Mesh

The following right-click actions and dialogs are available for meshes in Simcenter STAR-CCM+ In-cylinder.

Mesh Right-Click Actions

Object Right-Click Action
Mesh
Edit Mesh Settings
Opens a dialog that allows you to specify the global characteristics of the mesh. See Mesh Settings Dialog.
Generate Surface Mesh
Re-meshes the initial surface to provide a quality discretized mesh that is suitable for CFD.
Generate Volume Mesh
Generates a volume mesh by cutting a hexahedral template mesh.
Custom Controls
New > [custom control]
Creates a new custom control. The following types are available:
  • Surface Control
  • Volume Control
A separate Edit tab opens and allows you to set the mesh settings of the respective custom control. Custom Mesh Settings Dialog.
[custom control]
Highlight
Highlights the respective surfaces or parts of the selected custom control in the Graphics window.
Edit Control
Allows you to edit the custom mesh settings.

Mesh Settings Dialog

Custom Mesh Settings Dialog

Mesh Properties
Number of Layers (only for cylinder sector model) Specifies the Number of Layers between the periodic boundaries in the volume mesh.
Base Size Specifies the target cell size in the core of the cylinder. The minimum cell size and the fluid boundary layer thickness can be set as a percentage of this value.
Minimum Size Specifies the lower limit of cell size.

Decreasing this value allows more refinement in areas where the mesher is trying to capture highly curved features. See Surface Curvature.

Sharp Edge Angle (deg) Creates part curves based on the specified angle. See Part Surfaces and Part Curves.

The default angle is the Keep feature edges (deg) angle as specified in the Engine Parts Creation dialog. Changing the default value automatically re-tessellates the Engine Part geometries.
Prism Layer Controls the prism layer mesh that is intended to capture the fluid boundary layer across the surface.
Total Thickness
Specifies the overall thickness of the prism layer.
Number of Layers
Specifies the number of cell layers that are generated within the prism layer.
Stretching
Specifies the target growth rate of successive prism layers away from the wall.
Prism Layers at Closed Interface
When On, generates prismatic cells at the valve curtain interfaces and around the valves as follows:
  • When a valve lift drops below the valve closure tolerance, generates one prism layer at the valve curtain interface and around the valve.
  • When a valve lift exceeds the valve closure tolerance, generates no prism layers at the valve curtain interface and two prism layers around the valve.
When Off, generates no prism layers at the valve curtain interfaces and two prism layers around the valves—irrespective of the valve lift.
In general, activating this option improves the stability of the simulation due to the following aspects:
  • Improves the mesh quality at the closed valve curtain wall.
  • Avoids corner cells with various wall boundary conditions.
  • Increases the minimum y + -value in the closed valve gap area.
If you want to change the default number of two prism layers around the valves, you must change the number of prism layers for the mesh refinement zones that encapsulate the valves (in the Simulation object tree, under Geometry > Operations > Engine Fluid Volume Meshing > Custom Controls > Intake/Exhaust Valve [n] Head/Port Volume Controls > Values > Custom Prism Values).
Extrusion Controls the orthogonal extruded cells at the inlet and outlet boundaries.
Thickness
Specifies the distance by which the mesh is extruded in normal direction to the boundary.
Number of Layers
Specifies the number of cells in the direction of the extrusion.
Re-mesh Criteria

Controls the criteria for re-meshing the engine.

Base Criteria (any one can be satisfied)
Simcenter STAR-CCM+ In-cylinder re-meshes the engine geometry if any of the following criteria is satisfied:
  • Min Cell Quality: Specifies the minimum Cell Quality. Simcenter STAR-CCM+ In-cylinder re-meshes the engine if any cell in the mesh drops below this value.
  • Max Piston Stretching: Piston stretching is defined as the ratio of the current piston position to the piston position after the last re-mesh. The piston position is defined as the minimum z-position of the Liner surface in the Laboratory coordinate system. The Laboratory coordinate system is placed on the firedeck with its z-axis pointing up. Simcenter STAR-CCM+ In-cylinder re-meshes the engine if the piston stretching exceeds the specified value in either direction (up or down). This criterium becomes active as soon as the piston passes the specified Piston Tolerance.
  • Max Valve Stretching: Valve stretching is defined as the ratio of the current valve lift to the valve lift after the last re-mesh. Simcenter STAR-CCM+ In-cylinder re-meshes the engine if the valve stretching exceeds the specified value in either direction.
  • Max Valve Displacement: Valve displacement is defined as the distance between the current valve lift and the valve lift after the last re-mesh. Simcenter STAR-CCM+ In-cylinder re-meshes the engine if one of the valves passes a distance that exceeds the specified value in either direction.
  • Piston Tolerance: Specifies the distance that the piston is allowed to move away from TDC position without considering the Max Piston Stretching criterion. This property allows you to ignore the Max Piston Stretching criterion for small position changes away from TDC. Note: The value is negative because the piston moves in negative z-direction.
  • Min Cell Quality Reference: Displays the minimum cell quality after the last re-mesh. This value is calculated automatically. Note: DO NOT modify this value.
Cell Skewness Criteria (both must be satisfied)
Simcenter STAR-CCM+ In-cylinder re-meshes the engine geometry if any cell in the mesh satisfies both of the following criteria (a max/min criterion is satisfied, if the cell exceeds/drops below the specified value):
Bad Morphed Cell Criteria (all must be satisfied)
Simcenter STAR-CCM+ In-cylinder re-meshes the engine geometry if any cell in the mesh satisfies all of the following criteria:
  • Max Cell Skewness Angle 2: As for Cell Skewness Criteria.
  • Min Cell Aspect Ratio 2: As for Cell Skewness Criteria.
  • Min Cell Quality 2: As for Base Criteria.
  • Min Volume Change: Specifies the minimum Volume Change.
  • Min Least Square Quality: Specifies the minimum Least Square Quality.
Valid Face Criteria (both must be satisfied)
Simcenter STAR-CCM+ In-cylinder re-meshes the engine geometry if any cell in the mesh satisfies both of the following criteria:
  • Max Cell Skewness Angle 3: As for Cell Skewness Criteria.
  • Min Face Validity: Specifies the minimum Face Validity.
Custom Mesh Properties Surface Control Volume Control
Name Specifies the name of the custom control under which it is stored in the tree.
Surfaces Specifies the Engine Part Surfaces to which the custom properties apply.
Parts Specifies the Construction Geometries in which the custom properties apply.
Target Size Specifies the custom target cell size.
Minimum Size As in Mesh Settings Dialog.
Fluid Boundary Layer As in Mesh Settings Dialog.

Property Options

The following options control the specification of various properties within the global and customized settings:

Relative to Base Specifies the reference value as percentage of the base size that is defined within the Edit Mesh Settings dialog. The advantage of a relative size specification is that changing the base size scales both global and object specific sizes.
Absolute Specifies the reference value as absolute in any of the allowable length units.
Use Parent Value Applies the global value to the mesh setting as defined in the Edit Mesh Settings dialog.
Specify Custom Value Applies a customized value to the mesh setting.
Disable Does not apply prismatic cell layers to the surface.