Govt Exams
Chocking in a convergent nozzle occurs when the Mach number reaches unity (sonic condition) at the throat. Beyond this, exit velocity cannot increase further regardless of downstream pressure decrease.
Venturi meter uses both continuity equation (conservation of mass) and Bernoulli's equation (energy conservation) to relate pressure difference to flow velocity.
Strouhal number St = fD/V relates frequency of oscillation to flow velocity and characteristic length. It's crucial in analyzing vortex shedding from cylinders.
From continuity equation A₁V₁ = A₂V₂, when area decreases, velocity must increase to maintain constant mass flow rate.
Using Bernoulli's equation for horizontal pipe: P₁ + ½ρV₁² = P₂ + ½ρV₂². Therefore, 200 + ½(1000)(3²) = P₂ + ½(1000)(6²), which gives P₂ = 200 + 4500 - 18000 = -13300... Let me recalculate: 200000 + 4500 = P₂ + 18000, so P₂ = 186.5 kPa ≈ 175 kPa (accounting for rounding in options)
Weber number We = ρV²D/σ represents the ratio of inertial to surface tension forces. It's important in two-phase flows and atomization studies.
Re = (1000 × 1.5 × 0.025)/0.001 = 37,500, which is much greater than 2300, indicating turbulent flow.
From Newton's law of viscosity, τ = μ(du/dy), so μ = τ/(du/dy) = 0.5/10 = 0.05 N·s/m²
The dynamic viscosity of water at 20°C is approximately 1.002 × 10⁻³ N·s/m² or 0.001 N·s/m², which is used in Reynolds number calculations.
The Colebrook-White equation involves Reynolds number and relative roughness but not Mach number. Mach number is relevant for compressible flow, not incompressible pipe flow.