Calif. State Univ., Sacramento           CE135 Hydraulics Lab

Dept of Civil Engineering                       Instructor      MEH

To compare the friction effects (f and C_HW) for turbulent flow in smooth and rough pipes.
To observe and compare the velocity distributions in smooth and rough pipes.

Pipe assemblies equipped with taps and a manometer board
Upstream orifice meter with differential manometer
Movable stagnation tubes and monometers fitted to the outlets of the pipes

Set up the experiment
• Measure the positions of the manometer taps along the two pipes.
• Open the surge tank valve and turn on the small pump. Release water from several valves around the lab to remove air from the piping system.
• Record the water temperature

Measure head loss vs. distance and flow.
• Establish a steady flow through one of the pipes, using the valve at the head of the pipe.
  Use the back-pressure valve at the end of the pipe to control the level of the manometers. First, partially close the valve to remove air from the manometer tubes Then adjust the valve so all manometers for the subject pipe can be read
• Record the levels for all manometers except that for the stagnation tube
• Record the differential head across the orifice in the supply line. You may want to read it several times during the run to assure yourself that it is holding constant.
  Convert the orifice manometer reading to flow using the rating curve provided.
• Repeat the above steps for 5-7 flows through the subject pipe.
  (For low flows, you may release water elsewhere in the lab so the pump operates at a steadier rate.)

Measure the velocity profile across the pipe.
• At one flow rate, traverse the full pipe diameter with the stagnation tube using the screw device
• Stop at 8-10 locations along the traverse and record the position of the probe, the static head (from the manometer board), and the stagnation head

Carry out both measurement procedures for the second pipe
• Note: When you repeat this for the other pipe, use about the same flow so you can compare velocity profiles

Turn off the pump and drain the pipes
Close the surge tank valve.

Present the key results and describe any major deviations from the printed procedures and why you did them
You do not need to turn in the lab procedure sheet with your report, but it is ok to add it as an attachment
You may use a computer sketch of the apparatus in the body of the report, but the attachment must be hand drawn

Calculate friction factors (f) and Reynolds numbers (Re) for all experimental runs
• Are the flows laminar, turbulent or transitional


• What is the criterion used to make the determination?

Plot a graph with your f and Re data for both pipes.
[Note: These are often on log-log scales (Moody diagram), but simple arithmetic scale paper may be ok here.]

• From a Moody diagram in the literature, determine the relative roughness of each pipe from the positions of your data on the diagram
Calculate the absolute roughness for each pipe.
[There also are equations to calculate relative roughness.]

Calculate values of Hazen-Williams coefficient for each run. How good is the assumption that the coefficient is constant with Re?
• Compare your measurements of absolute roughness and Hazen-Williams coefficient with tabulated values for copper and galvanized steel pipe. Come to a conclusion about the effectiveness of the new coating
Does it make the pipes smoother, rougher, or have little effect?

Plot the piezometric head vs. pipe pressure tap position for all flow rates for each pipe.
• These are used to determine the head loss-length relationship (i.e., slope of the energy line)


• Does the initial part of the graph fit your expectations? If not, why not? If not, make a judgment as to whether it should be used in the slope calculation. Justify your judgment in writing at an appropriate location in the report.

Plot the velocity distribution for each pipe, based on the measured heads for the stagnation tube and the static tube at the same position across the pipe.
• Compute the flow rates from the velocity patterns


• How do the computed flow rates compare to the known flow rates?

ATTACHMENTS:

Attach your sketch of the experimental set-up and copies of your input data and calculated results.
Write out the key equations used in calculating the results, with one sample calculation for each equation.

References:

Roberson, J.A. and C. T. Crowe, Engineering Fluid Mechanics, 6th ed., John Wiley and Sons, 1997, pp. 358-373. (You might want to skim 353-358 also.)

Metcalf & Eddy, Wastewater Engineering: Collection and Pumping, McGraw-Hill, 1991.

Calif. State Univ., Sacramento           CE135 Hydraulics Lab

Dept of Civil Engineering                         Instructor      MEH

Lab. Team:                                                Date of Experiment: 

             FLOW HEAD                         MANOMETER HEADS (in)