Error when attaching a mass point and a longitudinal spring to a surface at different locations!!

[Rana Nasser]

Hi,

To apply the below water modeling approach in ansys WB (mechanical) I have used remote attached point masses to model (M0) and a 1 m^3 solid box ( I had added it to the model in design modeler) connected to the structure with 2 longitudinal springs as shown in the images below.

Note: I have divided M0 into to point masses and attached one point mass to the left wall and the other to the right wall.

when I tried to solve the model this warning "Two or more remote boundary conditions are sharing a common face, edge, or vertex. This behavior can cause solver overconstraint and is not recommended, please check results carefully. You may select the offending object and/or geometry via RMB on this warning in the Messages window."was appear then the solution stopped with this error "At least one contact pair or remote load has no elements in it. This may be due to mesh based defeaturing of the geometry. You may select the offending object via RMB on this warning in the Messages window.".

To handle the error I turned the mesh defeaturing option to "no" and tried to solve again, but I get the same warning and the same error. I also edited the pinball region of the mass point from all the face to 0.05 meters and the pinball region of the longitudinal spring to .2 meters instead of all the face which means that each face have a pinball region of the mass point ans a pinball region of the spring and there is no contact between the 2 region.
I have also splited each wall into two face at a height half-way between H0 and H1 , but I have got the same erorr. Then in another trial I have used remote points using the "promote to remote point" option for each point mass and each end of the longitudinal springs, but I have faced the same error again!!
I have also used this tip to overcome the error ( Mechanical Menu, Tools > Variable Manager
In the window that pops up, right click and select 'Add'. Then set the variable name to be contactAllowEmpty, and its value to be 1.), but it didn' work too
Could anyone give a hand please?!!

 

[L_K]

Did the model solve? Although Ansys issues warning, the results can still be ok.
You could try to split the surface so that the mass and spring elements would have their
own surfaces. What are the point masses representing?

About the second error: Post a few pictures of the mesh. Too coarse mesh can cause this.

Edit: Post a few pictures of the mesh/springs/point masses.

 

[scheah]

Hi Rana,

You could try looking into acoustic elements to model water instead of approximating it with artificial mass and springs. Note the sloshing surface must be parallel to the coordinate plane of the global Cartesian system and can be flagged via the FREE surface load label


Kind regards,
Jason

 

[Rana Nasser]

[sup][/sup]
Hi L_K
No the model didn't solve. I have already splited the surface into 2 surfaces and I have got the same error.
The mesh size of the structure is 0.5 m *0.5 m except the 2 walls of the regulator where the element size is 0.25 m *0.25 m

 

[L_K]

You could add a contact tool under Connections and check the status of all the contacts before solving. Some of the contacts might be sharing the same surfaces on either contact or target size and this leads to the error.

 

[Rana Nasser]

This is what I have found in the initial information of the contact tool. I tried to change the formulation and regenerate the initial information results, but I got the same table. there is another ansys file for the same model but without the mass points and longitudinal springs- block system which have the same contact tool initial information table and it was solved without errors!! do you have any inspirations?!!
I'm wandering also why there is no any information about the longitudinal springs or mass points which are attached to the structure surfaces under connections??

 

[L_K]

You can add status plot to the contact tool by right clicking it to visualize the contacts.
Contact tool only includes information about contacts.

"At least one contact pair or remote load has no elements in it."

If you look through the "Number contacting" column of the table, can you spot a faulty
contact with 0? As you can see the number is reported only for contact side, not target.

Ok, I read your whole post (model works without masses and springs). You could debug
the model by activating them one by one. Are those boxes between walls solid? Why are they not meshed?
What is the spring attaching to if there is no mesh?

 

[Rana Nasser]

Yes the boxes are solids, but they are rigid so they are not meshed.