Steady state simulation of a mixing tee geometry using ANSYS-FLUENT

OBJECTIVE:

To perform a steady state simulation on the mixing tee geometry using ANSYS-FLUENT.

Geometry model :

i) Short Mixing Tee:

ii) Long mixing Tee:

METHODOLOGY:

1. Geometry-spaceclaim:

• The two Geometry model has solid parts which is not going to be involve or necessary for simulation so it is suppressed for physics.

Fig.short mixing tee geometry model after suppressed the solid part.

• similarly,same procedure is done to long mixing tee model.

2. Mesh:

• Naming the selection of faces such as inlet_x - for hot air inlet , inlet_y - for cold air inlet,outlet and walls.
• Default tetrahedral mesh is generated.

fig.Meshing of long mixing tee with default element size as 10mm.

fig.Meshing of short mixing tee with default element size as 10mm.

3. Setup:

i)Performed mesh check to check whether the mesh is perfectly done or not.

ii)Under setting up physics

• Solver->Type-> pressure based.velocity formulation-> Absolute.Time->steady.
• Models -> energy -> viscous-k(epsilon) model->standard wall function is used.
• Zones ->boundaries -> assigned the boundary values of inlet_x,inlet_y,outlet.

iii) Solution

• Definitions-> Average weighted and standard deviation of temperature at the outlet is assigned to get the plots and reports once the solution is done.
• Initialize the values at t=0.
• Run the calculation for different iterations.

4. Solution:

Case 1:

Short mixing tee with hot air inlet veocity and temperature of 3 m/s , `25^0C`

cold inlet velocity and temperature of 6 m/s , `10^0 C`

i)

fig. plot for average weighted temperature at outlet.

• from the plot ,we state that the average temperature reaches `19.9^0C`
• 450 iterations has been made to run the calculation.

ii)

fig.plot for standard deviation of temperature at outlet

• Standard deviation of temperature at outlet has been made to see the effectiveness of mixing.
• Here it reaches `1.4^0C`which means a good mixing.

iii)

fig.Residual plot

• In numerical simulation,as time progresss and as steady-state is approached the numerical values are not precisely zero,they are called residuals.
• In this case,it starts approaching steady state after 150 iterations.

iv)

fig.contour plot of temperature distribution

v)

fig. contour plot of velocity distribution

Case 2:

Long mixing tee with hot air inlet veocity and temperature of 3 m/s , `25^0C`

cold air inlet velocity and temperature of 6 m/s , `10^0C` .

i)

fig. plot for average weighted temperature at outlet.

• In this case the average temperature at outlet reaches `19.9^0C` .

ii)

fig.plot for standard deviation of temperature at outlet.

• Standard deviation of temperature reaches `1.1^0C` which represent more efficient mixing than case 1.

iii)

fig.Residual plot

• 300 iterations has been made to run the calculation.
• After 251 iteration it reaches a steady state.

iv)

fig. contour plot of temperature distribution.

• we see that the long mixing tee gives a better temperature distribution compared to short mixing tee.

v)

fig. contour plot of velocity distribution.

Case 3:

Short mixing tee with hot air inlet veocity and temperature of 3 m/s ,`25^0C`

cold air inlet velocity and temperature of 12 m/s , `10^0C`

i)

fig. plot for average weighted temperature at outlet.

• In this case, the average temperature at outlet reaches `17.5^0C`which is lower than previous cases.

ii)

fig.plot for standard deviation of temperature at outlet

• Standard deviation of temperature at outlet reaches approximately `1^0C`

iii)

fig.Residual plot

• 300 iterations has been made to run the calculation.
• The solution is converged at 133 iteration.

iv)

fig. contour plot of temperature distribution.

v)

fig. contour plot of velocity distribution.

RESULTS:

• From the table , we state that case 3 produces a very effective in mixing because of its momentum ratio when compared to rest of the cases.
• Case 1 and case 2 are differ from cell count and number of iteration for convergence.
• so we conclude that momentum ratio plays a major role to define the temperature at outlet.
• standard deviation has done to see the effectiveness of mixing.In case 3 , it shows a lesser deviation than the other which is a good mixing.

CONCLUSION:

Performed a steady state simulation for the three cases and defined the results accordingly.

Link:

https://drive.google.com/open?id=19Lg3qWjzzynXkYNxPpMbOpakOwZPWBXo