Question

28. Fluid Momentum problems are solved with the aid of two diagrams of such problems. Explain, list or define items which would be included on each of the two diagrams required, and describe or show features common to both diagrams. Why are these two drawings typically kept separate?

29. Propellers and turbines are similar in that both act as screws. Attribute each of the following to Props, Turbines, or Both:

a. __________Average velocity through the blades, (V1 + V2)/2

b. __________Flow increases in velocity through the blades, increasing momentum of the flow

c. __________Flow decreases in velocity through the blades, decreasing momentum of the flow

d. __________CV Power output represented by Force times Velocity of the control volume

e. __________CV Power output represented by Force time Velocity through the blades

f. __________CV Power input represented by Force time Velocity through the blades

g. __________CV Power input represented by Force times Velocity into the control volume

h. __________Efficiency best at a ratio of Vout/Vin = 1/3, 59.3% efficiency at this point

i. __________Efficiency varies greatly with speed, but in airflow, 60-80%, in water 40-60% might be typical for applications

j. __________Froude’s Theorem applies (also identify application of this theorem in this list)

k. __________Bette’s Law applies (also identify application of this law in this list)

30. For applications with control volumes having accelerated motion, how is Newton’s 2nd Law, the standard momentum equation, expanded to include inertial effects plus local and convective changes in momentum through the control volume?

Answer 1