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Improving the Accuracy of Thermochemical Convection Models: Mass Conservation in the Tracer Ratio Method

Posted on 2018-01-05 in Events
Jan 12, 2018

Please join us for a special seminar next Friday Jan 13 at 3:30 pm in rm 155 Geology presented by Sean Trim, Geophysics Post Doctoral Fellow:

Improving the Accuracy of Thermochemical Convection Models: Mass Conservation in the Tracer Ratio Method

Thermochemical convection occurs when fluid buoyancy depends upon both temperature and composition. Applications include convection in planetary cores, mantles and atmospheres. However, modeling sharp compositional contrasts is very difficult numerically. In particular, fixed grid numerical schemes often produce spurious oscillations and diffusion errors near changes in material composition. To avoid such errors, tracer methods that use moving grid points can be used. One popular tracer method is the tracer ratio method, which offers the advantage that material concentrations can never artificially exceed 100%. However, tracer coverage can vary widely during model evolution such that some regions contain an excessive amount of tracers while others have none. In this talk, an algorithm designed to evenly distribute tracers within the model domain is presented. Benchmark tests are also presented comparing models run with and without the use of the tracer repositioning algorithm. For all cases, the error in mass conservation is significantly reduced when the repositioning algorithm is used. Without the algorithm, mass errors range between 8-15%. With the algorithm, mass errors range between 0.16-4%.