Flow through a pipe
Aim : To analyze the flow through a pipe at different Reynolds numbers. To compare and discuss the results of normalised velocity profiles after refining the mesh grid at different Reynolds numbers.
Description and Procedure:
Pipe of Diameter 30mm is designed and extruded to a length of 1m and the line probes are placed at 95%, 90% and 85% of the pipe length which is at a distance of 50mm,100mm and 150 mm from the other End.
In Fluids, water is selected as project fluid, flow type as Laminar and turbulent third cases .
Initial Conditions pressure as 101325Pa, Temperature as 293.2K and velocity as 0 m/s.
Right click on boundary conditions and select Insert boundary conditions.
Once the boundary conditions are given, Basic mesh is to be setup and refined if needed.
After running the simulation, velocity cut plots between different line probes is plotted and parametric study is done with simulation parameters and design points.
The first boundary condition for out-flow, select static pressure of 101325Pa.
The boundary condition for inflow is the three inlet velocity at three different cases on another end of the pipe. The last boundary condition for Wall is the Real wall and select the inner wall of the pipe.
Considering a steady flow and water as the fluid inside the pipe, kinematic viscosity at the room temperature is noted.
The inlet velocity of the pipe is calculated from the Reynolds number.
where:
V is the flow velocity,
D is a hydraulic diameter = diameter of the flow pipe in this case.
ρ fluid density (kg/m3),
μ dynamic viscosity (Pa.s),
ν kinematic viscosity (m2/s); ν = μ / ρ = 9 *10^-5.
On substituing,
The inlet velocity calculated is 0.003m/s, 0.03 m/s, 0.3m/s at the inlet Reynolds number 100,1000 and 10000 respectively.
When the Reynolds number is 100 i.e. inlet velocity is 0.003 m/s.
The graph is plotted in excel with th evalues that are obtained from the design points.
When the Reynolds number is 1000 i.e. inlet velocity is 0.03 m/s.
The graph is plotted in excel with th evalues that are obtained from the design points.
When the Reynolds number is 10000 i.e. inlet velocity is 0.3 m/s.
The graph is plotted in excel with th evalues that are obtained from the design points.
Results and Inferences:
* The shear stress is high at the wall and is low at the centre of the pipe.
* As we increase the velocity, the velocity profile becomes more straight this is because of teh turbulence and can be explained by the Prandtl mixing theory. Turbulence takes place and hence the effect of viscosity is less.
*Effect of the velocity and its variation is shown and explained at different line probes. Viscous effects play a major role here. At the entry, characteristic length is calculated for the fully developed flow analysis.