Lab Report 2 3n4d5d

CE 612 Fluid Mechanics Laboratory

Report on Experiment:

Energy losses in Bends By Sudarshana Mukhopadhyay Roll No 12103060 1st Semester, M. Tech.

Department of Civil engineering Indian Institute of Technology, Kanpur

Comments:   

Head loss coefficient K for long bend is less than that for short bend. This is due to gradual change in direction of flow in case of long bends. Area of flow remains same for the bends. Therefore no additional static head is induced. For bends 𝑘 = 𝑓(𝜃, 𝑅 𝐷)

Q. What is the dependence of head losses across pipe fittings upon velocity? 𝑉2

Ans. Head loss across a pipe fitting is given by 𝑕𝑙 = 𝑘 2𝑔 .From this it is obvious that the head loss 𝑉2

varies as the square of the velocity. In the plot of head loss against dynamic head (2𝑔 ) same trend can be observed. This dependence of head loss upon velocity also depends on the pipe fittings under consideration. As can be seen from the plots, curves for different pipe bend and fitting have different slope. Q. Examining the Reynolds number obtained, are the flows laminar or turbulent?

Ans. Reynolds number is given by 𝑅𝑒 = 4𝑄 𝜋𝜈𝐷

Where Q = discharge, 𝜈 = kinematic

viscosity of water, D= diameter of pipe. Value of Reynolds number has been shown in tabular form. As Reynolds number is always greater than 2000, the flow of water throughout the experiment was turbulent. Q. Is it justifiable to treat the loss coefficient as constant for a given fitting? Ans. Yes. For a given pipe fitting K can be treated as a constant. Value of K remains almost same for different velocity and head loss values for a given pipe fitting. Crane Company (Crane Company, Flow of fluids, Tech. Paper 409, 1942) published a summary of representative head loss coefficients for typical pipe fittings. In case of sudden contraction, value of Cc (contraction coefficient) can be determined Weisbach equation. Value of Cc depends on the ration of contracted pipe area to the initial pipe area. So for a given ratio, Cc and hence K can be regarded as constant.

Head loss (m)

Plot of head loss against dynamic head 0.05 0.045 0.04 0.035 0.03 0.025 0.02 0.015 0.01 0.005 0

long bend short bend Enlargement Contraction

0

0.05

0.1

0.15

0.2

0.25

Dynamic head (v2/2g)

head loss coefficient K

Plot of K against Q 2 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0

Long bend short bend Enlargement Contraction 0

0.0002

0.0004

0.0006

0.0008

Discharge Q (m3/s)

0.001

0.0012