- When i ran my project first time i got a one result. and when i ran second time i got a different result. and when i checked with my and he ran it two times he also got what i got second time.
- But i cant figure why first gave the solution like that. and it is the correct one all other are wrong results not intended.
Hello! I understand you’re encountering inconsistent results between simulation runs, and that the first run provided the correct, intended outcome. This can certainly be a frustrating experience, but it’s a common challenge in the world of simulation. Let’s break down some potential causes and how to address them.
Common Causes for Inconsistent Results
Several factors can contribute to variations in simulation results between runs. Here are some of the most common culprits:
- Mesh Sensitivity: The mesh is a critical component of any simulation. Even slight variations in the mesh between runs can lead to different results, especially if the mesh is not sufficiently refined in areas of high gradients (e.g., near sharp corners, inlets, or outlets). As discussed in the forum post “CFD Pipe Flow - Results Diverge”, a poor mesh near outlets was the cause of inconsistent results.
- Convergence Criteria: The convergence criteria you set for your simulation determine when the solver stops iterating. If the criteria are too loose, the simulation may terminate before it has reached a stable solution, leading to variations in the results. The forum post “Help with CFD problem/ wavy force plots” highlights how insufficient convergence can lead to unstable force plots.
- Numerical Settings: The numerical schemes and solvers used in the simulation can also influence the results. Different schemes have different levels of accuracy and stability, and the choice of solver can affect the convergence of the simulation.
- CAD Model Quality: As highlighted in the SimScale blog post “CAD Faults & Automatic Simulation Core Choice”, errors or inconsistencies in the CAD model can lead to a bad quality mesh and unstable simulation runs.
- Transient Phenomena: If your simulation involves transient (time-dependent) phenomena, such as vortex shedding or turbulence, it’s possible to see variations in the results even with identical setups. This is often due to the chaotic nature of these phenomena.
Troubleshooting Steps
To help you pinpoint the cause of the inconsistency, I recommend the following steps:
Perform a Mesh Convergence Study: This involves running the simulation with progressively finer meshes to see if the results converge to a stable solution. If the results change significantly with each refinement, it’s an indication that your mesh is not yet fine enough.
Tighten Convergence Criteria: Try running the simulation with stricter convergence criteria to ensure that the solution is fully converged.
Review Numerical Settings: If you’ve made any changes to the default numerical settings, I recommend reverting them to their original values to see if that resolves the issue.
Inspect Your CAD Model: Check your CAD model for any potential issues, such as small gaps, overlapping surfaces, or other imperfections that could be affecting the mesh quality.
I hope this helps you get to the bottom of the issue. Please get back to us once you try all this out!