beatriba

• Baldelli, Beatrice; Linga, Gaute & Flekkøy, Eirik Grude (2022). Thermal conduction through a cool well. Physical Review Fluids. 7(10). doi: 10.1103/PhysRevFluids.7.103503. Fulltekst i vitenarkiv Vis sammendrag

  We study a differentially heated square cavity with inlet and outlet ports at the top of the side walls, quantifying how the effective thermal conductivity changes with the temperature difference across the system. The side walls are insulating, the top surface is kept at a fixed high temperature, and the bottom surface at a fixed low temperature, leading to buoyancy-stabilized flow. We visualize the flow pattern for Reynolds number, Re=1, and Prandtl number, Pr=50, and characterize the heat transfer at the bottom surface using the Nusselt number, Nu, for Re=0.1,1,10 and Pr=1,50. As the Richardson number, Ri, is increased, we observe the formation of a series of system-spanning vortices through the merging of Moffatt eddies growing from the bottom corners of the cavity. We find that the convection, which enhances the transport of heat, is strongly suppressed by increasing the temperature drop. As a result Nu drops by a factor 1–3 depending on the Reynolds number.

• Flekkøy, Eirik Grude; Hansen, Alex & Baldelli, Beatrice (2021). Hyperballistic Superdiffusion and Explosive Solutions to the Non-Linear Diffusion Equation. Frontiers in Physics. 9. doi: 10.3389/fphy.2021.640560. Fulltekst i vitenarkiv Vis sammendrag

  By means of a particle model that includes interactions only via the local particle concentration, we show that hyperballistic diffusion may result. This is done by finding the exact solution of the corresponding non-linear diffusion equation, as well as by particle simulations. The connection between these levels of description is provided by the Fokker-Planck equation describing the particle dynamics.

• Hansen, Alex; Flekkøy, Eirik Grude & Baldelli, Beatrice (2020). Anomalous diffusion in systems with concentration-dependent diffusivity: exact solutions and particle simulations. Frontiers in Physics. 8:519624, s. 1–9. doi: 10.3389/fphy.2020.519624. Fulltekst i vitenarkiv Vis sammendrag

  We explore the anomalous diffusion that may arise as a result of a concentration dependent diffusivity. The diffusivity is taken to be a power law in the concentration, and from exact analytical solutions we show that the diffusion may be anomalous, or not, depending on the nature of the initial condition. The diffusion exponent has the value of normal diffusion when the initial condition is a step profile, but takes on anomalous values when the initial condition is a spike. Depending on the sign of the exponent in the diffusivity the diffusive behavior will then be either sub-diffusive or super-diffusive. We introduce a particle model that behaves according to the non-linear diffusion equation in the macroscopic limit. This correspondence is demonstrated via kinetic theory, i.e. by means of Chapman-Kolmogorov equation, as well as by direct simulations.

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• Lanza, Federico; Baldelli, Beatrice; Linga, Gaute; Barras, Fabian & Flekkøy, Eirik Grude (2024). The Cooling Instability. Fulltekst i vitenarkiv
• Lanza, Federico; Baldelli, Beatrice; Linga, Gaute; Barras, Fabian & Flekkøy, Eirik Grude (2024). Dynamic instability of a temperature-dependent viscous fluid in a Hele-Shaw cell. Fulltekst i vitenarkiv
• Lanza, Federico; Baldelli, Beatrice; Linga, Gaute; Barras, Fabian & Flekkøy, Eirik Grude (2024). Simulating finger structures that may form when a warm liquid (lava) cools and becomes more viscous during flow through a fracture. Fulltekst i vitenarkiv

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