the velocity of water.

Before handing on the solution, we must know that, A = πr^{2} = π(d/2)^{2} and 1 mm-Hg = 133 pascal