Since the intake aperture is fixed, a larger but still duct wall defined and confined {TAIL ~ air mass} must undergo {HEAD ~ a velocity step} up when moving into a larger volume exhaust terminated aperture, according to the Bernoulli or venturi principle 
Since the intake aperture is fixed , a larger but still duct wall defined and confined { TAIL ~ air mass } must undergo { HEAD ~ a velocity step } up when moving into a larger volume exhaust terminated aperture , according to the Bernoulli or venturi principle
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH