Creo Simulate > Creo Simulate > Reference Links > Automatically Smooth Convections
  
Automatically Smooth Convections
If the convective heat exchange rate for a model entity is rapid, increased numerical errors can occur. Select the Automatically smooth convections option to turn on the convection conditions gradually, reducing these numerical errors.
This feature is selected by default.
Return to Temperature Options for Transient Thermal Analysis or To Select Temperature Options for a Transient Thermal Analysis.