ANSYS

** Turbulent viscosity limited to viscosity ratio of 1e+05 *** reason The possible *causes* for large turbulent viscosity ratio include: - Bad initial conditions for the turbulence quantities (k and e) - Improper turbulent boundary conditions - Skewed cells *** solution If the problem is not caused by *bad mesh*, then *the beginning of the phenomena* can usually be avoided by: -Turn off solving *turbulence equations* for the first 100-200 iterations -Turn on turbulence and continue iterations If the problem occurs *in the middle of the iteration process*, then use the following procedure: - Stop the iteration - Turn *off* all equations except the *turbulence equations* - Increase turbulence under relaxation factors (URFs) (k and e) to 1 and iterate for 20-50 iterations - *Turn back all equations* and reduce the turbulence URFs to 0.5-0.8 and then continue iterations - Repeat the above steps for several times For *faster convergence*, it might be useful to obtain an initial solution wit...

‎ Table of Contents 1. Reverse flow    reversed_flow 1.1. reasons 1.2. solutions 1 Reverse flow    reversed_flow It is common to encounter the regions of reversed flow at the initial stages of the simulation – This is normal. However, if the “reversed flow” warnings do not disappear as the simulation progresses, then one needs to address the issue and move the outlet boundaries to a location where the inflow is no longer encountered. Normally, it has to do with the outlet boundary condition. if you were to use the "pressure outlet" boundary condition at the outlet, your outlet must be set far away from the object of interest. In Fluent, I normally use the " outflow" boundary condition at the outlet and it does not give me reverse flow. 1.1 reasons It is virtually impossible to prescribe correct values for varying turbulence characteristics, temperature and species concentrations i...

‎ Table of Contents 1. TUI 1.1. Examples 1.1.1. Steady 1.1.2. Unsteady 1.2. discretization schemes 1.3. Turbulence model 1.4. Reference 1.5. Save residual 1.6. Journal 1.6.1. record journal GUI 1.6.2. The interactive TUI inside Fluent helps: 1.7. define 1.7.1. boundary-conditions 1.8. change rotational velocity of moving reference frame 1.8.1. batch model 1.8.2. interactive console TUI 1.9. set background color 1.9.1. invalid command [background] 1.10. syntax 1.11. Batch model 1.12. Boundary condition 1.12.1. Inlet BC 1.13. Animation/residual/monitor on cluster 1.14. Solver 1.15. Change pressure-velocity-coupling model in batch mode 1.16. time step size 1.17. Modifying the View 1.18. initialization 1.19. discretization schemes 1.20. Set under relaxation 1.21. log of execute makefile 1 TUI keywords: Background Execution on Linux Systems, journal file Programming language : Scheme , as a Lisp d...

  Process 1928: Received signal SIGSEGV. Running on windows Mesh size, 12M serial     Error:  received a fatal signal (Segmentation fault).     Error Object: #f parallel     select 4 processors         error information     Node 0: Process 1928: Received signal SIGSEGV.         Node 5: Process 2824: Received signal SIGSEGV.     MPI Application rank 0 exited before MPI_Finalize() with status 2      The fl process could not be started.         Reason         This is primarily a Windows issue.                 If running Fluent with -t1 or higher number of processes and leave the session for an extended period of time (2-20 hours), it receives the following message in the console: ...

Method use UDF to strip the interest surface(where force is applied) Steps    - open case file, check the *ID* of  solid sourface ( cylinder/blade surface) - check the spanwise direction(such as z direction), and force direction( such lift, y axis, drag, x axis)  - Make the appropriate changes in the UDF    +(Axis direction, Force direction, no. of strips and ID of the wall zone) - lauch Fluent from command line   + Open the Start screen (press Windows button on your keyboard, Type 'VS2013 x86 x64 Cross Tools Command Prompt'   + Navigate to your working folder, i.e. the folder where your case and data files are (.cas & .dat).   + Type “fluent” in the command window to launch Fluent  or  “C:\Program Files\ANSYS Inc\v161\fluent\ntbin\win64\fluent.exe” (quotation signs included, in case of standard installation; fluent version: 16.1).   + Make sure that on the *Environment tab* 'Setup Compilation Environment for UDF' is...

Fluent orthogonal quality minimum orthogonal quality>0.01 Aspect ratio: No specific value, avoid sudden and large changes in cell aspect ratios in areas where the flow field exhibit large changes or strong gradients Skewness <0.95   ANSYS Meshing For surface mesh , Min orthogonal quality 0.4-0.5 For volume mesh minimum orthogonality > 0.15 maximum skewness < 0.95 For orthogonal quality below 0.1, divergence is likely ICEM Pre-Mesh quality Determinant >0.3 Angle, (18, 90) Warpage < 45 degrees