Let the flow straighteners in Fig. P$7\mathrm{.}28$ form an array of $2020$ boxes of size a $=4$ cm and L $=25$ cm $.$ If the approach velocity is U$0=12$ m$/$s and the fluid is sea$-$level standard air, estimate $($a$)$ the total array drag and $($b$)$ the pressure drop across the array. Compare with Sec. $6\mathrm{.}8.$

Known answers are

a$.4\mathrm{.}09$ N

b$.6\mathrm{.}4$ Pa

explain process