Pipe Flow Simulation Using SoliWorks

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.

Objective:

The purpose of this project is to Calculate the Entrance length and observe the flow for Reynolds number in 3 different cases when Re is 100, 1,000, 10,000 by setting up probes at Different positions namely at 95% , 90% and 85% of pipe length.

Laminar Flow:

Laminar flow, type of fluid (gas or liquid) flow in which the fluid travels smoothly or in regular paths, in contrast to turbulent flow, in which the fluid undergoes irregular fluctuations and mixing. In laminar flow, sometimes called streamline flow, the velocity, pressure, and other flow properties at each point in the fluid remain constant. Laminar flow over a horizontal surface may be thought of as consisting of thin layers, or laminae, all parallel to each other. The fluid in contact with the horizontal surface is stationary, but all the other layers slide over each other.

Turbulent flow:

Turbulent flow, type of fluid (gas or liquid) flow in which the fluid undergoes irregular fluctuations, or mixing, in contrast to laminar flow, in which the fluid moves in smooth paths or layers. In turbulent flow the speed of the fluid at a point is continuously undergoing changes in both magnitude and direction.

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

Boundary Layer:

The layer in which the shearing viscous forces are significant, is called the boundary layer.This boundary layer is a hypothetical concept. It divides the flow in pipe into two regions.

1. Boundary layer region: The region in which viscous effects and the velocity changes are significant
2. The irrotational (core) flow region: The region in which viscous effects and velocity changes are negligible, also known as the inviscid core.

Shear stress

In the hydrodynamic entrance region, the wall shear stress (τw ) is highest at the pipe inlet, where the boundary layer thickness is the smallest. Shear stress decreases along the flow direction.^[6] That is why the pressure drop is highest in the entrance region of a pipe, which increases the average friction factor for the whole pipe. This increase in the friction factor is negligible for long pipes.
In fully developed region the pressure gradient and the shear stress in flow are in balance.

Entrance length:

It is the distance a flow travels after entering a pipe before the flow becomes fully developed.Entrance length refers to the length of the entry region, the area following the pipe entrance where effects originating from the interior wall of the pipe propagate into the flow as an expanding boundary layer. When the boundary layer expands to fill the entire pipe, the developing flow becomes a fully developed flow, where flow characteristics no longer change with increased distance along the pipe.

For Laminar Flow the entrance length is given by:

Le = 0.05*Re*D

Where Le is entrance length

Re is Reynolds Number

D is Diameter of pipe

For Turbulent Flow the entrance length is given by:

Le = `4.4*D*(Re)^(1/6)`

Where Le is entrance length

Re is Reynolds Number

D is Diameter of pipe

Specification:

Outer Diameter of Pipe: 42.5 mm

Inner Diameter of Pipe: 40 mm

Density(`rho`): 1,000 kg/m^3

Dynamic viscosity of water: 8.90 × 10⁻⁴ Pa·s

Formula:

`Re = (rho * V*D)/mu`

Calculation:

For Re = 100 (Laminar)

Velocity,V = 0.0022350 m/s

Entrance Length, Le = 0.2 m

For Re = 1,000 (Laminar)

Velocity,V = 0.022350 m/s

Entrance Length, Le = 2 m

For Re = 10,000 (Turbulent)

Velocity,V = 0.22350 m/s

Entrance Length, Le = 0.817 m

Pipe Design For Re 100,

Pipe Design For Re 1,000 ,

Pipe Design For Re 10,00 ,

Output plots Obtained:

for Pipe Design with Re 100,

Velocity Plot at probe placed at 95% of pipe Length,

Velocity Plot at probe placed at 90% of pipe Length,

Velocity Plot at probe placed at 85% of pipe Length,

Cutplot for Re 100,

for Pipe Design with Re 1,000 ,

Velocity Plot at probe placed at 95% of pipe Length,

Velocity Plot at probe placed at 90% of pipe Length,

Velocity Plot at probe placed at 85% of pipe Length,

Cutplot for Re 1,000 ,

for Pipe Design with Re 10,000 ,

Velocity Plot at probe placed at 95% of pipe Length,

Velocity Plot at probe placed at 90% of pipe Length,

Velocity Plot at probe placed at 85% of pipe Length,

Cutplot for Re 10,000 ,

Comparison of Velocity plot at 95% , 90% and 85% Probe Length when Re is 100:

Comparison of Velocity plot at 95% , 90% and 85% Probe Length when Re is 1,000:

Comparison of Velocity plot at 95% , 90% and 85% Probe Length when Re is 10,000: