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?

Related Mcqs:

1. 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

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

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

4. 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.

5. 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

6. Existence of boundary layer in fluid flow is because of the_________________?

   A. Surface tension
   B. Fluid density
   C. Fluid viscosity
   D. Gravity forces

7. Boundary layer thickness in laminar flow over a flat plate increases as(where, d = distance from the leading edge.) ?

   A. √d
   B. d1/3
   C. d2
   D. d2/3

8. Boundary layer thickness in turbulent flow over a flat plate increases as(where, d = distance from the leading edge.) ?

   A. √d
   B. d2/3
   C. d4/5
   D. d1/3

9. In fluid flow, the boundary layer separation cannot occur___________________?

   A. In case of boundaries experiencing form drag
   B. At points of abrupt changes in the flow directions
   C. In laminar flow
   D. None of these

10. 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