Pipe Flow Simulation Using SolidWorks

Aim:-

To run a pipe flow simulation with an inlet Reynolds number of 100,1000 and 10,000.

Objective:-

• To run an internal pipe flow simulation with Solidworks
• For each of these cases, the following conditions must be applied:
  1. Place line probes at 95%, 90% and 85% of the pipe length.
  2. Compare the normalized velocity profile at each of these locations.
  3. Normalize the velocity profile by the inlet velocity.

Introduction:-

Liquids and gases are sometimes grouped in a single category called fluids. The main difference between fluids and solids is their different rigidity. Solids are more rigid than fluids, thus solids are more difficult to deform than fluids.

In fluid dynamics, laminar flow is characterized by smooth or in regular paths of particles of the fluid, in contrast to turbulent flow, that is characterized by the irregular movement of particles of the fluid. The fluid flows in parallel layers (with minimal lateral mixing), with no disruption between the layers. Therefore the laminar flow is also referred to as streamline or viscous flow.

In fluid dynamics, turbulent flow is characterized by the irregular movement of particles (one can say chaotic) of the fluid. In contrast to laminar flow the fluid does not flow in parallel layers, the lateral mixing is very high, and there is a disruption between the layers. Turbulence is also characterized by recirculation, eddies, and apparent randomness. In turbulent flow, the speed of the fluid at a point is continuously undergoing changes in both magnitude and direction. Figure 1 shows the difference between laminar flow and turbulent flow in a pipe.

Figure 1: Laminar and Turbulent flow in a pipe 

 

The main tool available for pipe flow analysis is CFD analysis. CFD is a branch of fluid mechanics that uses numerical analysis and algorithms to solve and analyse problems that involve turbulent fluid flows. It is widely accepted that the Navier–Stokes equations (or simplified Reynolds-averaged Navier–Stokes equations) are capable of exhibiting turbulent solutions, and these equations are the basis for essentially all CFD codes.

The Reynolds number is the ratio of inertial forces to viscous forces and is a convenient parameter for predicting if a flow condition will be laminar or turbulent. It can be interpreted that when the viscous forces are dominant (slow flow, low Re) they are sufficient to keep all the fluid particles in line, then the flow is laminar. Even exceptionally low Re indicates viscous creeping motion, where inertia effects are negligible. When the inertial forces dominate over the viscous forces (when the fluid is flowing faster and Re is larger) then the flow is turbulent. Figure 2 shows the Reynolds number formula.

 

Figure 2: Reynolds number formula and parameters

where:

V is the flow velocity.
D is the pipe diameter. 
ρ fluid density (kg/m³)
μ dynamic viscosity (Pa.s)
ν kinematic viscosity (m²/s);  ν = μ / ρ.

 

Laminar flow. For practical purposes, if the Reynolds number is less than 2100, the flow is laminar. The accepted transition Reynolds number for flow in a circular pipe is Re_d,crit = 2300. Transitional flow. At Reynolds numbers between about 2100 and 4000, the flow is unstable as a result of the onset of turbulence. These flows are sometimes referred to as transitional flows. Turbulent flow. If the Reynolds number is greater than 4000, the flow is turbulent. Most fluid systems in nuclear facilities operate with turbulent flow. 

 

Procedure:-

To start the simulation, a 3D model of the pipe was sketched then extruded. Figure 3 shows the pipe flow's sketch dimension ( in meters).

Figure 3: Pipe flow dimensions

Then the pipe was extruded via the Boss Extrude command to 1 meter. Figure 4 shows the 3D model for the pipe.

Figure 4: The 3D model for a pipe 

 

The Shell command was used with a thickness of 0.001 m to determine the inner diameter. 

The next step is to sketch three vertical line probes in the front plane at a distance of 0.95m, 0.90m, and 0.85m from the inlet circular part of pipe. Probes are used to visualize the pipe flow at a certain location. 

Figure 5 shows the hollow model with the three vertical line probes.

 

Figure 5: The hollow pipe model with the three vertical line probes

 

In order to perform a flow simulation so, the fluid type must be defined. For this project,  water will be the chosen fluid for the flow simulation study.

 

Calculation:-

The next step is to calculate the inlet velocity of the pipe.  The Reynolds number has been defined as:

Since the Fluid used will be water, the following properties of the fluid are defined as.

Dynamic viscosity of water (μ) = 8.90 × 10⁻⁴

The density of water (ρ) = 1000 kg/m3">1000 kg/m3

And finally the inner diameter of the pipe (D) = 0.048 m

The values for the inlet velocity is shown in table 1.

for Re = 100	for Re = 1000	for Re = 10,000
u = 0.00185 m/s	u = 0.0185 m/s	u = 0.185 m/s

 

 The final step before starting the simulation is to insert lids on both faces of the pipe. Internal flow studies often contain geometry that has inlets and outlets. The flow simulation requires that these inlets and outlets be bounded by a face. These bounded faces will then contain the info necessary to describe the flow for the inlets and outlets. the inlets and outlets are bounded by using lids.

 

Simulation:-

After creating Lids, the boundary conditions will be assigned as follows:

1. Inlet velocity at lid1 (inlet side of the pipe)
2. Static pressure at lid2 (outlet side of the pipe)
3. A real wall across the length of the pipe.

After assigning the boundary conditions, the mesh will also need to be defined. 

The mesh will be defined from ‘global mesh’ along different axes as follows:

1. Along X-axis → 10
2. Along Y-axis → 10
3. Along Z-axis → 50

The final step is to create cut plots at the 0.95m,0.90m and 0.85m line probes for better visualization and to create XY plots for the velocity at the line probes.

After completing all the steps above, the simulation is run by using a parametric study. SolidWorks has two types of parametric study: Goal optimization and What if analysis. For this project, what if analysis will be used. What If allows you to vary a set of selected variable parameters (such as model dimensions, boundary condition parameters, initial mesh settings. etc.) in order to analyze the selected flow parameters (defined as goals).

 

Results:-

 Study-1: Pipe flow simulation with inlet Reynolds number (Re) = 100 & flow speed (u) = 0.00185 m/s

 a. for Line Probe at 95% 

Figure 6: line probe cut plot at 95%

 

Figure 7: Graph of velocity vs length at line probe (0.95 m)

 

b. for Line Probe at 90% -

Figure 8: line probe cut plot at 90%

 

Figure 9: Graph of velocity vs length at line probe (0.90 m)

 

Figure 10: line probe cut plot at 85%

 

Figure 11: Graph of velocity vs length at line probe (0.85 m)

 

Figure 12: Velocity comparison between the line probes

 

The link below is a video of the pipe simulation, this is done by inserting a cut plot on the right plane. 

 

Study-2: Pipe flow simulation with inlet Reynolds number (Re) = 1000 & flow speed (u) = 0.0185 m/s

 

a. for Line Probe at 95%

Figure 13: line probe cut plot at 95%

Figure 14: Graph of velocity vs length at line probe (0.95 m)

 

b. for Line Probe at 90% 

 

 Figure 15: line probe cut plot at 90%

 

Figure 16: Graph of velocity vs length at line probe (0.90 m)

 

c. for Line Probe at 85%

Figure 17: line probe cut plot at 85%

 

Figure 18: Graph of velocity vs length at line probe (0.85 m)

 

Figure 19: Velocity comparison at different line probes

 

 The link below is a video of the pipe simulation for the second study, this is done by inserting a cut plot on the right plane. 

Study-3: Pipe flow simulation with inlet Reynolds number (Re) = 10,000 & flow speed (u) = 0.185 m/s

 a. for Line Probe at 95%

 Figure 20: line probe cut plot at 95%

 

Figure 21: Graph of velocity vs length at line probe (0.95 m)

 

b. for Line Probe at 90%

Figure 22: line probe cut plot at 90%

 

Figure 23: Graph of velocity vs length at line probe (0.90 m)

 

c. for Line Probe at 85%

Figure 24: line probe cut plot at 85%

 

Figure 25: Graph of velocity vs length at line probe (0.85 m)

 

Figure 26: Velocity comparison at different line probes

 

The link below is a video of the pipe simulation for the third study, this is done by inserting a cut plot on the right plane. 

 

Conclusion:-

Velocity increases as we move towards the center of pipe from the wall due to more shear stress between the layers of fluid at the center. As the line probes at 95%, 90%, and 85% of pipe length are very close to each other that’s why the velocity profile does not change much. Increasing the value of Reynolds number, the pattern of flow changes as well as flow changes into turbulent from laminar flow. With the increase in Reynolds number, velocity gets more uniform. Increasing the number of mesh, gives a more accurate result and allows better visualization.

 

References: 

• https://www.reactor-physics.com/engineering/fluid-dynamics/laminar-flow-vs-turbulent-flow/#:~:text=In%20fluid%20dynamics%2C%20laminar%20flow,no%20disruption%20between%20the%20layers.
• https://www.reactor-physics.com/engineering/fluid-dynamics/reynolds-number/
• https://www.cati.com/blog/2018/06/solidworks-flow-simulation-lid-creation-non-planar-faces/
• https://blogs.solidworks.com/solidworksblog/2013/10/design-scenarios-for-fluid-flow-in-solidworks-flow-simulation.html