GATE XE concept:boundary-layer-thickness PYQs & Answers

Questions 1–9 of 9. Imported answers require independent review unless marked reviewed.

Consider a steady, and incompressible flow over a body with characteristic length

. The boundary layer thickness at a distance

from the leading edge is

. Which one of the following assumptions is correct for deriving the Prandtl boundary layer equations?

Your answerChoose one option.

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Consider a steady, laminar, and incompressible flow over a flat plate, as shown in the figure. With freestream velocity

and kinematic viscosity

, the boundary layer thickness at a distance

from the leading edge is

. If the kinematic viscosity of the fluid is increased by a factor of four (

), the boundary layer thickness (

) at

with same

will be equal to

Diagram for Engineering Sciences question 35

Your answerChoose one option.

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A sharp flat plate of length

and infinite width is immersed parallel to a fluid stream having velocity

. At a point on the plate, far away from the leading edge and not near the trailing edge, the boundary layer thickness, the displacement thickness, and the momentum thickness are denoted as

, and

, respectively. Which one of the following options correctly represents the relation between these thicknesses?

Your answerChoose one option.

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Consider the incompressible fluid flow over a flat plate with a free stream velocity,

m/s. The fluid kinematic viscosity is

m²/s and density is 1 kg/m³. The velocity profile within the boundary layer at any location

is given by

, where boundary layer thickness,

. The local wall shear stress at

m from the leading edge is _____ × 10⁻³ N/m² (rounded off to two decimal places).

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Consider steady incompressible flow of a Newtonian fluid over a horizontal flat plate, as shown in the figure. The boundary layer thickness is proportional to

Diagram for Engineering Sciences question 34

Your answerChoose one option.

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Water flows around a thin flat plate (0.25 m long, 2 m wide) with a free stream velocity (

) of 1 m/s, as shown in the figure. Consider linear velocity profile

for which the laminar boundary layer thickness is expressed as

. For water, density = 1000 kg/m

and dynamic viscosity = 0.001 kg/m.s. Net drag force (in N, rounded off to two decimal places) acting on the plate, neglecting the end effects, is ______.

Diagram for Engineering Sciences question 41

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For steady laminar flow at zero incidence over a flat plate, the component of velocity parallel to the plate in the boundary layer is given by

, where

is the distance measured normal to the flat plate. If

is the coefficient of dynamic viscosity,

is the velocity parallel to the wall at the edge of the boundary layer and

is the boundary layer thickness, the wall shear stress is given by

Your answerChoose one option.

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On a flat plate, transition from laminar to turbulent boundary layer occurred at a critical Reynolds number (Re_cr). The empirical relations for the laminar and turbulent boundary layer thickness are given by

and

, respectively. The ratio of laminar to turbulent boundary layer thickness, at the location of transition, is 0.3. The value of Re_cr is ________.

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Air flows over a smooth flat plate at a velocity of 4.39 m/s. The density of air is 1.031 kg/m³ and the kinematic viscosity is 1.34×10⁻⁵ m²/s. The plate length is 12.2 m in the direction of the flow. The boundary layer thickness (

) is given as

, where

is the distance from the leading edge and

is the Reynolds number. The boundary layer thickness (in meters, rounded off to the second decimal place) at 12.2 m from the leading edge will be ________

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GATE XE concept:boundary-layer-thickness PYQs

How to practice concept:boundary-layer-thickness

Question 24

Question 35

Question 23

Question 43

Question 34

Question 41

Question 15

Question 18

Question 31