Problem $10$: low$-$speed wind tunnel $(15$ pts $).$ We wish to operate a low$-$speed subsonic wind tunnel $($a$)$ A nozzle and a constant$-$area test section, where the flow at the exit of the test section simply

dumps out to the surrounding atmosphere $($that is$,$ there is no diffuser$)$

$($b$)$ A conventional arrangement of nozzle, test section, and diffuser, where the flow at the exit of the

diffuser dumps out to the surrounding atmosphere

For both wind tunnels $($a$)$ and $($b$),$ calculate the pressure differences across the entire wind tunnel re$-$

quired to operate them so as to have the given flow conditions in the test section. For tunnel $($a$),$ the

cross$-$sectional area of the entrance is $20f{t}^2,$ and the cross$-$sectional area of the test section is $4f{t}^2.$ For

tunnel $($b$),$ a diffuser is added to $($a$)$ with a diffuser exit area of $18f{t}^2.$ After completing your calculations,

examine and compare your answers for tunnels $($a$)$ and $($b$).$ Which requires the smaller overall pressure

difference? What does this say about the value of a diffuser in a subsonic wind tunnel?

so that the flow in the test section has a velocity of $200m\frac{i}{h}.$ Consider two different types of wind tunnels: