Getting Started with Flow simulation in Solidworks
Aim: Internal flow simulation of a pipe with different Reynold's number i.e. 100, 1000, 10000.
Software Used: Modeling and simulation were performed in Solidworks.
Theory: Flow can be of 2 types, one is internal flow and 2nd one is external flow and this study is based upon the internal flow. Internal flow refers to analyze the fluid dynamics when fluid/gas flow internally and in contact with the internal boundary.
Moreover, as in the case of Reynold's no. helps us to determine the type of flow it is. For a circular pipe channel flow if Reynold's no. is less than 2000 then it is said to be a laminar flow but when it is greater than 2000, it comes under the transient or turbulent flow.
If the flow is laminar, a lower Reynold's no. indicate that viscous force is a major factor compared to inertia forces.
If the flow is turbulent, a higher Reynold's no. indicate that inertia force dominates compared to viscous forces.
Reynold's No. : It is a non- dimensional parameter and defined as the ratio of inertia forces to the viscous force within a fluid. For a particular channel flow, Reynold's no. helps to determine the kind of flow it is. For eg. laminar, turbulent, etc.
Formula Used: Re = ( ρ.V. l)/ μ
where, μ is the dynamic viscosity. (Pa.sec)
l = characteristic length of fluid (m)
V = velocity of flowing fluid (m/s)
ρ = density of fluid (Kg/m3)
Flow Simulation: It is a feature in Solidworks which helps us to understand the behavior of fluid/gases under various conditions and even for complex geometries too.
Objective: The main objective is to determine and compare the velocity profile at 85, 90, and 95% of tube length and create plots for different values of Reynold's no.
We'll model the pipe and sketch those probe at the required lengths after that simulation will be performed and plots will be analyzed.
Procedure: 1. A rod of 0.03m dia and 0.5m in length was created. Using the shell feature we have generated the required thickness of 0.001m.
2. Line probes were drawn at the top plane for 85, 90, and 95% of length i.e 0.425m, 0.450m, and 0.475m respectively.
3. Lids were provided at both ends to make sure that the pipe is closed.
4. Choosing wizard option, clicking internal flow, initial temp is 293.2K AND 1010325Pa with air as a working fluid
5. Using global mesh, it is manually defined as 20 in the X direction, 20 in the Y direction, and 100 in the Z direction.
6. Providing inlet velocity and static pressure at outlet along with defining walls as a real wall, all this helps us to define the boundary conditions.
Inlet velocity was determined using the above formula and values used are mentioned below in the table.
Flow diameter of the pipe = 0.03- 2*(0.001) = 0.028m (Characteristic Length)
μ= 18.03 * 10^-6 Pa-s (Dynamic Viscosity)
| Reynold's No. | Velocity |
| 100 | 0.0532 |
| 1000 | 0.532 |
| 10000 | 5.32 |
7. After completing the simulation, the XY plots were plotted for various probes to compare the velocity profile and get a better understanding.
Outputs
Results: For Reynold's no 100
For 85% probe length
For 90% probe length
For 90% probe length
Overall velocity distribution
Velocity Plot
Things to observe are that the cut plot is similar for the 3 different probe lengths, as this case comes under laminar flow. The velocity profile is parabolic in nature and can be seen in overall velocity distribution. Velocity is maximum at the center as the least shear resistance is offered there and minimum at the boundary.
For Reynold's no 1000
For 85% probe length
For 90% probe length
For 95% probe length
Overall velocity distribution
Velocity Plot
Here sketch 2 represents a plot for 85% velocity.
sketch 3 represents a plot for 90% velocity.
sketch 4 represents a plot for 95% velocity.
Things to observe are that the cut plot is similar for the 3 different probe lengths, as this case comes under laminar flow too. The velocity profile is parabolic in nature and can be seen in overall velocity distribution. Velocity is maximum at the center as the least shear resistance is offered there and minimum at the boundary. Moreover, the inertia forces are more considerable than in case 1 due to which the overall velocity profile looks a bit different.
For Reynold's no 10000
For 85% probe length
For 90% probe length
For 95% probe length
Overall velocity distribution
Velocity Plot
Here sketch 2 represents a plot for 85% velocity.
sketch 3 represents a plot for 90% velocity.
sketch 4 represents a plot for 95% velocity.
Here Reynold's no. is 10000 which is greater than 2000 it indicates that flow is turbulent in nature and inertia forces dominate here. The velocity profile is different from the laminar case which can be compared with theoretical concepts which are matching here. Moreover, the velocity, cut plots for velocity are compared for the specific Reynold's no.
Conclusion: Flow varies from 0 at the initial surface to the maximum at the center. This is because we know that it follows a parabolic profile according to which least offered resistance is at the center and velocity is maximum there.
Moreover, one more thing to notice is that velocity near the boundary is tending to zero, the main reason is the formation of the boundary layer near the surface.