[nuzzknacker]

Hey everyone,

I have a weird problem with my simulation of a stirred vessel partially filled with water. Above the air-water interface, the velocity of water (UWater) gradually increases over time and I can't figure out why. I think this increase over time causes my simulation to fail after simulating a few seconds

I mostly used the case from this link as a reference: https://www.cemf.ir/simulating-two-p...sing-openfoam/

I can't figure out what the problem is for the increase. Does anyone know what could be the cause for this or had similar issues in the past?

Best
Oli

Uwater.gif

[Martin_Sz]

The unexpected velocity increase in your partially filled stirred vessel simulation could stem from a few factors:
* Unphysical Initial Conditions: Ensure your initial UWater values are realistic and stable. Avoid setting them too high, especially near the air-water interface.
* Inaccurate Boundary Conditions: Double-check the boundary conditions, particularly at the air-water interface. There might be an inconsistency causing unphysical momentum buildup.
* Numerical Instability: Factors like high Courant number (related to time step size) can lead to numerical instabilities. Try reducing the time step and see if it resolves the issue.
* Missing Interfacial Forces: For air-water interfaces, surface tension effects might be crucial. Ensure your simulation captures these forces if relevant to your application.
Refer to the provided reference case to compare your setup and boundary conditions. If the issue persists, consider seeking help from OpenFOAM user forums or contacting the reference case's authors for specific guidance.