Kinematic viscosity is the ratio of dynamic viscosity to density. Its SI unit is m²/s or Stoke (1 Stoke = 10⁻⁴ m²/s).
Q.2Easy
Which of the following statements about streamline flow is correct?
Answer: B
Streamlines represent the paths followed by individual fluid particles in steady flow. They cannot intersect, and velocity is always tangential to streamlines.
Q.3Easy
The continuity equation for incompressible flow states that:
Answer: A
The continuity equation for incompressible flow is based on mass conservation: ρA₁V₁ = ρA₂V₂, which simplifies to A₁V₁ = A₂V₂ when density is constant.
Q.4Easy
What is the dimension of pressure coefficient (Cₚ)?
Answer: A
Pressure coefficient Cₚ = (P - P∞)/(0.5ρV∞²) is a dimensionless quantity used in aerodynamics and fluid mechanics.
Q.5Easy
Bernoulli's equation applies to:
Answer: B
Bernoulli's equation is valid for inviscid (frictionless), incompressible, steady flow along a streamline. It represents energy conservation in such flows.
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Q.6Medium
A pump delivers 0.05 m³/s of water. If the pipe diameter is 0.1 m, the velocity of flow is:
Answer: A
Using Q = AV = (π/4)D²V, we get V = Q/A = 0.05/(π/4 × 0.1²) = 0.005.00785 = 6.37 m/s
Q.7Medium
The Darcy friction factor for fully developed laminar flow in a pipe depends on:
Answer: B
For laminar flow, friction factor f = 64/Re is independent of surface roughness. Roughness effects become significant only in turbulent flow.
Q.8Medium
Water flows through a horizontal pipe with diameter 0.05 m at a velocity of 2 m/s. The volumetric flow rate is:
Answer: A
Q = AV = (π/4)D² × V = (π/4) × 0.05² × 2 = 0.00393 m³/s
Q.9Medium
The Mach number is the ratio of:
Answer: B
Mach number M = V/a, where V is flow velocity and a is the speed of sound. It indicates whether flow is subsonic (M<1), sonic (M=1), or supersonic (M>1).
Q.10Medium
For turbulent flow in pipes, the Colebrook-White equation is used to find the friction factor. Which of the following is NOT an input parameter?
Answer: C
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.
Q.11Easy
Water at 20°C flows through a pipe network. The dynamic viscosity of water at 20°C is approximately:
Answer: A
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.
Q.12Medium
A fluid element has shear stress τ = 0.5 Pa and velocity gradient du/dy = 10 s⁻¹. The dynamic viscosity of the fluid is:
Answer: A
From Newton's law of viscosity, τ = μ(du/dy), so μ = τ/(du/dy) = 0.105 = 0.05 N·s/m²
Q.13Medium
The Reynolds number for flow in a circular pipe is given by Re = ρVD/μ. If the flow transitions from laminar to turbulent at Re ≈ 2300, then for a pipe with D = 0.025 m and V = 1.5 m/s (ρ = 1000 kg/m³, μ = 0.001 N·s/m²), the flow regime is:
Answer: B
Re = (1000 × 1.5 × 0.025)/0.001 = 37,500, which is much greater than 2300, indicating turbulent flow.
Q.14Medium
Which of the following is a dimensionless number used in fluid mechanics that compares inertial forces to surface tension forces?
Answer: A
Weber number We = ρV²D/σ represents the ratio of inertial to surface tension forces. It's important in two-phase flows and atomization studies.
Q.15Easy
In a converging nozzle, as the cross-sectional area decreases, the velocity of incompressible flow:
Answer: B
From continuity equation A₁V₁ = A₂V₂, when area decreases, velocity must increase to maintain constant mass flow rate.
Q.16Hard
The Strouhal number is used to characterize:
Answer: B
Strouhal number St = fD/V relates frequency of oscillation to flow velocity and characteristic length. It's crucial in analyzing vortex shedding from cylinders.
Q.17Medium
A venturi meter is used to measure fluid flow rate. The principle it operates on is:
Answer: B
Venturi meter uses both continuity equation (conservation of mass) and Bernoulli's equation (energy conservation) to relate pressure difference to flow velocity.
Q.18Hard
For compressible flow through a convergent nozzle, chocking occurs when:
Answer: B
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.
Q.19Medium
The major loss in pipe flow (Darcy-Weisbach equation: hf = f(L/D)(V²/2g)) is primarily due to:
Answer: C
Major losses or friction losses occur due to wall shear stress and account for the majority of energy dissipation in long straight pipe sections. This is captured by the Darcy friction factor.
Q.20Easy
A fluid with dynamic viscosity μ = 0.8 Pa·s and density ρ = 800 kg/m³ flows through a pipe. What is the kinematic viscosity?
