Orienting Face Normals

Fluid particles consider a boundary condition only if the boundary normals are facing away from the particles. For closed surfaces, the boundary normals are facing inwards by default. For this reason, you must reverse the orientation of the face normals for the gear housing so that the boundary normals are facing outwards.

The orientation of face normals is a region setting. As all gearbox parts are assigned to a single region, you must first subgroup the parts. Then, you reverse the orientation for the subgroup that contains the housing.
To orient the face normals:
  1. Select the Regions > gearbox node and activate Allow Per-Part Values.
  2. Select the gearbox > Part Subgroupings > Subgrouping 1 > Subgroup 1 node.
    The read-only Objects property contains all the parts that the gearbox region consists of.
  3. Right-click the Subgrouping 1 node and select New.
  4. Rename the Subgroup 2 node to Gear.
  5. Select the Gear node and set Objects to gear.
  6. Create two more subgroups, Subgroup 2 and Subgroup 3, then set the following properties:
    NodePropertySetting
    Subgroup 2NamePinion
    Objectspinion
    Subgroup 3NameInjector
    Objectsinjector
    The default subgroup Subgroup1 now only contains the housing.
  7. Rename Subgroup 1 to Housing.
  8. Select the gearbox > Physics Values > Part Orientation node and activate Specify by Part Subgroup.
  9. Select the By Part Subgroup > Housing node and activate Reverse Orientation.
  10. Save the simulation.