FLOW SIMULATION THROUGH A PIPE IN SOLIDWORKS

AIM: Flow Simulation in a pipe using SolidWorks

INTRODUCTION:

The Reynolds number (Re) is an important dimensionless quantity in fluid mechanics used to help predict flow patterns in different fluid flow situations. At low Reynolds numbers, flows tend to be dominated by laminar (sheet-like) flow, while at high Reynolds numbers turbulence results from differences in the fluid's speed and direction, which may sometimes intersect or even move counter to the overall direction of the flow (eddy currents). These eddy currents begin to churn the flow, using up energy in the process, which for liquids increases the chances of cavitation. The Reynolds number has wide applications, ranging from liquid flow in a pipe to the passage of air over an aircraft wing. It is used to predict the transition from laminar to turbulent flow and is used in the scaling of similar but different-sized flow situations, such as between an aircraft model in a wind tunnel and the full size version.

Laminar Flow

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 stream line or viscous flow.

Turbulent 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.

The flow is

• laminar when Re < 2300
• transient when 2300 < Re < 4000
• turbulent when 4000 < Re

GOVERNING EQUATIONS:

Reynolds Number –

`R_e= (ρ×v×D)/μ`

where,

`ρ`= Density

`v`= Average velocity at inlet

`D`= Equivalent diameter

`μ`= Dynamic viscosity of fluid

OBJECTIVE:

1. To perform Pipe Flow Simulation at given Reynolds number.
2. To compare the velocity profile at different line probes.
3. To normalize the velocity profile by the inlet velocity.

Geometry and parameters:

Fluid: Water

Length of pipe: 1 m

Thickness: 0.002 m

INITIAL CONDITIONS:

At Re = 100

v = 0.00154 m/s

At Re = 1000

v = 0.00154 m/s

At Re = 10000

v = 0.00154 m/s

PROCEDURE:

Case Setup:

• A pipe of required length is constructed in SolidWorks and to make it watertight lids are attached on both sides.
• A watertight geometry is an essential feature which object possess, for performing CFD simulations.
• Line probes are constructed at three positions 85%, 90% &95% of the length of the pipe.
• In Flow simulation tab, initial conditions using the wizard option are assigned with flow type depending upon the conditions to simulate.,. i.e., Reynolds number predicts the flow through pipe.
• The boundary conditions are specified with proper values followed by discretization. The basic mesh was generated by providing values manually which includes

Along X = 10 divisions

Along Y = 10 divisions

Along Z= 50 divisions

• Baseline simulation was run to solve the above set of condition
• Plots are made by using the XY plot option and velocity plots at different position of the line probes are created and plots for velocity comparison at different line probes is also created.
• Always remember to obtain a clear visual representation of the results, the max. and min. values should be taken as global maxima/minima.
• Cut plots were made along lateral and longitudinal directions of the pipe.

RESULTS:

Re = 100

Probe at 95%

The velocity profile at boundary is zero due to wall friction and the max. value is attained at the centre of pipe.

Probe at 90%

The profile is lesser developed at shorter lengths and thus show the transitioning into a fully developed flow.

Probe at 85%

In comparison to the line probe at 90 % of the length of the pipe, the flow is less developed.

Comparison of normalized Velocity profiles at different Line Probe locations

The velocity profile gets build up within shorter pipe length for low Reynolds no. .Also, farther from the face, greater velocity developed.

Re = 1000

Probe at 95%

The contour represent the boundary layer thickness which is smaller in comparison to the contours obtained with simulating flows at high Reynolds no.

Probe at 90%

Lesser developed flow is observed in the above plot

Probe at 85%

It shows the least development in comparison to other probe locations at a given Reynolds number.

Comparison of normalized Velocity profiles at different Line Probe locations

The velocity profile is flattened due to under-developed flow.

Re = 10000

Probe at 95%

The velocity close to the boundary possess some value, providing the perception of flow with highly undeveloped velocity profile.

Probe at 90%

The plot represents the high velocity possessed by the fluid at line probe locations with very high Reynolds number.

Probe at 85%

The contour represents least developed flow in comparison to the above two contours for Re = 10000.

Comparison of normalized Velocity profiles at different Line Probe locations

The transmission to a fully developed flow is far off due to high velocities at inlet. The flow is highly flattened at the max. velocity and the wall friction is getting overpowered by the momentum of fluid.

CONCLUSION:

• Using SolidWorks simulation of internal flow through pipe can be generated with some conditions.
• On increasing the Reynolds number, the velocity contour takes more time to build results.
• By improving the mesh size, the plots were finer but take more time to build.
• The Velocity profile was found to be parabolic in case of laminar flow than in the turbulent flow.