Flow Simulation inside a pipe in Solidworks

Aim:

To perform flow simulation inside a pipe in Solidworks.

Objective:

• To simulate the pipe flow at different Reynolds number of 100, 1000, 10000.
• Place line probes at 95%, 90% and 85% of the pipe length.
• Compare the normalized velocity profile at each of these locations.

Theory:

Considering a laminar fluid flow inside a pipe. The surface contact between the water and the wall of the pipe will cause the water molecules to slow down and come to a complete stop near the walls. This layer of water molecules will also cause the adjacent layer of water flow to slow down due to the result of friction. To compensate for this velocity, water drops in the core of the pipe needs to maintain a constant velocity to keep the volumetric flow rate constant. As a result, the velocity boundary layer develops along the boundary walls of the pipe and starts to develop in the flow direction until it hits the centre of the pipe. The distance from the pipe inlet to the point where the boundary layer merges is called the hydrodynamic entry length. The region beyond the hydrodynamic entry length is known as the fully developed region.

Reynolds number: is an important dimensionless quantity in fluid mechanics used to help predict flow patterns in different fluid flow situations. 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. It is the ratio of inertial forces to viscous forces within a fluid which is subjected to relative internal movement due to different fluid velocities, which is known as a boundary layer in the case of a bounding surface such as the interior of a pipe.

The Reynolds number is defined as

Where,

ρ is the density of the fluid (kg/m^3)

u is the velocity of the fluid with respect to the object (m/s)

L is a characteristic linear dimension (m)

μ is the dynamic viscosity of the fluid (Pa·s or N·s/m^2 or kg/m·s)

ν is the kinematic viscosity of the fluid (m^2/s).

In our Case:

Water is used as a medium. Which has,

Viscosity = 8.9 x 10^−4 pa.s

Density = 1000 kg/m^3

Thus,

for R = 100, inlet velocity = 0.0089 m/s

for R = 1000, inlet velocity = 0.089 m/s

for R = 10000, inlet velocity = 0.89 m/s

Setup Explanation:

1. First, the pipe is modelled with diameter = 100 mm, length = 1000 mm and thickness = 5 mm as shown.
2. Lids are added to the end faces to create a water tight geometry.
3. Create three line sketches at 850, 900 and 950 mm in the top plane as shown.

4. Then, under flow simulation option click on wizard tool and create a new setup with default options, internal flow study with water as the working fluid.
5. Edit the mesh definition manually and insert 20 elements in Y & Z direction and 100 elements in X direction to improve accuracy.

6. Insert the following boundary conditions:

• Inlet velocity of 0.0089 m/s at lid 1.

• Outlet static pressure of 101325 Pa at lid 2.

• Set inner surface of wall as a Real wall.

7. Insert cut plots at 850, 900 and 950 mm from starting point normal to the flow.
8. Insert XY plots along the three line sketches 1,2 & 3.
9. Run a new parametric study with the inlet velocity as an input variable with values 0.0089, 0.089 & 0.89 m/s and the cut plots and XY plots as the output parameters.

Results:

1. Cut Plots:

• For v = 0.0089 m/s

• For v = 0.089 m/s

• For v = 0.89 m/s

2. XY Plots:

• At 85%,

• At 90%,

• At 95%,

Observations:

1. The cut plots change slightly with position for a particular velocity.
2. The peak value of velocity profile is over a region and not at one single point.

Conclusions:

1. In all 3 cases, the velocity profile is under developed.
2. With increase in Reynolds number, the flow increases and the flow becomes more under developed and will require a longer length pipe to fully develop.

File Link:

https://drive.google.com/drive/folders/1vNqq7h5pxM_ibggJ8IGCmWB5gh7Qv01H?usp=sharing