Test: Boundary Layer Theory - 2 | 10 Questions MCQ Test Topicwise Question Bank for Civil Engineering Civil Engineering (CE)

QUESTION: 1

The maximum thickness of boundary layer in a pipe of radius r is

A.
0
B.
r/2
C.
r
D.
2r

Solution:

The thickness of the boundary layer represented, by 8(greek 'delta’) is arbitrarily defined as that distance from the boundary surface in which the velocity reaches 99% of the velocity of the main stream, in a pipe the free stream velocity is at the centre of the pipe. Therefore maximum thickness of boundary layer is r.

QUESTION: 2

The velocity profile for turbulent boundary layer is:

A.
B.
C.
D.

Solution:

Velocity profile follows 1/7^th power law for turbulent boundary layer.

QUESTION: 3

The drag force experienced by an object in a fluid stream is

A.
the resultant fluid dynamic force acting on the object
B.
the horizontal component of the resultant fluid ... dynamic force acting on the object
C.
the horizontal force due to pressure variation over the surface of object
D.
the component of the result fluid dynamic force in the flow direction

Solution:

QUESTION: 4

The correct relationship among displacement thickness ‘d’ momentum thickness ‘m’ and energy thickness ‘e’ is

A.
d > m > e
B.
d > e > m
C.
e > m > d
D.
e > d > m

Solution:

Displacement thickness,

Momentum thickness,

Energy thickness,

QUESTION: 5

What is the momentum thickness for the boundary layer with velocity distribution u/U = y/δ ?

A.
δ/6
B.
δ/2
C.
3δ/2
D.
2δ

Solution:

The momentum thickness is given by,

QUESTION: 6

If x is the distance from leading edge, then the boundary layer thickness in laminar flow varies as

A.
x^1/2
B.
x^4/5
C.
x^3/5
D.
x^1/7

Solution:

QUESTION: 7

If δ₁ and δ₂ denote the boundary layer thicknesses at a point distance x from the leading edge on a fiat plate when the Reynolds numbers are 100 and 256 respectively, then the ratio of δ₁ to δ₂ will be