Week 1- Mixing Tee

AIM:

To compare the solving models of k epsilon and k omega and find the best solution for the given cases of both long and short tee models with different momentum ratios 2 and 4.

SOLUTION:

From the results of Long Tee with a momentum ratio of 4 of both solving methods, k- epsilon shows promising results from my point of view because the instabilities in temperature difference are more in the k- omega model.

Figure 1: Long tee model for both solvers k epsilon and k-omega respectively

From the observed results, the K-epsilon model is followed for further momentum ratios and working models.

GEOMETRY:

• SpaceClaim from the Geometry in the workbench panel.
• Import the respective file.
• The procedure followed for both models is the same.
• Our consideration lies only in the fluid flow, not in its interaction.
• Volume is extracted where the flow happens from the parent body.
• Prepare-----volume extraction-----select edges.
• Suppressing physics is very important; otherwise, it would be in the further analysis.
• Closing the spaceclaim automatically saves the file.

Figure 2: SpaceClaim figures, which are common to both Solvers.

MESH:

• Clicking mesh loads the respective file from SpaceClaim
• Generate the model file with ANSYS default mesh.
• Fine the mesh and get accurate results during the analysis
• Elemental quality must be checked and ensured not below 5%
• Name the sections that are very useful for setting up boundary conditions.
• Close and move forward to the Setup and Solution part.

Figure 3: Meshing of the models.

Figure 4: Naming sections.

Setup and Solution :

• Check the mesh quality in the ANSYS fluent. Once the check is done, move to the next step.
• Setting up physics like energy on, steady, material as air, pressure-based and setting the boundaries.
• Boundaries should be a special concern because we have different velocity conditions and the same thermal conditions.
• Once the boundary checks are done, create a report.
• Reports like area-weighted average and standard deviation for the temperature at the outlet.
• Those sections must include a plot option for the respective values.
• Initialise the Hybrid mode and make the iterations until the solution converges.

Figure 5: Pictures of the above process are included.

Figure 6: Solutions from the plots of MR 2 and 4 short tee, respectively.

For MR 4;

Figure 7: For Long tee for same MR 2 and 4 are as follows.

for MR 4;

Results:

• By placing a location plane on the XY axis of the section, the different contours and vectors for given results can be obtained.
• In legend, the values can be changed to fixed and reduced to the size, showing cleaner results than in exponentials.

Figure 8: Plots of different contours like velocity, pressure, temperature and vectors for both short and long tee cases with the respective MRs 2 and 4.

short tee for MR 4,

Long tee's for MR 2 and 4,

for MR 4,

Result:

• A high momentum ratio has always had an impact on mixing
• length of the pipe doesn't play a major role in mixing than the velocity, but it also matters
• here, a shorter with MR seems to be good but longer pipe with larger velocity makes sense.

Table: