EDEM API - Contact Model Example: Liquid Bridge Cohesion
Altair EmployeeOverview
The presence of moisture content leads to cohesion due to capillary forces. When liquid surfaces are nearby, a liquid bridge is created leading to an attractive force due to surface tension and the hydrostatic pressure inside the bridge. Moisture content also leads to the development of viscous forces which are secondary to the secondary effect of capillary forces in the case of low moisture content. The present Liquid Bridge model is used to model the effect of the capillary forces. This model does not take into account the effect of viscous force and is therefore only relevant for simulation of a system with low moisture content.
Here you will find the the source code and documentation of the liquid bridge contact model.
Assumptions
- The particle shape is single sphere, multi sphere, or spherocylinder.
- The surface tension dominates the liquid bridge force, and not the viscous effect. The capillary number (ratio of dynamic force to static force) is less than 1.
- The wetting angle used in the model is the arithmetic mean of the wetting angles of the two surfaces in contact.
Usage/Installation Instructions
Please refer to the attached pdf for the equations used in the liquid bridge force model.
A preference file is needed which takes the density of the liquid and the time after which the liquid bridge physics must be applied. You must also specify the surface tension and the wetting angle of all the relevant interactions in the preference file.
The initial liquid content is represented as volume added per particle in the simulation. This can be specified in the Factory of the particle.
The zip file contains the source code, and also the compiled library file (.dll) for CPU and the CUDA file (.cu) for GPU.
Post-Requisite
This model may also be combined with the in-built EDEM Spray Coating Model. More details about the spray coating model can be found at https://help.altair.com/edem/Creator/Physics/Additional_Models/Spray_Coating.htm
If you wish to use a liquid exchange model, please refer to this post: https://community.altair.com/community/en/edem-api-contact-model-example-liquid-exchange-model?id=kb_article&sysparm_article=KB0124628
Please note that the inputs required for the liquid exchange model may be a little different.
Comments
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Hi Jerrin，
This is a very useful API and thanks for sharing,
I have a small question about the contact radius setting. How do you decide the value of the contact radius? Does it just need to be greater than the rupture distance?
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Alice Sun said:
Hi Jerrin，
This is a very useful API and thanks for sharing,
I have a small question about the contact radius setting. How do you decide the value of the contact radius? Does it just need to be greater than the rupture distance?
Yes, as long as the contact radius is greater than the rupture distance, the API will work.
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Jerrin Job Sibychan said:
Yes, as long as the contact radius is greater than the rupture distance, the API will work.
Thank you For your reply.
I need to use both the liquid bridge force model and the electrostatic force model simultaneously. The electrostatic force model requires a much larger contact radius. Will this not affect the liquid bridge model?
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Alice Sun said:
Thank you For your reply.
I need to use both the liquid bridge force model and the electrostatic force model simultaneously. The electrostatic force model requires a much larger contact radius. Will this not affect the liquid bridge model?
There is no issue with using both models together. Even if the contact radius is very large, this model does not create liquid bridges every time the contact radii are in contact. The liquid bridge is formed only if the physical radii are in contact, and once the bridge is ruptured, the particles will have to come into contact again for bridge to reform.
Hope this helps.
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