Mechanical contacts simulate physical contact between solid bodies. In this case, the stopper and contact prevent the valve from swinging into the mesh wall with negative pressure.
Verify that a contact has been defined between the valve and faces.
In the Outline under Model, expand Connections then Contacts.
Note that a frictionless contact (Frictionless – FEA\Valve To FEA\Stopper) has been defined.
Click the frictionless contact.
Corresponding settings are shown below in the Details view.
Under Scope, verify the following contact definitions:
Contact Bodies are defined on the Valve geometry, with Contact scoped to the high-y face, just above the stopper.
This setting specifies the faces on the moving body that will be in contact with other faces.
Target Bodies are defined on the Stopper geometry, with Target scoped to the low-y face of the stopper.
This setting specifies the faces to be the target for the contact bodies.
Under Geometric Modification, verify that the Interface Treatment property is set to Adjust to Touch.
This setting specifies the minimum distance to be maintained between the faces of the moving bodies equal to the current gap size. This will prevent the fluid mesh from collapsing.