Inflation Mesh And Transition Ratio

Inflation mesh is an option to use when we need to refine the zone near to the wall. Inflation is use when analysis of boundary condition is done accurately by create finer mesh near to wall or near to boundary. Inflation is also useful for CFD boundary layer resolution, electromagnetic air gap resolution or resolving high stress concentrations.

Inflation is supported for the following mesh methods:

Volume Meshing:
• Patch Conforming
• Patch Independent
• Sweep
• MultiZone
• CutCell

Surface Meshing:
• Quad Dominant
• All Triangles

Global Inflation Controls :

The Inflation group of global mesh controls available in the Details View when the Mesh option is selected in the Tree Outline. There are many different basic options available in inflation. The options in the Inflation group provide global control over all inflation boundaries.


These options are below :

  1. Use Automatic Inflation
  2. Inflation Option
  3. Transition Ratio
  4. Maximum Layers
  5. Growth Rate
  6. Number of Layers
  7. Maximum Thickness
  8. First Layer Height
  9. First Aspect Ratio
  10. Aspect Ratio (Base/Height)
  11. Inflation Algorithm
  12. View Advanced Options

Now, we see the use of these basic options one by one…

 Use Automatic Inflation :

If you are doing simple analysis near to boundary & no much accuracy is necessary, then you can use “Use Automatic Inflation” option. You can set the Use Automatic Inflation control so that inflation boundaries are selected automatically depending on whether or not they are members of Named Selections groups. While using inflation, keep in mind that

The following options are available in Use Automatic Inflation :

  • None
  • Program Controlled
  • All Faces in Chosen Named Selection

While using inflation, keep in mind that Automatic inflation is supported only for 3D inflation on volume models. It is not supported for 2D inflation on the shell model. You cannot select Program Controlled or All Faces in Chosen Named Selection option for the Use Automatic Inflation option to mesh a 2D model. To apply 2D inflation on a shell model, use local inflation mesh controls.

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Here, I create basic geometry & assigned a name on the face of an object, showing how inflation work & what change occurs in an object. This geometry is just for example for understanding inflation.


  • If you select None, inflation boundaries are not selected globally.

Program Controlled

  • If you select Program Controlled, all faces in the model are selected to be inflation boundaries, except Faces which is used in Named Selection(s).
inflation in ansys meshing
program control inflation

All Faces in Chosen Named Selection

  • If you selectAll Faces in Chosen Named Selection, then you can able to apply inflation on Face(s) on which name is assigned.
inflation in ansys meshing
‘All Faces in Chosen Named Selection’ inflation option
inflation in ansys meshing
‘All Faces in Chosen Named Selection’ inflation option

you can choose only one face at one time on which name is assigned.

  • The effect of inflation is applied to the Named Selections group is depends on values that you enter for the following options:
  1. Inflation Option
  2. Inflation Algorithm
  3. View Advanced Options

Inflation Option :

Total Thickness

The Total Thickness option creates inflation layers using the values of the Number of LayersGrowth Rate controls & Maximum thickness. By this option, we can create no. of inflation layers in particular thickness. for example, I want to create inflation layers in 10 mm thickness from selected face & no. of inflation layers is 5.
face selection in ansys

So, i will enter Number of Layers = 5, & Maximum Thickness = 10 mm and the result is….

You can check also by measuring the distance between nodes.. just click on Node option & select 2 nodes by press ctrl key as shown in the image. 


First Layer Thickness

This is the same as the total thickness option. The change is only, By this option, you can set the thickness of the 1st layer from the selected face. For example, I want to create a thickness of the 1st layer is 0.5 mm.

Smooth Transition

In this option, a new parameter appears called the ‘Transition ratio’.  The transition ratio is the ratio between the cell area of the last layer of inflation and the first cell area out of the inflation. The Transition Ratio determines the rate at which adjacent elements grow. As transition ratio increases, the gap between the adjacent layer is increased. The Transition Ratio control is applicable only when the Inflation Option is Smooth Transition. The transition Ratio is valid from 0 to 1. When Physics Preference is set to CFD  and Solver Preference is set to CFX, the default for Transition Ratio is 0.77. For all other physics preferences, including CFD when Solver Preference is set to either Fluent or POLYFLOW, the default is 0.272.

transition ratio

Inflation Algorithm

The Inflation Algorithm control determines which inflation algorithm will be used. There are two types of algorithm.

  1.  Pre
  2. Post


  • When Pre is selected, the surface mesh will be inflated first, and then the rest of the volume mesh will be generated. This is the default for all physics types.


  • A benefit of this option is that the tetrahedral mesh does not have to be generated each time the inflation options are changed.
  • Post inflation is not supported when there is a mixture of the tetrahedron and non-tetrahedron mesh methods applied to the bodies which are made from multi-part. If you want to apply Post inflation to a multi-body part, all bodies in the part must have a tetrahedron mesh method applied to them.
  • Post inflation is not supported when Inflation Option is either First Aspect Ratio or Last Aspect Ratio.

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