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DY: Fachverband Dynamik und Statistische Physik
DY 2: Fluid Physics 1 - organized by Stephan Weiss and Michael Wilczek (Göttingen)
DY 2.1: Talk
Monday, March 22, 2021, 09:00–09:20, DYa
Transition to the ultimate regime in a stochastic model for radiatively driven turbulent convection — •Marten Klein1, Heiko Schmidt1, and Alan R. Kerstein2 — 1Lehrstuhl Numerische Strömungs- und Gasdynamik, Brandenburgische Technische Universität Cottbus-Senftenberg, Germany — 2Consultant, Danville, California, USA
Heat transfer in thermal convection is investigated using the stochastic one-dimensional-turbulence model (ODT). A Boussinesq fluid of Prandtl number 1 is confined between two horizontal adiabatic no-slip walls (located at z=0 and H) and exposed to constant gravity that points in vertical (−z) direction. A flow is driven by radiative heating from below yielding the local heating rate Q(z)= (P/ℓ) exp(−z/ℓ), where P is the prescribed heat flux and ℓ the absorption length. ODT resolves all relevant scales of the flow, including molecular-diffusive scales, along a vertical one-dimensional domain, whereas stochastically sampled eddy events represent the effects of turbulent advection. ODT results reproduce and extrapolate available reference experiments direct numerical simulations of Lepot et al. (Proc. Natl. Acad. Sci. USA, 115, 2018, pp. 8937–8941) and Bouillaut et al. (J. Fluid Mech., 861, 2019, R5) in particular capturing the turbulent transition from the classical to the ‘ultimate’ regime. For these regimes, the exponent values in Nu∼ Rap scaling are found to be p≈0.3 and p≈0.55, respectively, in agreement with measured values. Joint probabilities of eddy size and location indicate that the regime transition is accompanied by a relative increase of bulk turbulence.