The main objective of this research was to investigate the flow of water in a pipe at the various conditions. The experiment had the following specific objectives:
Apparatus
The apparatus used in the experiment are listed below:
- A hydraulic bench
- Osborne Reynolds apparatus
- Digital flow meter (one)
- Thermometer (one)
- Purple vegetable dye
Apparatus
The apparatus consists of a vertical clear pipe through which the flow visualization at the various flow conditions (laminar, transitional and turbulent) is done. The Osborne Reynolds apparatus used in the experiment is as shown below:
Figure 1: Osborne Reynolds Experimental apparatus
Results and Data Analysis
Fluid flow in conduits (pipes) is either laminar, turbulent on in the transition region between laminar and turbulent. Fluid circulation eddies and turbulent characterizes turbulent flow. Engineers use the Reynolds number of the flow to distinguish the type of flow. The Reynolds’s numbers is expressed as the ratio of viscous forces to inertia forces. The Reynolds number (Re) was computed from the following equation
Re=UDv..Equation 1
Where, v is kinematic viscosity of water in m2/s, D is the diameter of the pipe and U is the average velocity of water in m/s. Engineers use the following criterion to distinguish between the various types of flow.
Velocity (U)=discharge (m3s)cross-section area(m2)
Sample calculation
The following flow parameters were recorded for this flow condition:
Temperature=20o C.
Kinematic viscosity (at 20o C)=100.3*10-8 m2/s.
Diameter=0.01 mm.
Volumetric flow rate of water= 12x10-6 m3/s.
The velocity of flow is computed as:
U=12x10-6π4*0.012=0.152788 m/s
The Reynolds number of flow:
Re=UDv=0.152788*0.01100.3*10-8=1523.31
The following flow parameters were recorded for this flow condition:
Temperature=20o C.
Kinematic viscosity (at 20o C)=100.3*10-8 m2/s.
Diameter=0.01 mm.
Volumetric flow rate of water= 36.8 x10-6 m3/s.
The velocity of flow is computed as:
U=36.8 x10-6π4*0.012=0.468552m/s
The Reynolds number of flow:
Re=UDv=0.468552*0.01100.3*10-8=4671.5
The following flow parameters were recorded for this flow condition:
Temperature=20o C.
Kinematic viscosity ( at 20o C)=100.3*10-8 m2/s.
Diameter=0.01 mm.
Volumetric flow rate of water= 100 x10-6 m3/s.
The velocity of flow is computed as:
U=100 x10-6π4*0.012=1.27324 m/s
The Reynolds number of flow:
Re=UDv=1.27324*0.01100.3*10-8=12694.3
Figure 2: Flow visualization in the three regions
In this experiment, the flow visualization of the colored dye stream injected into the core of the vertical clear pipe was as shown in Fig. 2 for the various flow regimes. For laminar flow, the dye remained as a solid line at the center of pipe without separation. However, when the velocity of water was increased the transition region was reached where the dye started breaking and wandering throughout the cross section of the pipe. Finally, in turbulent region the dye broke completely and mixed with water. Figure 2 illustrates the flow visualization in these three flow regions. This was consistent with our expectations. In laminar flow, the stream lines do not mix thus the dye does not break. Oh the other hand, in transitional flow and turbulent flow there is flow randomness causing the water streamlines to mix. However, the degree of mixing is more in turbulent flow. The magnitudes of the Reynolds number computed for laminar, transition and turbulent flow were in consistent with the flow conditions observed. This implies that the experiment was very successful.
