Submits to ilearn

Computational Fluid Dynamics (CFD) is a branch of Fluid Dynamics which is used for

numerical engineering to solve and analyse problems in which fluid flows are involved. A static

mixer is a device widely used in various industries to blend and homogenize fluid streams. It

consists of stationary blades or elements within a pipe, creating a tortuous path for the fluids to

mix thoroughly. This mixing process is crucial in applications such as chemical processing,

food production, and water treatment, where achieving a consistent blend of different

components is essential.

In this assignment, water enters both pipes simultaneously but at different temperatures. The

first entry has a speed of 2 m/s and a temperature of 3XY K (student ID dependent), while the

second entry has a speed of 2 m/s and a temperature of 285 K. The objective of this assignment

is to gain proficiency in using CFX to determine the speed and temperature of the water as it

exits the static mixer. Additionally, you are tasked with implementing mesh refinement

techniques and exploring discretisation schemes that may impact the solution.

2 m/s

3XY K

r=2m

0 Pa

2 m/s

285 K

Figure 1: Static Mixer with 2 Inlet Pipes and I

Outlet Pipe

XY is the last two digits of your student ID. For example, if your student ID is 41234567, then

temperature at the specified inlet is 3XY=367 K.

There is a 50% deduction if these parameters do not match your student ID number./nTo determine if the flow is in the laminar or turbulence regime, Reynold number can be evaluated

based on the inlet velocity:

Re = pvD/μ

where p is the density, μ is the viscosity of the water and D is the diameter.

The steps to conducting CFD simulations in ANSYS CFX are

a. Import geometry (static.x_t-available in week 8 ilearn page)

b. Construct a suitable mesh

c. Set up the CFD model that requires the following steps:

Setup

General: Select solver as a steady state solution

•

• Models: Turn on energy equations and select viscous model (laminar or

turbulence)

(1)

• Add material properties i.e. water

•

Assign the boundary conditions, including two inlets and one outlet with the

correct boundary conditions according to your student ID.

Solution

•

Methods: Conduct the simulation using the correct flow regime (laminar/turbulent flow)

• Solution: Set the relaxation factors and/or residuals (convergence criteria).

•

Initialisation: Initialise domain-flow field can be initialized with 0 m/s velocity

Report files and Report definitions: identify parameters, values, and plots that are

required to be reposted.

Run calculation: Set-up time step, the maximum number of iterations per time step,

number of time steps, and reposting intervals. The total physical time is given in

each section.

d. Conduct another simulation with a refined mesh.

e. Conduct a validation study (suggestion: analytical solution to compare your numerical result)

f. Check if the solution converges and physical models are correctly selected.

g. Visualise and analyse the results.

A professional report in conference proceeding format should be prepared using the provided

template (refer to MECH3004_assignment2_template.docx) and address the following within your

report. The page limit for this report is 10 pages. The choice to adopt the conference proceeding

format is strategic, aiming at effective communication of your findings. This format not only

facilitates a structured presentation of your research but also ensures that your work reaches a broader

audience. The dissemination of information through conference proceedings allows for knowledge

exchange and engagement with peers, experts, and professionals in the field./nYour professional report can be structured with the following headings:

1. Problem Description & Introduction (5%)

Introduction with references.

2. Governing equations, boundary conditions and assumption (20%)

Report on the boundary conditions. Are your boundaries placed at the correct location? Any

simplification approach you use for this problem and is it valid? Use figure to report.

3. Validation (5%)

Discuss how you have validated. How valid are they?

4. General results (30%)

Discuss some of the flow features you have found in your analysis. Discuss the mixing and the

temperature distribution. Consider using streamline plot, velocity vector, velocity contour,

temperature contour, velocity and temperature profiles at different locations.

5. Mesh Refinement & Result (20%)

Obtain solutions on a refined grid size. Discuss the features of your grids, why you have designed

them this way, and how the grid refinement affects the solution. Suggest whether you have reached

grid convergence. It is recommended to use somewhere between 100,000 to 500,000 cells, for a

reasonable accuracy but still able to solve in a reasonable time.

6. Discretization Schemes & Convergence (15%)

Obtain solutions using two different discretization schemes. Explain the scheme and the relative

advantages / disadvantages. Are the results as you expect? Which scheme do you recommend for

this problem?

What convergence level do you suggest for your problem? Why?

7. Conclusion & Reference (5%)

Summarise your analysis. Include your references.