# 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) $\delta \propto 1 / R e$

## Question ID - 155717 :- 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) $\delta \propto 1 / R e$

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(B) $\delta \propto 1 / \sqrt{R e}$

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Isentropic efficiencies of an aircraft engine operating at typical subsonic cruise conditions with the following components - intake, compressor, turbine and nozzle - are denoted by $\eta_{i}, \eta_{c}, \eta_{t}$ and $\eta_{n},$ respectively. Which one of the following is correct?
(A) $\eta_{i}<\eta_{c}<\eta_{t}<\eta_{n}$
(B) $\eta_{t}<\eta_{i}<\eta_{c}<\eta_{n}$
(C) $\eta_{c}<\eta_{t}<\eta_{i}<\eta_{n}$
(D) $\eta_{c}<\eta_{i}<\eta_{t}<\eta_{n}$ 