Free Fluid Flow Operations MCQs with Answers

• A. MLT-1
• B. L2T-1
• C. L2T
• D. L2T-2

Explanation: Kinematic viscosity is dynamic viscosity divided by density, giving dimensions L02/T, or L2T-1.

• A. Viscous
• B. Gravity
• C. Surface tension
• D. Elastic

Explanation: The Weber number compares inertial forces with surface-tension forces, typically written as We = rho V2 L/sigma.

• A. Compressible fluids with shear
• B. Compressible fluids with no shear
• C. Incompressible fluids with shear
• D. Incompressible fluids with no shear

Explanation: In the usual chemical-engineering idealisation, potential flow is irrotational and has no viscous shear, and it is commonly treated as…

• A. V2
• B. 1/V2
• C. 1/V
• D. V

Explanation: For a fixed pipe and approximately constant turbulent friction factor, Darcy-Weisbach loss varies as V2.

• A. ⅔Dp (1- ε/ε)
• B. (Dp/6) (1- ε/ε)
• C. (Dp/6) (ε/1- ε)
• D. ⅔Dp (ε/1- ε)

Explanation: Hydraulic mean radius equals void volume divided by wetted solid surface area.

• A. Only when the fluid is frictionless
• B. Only when the fluid is at rest having zero velocity
• C. Regardless of the motion of one fluid layer relative to an adjacent layer
• D. When there is no motion of one fluid layer relative to an adjacent layer

Explanation: Pressure is isotropic when there is no shear stress, which occurs when adjacent fluid layers have no relative motion.

• A. Velocity of gases
• B. Temperature of liquids
• C. Velocity of liquids
• D. Pressure of liquids

Explanation: A hot-wire anemometer measures gas velocity by detecting the cooling effect produced as moving gas passes over a heated wire.

• A. 1.8
• B. 12.4
• C. 186.2
• D. 736.4

Explanation: Peripheral velocity is u = πDN/60. Substituting D = 0.25 m and N = 950 rpm gives u = π(0.25)(950)/60 ≈ 12.4 m/s.

• A. Newtonian
• B. Pseudo-plastic
• C. Dilatent
• D. Bingham plastic

Explanation: For a power-law fluid, average velocity varies as D^(1+1/n); a cubic dependence occurs for a shear-thinning, or pseudoplastic, fluid when…

• A. Bingham plastic
• B. Newtonian
• C. Dilatant
• D. Pseudo plastic

Explanation: Quicksand becomes more resistant when disturbed because its apparent viscosity increases with increasing shear rate, which is…

• A. Back flow through impeller
• B. None of these
• C. Loss of static head
• D. Loss of kinetic head

Explanation: The casing gradually converts the impeller's velocity head into pressure head through diffusion, so its design should minimise loss of…

• A. CD = 16/Re.p
• B. CD = 18.4/Re.p
• C. CD = 24/Re.p
• D. CD = 0.079/Re
• E. 25.p

Explanation: In the Stokes-law range, a small spherical particle has drag coefficient C_D = 24/Re_p.

• A. Q1 = Q2 = Q3
• B. V1 = V2 = V3
• C. Q = Q1 + Q2 + Q3
• D. f = f1 + f2 + f3

Explanation: For parallel branches, the pressure drop between the common inlet and outlet is the same, while the total flow is the sum of the branch…

• A. Butterfly
• B. Globe
• C. Gate
• D. Needle

Explanation: A needle valve has a tapered stem and small passage, allowing fine adjustment of flow even at low rates.

• A. All A., B. and C.
• B. Used to release any gases that might be vapour locking the pump
• C. Helpful in easy removal of samples
• D. Generally a needle valve

Explanation: A vent valve is commonly a small needle valve used to bleed trapped gas or vapour that can cause vapour locking, and it may also permit…

• A. Passing the centroid of the body at 60°to the direction of motion
• B. The component being parallel to the flow direction
• C. The component being normal to the flow direction
• D. None of these

Explanation: Drag is the component of fluid force parallel to the relative flow or motion direction. The normal component is called lift.

• A. It is not very accurate
• B. It is very costly
• C. Most of the pressure drop is not recoverable
• D. It is not suitable for measuring gas flow

Explanation: An orifice meter is simple and inexpensive, but its sharp restriction creates a largely permanent pressure loss that is not recovered…

• A. Of ideal fluids only
• B. Over flat surfaces only
• C. In pipes only
• D. Of real fluids

Explanation: A boundary layer forms when viscosity causes the fluid velocity to change from zero at a solid wall to the external-flow value.

• A. Pressure fluctuation
• B. All A., B. & C.
• C. Deviating velocities
• D. Eddies

Explanation: In ideal steady laminar flow, adjacent layers move without random eddies or turbulent velocity and pressure fluctuations.

• A. Dependent on the speed of the pump
• B. Dependent on the power of the pump
• C. 34 feet
• D. 150 feet

Explanation: The theoretical suction limit is about 34 ft of water, corresponding to one atmosphere of pressure head, although practical losses make…