Flow Simulation Project 1 : Pipe Flow Simulation

Objective : To simulate pipe flow at different conditions.

Problem statement :

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 :

Pipe flow :

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 behaviour 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: Laminar flow and Turbulent flow

Reynolds number :

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. The predictions of the onset of turbulence and the ability to calculate scaling effects can be used to help predict fluid behaviour on a larger scale, such as in local or global air or water movement and thereby the associated meteorological and climatological effects.

The Reynolds number is defined as

ρ is the density of the fluid (SI units: kg/m3)

u is the flow speed (m/s)

D is the diameter of the tube (m)

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

ν is the kinematic viscosity of the fluid (m2/s).

Calculation :

Given

Water density = 1000 kg/`m^3`

Diameter of tube(outer) = 0.04 m

Diameter of tube(inner) = 0.038 m

Dynamic Viscosity = 8.90 × 10⁻⁴ Pa·s

Using this data and above equation we get

1. For Re = 100 we get

u = 0.00234 m/s

2. For Re = 1000 we get

u = 0.0234 m/s

3. For Re = 10000 we get

u = 0.234 m/s

Study figure :

1. SolidWorks Model

2. Inital and Boundary Conditions

3. Mesh

4. Solver

Result :

1. At Reynold Number= 100

A. Velocity Profile at line probe(at 85%)

B. Velocity Profile at line probe(at 90%)

C. Velocity Profile at line probe(at 95%)

D. Comparison of Velocity Profile

2. At Reynold Number= 1000

A. Velocity Profile at line probe(at 85%)

B. Velocity Profile at line probe(at 90%)

C. Velocity Profile at line probe(at 95%)

D. Comparison of Velocity Profile

3. At Reynold Number= 10000

A. Velocity Profile at line probe(at 85%)

B. Velocity Profile at line probe(at 90%)

C. Velocity Profile at line probe(at 95%)

D. Comparison of Velocity Profile

Conclusion and observation :

From this project it is learn about how to simulate the flow in a pipe. From figure it is shown that the centre of diameter the velocity of the flow is maximum and at the wall of pipe the velocity of flow is minimum. It is also observed that with the change in the Reynold number the change in the profile of flow is also occure. It is also observe that due to taken of less diameter of pipe the profile of flow is similar at those 85,90 and 95% line probes. If we use a large diameter the observation of the changes in profile is can be observed on this probes.