TY - GEN A1 - Schmidt, Heiko A1 - Kerstein, Alan R. A1 - Nédélec, Renaud A1 - Wunsch, Scott A1 - Sayler, Ben J. T1 - One-dimensional turbulence simulation of a laboratory analog of radiatively induced cloud-top entrainment Y1 - 2011 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/2011_Metstroem_Berlin.pdf N1 - MetStröm Conference 2011 on Multiple Scales in Fluid Dynamics and Meteorology ER - TY - GEN A1 - Klein, Marten A1 - Schmidt, Heiko A1 - Kerstein, Alan R. T1 - Transition to the ultimate regime in a stochastic model for thermal convection with internal sources Y1 - 2021 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Klein_poster_ipam21.pdf CY - IPAM Workshop: Transport and Mixing in Complex and Turbulent Flows (CTF2021), University of California, Los Angeles, CA, USA ER - TY - GEN A1 - Klein, Marten A1 - Schmidt, Heiko A1 - Kerstein, Alan R. T1 - Transition to the ultimate regime in a stochasticmodel for thermal convection with internal sources N2 - It is well established that heat transfer in turbulent Rayleigh–Bénard convection and angular momentum transfer in turbulent Taylor–Couette flow are similar in nature. This similarity manifests itself by isomorphic scaling laws for corresponding flow regimes. However, it is not clear at present if this similarity extends to flows with internal sources and different types of boundary conditions. Internal sources may occur, for example, due to radiative heating in dry or condensation in moist convection, or due to internal wave breaking and mean flow excitation in rotating Taylor–Couette-like flows. In this study, heat transfer in radiatively-driven turbulent Rayleigh–Bénard 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 that are located at z = 0 and H, respectively. The fluid is exposed to constant background 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 mean total heat flux and l the absorption length that controls the thermal boundary layer thickness. 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 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 N u ∼ Ra^p scaling are found to be p ≈ 0.33 and p ≈ 0.55, respectively, in agreement with measured values. Joint probabilities of turbulent eddy size and location suggest that the regime transition is associated with a suppression of small-scale near-wall turbulent motions. The latter observation is found consistent with recent direct numerical simulations of heat transfer between permeable walls (Kawano et al., J. Fluid Mech., 914, 2021, A13). KW - one-dimensional turbulence KW - turbulent thermal convection KW - heat transfer KW - high Rayleigh number Y1 - 2021 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Klein_poster_ictw21.pdf UR - https://www.b-tu.de/media/video/Transition-to-the-ultimate-regime-in-a-stochastic-model-for-thermal-convection-with-internal-sources/52aa69a52b8ab3ef29cc1d8bf9f20243 UR - https://pof.tnw.utwente.nl/ictw/schedule.html ER - TY - GEN A1 - Klein, Marten A1 - Schmidt, Heiko A1 - Kerstein, Alan R. T1 - Stochastic modeling of transient boundary layers in high-Rayleigh-number thermal convection, 25th International Congress of Theoretical and Applied Mechanics (ICTAM 20+1) N2 - One-dimensional turbulence (ODT) modeling is used to investigate the boundary layer in high-Rayleigh-number thermal convection for a notionally infinite horizontal layer of fluid. The model formulation distinguishes between turbulent advection, which is modeled by a stochastic process, and deterministic molecular diffusion to capture relevant vertical transport processes (including counter-gradient fluxes). For this study, statistical homogenization is applied to the two horizontal dimensions so that we use ODT as stand-alone tool. We show that the model yields mean and fluctuation temperature profiles that are in several respects consistent with available reference data. Furthermore, the profile of a surrogate for the fluctuation velocity is reminiscent of canonical wall turbulence. Y1 - 2021 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Klein_poster_ictam21.pdf UR - https://www.b-tu.de/media/video/Stochastic-modeling-of-transient-boundary-layers-in-high-Rayleigh-number-thermal-convection/f511d6b395472dc729543db3aa02dbc9 UR - https://www.ictam2020.org/assets/pdf/ICTAM2021-Fulllist-26-08.pdf ER -