Venturimeter and Pitot tube
Fluid dynamics · Physics
Study notes
Example: Find the flow rate of water through a venturimeter. Given: diameter of inlet D1 = 0.2 m, diameter of throat D2 = 0.1 m, pressure at inlet P1 = 150 kPa, pressure at throat P2 = 120 kPa, density of water ρ = 1000 kg/m³. Steps: 1) Calculate areas: A1 = πD1²/4 = 0.0314 m², A2 = πD2²/4 = 0.00785 m². 2) Use Bernoulli and continuity to find velocity at throat: V2 = sqrt[(2(P1‑P2))/(ρ(1‑(A2/A1)²))]. Compute A2/A1 = 0.25, (A2/A1)² = 0.0625. Then V2 = sqrt[(2×30,000)/(1000(1‑0.0625))] = sqrt[60,000/(937.5)] = sqrt[64] = 8 m/s. 3) Flow rate Q = A2 × V2 = 0.00785 × 8 = 0.0628 m³/s. So about 0.063 cubic metres per second of water passes through.