GATE Overflow for GATE XE - Recent questions and answers in Boundary Layer Characteristics

GATE XE 2026 | Question: 14

Tue, 24 Feb 2026 15:49:21 +0000

Consider a steady, and incompressible flow over a body with characteristic length $\text{L}$. The boundary layer thickenss at a distance $x$ from the leading edge is $\delta$. Which one of the following assumptions is correct for deriving the prandtl boundary layer equations?

$\delta \approx L$
$\delta>L$
$\delta \gg L$
$\delta \ll L$

GATE XE 2026 | Question: 25

Tue, 24 Feb 2026 15:48:24 +0000

Consider a steady, laminar, and incompressible flow over a flat plate, as shown in the figure. With freestream velocity $U_{\infty}$ and kinematic viscosity $v_{1}$, the boundary layer thickness at a distance $x_{1}$ from the leading edge is $\delta_{1}$. If the kinematic viscosity of the fluid is increased by a factor of four $\left(v_{2}=4 v_{1}\right)$, the boundary layer thickness $\left(\delta_{2}\right)$ at $x_{1}$ with same $U_{\infty}$ will be equal to

$\dfrac{\delta_{1}}{2}$
$\delta_{1}$
$2 \delta_{1}$
$4 \delta_{1}$

GATE XE 2025 | Question: 23

Sun, 04 May 2025 19:08:23 +0000

A sharp flat plate of length $L$ and infinite width is immersed parallel to a fluid stream having velocity $u_{\infty}$. 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 $\delta, \delta^{*}$, and $\theta$, respectively.

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

$\delta>\delta^{*}>\theta$
$\delta>\theta>\delta^{*}$
$\delta^{*}>\delta>\theta$
$\theta>\delta^{*}>\delta$

GATE XE 2024 | Question: 15

Sun, 21 Jul 2024 16:42:34 +0000

For the laminar, incompressible flow over a flat plate with uniform free stream velocity, the axial pressure gradient within the boundary layer is

greater than zero.
less than zero.
equal to zero.
equal to the axial velocity gradient.

GATE XE 2024 | Question: 33

Sun, 21 Jul 2024 16:42:20 +0000

Consider the incompressible fluid flow over a flat plate with a free stream velocity, $U_{\infty}=1 \mathrm{~m} / \mathrm{s}$. The fluid kinematic viscosity is $10^{-6} \mathrm{~m}^{2} / \mathrm{s}$ and density is $1 \mathrm{~kg} / \mathrm{m}^{3}$. The velocity profile within the boundary layer at any location $x$ is given by $u(y)=U_{\infty}\left(\frac{3}{2} \frac{y}{\delta}-\frac{1}{2} \frac{y^{2}}{\delta^{2}}\right)$, where boundary layer thickness, $\delta=\frac{4.64 x}{\sqrt{R e_{x}}}$. The local wall shear stress at $x=1 \mathrm{~m}$ from the leading edge is ___________ $\times 10^{-3} \mathrm{~N} / \mathrm{m}^{2}$ $\text{(rounded off to two decimal places)}$.

GATE XE 2023 | Question: 14

Wed, 14 Feb 2024 18:10:07 +0000

For an incompressible boundary layer flow over a flat plate shown in the figure, the momentum thickness is expressed as

$\int_0^{\infty} \frac{u}{U_{\infty}} d y$
$\int_0^{\infty}\left(1-\frac{u}{U_{\infty}}\right) d y$
$\int_0^{\infty} \frac{u}{U_{\infty}}\left(1-\frac{u}{U_{\infty}}\right) d y$
$\int_0^{\infty}\left(1-\frac{u^2}{U_{\infty}^2}\right) d y$

GATE XE 2023 | Question: 24

Wed, 14 Feb 2024 18:09:57 +0000

\begin{tabular}{|c|c|}
\hline Q. 34 & \begin{tabular}{l}
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
\end{tabular} \\
\hline & $U_{\infty}$ \\
\hline (D) & $x^{2}$ \\
\hline
\end{tabular}

GATE XE 2023 | Question: 31

Wed, 14 Feb 2024 18:09:51 +0000

\begin{tabular}{|c|c|c|}
\hline Q. 41 & \multicolumn{2}{|c|}{\begin{tabular}{l}
Water flows around a thin flat plate ( $0.25 \mathrm{~m}$ long, $2 \mathrm{~m}$ wide) with a free stream \\
velocity $\left(U_{\infty}\right)$ of $1 \mathrm{~m} / \mathrm{s}$, as shown in the figure. Consider linear velocity profile \\
$\left(\frac{u}{U_{\infty}}=\frac{y}{\delta}\right)$ for which the laminar boundary layer thickness is expressed as \\
$\delta=\frac{3.5 x}{\sqrt{R e_{x}}}$. For water, density $=1000 \mathrm{~kg} / \mathrm{m}^{3}$ and dynamic viscosity $=0.001$ \\
$\mathrm{~kg} / \mathrm{m} . \mathrm{s}$. Net drag force (in $\mathrm{N}$, rounded off to two decimal places) acting on the \\
plate, neglecting the end effects, is
\end{tabular}} \\
\hline & & $y$ \\
\hline & & $\overrightarrow{0.25 \mathrm{~m}}$ \\
\hline
\end{tabular}

GATE XE 2022 | Question: 19

Fri, 17 Feb 2023 06:52:24 +0000

A boundary layer develops due to a two-dimensional steady flow over a horizontal flat plate. Consider a vertical line away from the leading edge which extends from the wall to the edge of the boundary layer. Which of the following quantity/quantities is/are not constant along the vertical line? $u$ and $v$ represent the components of velocity in the direction along the plate and normal to it, respectively and $x$ is taken along the length of the plate while $p$ is the pressure.
Neglect body forces.

$u$
$\frac{\partial u}{\partial x}$
$v$
$p$

GATE XE 2022 | Question: 24

Fri, 17 Feb 2023 06:52:20 +0000

A typical boundary layer over a flat plate has a linear velocity profile with zero velocity at the wall and freestream velocity, $U_{\infty}$, at the outer edge of the boundary layer. What is the ratio of the momentum thickness to the thickness of the boundary layer?

$1 / 2$
$1 / 4$
$1 / 6$
$1 / 3$