The following are the objectives of this experiment:
Experimental Apparatus
The following apparatus were used in the experiment:
- One hydraulic bench
- Osborne Reynolds flow visualization apparatus
- A digital flow meter
- A mercury thermometer
- 1 liter of Purple vegetable dye
The Osborne Reynolds flow visualization apparatus used in the experiment is as shown in Fig. 1.
Figure 1: Osborne Reynolds flow visualization apparatus
Apparatus description
Osborne Reynolds apparatus consists of a vertical transparent pipe where the water flows. A valve is used to vary/adjust the flow rate or the velocity of water flow. The vegetable ink is injected into the water on the upper part of the vertical pipe through an injection needle. The glass beads in the water tank help to stabilize the flow by eliminating the turbulence. In the experiment, the various flow regimes are obtained by varying the rate of flow using the water outlet control valve.
Results
Mathematical formulations
The dimensionless Reynolds number (Re) of the flow was computed from the following equation
Re=UDv ( 1)
Where,
- v is kinematic viscosity of water in m2/s,
- D is the diameter of the pipe,
- and 'U' represents the velocity of water in m/s. The velocity of water is computed from the following expression
U=Flow ratecrosssection area of pipe
Calculations
1. Laminar flow
Experimental observation/visualization
The flow visualization in the vertical clear tube was as shown in Fig.2. The figure captures the three flow regions very well.
Figure 2: Experimental Observation
Discussions
Flow of water or liquid in pipes can either be laminar, transitional or in transitional state. This experiment has demonstrated this vividly well. For low water speeds, the flow was laminar and the dye followed a straight path. When the velocity of water was increased the dye started to fluctuate and intermittent bursts of the dye were seen, this was the transition region. When the velocity of water was increased further the dye was blurred and filled the whole pipe. This was the turbulent region. The dimensionless Reynolds number computed for the three flow regimes were within the expected range and they were consistent with the flow pattern observed. The main source of errors in this experiment is inability to stabilize water effectively before it gets to the vertical pipe. Flow stabilization and elimination of turbulence was achieved by use of beads in the apparatus.
Conclusions
The experiment was successful and the objectives were achieved. The flow visualization in the laminar, transitional and turbulent regimes was well captured in this experiment. From the data, the calculated values of Reynolds numbers compared very well with observed flow patterns for laminar, transitional and turbulent flow. The experimental values compared very well with theoretical data of flow visualization presented in various manuals.
