about transient computation in cfx

[hu xiaowei]

How to perform transient calculation of axial flow compressor acceleration using CFX

[Yuanyuan Xiao]

Hi Xiaowei,

Sorry for late. Due to AIS system maintenance in June, your question was automatically closed, and I was unable to respond at that time. I’ve only just now been granted permission to reopen and reply to your question. I apologize for the late response and appreciate your understanding.

The answer for your question is as below:

• The general workflow is:
‐ Set the Analysis Type to Transient 
‐ Specify the transient time duration to solve and the time step size
‐ Set up physical models and boundary conditions as usual
• Boundary conditions may change with time
‐ Prescribe initial conditions
• Use physically realistic initial conditions, such as a steady solution
‐ Assign solver settings
‐ Configure transient results files, transient statistics, monitor points
‐ Run the solver

There is tutorial called "Chapter 14: Flow in an Axial Turbine Stage"

https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v242/en/cfx_tutr/i1342578.html

Hope they are helpful to you. Thank you.

[hebemiley]

1. Model Setup: Begin by creating a detailed 3D model of the axial flow compressor, ensuring that all geometrical features are accurately represented.
2. Mesh Generation: Generate a high-quality mesh that captures the flow features, particularly around the blades. A finer mesh may be necessary in regions with high gradients.
3. Define Physics: Set up the physics for the simulation. This includes defining the working fluid properties, boundary conditions, and initial conditions. Ensure that you select the appropriate turbulence model for transient simulations.
4. Transient Settings: In the CFX setup, configure the simulation to run in transient Paper io mode. Specify the time step size and total simulation time based on the dynamics of the compressor operation.
5. Boundary Conditions: Apply appropriate boundary conditions, such as inlet velocity profiles and outlet pressure conditions, to simulate realistic operating conditions.
6. Solver Settings: Choose the solver settings that are optimal for transient calculations, ensuring that the solver can handle the time-dependent nature of the flow.
7. Run Simulation: Execute the simulation and monitor convergence. Check for stability and ensure that the results are physically realistic.
8. Post-Processing: After the simulation completes, analyze the results using CFX-Post. Look for key performance indicators such as pressure ratios, flow velocities, and any transient phenomena like surge or stall.