Pipe flow simulation using Solidworks

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

For each of these cases do the following

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.

Theory- Reynolds Number
The Reynolds number is the ratio of inertial forces to viscous forces. The Reynolds number is a dimensionless number used to categorize the fluids systems in which the effect of viscosity is important in controlling the velocities or the flow pattern of a fluid. Mathematically, the Reynolds number, Re, is defined as

`Re = (rho*v*d)/mu`

rho = density

v = velocity

d = diameter

mu= viscocity

Fluid Flow in Pipes- Flow in a liquid pipeline may be smooth, laminar flow also known as viscous flow. In this type of flow, the liquid flows in layers or laminations without causing eddies or turbulence. If the pipe is transparent and we inject a dye into the flowing stream, it would flow smoothly in a straight line confirming smooth or laminar flow. As the liquid flow rate is increased, the velocity increases and the flow will change from laminar flow to turbulent flow with eddies and disturbances. This can be seen clearly when a dye is injected into the flowing stream.

An important dimensionless parameter called the Reynolds number is used in classifying the type of flow in pipelines.

Reynolds number of flow, R, is calculated as follows:

`Re = (rho*v*d)/mu`

where:

rho = liquid density (kg/m3)

v = average velocity (m/s)

d = pipe internal diameter (m)

mu= absolute viscosity (N-s/m2)

Re – Reynolds number is a dimensionless value

Because of, the kinematic viscosity ν = μ/ρ, the Reynolds number can also be expressed as

`Re = (v*d)/nu`

ν – kinematic viscosity, m2/s

Flow-through pipes are classified into three main flow regimes.

1.Laminar flow – R < 2000

2.Critical flow/Transition flow – R > 2000 and R < 4000

3.Turbulent flow – R > 4000

Depending upon the Reynolds number, flow-through pipes will fall in one of these three flow regimes. Let us first examine the concepts of the Reynolds number. Sometimes an R value of 2100 is used as the limit of laminar flow.

Inputs :

Diameter of pipe = 0.018m

Length of the pipe= 0.3m

liquid density = 1.2047(kg/m3)

Dynamic viscosity of air (at 20 degree celcius & 1 atm pressure)=`1.825*10^(-5)` (N-s/m2)

Temperature (T)	Density (ρ)	Dynamic Viscosity (μ)	Kinematic Viscosity (v)
◦c	kg/m3	x10-5 kg/m.s	x10-5 m2/s
-20	1.3958	1.6222	1.1622
-15	1.3687	1.6478	1.2039
-10	1.3426	1.6731	1.2462
-5	1.3175	1.6982	1.2890
0	1.2933	1.7231	1.3324
5	1.2699	1.7478	1.3763
10	1.2474	1.7722	1.4207
15	1.2257	1.7965	1.4657
20	1.2047	1.8205	1.5111
25	1.1845	1.8444	1.5571
30	1.1649	1.8680	1.6036
35	1.1459	1.8915	1.6507
40	1.1275	1.9148	1.6982

Calculation of inlet velocity

Reynolds number = (rho x Velocity x D)/Dynamic visosity

By applying the above inputs and formula for reynolds number, (Ra=100,1000 & 10000)

We get,

Velocity for (Re = 100) = 0.09445 m/s

Velocity for (Re = 1000) = 0.9445 m/s

Velocity for (Re = 10000) = 9.445 m/s

Procedure:

1. Create a new part model.
2. Make a circle of 18mm clameter and extrude it to 300 mm to make a cylinder.
3. Select shell, then select both face side of the cylnder and 1mm as thickness. Hence, making a pipe of 1mm thickness.
4. Create new sketch along the length of the pipe and create a vertical line at 85% of the length and similarly for 90% ard 95% of the length.
5. Go to Flow Simulatlon, and select create lid command and select end faces of the pipe to make a closed airtight volume for CFD simulation.
6. Click on new in flow simulation toolbar. Right click on input data on flow simulation tree, and select gerneral setting.
7. In Fluids, select air in gas as project fluid, flow type as Laminar for first two cases and turbulent for third case and in initial conditions pressure as 101325 Pa, temperature as 293.2 K and velocity as 0m/s.
8. Right click on boundary conditions and select insert boundary conditions. The boundary condition for inflow is the three inet velocity at three different cases on inlet of the pipe. The boundary conditicn for wall is the Real wall and select the inner wall of the pipe.
9. The first boundary condition for out-flow, select static pressure of 101325 Pa
10. Right click on Gloal Mesh and select edit definitions, change mesh manually, in X-direction 10, Y-direction 10, in Z-direction 50.
11. Right click on XY plot for velocity in normal to the plane direction (Z-direction) and select insert then select the 85% line sketch. Similarly, make XY plot tor 90% and 95% and similarly right click on cut plot for velocity in XY plane at distances of 85% 90% & 95% of length and than Run.
12. Right click on project name and select new parametric study. Then select inlet velocity in input variables than, select all XY plots & cut plots. Go to scenario tab and select design point 1 and copy paste it two more times. Change mesh in design point 2 and 3 by doubling them & run.
13. Now after case 1 create new project & change the inlet velocity and click on run and than similarly run a new parametric study for the two velocities.

Output -

Case 1: Re = 100

1) At 85% of length

A) Cutplot at 85% of length

• Design point 1

• Design point 2

• Design point 3

B) XY plot at 85% of length

2) At 90% of length

A) Cutplot at 90% of length

• Design point 1

• Design point 2

• Design point 3

B) XY plot at 90% of length

3) At 95% of length

A) Cutplot at 95% of length

• Design point 1

• Design point 2

• Design point 3

B) XY plot at 95% of length

Case 2: Re = 1000

1) At 85% of length

A) Cutplot at 85% of length

• Design point 1

• Design point 2

• Design point 3

B) XY plot at 85% of length

2) At 90% of length

A) Cutplot at 90% of length

• Design point 1

• Design point 2

• Design point 3

B) XY plot at 90% of length

2) At 95% of length

A) Cutplot at 95% of length

• Design point 1

• Design point 2

• Design point 3

B) XY plot at 95% of length

Case 3: Re = 10000

1) At 85% of length

A) Cutplot at 85% of length

• Design point 1

• Design point 2

• Design point 3

B) XY plot at 85% of length

2) At 90% of length

A) Cutplot at 90% of length

• Design point 1

• Design point 2

• Design point 3

B) XY plot at 90% of length

3) At 95% of length

A) Cutplot at 95% of length

• Design point 1

• Design point 2

• Design point 3

B) XY plot at 95% of length

• Comparison of velocity in XY plot at 85% of length of design point 3 with Re = 100/1000/10000

• Comparison of velocity in XY plot at 90% of length of design point 3 with Re = 100/1000/10000

• Comparison of velocity in XY plot at 95% of length of design point 3 with Re = 100/1000/10000

Result- As from the above we can say that the area under the curve of Re=10000(turbulent) is maximum in all cases. And we can also say that the area increases if velocity increases. So,Reynolds number increases as turbulence increases.