Water flows through a pipe of diameter $20 \mathrm{cm}$ at a flow rate of $0.025 \mathrm{~m}^{3} / \mathrm{s}$. A pitotstatic tube is placed at the centre of the pipe and indicates the pressure difference of $5 \: \mathrm{ cm}$ of water column. Theoretical velocity measured through pitot-static tube when multiplied with velocity coefficient $C_{V}$ gives the actual velocity of the flow. If the mean velocity in the pipe is $90 \%$ of the actual velocity at the centre of the pipe and the gravitational acceleration is $10 \mathrm{~m} / \mathrm{s}^{2}$, the value of $C_{V}$ (rounded off to $2$ decimal places) is $\_\_\_\_\_\_$
