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Dear Telemac3D users,

I am now setting a river/lake flow model, including heat exchange and stratification. Reviewing examples and some previous posts (e.g. Post No. 6942, 8048 and 8228), I could set a river/lake flow model. My preliminary steady state tests indicated that the model seems to properly simulate vertical temperature profiles and stratified flow. However, I still cannot understand some simulation results.

(1) Swirling (vortex) Zones
As shown in Figure 1, UV vectors at a transient layer with a steep temp/density gradient had some swirling/vortex zones. Are these swirling zones expectable? If so, could you explain this phenomenon with supporting theories?

Figure 1. UV vectors at a transient layer. About 5m deep in 10m water>



(2) Horizontal (Spatial) Temperature Gradient
The contour of Figure 1 represents the depth-averaged water temperature. The horizontal (spatial) temperature gradient occurred around some shallow areas. Water temperature in shallow-water areas was found to be higher than in deep-water areas. Here, I want to know how the heat-exchange model can explain this horizontal temperature gradient, from shallow to deep waters. Which mechanism or process makes the shallow waters to be warmer? Could you give some reference documents for the heat-exchange model and theories?

Interesting is that not only the vertical gradient but also the horizontal temperature gradient seem to affect the velocity fields, developing the swirling areas.

For your information, I attach the CAS file as well.

Thank you!

Joon

Hello Joon
1- Are these vortices expectable ? : We can not know a priori, this kind of model is complew enough that it can not be validated only after a calibration step that uses comparison with measurements or observations.
In on the other side, you can manage these recirculation structure by handling advection schemes and turbulence models.
2- for horizontal distribution of temperature also, the phenomena that are included are very complex. However, you can understand partially the behaving of temperature by looking at source terms of the heat-exchange module (sources/waqtel). Documentation (though brief) is available in the user manual of Telemac2D and in the release note of version V7P1.

I hope that this helps

with my best regards

Riadh

Dear Riadh,

Thanks a lot for your suggestions.

I have tested with a higher horizontal diffusion of a tracer. It helps to reduce the horizontal temperature and velocity gradients. I am now also testing other advection schemes and turbulence models. Let me know about the progression.

Later, I have a plan to publish a research paper. So, I may have to read a reference paper or book for setting up the heat exchange model. Do you have any reference about the heat exchange model? I guess, anyhow, that the model might be based on a reference.

Thank you again!

Best Regards,
Joon