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.

The ratio of the thickness of thermal boundary layer to the thickness of hydrodynamic boundary layer is equal to (Prandtl number) n, where n is equal to

A

$$ - \frac{1}{3}$$

B

$$ - \frac{2}{3}$$

C

1

D

$$-1$$

Thickness of thermal boundary layer is more compared to that of hydrodynamic boundary layer, when the value of Prandtl number is

A

1

B

> 1

C

> 5

The ratio of hydrodynamic boundary layer to thermal boundary layer thickness in case of liquid metals is

A

[

A.

B. 1

B

> 1

C

2

At the point of boundary layer separation in fluid flow, the

A

Shear stress is maximum

B

Velocity gradient is flat

C

Density variation is maximum

D

Shear stress is zero

In fluid flow, the boundary layer separation can not 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

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 and B

D

Neither A nor B

Routers operate at layer _____. LAN switches operate at layer _____. Ethernet hubs operate at layer _____. Word processing operates at layer _____.

A

3, 3, 1, 7

B

3, 2, 1, none

C

3, 2, 1, 7

D

3, 3, 2, none

E

All of the above

Boundary layer separation is caused by the

A

Reduction of pressure to vapour pressure

B

Boundary layer thickness reducing to zero

C

Adverse pressure gradient

D

Reduction of pressure gradient to zero

In convection heat transfer from hot flue gases to water tube, even though flow may be turbulent, a laminar flow region (boundary layer of film) exists close to the tube. The heat transfer through this film takes place by

A

Convection

B

Radiation

C

Conduction

D

Both convection and conduction

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

$$\sqrt {\text{x}} $$

B

$$\frac{1}{{\sqrt {\text{x}} }}$$

C

x

D

$$\frac{1}{{\text{x}}}$$

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.

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