Common Errors

After each STEPS has been performed, it is possible to check its results by clicking on the steps summary button. This will report a summary table where RED items are problematic steps. For each problem an error message, with a brief description and suggested action is reported. For the sake of clarity, we report a more detailed description of the problem and the suggested solution to make even easier to our customers the web-application.

STEPS completed

Any messagge can be classified into two different ways: WARNING and ERROR. WARGNING are yellow coloured and generally they just advice users about possible problems that may happen in a later stage, in particular when some combinations of options are used. ERROR messages, coloured in red, report a problem that forbid and advancement to later steps in the CFD/FEM simulation.

Common GEOMETRY errors

Error message Type Fix
Open surfaces in internal flow are not allowed (Define an external flow for this type of geometry) ERROR Open surfaces must always be contained within a closed fluid volume. For this reason every time one is detected we must assure we are in an external flow type before proceeding.
Bounding Box intersects geometry (Use Hexahedral mesh to successfully create the grid) WARNING When defining an external flow, it is possible to impose a 0 distance between the input geometry file and one of the six external sides of the fluid domain. In this way the input geometry is tangent to the fluid domain. This configuration is currently stable only if used in combination with an HEXAHEDRAL meshing algorithm.
Surface seems to be open near [X.XXX, Y.YYY, Z.ZZZ] m, this is not allowed in internal flows (Check your geometry) WARNING Input file has a hole in the point coordinates expressed in the message. This hole can be a physical hole or, in case of bad quality STEP or STL files, is the result of a failure in file conversion. In both events, double check your input file in order to avoid problems during the meshing phase.

Common MESH errors

Error message Type Fix
Mesh seems to be too coarse (Use smaller mesh sizes and visualize corrupted mesh using the dedicated button) ERROR The refinement levels chosen returns a mesh division too coarse. This, beside giving problem in CFD/FEM analysis, is unacceptable. Generate a new mesh with higher refinement in all surfaces.
In some cases, when HEXAHEDRAL algorithm is used, this error is due to a problem in your input file triangulation. To solve it, generate a new mesh with a different "surface uniformity".
Stop Tetrahedral meshing since surface mesh is overlapping. (If possible use Hexahedral meshing or contact support@conself.com)
Surface mesh overlaps (If possible, use Hexahedral meshing, use a smaller mesh size or try STEP/IGES Fix Tool with tolerance X.XXX)
ERROR Overlapping surfaces in input geometry file. This error is due to a number of causes and can have different solutions such as:
  • Make sure you followed our guidelines for the input CAD Files
  • Increase the surface refinement level to increase the surface representation
  • For IGES files, use the STEP / IGES file healing tool, to sew faces into a single solid
Error in STL surface meshing (Check for STL consistency)
STL/OBJ file corrupted (Use STEP files for better geometry representation and portability)
ERROR Irregular STL/OBJ file uploaded. This may be due to non watertight models, very elongated triangles, etc. Try exporting a STEP or IGES file if possible.

If triangles overlap, the definition of a unique volume is not possible. In such a case try using HEXAHEDRAL mesh if possible.

Tetrahedral meshing failed (Use a smaller mesh size or try STEP/IGES Fix Tool with tolerance X.XXX and visualize geometry problems using dedicated button) ERROR Meshing algorithm fails because of troubles with a certain surface. CONSELF provides a STEP/IGES cleaning tool which allows to try and fix the STEP file. It is recommended to use it with the tolerance given in the error message before proceeding any further.

Open cells found in the mesh. (Use smaller mesh sizes to increase refinement) ERROR The current refinement used is too coarse to represent the geometry file. This generates open cells and others meshing failures. In order to fix it generate a new mesh with a higher refinement (i.e. reduce the surface element dimension).
Meshing out of memory (reduce wall refinement)
Mesh with too many cells (Increase mesh size parameter in surface refinement settings)
ERROR The current setup in meshing results into a very large number of elements. This requires more RAM than currently installed on the machine. Either reduce the number of elements in current mesh or choose a plan that gives you access to machines with more RAM available.

In some cases this error is generated by an incorrect definition of the input file units in GEOMETRY. Check everything is correct as explained in the video.

Tetrahedral volume meshing failed (If possible use Hexahedral meshing or increase surface refinement by reducing mesh size parameter) ERROR When this error happens there is an inconsistency in the refinement levels you are using. Make sure that:
  • The difference of refinements in two surfaces is not bigger that two order of magnitude
  • Surface refiments are not too small compared to your geometry features. Simplify your geometry or try to reduce the refinements.
Meshing phase failure: high aspect ratio face (check your input geometry file at location: x = xxxxxx y = yyyyyy z = zzzzzz) ERROR A face with a high aspect ration (very long triangle) has been detected. This type of shapes, beside resulting difficult to mesh, may lead to problematic elements shapes. It is recommended to check with your preferred CAD software the faces near to the location given in the error message.
BL Extension needs to be reduced too much to avoid surface mesh overlap (Increase surface mesh refinement or deactivate boundary layer) ERROR Surface mesh triangles are overlapping and this cause a failure. In order to solve this problem you have three possibilities:
  • Try a new mesh without boundary layer (CFD only)
  • Use an HEXA mesh with or without boundary layer (CFD only)
  • Check your input file for solid compenetration
Stop Tetrahedral meshing since surface mesh is not consistent. (If possible use Hexahedral meshing) ERROR Another problem related with surface meshing. In general this is due to incorrect input geometry file (i.e. problem with surfaces). Solution to this problem are multiple:
  • Try using hexahedral mesh if possible
  • Define different refinement on surfaces
  • Trying running the Step healing tool
  • Modify your geometry file

Common CFD errors

Error message Type Fix
Maximum number of iterations exceeded after XX iterations (check your mesh quality and increase its refinement)
Floating point exception after XX iterations (check your mesh quality and increase its refinement)
ERROR Poor mesh quality or wrong boundary condition lead to a diverging simulation. In general, check your mesh quality and make sure you don't have low quality cells.
A simple procedure to fix this problem is also reported in this blog post. A special hint for transient simulation is not to initialise velocity to (0,0,0).
No OUTLET BC detected (insert one OUTLET boundary condition in a new CFD step) ERROR Since we must specify pressure in at least one surface, CONSELF forces the definition of an outlet boundary condition. Create a new CFD step and define at least one surface as OUTLET.

Common MECH errors

Error message Type Fix
Singular matrix detected (insert one CONSTRAINED boundary condition in a new MECH step)
Singular matrix detected (make sure you avoid movement in X, Y and Z directions with constraint boundaries)
ERROR In static analysis we must guarantee our part to be at least isostatic. Make sure you are using at least one CONSTRAINT - FIXED boundary and that at lease one CONSTRAINT is imposed in every direction.
Singular matrix detected (Use CONSTAINT-FREE boundary in "bc_name" in a new MECH step) ERROR You are not limiting any degree of freedom in a CONSTRAINT - FIXED boundary. Make sure you re-run a new MECH step with a CONSTRAINT - FREE in that particular boundary.
Non convergence error (increase the number of iterations and check your boundary conditions in a new MECH step) ERROR The MECH step did not converged. In general this is due to an incorrect boundary definition, i.e. lack of external loads.
Out of RAM (generate a new mesh with fewer amout of elements) ERROR The RAM available in the current machine is not sufficient to perform your case. To fix this situation you generally have two different options:
  • Re-run the same MECH step in a bigger machine by selecting a higher number of cores
  • Reduce the mesh elements number by creating a new mesh with a lower level of refinement
First order simulation (increase the processors number to attempt a second order simulation) WARNING Second order simulation failed mainly because of memory reasons. Try to run a new MECH simulation with a higher number of processors to reserve a higher amount of RAM in your case.

Common TOOLS errors

Error message Tool Fix
Wrong data in CSV format.(Use one line for every point with x_coo,y_coo,z_coo for example: 0.3,0.4,1.2 ) PointsToTria Error in input file definition for this particular tool. Every input CSV file has to be made by three columns as follows:
  • coor_x_1,coor_y_1,coor_z_1
  • coor_x_2,coor_y_2,coor_z_2
  • coor_x_3,coor_y_3,coor_z_3
  • ...