Solved problems in flow in pipes and losses

Ex.1
To determine the viscosity of a liquid of specific gravity 0.95, you fill, to a depth of 12 cm, a large container which drains through a 30-cm-long vertical tube attached to the bottom. The tube diameter is 2 mm, and the rate of draining is found to be 1.9 cm3/s. What is your estimate of the fluid viscosity? Is the tube flow laminar?
Ex.2
A capillary viscometer measures the time required for a specified volume v?of liquid to flow through a small-bore glass tube, as in Fig. This transit time is then correlated with fluid viscosity. For the system shown, (a) derive an approximate formula for the time required, assuming laminar flow with no entrance and exit losses. (b) If L ??12 cm, l ??2 cm, ?v??8 cm3, and the fluid is water at 20?C, what capillary diameter D will result in a transit time t of 6 seconds?
Ans: d>=1.17mAns: hf = 63.8 ft, ?p= 23700 lbf/ft2.Ans: hf = 63.8 ft, ?p= 23700 lbf/ft2.

In flow past a sphere, the boundary layer becomes turbulent at about ReD ? 2.5E5. To
what air speed in mi/h does this correspond to a golf ball whose diameter is 1.6 in? Do the
pressure, temperature, and humidity of the air make any difference in your calculation?

Air at approximately 1 atm flows through a horizontal 4-cm-diameter pipe. (a) Find a
formula for Qmax, the maximum volume flow for which the flow remains laminar, and plot
Qmax versus temperature in the range 0°C ? T ? 500°C. (b) Is your plot linear? If not, explain.
Solution: (a) First convert the Reynolds number from a velocity form to a volume flow form: