The hydrodynamic and thermal boundary layers will merge, when ____________________?

Related Mcqs:

1. The ratio of hydrodynamic boundary layer to thermal boundary layer thickness in case of liquid metals is__________________?

   A. < 1
   B. 1
   C. > 1
   D. 2

2. Which of the following must be followed by the flow of a fluid (real or ideal)? (I) Newton’s law of viscosity. (II) Newton’s second law of motion. (III) The continuity equation. (IV) Velocity of boundary layer must be zero relative to boundary. (V) Fluid cannot penetrate a boundary?

   A. I, II, III
   B. II, III, V
   C. I, II, V
   D. II, IV, V

3. The effect of solid boundary on the fluid flow is confined to the boundary layer, except for fluids ?

   A. Having high viscosities
   B. Moving at low velocities
   C. Both A. & B.
   D. Neither A. nor B.

4. In the laminar boundary layer flow over a flat plate, the ratio (δ/x) varies as: (where, ‘δ’ is the boundary layer thickness and ‘x’ is the distance from the leading edge in the direction of flow)?

   A. Re
   B. √Re
   C. 1/Re
   D. Re-1/2

5. Boundary layer separation is caused by the ____________________?

   A. Reduction of pressure below vapour pressure
   B. Reduction of pressure gradient to zero
   C. Adverse pressure gradient
   D. Reduction of boundary layer thickness to zero

6. Boundary layer exists in flow_________________?

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

7. Which law is followed by the velocity distribution in the turbulent boundary layer ?

   A. Parabolic law
   B. Linear law
   C. Logarithmic law
   D. None of these

8. The length of the tube necessary for the boundary layer to reach the centre of the tube and for fully developed flow to be established is called the _____________ length?

   A. Equivalent
   B. Transition
   C. Prandtl mixing
   D. None of these

9. Boundary layer separation is characterised by one of the conditions given below, where ‘Re’ is the Reynolds number for the flow. Select the appropriate conditions ?

   A. Re <> 1, accelerating flow
   C. Re << 1, decelerating flow
   D. Re >>1, decelerating flow

10. For flow past a flat plate, if „x‟ is the distance along the plate in the direction of flow, the boundary layer thickness is proportional to________________?

    A. √x
    B. 1/√x
    C. x
    D. 1/x