# An ideal gas in a reservoir has a specific stagnation enthalpy of $h_{0}$. The gas is isentropically expanded to a new specific stagnation enthalpy of $\frac{h_{0}}{2}$ and velocity $u$. The flow is one-dimensional and steady. Then $\frac{u^{2}}{h_{0}}=$_____________

## Question ID - 155716 :- An ideal gas in a reservoir has a specific stagnation enthalpy of $h_{0}$. The gas is isentropically expanded to a new specific stagnation enthalpy of $\frac{h_{0}}{2}$ and velocity $u$. The flow is one-dimensional and steady. Then $\frac{u^{2}}{h_{0}}=$_____________

3537

Answer Key : (0.99 to 1.01) -

0.99 to 1.01

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The Reynolds number, $R e$ is defined as $\frac{U_{\infty} L}{v}$ where $L$ is the length scale for a flow, $U_{\infty}$ is its reference velocity and $v$ is the coefficient of kinematic viscosity. In the laminar boundary layer approximation, comparison of the dimensions of the convection term $u \frac{\partial u}{\partial x}$ and the viscous term v $\frac{\partial^{2} u}{\partial x^{2}}$ leads to the following relation between the boundary layer thickness $\delta$ and $R e$ :
(A) $\delta \propto \sqrt{R e}$
(B) $\delta \propto 1 / \sqrt{R e}$
(C) $\delta \propto R e$
(D) $\delta \propto 1 / R e$ 