# prb 8 T&F SMS



## Lily (Oct 17, 2010)

We know Delta P friction = rho * f * V^2 / 2 D.gc , the solution says that Delta P friction is proportional to the square of the velocity, but this assumes that the coefficient of friction is independant of the velocity, which is not true. in laminar flows f=64/Re and Re=V.D/kinematic viscisity. if you replace f in the equation of delta P, the delta P becomes proportinal to V not to V^2.

Do you agree?


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## tmacier (Oct 20, 2010)

Lily said:


> We know Delta P friction = rho * f * V^2 / 2 D.gc , the solution says that Delta P friction is proportional to the square of the velocity, but this assumes that the coefficient of friction is independant of the velocity, which is not true. in laminar flows f=64/Re and Re=V.D/kinematic viscisity. if you replace f in the equation of delta P, the delta P becomes proportinal to V not to V^2. Do you agree?


I cheated on this one and since I knew that the friction is proportional to the sqaure of the velocity I ruled out all the answers but A

Tim


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