111Equation Chapter 1 Section 1Cavitation is likely to occur at the thin diameter point 1 where

(there is no cavitation at point 2why because it is open to the atmosphere so cavitation will not occur here.

To determine if cavitation will occur we have to find the pressure at the point 1.

Therefore The overall flow rate.

By applying Bernoulli’s equation between the top of the large tank at point 0 and the exit point 2

From the figure

be neglected

The flow rate, Q,

.

Applying Bernoulli’s equation between this point 1and the exit point 2 gives.

Here z1 = z2 and p2 = 0.

Continuity equation

so that we can rewrite this equation as follows.

We can use the previous result that

.

Solving this equation for the gage pressure

The absolute pressure

Substituting the given data that

To determine the effects of D1 and D2

we can solve for h.

Note that since D2 > D1 we will be dividing by a negative number so we have to change the direction of the inequality.

The above equation shows that increasing D2 or decreasing D1 will increase h.

The physical reasoning for this is as follows.

Neglecting visclous forces, increasing D2 will decrease the overall flow rate and less material will have to flow through D1 for a given h.

Thus we can increase h. However, with D2 fixed, the flow rate is fixed, and decreasing D2 increases the flow rate through point 1 thus we would have to reduce h to avoid cavitation.