= Stephan Stellmach
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<Stephan Stellmach> is a researcher in <geophysics> and <fluid dynamics>. His University of Münster profile records work on density stratification, convective <turbulence> and <magnetic field> generation, alongside publications on rotating <convection>.<Research profile of Stephan Stellmach by University of Münster>[Projects Effects of Density Stratification on Convective Turbulence and Dynamo Action, and publication list]{ref}
His 2013 work with collaborators on <fingering convection> connects small-scale <fluid dynamics> to chemical transport inside <stars>. A stabilizing <temperature> gradient and an opposing composition gradient can have a stable combined <mass density> profile while still permitting fingers, because <thermal diffusion> and <molecular diffusion> act at different rates. Their paper develops a transport model supported by three-dimensional <direct numerical simulations>, with a prescription usable in one-dimensional models of <stellar evolution>.<Chemical Transport and Spontaneous Layer Formation in Fingering Convection in Astrophysics by Justin M. Brown and others>[Abstract, three-dimensional direct numerical simulations and use in one-dimensional stellar codes; §1, differential-diffusion mechanism]{ref}
The bridge between dimensions is the practical point: a one-dimensional calculation of a <star>'s evolution cannot explicitly resolve every three-dimensional finger. Estimating their average transport from local <numerical simulations> supplies a model for that unresolved motion. It is a physically tested approximation within the modeled parameter regime, not a direct observation of all mixing inside a <star>.
\Image[https://cms-cdn.lmu.de/media/20-geowissenschaften/deepdyn/photos/team/stellmach_stephan_ext_1_1_format_s.jpg]
{title=Stephan Stellmach; portrait credited to Stephan Stellmach on the LMU DeepDyn team page}
{height=240}
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