dc.contributor.advisor | Weiss, Stephan Dr. | |
dc.contributor.author | Wedi, Marcel Frederik | |
dc.date.accessioned | 2022-10-18T12:03:48Z | |
dc.date.available | 2022-10-25T00:50:08Z | |
dc.date.issued | 2022-10-18 | |
dc.identifier.uri | http://resolver.sub.uni-goettingen.de/purl?ediss-11858/14297 | |
dc.identifier.uri | http://dx.doi.org/10.53846/goediss-9502 | |
dc.language.iso | eng | de |
dc.rights.uri | http://creativecommons.org/licenses/by/4.0/ | |
dc.subject.ddc | 530 | de |
dc.title | Experimental investigation on the influence of rotation on thermal convection | de |
dc.type | doctoralThesis | de |
dc.contributor.referee | Dreizler, Stefan Prof. Dr. | |
dc.date.examination | 2022-02-14 | de |
dc.subject.gok | Physik (PPN621336750) | de |
dc.description.abstracteng | We report on experimental measurements of rotating Rayleigh-Bénard convection to study the influence of the Coriolis force on the heat transport and the flow structure. Two experimental setups were used. The first is a 2.24 m tall cylindrical cell with an aspect ratio between its diameter (D) and its height H, Γ = D/H = 0.5. It is filled with either nitrogen or pressurized gaseous sulfur hexafluoride to achieve Rayleigh numbers 7.5 × 10^9 ≤ Ra ≤ 7.5 × 10^14, while the Prandtl number Pr remained fairly constant at 0.72 ≤ Pr ≤ 0.96. We performed heat flux measurements (i.e. the Nusselt number Nu) and obtain scaling relations as function of Ra and the rotation rate in form of the inverse Rossby number 1/Ro. We find Nu_0 ∝ Ra^0.315 for the non-rotating and a collapse of Nu/Nu_0(1/Ro) for the rotating case. For sufficiently large 1/Ro, we find Nu/Nu_0 ∝ 1/Ro^-0.42. Three regimes were determined, with increasing influence of rotation. Their transitional values 1/Ro^*_1 = 0.8 and 1/Ro^*_1 = 4 could be found in numerous quantities throughout the analysis, where we relied on point-wise temperature measurements distributed throughout the cell. 1/Ro^*_1 was found as the onset of a travelling temperature wave around the circumference close to the sidewall, referred to as boundary zonal flow (BZF). This structure with wave number k_BZF = 1 drifts in counter-rotating direction with a frequency ω/Ω ∝ 1/Ro^-3/4.
In the smaller, optically accessible setup, we performed particle image velocimetry (PIV). It consists of a H = 0.196 m, Γ = 1, transparent setup made out of acrylic glass. With mixtures of water and glycerol at different mass concentrations we achieved 6.55 ≤ Pr ≤ 76 at various combinations of Ra and the dimensionless rotation rate (Ekman number - Ek ). We focussed on an horizontal layer at half-height, where we investigated the BZF in the velocity field. We found a thickness scaling relation δ_0 ∝ Ek^1/2, while the distance from the sidewall to the maximum azimuthal velocity was found to scale as δ^max_φ ∝ Ek^3/2Ra^1/2Pr^-0.8. | de |
dc.contributor.coReferee | Shishkina, Olga PD Dr. | |
dc.subject.eng | rotating flows | de |
dc.subject.eng | convection | de |
dc.subject.eng | Rayleigh-Bénard | de |
dc.subject.eng | rotating turbulence | de |
dc.identifier.urn | urn:nbn:de:gbv:7-ediss-14297-1 | |
dc.affiliation.institute | Fakultät für Physik | de |
dc.description.embargoed | 2022-10-25 | de |
dc.identifier.ppn | 1819407012 | |
dc.notes.confirmationsent | Confirmation sent 2022-10-18T12:15:01 | de |