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#1 2008-11-18 05:56:59

GemmaJ1988
Member
Registered: 2008-10-08
Posts: 39

fluid dynamics

air at pressure p=p0 is above a layer of oil of depth A and density D1.
the oil lies on water of density D2>D1.
find the pressure at a distance B>0 below the oil water boundary.

Ive looked at examples of pressure below water without an oil layer and i can see clearly how the fundamental equation of hydrostatics can be used:


where D=density and K is the vector component

but im not quite sure how to apply this to this type of question.
Here the pressure is a continuous function of position and the density varies.
can anyone please help me understand this example

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#2 2008-12-03 10:27:49

Spaindoctor
Guest

Re: fluid dynamics

You just have to apply the formula for each layer separately. Thus, the pressure at point A (bottom of oil layer) is PA = P0 + D1*g*A, while the pressure at point B (inside the water layer) is the pressure at point A plus D2*g*B. Hence, PB = PA + D2*g*B = P0 + D1*g*A +D2*g*B. As a check, note that if D1=D2=D, you just get PB = D*g*(A+B). as it should be.

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