A mechanically cleaned bar screen has $30$ parallel sharp$-$edged rectangular bars $12$ mm wide placed

at a clear spacing of $20$ mm $.$ The facility is provided as a preliminary treatment unit at a wastewater

treatment facility. The water depth and flow through the screen are $1\mathrm{.}5$ m and $0\mathrm{.}85\frac{m^3}{s},$ respec$-$

tively. The angle of inclination of bars is $10$ from the vertical. Calculate $(1)$ head loss across clean

screen, $C_d=0\mathrm{.}7,$ and $(2)$ head loss across the screen at $50\%$ clogging. $C_d=0\mathrm{.}6.$