I am trying to simulate my experiment conducted in microchannel with two newtonian and non-newtonian paraffin oil based fluids using comsol. While in the actual experiment, the two fluids flow in separate laminar layers with definite boundaries, but when I use comsol with same boundary conditions, rather than flowing in separate layers it forms bubbles of one fluid into another or cause backflow. I am using "Laminar multiphase, level set" (which I don't know if is right or wrong, I am new to comsol).
As in the attachment, the side fluid is paraffin oil while the middle fluid is oil-nanogel suspension, which I am simulating as a fluid using its overall rheological parameters in the input. Can someone guide me what I am doing wrong that it is causing bubble formation and/or backflow, and not flowing in layers like actual experiment.
Thank you!
Hi Ashhar,
Keep in mind that even a small different magnitude of parameters from real experiments or conflict parameters can lead to dramatic wrong output of simulations.
The reason I mention this is because it seems like COMSOL couldn't find a stable (or physical) initial state based on your key-in parameters.
Please check again that all your parameters (incl. inlet pressures/velocities, outlet pressure, contact angles, etc) are suit for real cases.
And also chech if the oil you used in your experiments are immiscible. Two phase flow only works if the liquids are immiscible.
Best regards,
Shao-Hsuan
Perhaps you should try the "Multiphase flow, mixture" interface, which was designed for suspended microparticles in liquids. It might make more sense if you are trying to simulate the distribution of the nanogel suspension in the laminal flow.
If all thing you have tried, but they seem not working. Try to calculate with a much finer mesh, because your system might be a non-linear system, which generates unanticipated errors. The errors can accumulate signficately if the mesh is not fine enough.
Shao-Hsuan Kuo Thanks! My oils are miscible, both are paraffin oil, one is pure other with nanaogel. If it doesn't count two phase then should I simulate using single phase flow? Is it possible for separate layers to form in single phase? Also I need to ignore the presence of nanogel as separate dispersed particles and consider it as a non-netonian fluid, so I am modelling it as a whole.
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