Simulation of flow through pipe using SolidWorks
AIM
To run a pipe flow simulation with Reynolds number of 100, 1000, 10000
GOVERNING EQUATION
Reynolds number, Re = `(rho*V*l)/mu` = `(V*l)/nu` , where
`rho` = density of the fluid (kg/`m^3`)
V = velocity of the fluid (m/s)
l = characteristic length of the fluid (m)
`mu` = dynamic viscosity (`Pa*s`)
`nu` = kinematic viscosity (`m^2`/s)
THEORY
Reynolds number is a dimensionless quantity. It is the ratio of the inertial forces to the viscous forces within a fluid. Reynolds number quantifies the relative importance of these forces over each other and helps in determining the type of flow under given conditions.
Low value of Reynolds number indicates dominance of viscous forces over inertial forces and the flow is said to be laminar flow. It is characterized by smooth and constant fluid motion.
Higher value of Reynolds number indicates dominance of inertial forces over viscous forces and the flow is said to be turbulent flow. It is characterized by chaotic eddies, vortices and other fluid instabilities.
Flow simulation
It allows prediction and analysis of how a fluid (liquid or gases) might be impacted by complex geometries or varying conditions in an operational environment. It is helpful in determining the behaviour of system under various and extreme circumstances.
OBJECTIVE
The objective is to determine and compare the velocity profiles at 85%, 90% and 95% length of the tube and create cut plots for different values of Reynolds number. In order to do so, first a pipe would be created and line probes would be placed at desired lengths. Following this, a flow simulation would be done and required plots would be created and analysed.
PROCEDURE
1) A random rod of diameter 0.03 m and length 0.5 m is created on the front plane. Shell feature is used to generate a pipe out of it having thickness of 0.001 m.
2) Line probes are drawn at the top plane, each at 85%, 90% and 95% of the length of pipe from the inlet, that is at 0.425m, 0.45m and 0.475m respectively. Lids are provided at both the openings of the pipe.
3) Air is selected as the flowing fluid and initial temperature and pressure are set to 293.2 K and 101325 Pa respectively.
4) Under global mesh option, edit definition is selected and the mesh is changed to 20 in X-direction, 20 in Y-direction and 100 in Z-direction.
5) Now, boundary conditions are set. Velocity is provided at the inlet, static pressure at the outlet and the pipe walls are set to be real walls. Inlet velocity is determined using the Reynolds number. in the formula, the values of Reynolds number, characteristic length and kinematic viscosity is known. Substituting these values provide the inlet velocity for each case.
Here, Characteristic length = flow diameter of the pipe = 0.03 - 2*(0.001) = 0.028m
Kinematic viscosity of air at`20^oC` = 1.506 x `10^-5``m^2`/s
| Re | V |
| 100 | 0.0532 |
| 1000 | 0.532 |
| 10000 | 5.32 |
6) Once the boundary conditions are set, the flow simulation is run. In order to compare the velocity at different line probes, XY plot is used. Cut plot is also created for a better understanding of the velocity profile. The transparency is given to the pipe in order to visualise the cut plot.
7) By right-clicking on the project name, parametric study is selected and inlet velocity is chosen as the input variable. The inlet velocity is varied according to the Reynolds number and the flow simulation is run.
OUTPUT
For Reynolds number = 100
For Reynolds number = 1000
For Reynolds number = 10000
CONCLUSION
Flow velocity varies from 0 at the wall of the pipe to maximum at the centre. There is no velocity gradient at the centre of the pipe during the fluid flow through it. Thus, there is no resistance offered by the pipe surface to the fluid flow due to which there is no shear resistance at centre.
The velocity is 0 near the surface of the pipe due to the formation of boundary layer. A boundary layer is a layer of viscous fluid close to the solid surface of the wall, in contact with the stream of flowing fluid. The flow velocity varies from 0 at the wall to nearly streamline velocity at the end of the boundary.