Tilgner, Andreas

[["dc.bibliographiccitation.firstpage","231"],["dc.bibliographiccitation.journal","Journal of Fluid Mechanics"],["dc.bibliographiccitation.lastpage","254"],["dc.bibliographiccitation.volume","572"],["dc.contributor.author","du Puits, R."],["dc.contributor.author","Resagk, C."],["dc.contributor.author","Tilgner, Andreas"],["dc.contributor.author","Busse, Fritz H."],["dc.contributor.author","Thess, A."],["dc.date.accessioned","2018-11-07T11:05:03Z"],["dc.date.available","2018-11-07T11:05:03Z"],["dc.date.issued","2007"],["dc.description.abstract","We report high-resolution local-temperature measurements in the upper boundary layer of turbulent Rayleigh-Benard (RB) convection with variable Rayleigh number Ra and aspect ratio Gamma. The primary purpose of the work is to create a comprehensive data set of temperature profiles against which various phenomenological theories and numerical simulations can be tested. We performed two series of measurements for air (Pr = 0.7) in a cylindrical container, which cover a range from Ra approximate to 10(9) to Ra approximate to 10(12) and from Gamma approximate to 1 to Gamma approximate to 10. In the first series Gamma was varied while the temperature difference was kept constant, whereas in the second series the aspect ratio was set to its lowest possible value, Gamma = 1.13, and Ra was varied by changing the temperature difference. We present the profiles of the mean temperature, root-mean-square (r.m.s.) temperature fluctuation, skewness and kurtosis as functions of the vertical distance z from the cooling plate. Outside the (very short) linear part of the thermal boundary layer the non-dimensional mean temperature Theta is found to scale as Theta(z)similar to z(alpha), the exponent alpha approximate to 0.5 depending only weakly on Ra and Gamma. This result supports neither Prandtl's one-third law nor a logarithmic scaling law for the mean temperature. The r.m.s. temperature fluctuation or is found to decay with increasing distance from the cooling plate according to sigma(z)similar to z(beta), where the value of beta is in the range -0.30 > beta > -0.42 and depends on both Ra and Gamma. Priestley's beta = -1/3 law is consistent with this finding but cannot explain the variation in the scaling exponent. In addition to profiles we also present and discuss boundary-layer thicknesses, Nusselt numbers and their scaling with Ra and Gamma."],["dc.identifier.doi","10.1017/S0022112006003569"],["dc.identifier.isi","000244434700012"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/51980"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Cambridge Univ Press"],["dc.relation.issn","0022-1120"],["dc.title","Structure of thermal boundary layers in turbulent Rayleigh-Benard convection"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","064501"],["dc.bibliographiccitation.issue","6"],["dc.bibliographiccitation.journal","Physical Review Letters"],["dc.bibliographiccitation.volume","91"],["dc.contributor.author","Hartlep, T."],["dc.contributor.author","Tilgner, Andreas"],["dc.contributor.author","Busse, Fritz H."],["dc.date.accessioned","2018-11-07T10:37:02Z"],["dc.date.available","2018-11-07T10:37:02Z"],["dc.date.issued","2003"],["dc.description.abstract","Direct numerical simulations of Rayleigh-Benard convection in a plane layer with periodic boundary conditions at Rayleigh numbers up to 10(7) show that flow structures can be objectively classified as large or small scale structures because of a gap in spatial spectra. The typical size of the large scale structures does not always vary monotonically as a function of the Rayleigh number but broadly increases with increasing Rayleigh number. A mean flow (whose average over horizontal planes differs from zero) is also excited but is weak in comparison with the large scale structures. The large scale circulation observed in experiments should therefore be a manifestation of the large scale structures identified here."],["dc.identifier.doi","10.1103/PhysRevLett.91.064501"],["dc.identifier.isi","000184678200025"],["dc.identifier.pmid","12935082"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/45466"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","American Physical Soc"],["dc.relation.issn","0031-9007"],["dc.title","Large scale structures in Rayleigh-Benard convection at high Rayleigh numbers"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","309"],["dc.bibliographiccitation.journal","Journal of Fluid Mechanics"],["dc.bibliographiccitation.lastpage","322"],["dc.bibliographiccitation.volume","544"],["dc.contributor.author","Hartlep, T."],["dc.contributor.author","Tilgner, Andreas"],["dc.contributor.author","Busse, Fritz H."],["dc.date.accessioned","2018-11-07T10:53:36Z"],["dc.date.available","2018-11-07T10:53:36Z"],["dc.date.issued","2005"],["dc.description.abstract","Numerical simulations of Rayleigh-Benard convection in a fluid layer heated from below between two rigid horizontal boundaries have been performed for Rayleigh numbers Ra up to 10(7), Prandtl numbers in the range between 0.7 and 60 and for aspect ratios Gamma up to 20. Periodic boundary conditions in the horizontal plane have been used. To a considerable extent, the evolution towards turbulent convection at high values of Ra is governed by processes exhibited by instabilities of steady or time periodic forms of convection at lower Rayleigh numbers. With increasing Ra, the properties of convection are increasingly determined by the thermal boundary layers. The role of mean flows which may be symmetric or antisymmetric with respect to the mid-plane of the layer is emphasized."],["dc.identifier.doi","10.1017/S0022112005006671"],["dc.identifier.isi","000234012800012"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/49382"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Cambridge Univ Press"],["dc.relation.issn","0022-1120"],["dc.title","Transition to turbulent convection in a fluid layer heated from below at moderate aspect ratio"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","729"],["dc.bibliographiccitation.issue","7"],["dc.bibliographiccitation.journal","Comptes Rendus Physique"],["dc.bibliographiccitation.lastpage","740"],["dc.bibliographiccitation.volume","9"],["dc.contributor.author","Mueller, Ulrich"],["dc.contributor.author","Stieglitz, Robert"],["dc.contributor.author","Busse, Fritz H."],["dc.contributor.author","Tilgner, Andreas"],["dc.date.accessioned","2018-11-07T11:11:14Z"],["dc.date.available","2018-11-07T11:11:14Z"],["dc.date.issued","2008"],["dc.description.abstract","This article outlines the experimental realization of the Roberts-Busse kinematic dynamo model at the Forschungszentrum Karlsruhe. Essential observations of the spatial and temporal structures of the self-induced magnetic field and features of its saturation mechanism are presented and the experimental findings are compared with predictions from model calculations."],["dc.identifier.doi","10.1016/j.crhy.2008.07.005"],["dc.identifier.isi","000260036600007"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/53384"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier France-editions Scientifiques Medicales Elsevier"],["dc.relation.issn","1631-0705"],["dc.title","The Karlsruhe two-scale dynamo experiment"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]