Atle Jensen

• Feneuil, Blandine Fleur Prudence; Iqbal, Kazi Tassawar; Jensen, Atle; Brandt, Luca; Tammisola, Outi & Carlson, Andreas (2022). Experimental and numerical investigation of bubble migration in shear flow: deformability-driven chaining and repulsion. arXiv. Show summary

  We study the interaction-induced migration of bubbles in shear flow and observe that bubbles suspended in elastoviscoplastic emulsions organise into chains aligned in the flow direction, similarly to particles in viscoelastic fluids. To investigate the driving mechanism, we perform experiments and simulations on bubble pairs, using suspending fluids with different rheological properties. First, we notice that, for all fluids, the interaction type depends on the relative position of the bubbles. If they are aligned in the vorticity direction, they repel, if not, they attract each other. The simulations show a similar behavior in Newtonian fluids as in viscoelastic and elastoviscoplastic fluids, as long as the capillary number is sufficiently large. This shows that the interaction-related migration of the bubbles is strongly affected by the bubble deformation. We suggest that the cause of migration is the interaction between the heterogeneous pressure fields around the deformed bubbles, due to capillary pressure.

• Løken, Trygve Kvåle; Marchenko, Aleksey; Ellevold, Thea Josefine; Rabault, Jean & Jensen, Atle (2022). Experiments on turbulence from colliding ice floes. Physics of Fluids. ISSN 1070-6631. 34(6). doi: 10.1063/5.0088953. Full text in Research Archive Show summary

  Increased knowledge about energy dissipation processes around colliding ice floes is important for improved understanding of atmosphere-ice-ocean energy transfer, wave propagation through sea ice, and the polar climates. The aim of this study is to obtain such information by investigating colliding ice floe dynamics in a large-scale experiment and directly measuring and quantifying the turbulent kinetic energy (TKE). The field work was carried out at Van Mijen Fjord on Svalbard, where a 3x4 m ice floe was sawed out in the fast ice. Ice floe collisions and relative water–ice motion were generated by pulling the ice floe back and forth in an oscillatory manner in a 4x6 m pool, using two electrical winches. Ice floe motion was measured with a range meter and accelerometers, and the water turbulence was measured acoustically with Doppler velocimeters and optically with a remotely operated vehicle and bubbles as tracers. Turbulent kinetic energy spectra were found to contain an inertial subrange where energy was cascading at a rate proportional to the -5/3 power law. The TKE dissipation rate was found to decrease exponentially with depth. The total TKE dissipation rate was estimated by assuming that turbulence was induced over an area corresponding to the surface of the floe. The results suggest that approximately 37% and 8% of the input power from the winches were dissipated in turbulence and absorbed in the collisions, respectively, which experimentally confirms that energy dissipation by induced turbulent water motion is an important mechanism for colliding ice floe fields.

• Feneuil, Blandine; Strøm Lillebø, Eirik; Larris Honstad, Christian; Jensen, Atle & Carlson, Andreas (2022). Elastic modulus measurements of cooked Lutefisk. Physics of Fluids. ISSN 1070-6631. 34(4). doi: 10.1063/5.0082963. Full text in Research Archive
• Ramirez de La Torre, Reyna Guadalupe; Vollestad, Petter & Jensen, Atle (2022). Experimental Investigation of Droplet Generation by Post-Breaking Plunger Waves. Water Waves. ISSN 2523-367X. p. 1–21. doi: 10.1007/s42286-022-00056-6. Full text in Research Archive
• Rabault, Jean; Nose, Takehiko; Hope, Gaute; Müller, Malte; Breivik, Øyvind & Voermans, Joey [Show all 20 contributors for this article] (2022). OpenMetBuoy-v2021: An Easy-to-Build, Affordable, Customizable, Open-Source Instrument for Oceanographic Measurements of Drift and Waves in Sea Ice and the Open Ocean. Geosciences. ISSN 2076-3263. 12(3). doi: 10.3390/geosciences12030110. Full text in Research Archive
• Vollestad, Petter & Jensen, Atle (2021). Modification of Airflow Structure Due to Wave Breaking on a Submerged Topography. Boundary-Layer Meteorology. ISSN 0006-8314. 180, p. 507–526. doi: 10.1007/s10546-021-00631-3. Full text in Research Archive

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• Feneuil, Blandine Fleur Prudence; Carlson, Andreas; Jensen, Atle; Iqbal, Kazi Tassawar; Tammisola, Outi & Brandt, Luca (2022). Bubble migration in complex fluids: experiments and simulations.
• Feneuil, Blandine Fleur Prudence; Carlson, Andreas & Jensen, Atle (2021). Bubble alignments in concentrated emulsions in shear flow.
• Løken, Trygve Kvåle; Marchenko, Aleksey; Ellevold, Thea Josefine; Rabault, Jean & Jensen, Atle (2021). An investigation into the turbulence induced by moving ice floes.
• Løken, Trygve Kvåle; Marchenko, Aleksey; Rabault, Jean; Gundersen, Olav & Jensen, Atle (2021). Iceberg stability during towing in a wave field.

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