# Heat Transfer Questions and Answers – Hydrodynamic Boundary Layer

«
»

This set of Heat Transfer Multiple Choice Questions & Answers (MCQs) focuses on “Hydrodynamic Boundary Layer”.

1. The concept of the hydrodynamic boundary layer was first suggested by
a) Isaac Newton
b) Ludwig Prandtl
c) Rodridge
d) Fourier

Explanation: It was suggested by Ludwig Prandtl in 1904. This is the thin layer where velocity changes continuously.

2. The free stream undisturbed flow has a uniform velocity U INFINITY in the
a) X-direction
b) Y-direction
c) Z-direction
d) Any direction

Explanation: It is in the x-direction only. Particles of fluid adhere to the plate surface as they approach it and the fluid is slowed down considerably.

3. The thin layer where velocity changes continuously is called
a) Differential layer
b) Thermal boundary layer
c) Hydrodynamic boundary layer
d) Velocity distribution layer

Explanation: In this layer the flow is rotational and shear stresses are present.
Note: Join free Sanfoundry classes at Telegram or Youtube

4. The conditions for flow beyond the boundary layer and its outer edge are
a) d u/d y = 0 and u = U 0
b) d u/d y = Infinity and u = U INFINITY
c) d u/d y = 1 and u = U 0
d) d u/d y = 0 and u = U INFINITY

Explanation: All the variation in fluid velocity is concentrated in a comparatively thin layer in immediate vicinity of the plate surface.

5. The pattern of flow in the boundary layer is judged by the
a) Reynolds number
b) Fourier number
c) Peclet number
d) Grashof number

Explanation: Re = U INFINITY x/v.

6. Consider the diagram given below and identify the correct option

a) The velocity gradient is zero everywhere
b) The velocity profile changes at every instant of time
c) Boundary layers from the pipe walls meet the pipe anywhere
d) Thickness of the boundary layer is limited to the pipe radius

Explanation: Thickness of the boundary layer is limited to the pipe radius because of the flow being within a confined passage.

7. The transition from laminar to turbulent pattern of flow occurs at values of Reynolds number between
a) 1000-2000
b) 300000-500000
c) 500000-700000
d) 35750-45678

Explanation: It occurs at a higher value. The pattern of flow in the boundary layer is judged by the Reynolds number, Re = U INFINITYY x/v.

8. The entrance length required for the flow to become fully-developed turbulent flow is dependent on
(i) Surface finish
(ii) Downstream conditions
(iii) Fluid properties
a) ii and iii
b) i and iii
c) i, ii and iii
d) i and ii

Explanation: It depends on surface finishing, various upstream and downstream conditions and various fluid properties.

9. What is the value of the thickness of the boundary layer at leading edge of the plate?
a) 0.33
b) 1
c) 0.5
d) 0

Explanation: The thickness of the boundary layer is variable along the flow direction.

10. The boundary layer thickness is taken to be at a distance from the plate surface to a point at which the velocity is given by
a) u = 0.99 U INFINITY
b) u = 0.75 U INFINITY
c) u = 0.50 U INFINITY
d) u = 0.33 U INFINITY

Explanation: Velocity is one per cent of the asymptotic limit.

Sanfoundry Global Education & Learning Series – Heat Transfer.

To practice all areas of Heat Transfer, here is complete set of 1000+ Multiple Choice Questions and Answers.