• question_answer The displacement thickness at. Section, for an air stream $\left( \rho \,\,=\,\,1.2\,\,\text{kg/}{{\text{m}}^{\text{3}}} \right)$ moving with a velocity of 10 m/s over a flat plate is 0.5 mm. What is the loss of mass rate of flow of air due to boundary layer formation in kg per meter width of plate per second? A) $6\times {{10}^{-3}}$            B) $6\times {{10}^{-5}}$C) $3\times {{10}^{-3}}$            D) $2\times {{10}^{-3}}$

$\delta *=0.5\,\,mm,$ $\rho =1.2\,\,\text{kg/}{{\text{m}}^{\text{3}}}\text{,}$ $u=10\,\text{m/s}$ Loss of mass rate of flow of air $=\delta *\rho u$ $=0.5\times {{10}^{-3}}\times 1.2\times 10=6\times {{10}^{-3}}\,\,\text{kg/m}$