Pipe Flow Simulation

Aim: To perform Flow simulation of pipe

Objectives:

1. To model pipe system in solid work.
2. Placing line probes at 95%, 90% and 85% of the pipe length and compare velocity at each location for three cases.
3. Simulate the flow at different Reynold number (i.e. 100,1000,10000) and analyze the result.

Theoretical background:

Introduction:

Pipe flow, a branch of hydraulics and fluid mechanics, is a type of liquid flow within a closed conduit (conduit in the sense of a means of containment). The other type of flow within a conduit is open channel flow. These two types of flow are similar in many ways, but differ in one important aspect. Pipe flow does not have a free surface which is found in open-channel flow. Pipe flow, being confined within closed conduit, does not exert direct atmospheric pressure, but does exert hydraulic pressure on the conduit.

The behavior of pipe flow is governed mainly by the effects of viscosity and gravity relative to the inertial forces of the flow. Depending on the effect of viscosity relative to inertia, as represented by the Reynolds number, the flow can be either laminar or turbulent. At a Reynolds number below the critical value of approximately 2040. pipe flow will ultimately be laminar, whereas above the critical value turbulent flow can persist. In addition, the transition between laminar flow and turbulence can be sensitive to disturbance levels and imperfections.

Flow through pipes can roughly be divided into two:

1. Laminar flow:

In fluid dynamics, laminar flow is characterized by fluid particles following smooth paths in layers, with each layer moving smoothly past the adjacent layers with little or no mixing. 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 particles close to a solid surface moving in straight lines parallel to that surface. Laminar flow is a flow regime characterized by high momentum diffusion and low momentum convection.

When a fluid is flowing through a closed channel such as a pipe or between two flat plates, either of two types of flow may occur depending on the velocity and viscosity of the fluid: laminar flow or turbulent flow. Laminar flow occurs at lower velocities, below a threshold at which the flow becomes turbulent. The velocity is determined by a dimensionless parameter characterizing the flow called the Reynolds number, which also depends on the viscosity and density of the fluid and dimensions of the channel.

2. Turbulent flow:

In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to a laminar flow, which occurs when a fluid flows in parallel layers, with no disruption between those layers. Turbulence is caused by excessive kinetic energy in parts of a fluid flow, which overcomes the damping effect of the fluid's viscosity. For this reason, turbulence is commonly realized in low viscosity fluids.

Governing equation:

1] Reynold Number:

`Re=(ρ .u.D)/μ=(u.D)/v=(Q.D)/(v.A)`

where:

D is the hydraulic diamete of the pipe (m);

Q is the volumetric flow rate (m³/s);

A is the pipe's cross-sectional area (m²);

u is the mean speed of the fluid (SI units: m/s);

μ is the dynamic viscosity of the fluid (Pa·s = N·s/m² = kg/(m·s));

ν is the kinematic viscosity of the fluid, ν = μ/ρ (m²/s);

ρ is the density of the fluid (kg/m³).

Problem statement:

Diameter of pipe = 0.098 m

Dynamic viscosity of water at (25 degree) =8.90e-4 Pa.s

Density of water = 1000 kg/m^3

Reynold number = 100,1000,10000

Calcuation of inlet velocity for different reynold number:

close all
clear all 
clc
Reynold_no = [100 1000 10000]
dyanamic_viscosity = 0.000890
fluid_density = 1000
diameter = 0.098

velocity= ((Reynold_no*dyanamic_viscosity)/(fluid_density*diameter))

Reynold number	Inlet velocity (m/s)
100	0.00090861
1000	0.0090816
10000	0.090816

Procedure :

1] Create new pipe geometry of diameter 100 mm and length 1000 mm.

2] Select the shell option and select two faces of model and input 2 mm thickness to pipe geometry.

3] Create the new sketch at 850 mm from inlet and draw line in that sketch and similarly make the different sketch at 900mm and 950 mm from inlet do the same thing.

4] Make sure flow simulation is enabled in software and select the create lid option and select inlet and outlet face to make close geometry.

5 Click on wizard or new project in flow simulation toolbar.

6]Right click on input data on flow simulation tree and select general setting.

7]In the fluid select water as project fluid and flow type as laminar and turbulent.

8]Insert boundary conditions like inlet velocity of fluid, outlet pressure, wall boundary condition by selecting appropriate faces .

9] We can update mesh with global mesh option by right clicking on it and selecting the edit mesh option.

10] Before calculation make cut plot at 850mm,900mm,950mm respectively for velocity

11] Click on run icon it will show result.

12] To get result or cut plot for different velocity we need to do parametric study so to do right click on project option and select new parametric study.

13] Add the goals that you want to varied and also add result whichever we want and run the simulation.

Probiem encountered:

1] make sepearate skecth for each cut plot do not make it in one sketch.

plots:

1] case-I : Reynold no is 100

• cut plot at 850mm

• cut plot at 900mm

• cut plot at 950mm

• xy- plot

2] case-I : Reynold no is 1000

• cut plot at 850mm

• cut plot at 900mm

• cut plot at 950mm

• xy- plot

3] case-I : Reynold no is 10000

• cut plot at 850mm

• cut plot at 900mm

• cut plot at 950mm

• xy- plot

• velocity comparision:

conclusion:

• Velocity of water near pipe wall is very less as per as no slip condition is concerned and velocity is maximun at at centre of pipe.
• When we increase the velocity of water velocity near wall also increases.
• There is approximate parabolic profile of velocity along diameter.

Result:

• Pipe flow simulation study has been performed successfully.