Pipe Flow Simulation in SolidWorks

AIM : To run a pipe flow simulation with an inlet Reynolds number of 100,1000 and 10,000 in Solidworks

OBJECTIVES :

1. To create a 3D model of a pipe in Solidworks,
2. To Simulate and analyse the fluid flow in pipes using the SolidWorks Flow Simulation add-ins.
3. Place line probes at 95%, 90% and 85% of the pipe length.
4. Compare the normalized velocity profile at each of these locations.

BACKGROUND : The purpose of this study is to simulate flow in pipes utilizing SolidWorks software. Fluid flow may be very hard to predict and differential equations that are used in fluid mechanics are difficult to solve. SolidWorks add-ins enable you to simulate flow of liquids and gases and efficiently analyse the effects of fluid flow. SolidWorks has tools that enable you to simulate liquid and gas flow in real world condi-tions, run “what if” scenarios, and efficiently analyse the effects of fluid flow, heat transfer, and related forces on immersed or surrounding components.

The motion of a fluid is usually very complex. The observed fluid flow behaviour becomes much more understandable after defining the flow into laminar or turbulent regimes. The momentum equation provides one of the most recurring tools to be used in understanding fluid flows. Another fundamental tool for fluid flow analysis is continuity equation, both in its volumetric and its more widely applicable mass flow form.
Along with the energy equation, the aforementioned equations, momentum and continuity, are also known as Navier–Stokes equations. Newtonian fluid flow is incompressible when the density is constant. In such case Navier - Stokes equations can be simplified.

Laminar flow or streamline flow in pipes (or tubes) occurs when a fluid flows in parallel layers, with no disruption between the layers. At low velocities, the fluid tends to flow without lateral mixing, and adjacent layers slide past one another like playing cards. There are no cross-currents perpendicular to the direction of flow, nor eddies or swirls of fluids. In laminar flow, the motion of the particles of the fluid is very orderly with all particles moving in straight lines parallel to the pipe walls. Any lateral mixing (mixing at right angles to the flow direction) occurs by the action of diffusion between layers of the liquid. Diffusion mixing can be slow however if the diameter of the pipe of tube is small then this diffusive mixing can be very significant.

Turbulent flow is a flow regime characterized by chaotic property changes. This includes rapid variation of pressure and flow velocity in space and time. In contrast to laminar flow the fluid no longer travels in layers and mixing across the tube is highly efficient. Flows at Reynolds numbers larger than 4000 are typically (but not necessarily) turbulent, while those at low Reynolds numbers below 2300 usually remain laminar. Flow in the range of Reynolds numbers 2300 to 4000 and known as transition.

PROCEDURE :

• 1. Modelling of pipe and Simulation setup -
• At first a pipe was created with diameter `25 mm` and extruded to a length of `1000 mm`. A shell of thickness `0.5 mm` was created on the two parallel faces to make it a hollow pipe. Three line probes at the distance of `85%,90%,95%` of the total pipe length were provided. Then lids were applied on the these two faces for running the simulation.
• A wizard was opened in the Solidworks flow and initial inputs were given. The fluids selected was air at `101325 Pa` and `293.20 K`. From these two data, the density (`rho`) and dynamic viscosity (`mu`) of air at these property is as follows :-
• `rho = 1.2041``(kg)/(m^3)` and `mu = 1.825``*10^-5``(kg)/(ms)`,
• Reynolds Number (`R_e`) = `(rho*v*D)/(mu)` `implies v = (R_e*mu)/(rho*D)`,
• Case 1: For `R_e=100` , `v=0.06062``m/s`,
• Case 2: For `R_e=1000` , `v=0.6062``m/s`
• Case 3: For `R_e=10000` , `v=6.062``m/s`
• Hence for boundary conditions, at inlet of the pipe, the above calculated inlet velocities are provided. At the outlet of the pipe, a static pressure of `101325 Pa` were given and the outer wall of pipe were provided as a real wall.
• The final step before the simulation is meshing. Meshing is a representation of a given model expressed as finite set of geometric shapes. There are two types of Mesh to choose from: Global Mesh and Local Mesh. The former is used for the entire model; the latter only within a selected region. Modification in meshing were given to stretch the meshes in all three directions for proper solutions. In results cut plot and x-y plots were setup according to the requirements of Parametric study and a parametric study was setup and input, output and scenario for three meshes data (the first one,twice of first one, four times of first one) were given and made to run.

• Figure representing cross-sectional views of the pipe

OUTPUTS :

• Case 1: For `R_e = 100`
• Cutplots obtained :-
• For coarse mesh size (Design Point1) -

• For a medium mesh size (Design Point2) -

• For much fine mesh size (Design Point3)-

• Velocity versus length plots at different line probes -

• Comparison of velocities at different line probes (for different mesh sizes)-

• Normalising all of them in a single plot-

• Case 2: For `R_e = 1000`
• Cutplots obtained :-
• For coarse mesh size (Design Point1) -

• For a medium mesh size (Design Point2)-

• For much fine mesh size (Design Point3) -

• Velocity versus length plots at different line probes -

• Comparison of velocities at different line probes (for different mesh sizes)-

• Normalising all of them in a single plot-

• Case 3: For `R_e = 10000`
• Cutplots obtained :-
• For coarse mesh size (Design Point1) -

• For a medium mesh size (Design Point2)-

• For much fine mesh size (Design Point3) -

• Velocity versus length plots at different line probes -

• Comparison of velocities at different line probes (for different mesh sizes)-

• Normalising all of them in a single plot-

CONCLUSIONS :

1. The basic idea of this report is to design a pipe system and run a flow simulation for the observation of the flow of fluids in pipes. Under most practical conditions, the flow in a circular pipe is:
   • Laminar when `R_e ≤ 2300`
   • Transitional when `2300 ≤ R_e ≤ 4000`
   • Turbulent when `R_e ≥ 4000`
2. As the velocity increases the red region in the cut plot increses as flow increases from laminar to turbulant.
3. Meshing is a crucial step in design analysis. Mesh allows user customization; however extensive knowledge is required for such a task to yield successful simulation. The auto-matic mesh generates a mesh considering model’s geometry, volume, surface area, and other specifications. This is by far a superior option for new users.

REFERENCES :

1. Theory