Some animals have learned to take advantage of the Bernoulli effect without havi

Question

Some animals have learned to take advantage of the Bernoulli effect without having read a fluid mechanics book. For example, a typical prairie dog burrow contains two entrances - a flat front door, and a mounded back door as shown in the figure below. When the wind blows with Velocity V_o across the front door, the average velocity across the back door is greater than V_o because of the mound. Assume the air velocity across the back door is 1.1 V_o. For a wind speed of 5 m/s, what pressure difference (in SI units) is generated to provide a puff of fresh air?

Explanation / Answer

bernoulli equation:

P1+0.5*pho*v1^2+pho*g*h1=P2+0.5*pho*v2^2+pho*g*h2

P1,P2 are pressure 1 and 2.

pho=air density

g=acceleration due to gravity

v1,v2 are speed at 1 and 2.

h1 ,h2 are height at 1,2

v1=5 m/s

v2=1.1*5=5.5 m/s

h1=h2

pho=1.225 kg/m^3

so P1-P2=0.5*pho*(v2^2-v1^2)

=0.5*1.225*(5.5^2-5^2)=3.215625 N/m^2

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