Displays

In the earth and planetary sciences, the term "analog experiment" indicates laboratory experiments that use analog materials to investigate natural processes. Scaled experiments constitute a representative sub-category of analog experiments. They are designed to have the same dominant dimensionless parameter in the same range as the targeted natural processes. Other primary uses of analog experiments are education and outreach. Reproducing similar phenomena in front of the audience is useful in explaining the essence of the complex dynamics of natural processes. However, it is often the case that we do not fully understand the physics of the experimental systems or the targeted natural phenomena. In such cases, especially when the process is complex, it is difficult to guarantee the scaling similarity. When we take such laboratory phenomena as a research subject of earth science, we encounter critical comments about the scaling issue.

Nevertheless, I think it scientifically important to consider questions like follows. What is the mechanism of the experimental phenomena? Why the behaviors of the experiment look similar to the natural phenomena? To what extent the laboratory and the natural systems are similar. To indicate experimental studies to elucidate these questions, I would like to define "analogy experiment" as a new sub-category of analog experiments.  Some recent experiments are presented as examples.

How to cite: Ichihara, M.: Proposing "analogy experiment" as a sub-category of "analog experiment" in earth science, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3933, https://doi.org/10.5194/egusphere-egu2020-3933, 2020.

When a droplet with a relatively high density falls into a miscible solution with a relatively low density, the droplet breaks up spontaneously. We investigated the number m of breakup in experiments with several density differences Δρ between two solutions, viscosities μ, and droplet radii r. The mode number m has a distribution even under the same experimental conditions. We propose a simple model of mode selection based on the linear Rayleigh-Taylor instability and the growing radius of a vortex ring deformed from the droplet. The model provides the probability distribution P(m) and a relationship between the nondimensional parameter G ∝ Δρgr³/μ² and the average value of m, which are consistent with experimental results.

How to cite: shimokawa, M. and Sakaguchi, H.: A breakup of a droplet falling into a miscible solution, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1912, https://doi.org/10.5194/egusphere-egu2020-1912, 2020.

Landslides, rockfalls, and avalanches are re-occurring natural hazards in many parts of the world. Especially snow avalanches are triggered by unaware skiers and hikers. Hazard mitigation technologies are visible to the public in many places, such as along roads or train tracks. To raise awareness of the hazard and to boost acceptance for mitigation strategies, public education about initiation and dynamics of gravitational driven granular mass flows is required. Due to the importance and commonness of those hazards, granular flows are part of the curriculum for geoscience and civil engineering students. In this work, I present an experimental approach using LEGO bricks to educate and talk about granular flow dynamics without oversimplification or a trade-off in scientific value. The chosen setup is highly flexible, allows easy testing of various scenarios and parameter variations, and provides high-quality, scientifically profound data at the laboratory scale. The separate pieces are almost unbreakable and can be reassembled in various combinations. Release height, released amount of mass, flow material, surface roughness, slope shape, channel width and length, as well as position or shape of one or more obstacles can be easily modified. Measurements can be taken using video recordings at high speed from various angles as well as through quantitative analysis of the mass deposit. The presented design is approximately 80 x 60 x 20 cm in length, height and width with material costs less than 50€ without a camera. Flexibility and data quality make the chosen approach a good alternative to handcrafted, single-piece laboratory setups. However, in terms of outreach, science communication, and education, the toy-based approach shows its strongest benefit. Due to the very popular and well-known toy's character, the presented experimental design allows easy interaction with a low inhibition threshold. Due to the easy brick-combining technology of LEGO effects of various protection designs can be quickly tested and visualized. The presented setup has successfully been used in consecutive years in higher education for geoscience and geophysics students as well as on public science fairs. Cameras of commonly available smartphones have been given satisfying results for education purposes. Experience shows that the presented setup stimulates creativity in the user group, as for example with regard to parameter variation, improvements of the experimental design and protection constructions. The practical experience at the laboratory scale facilitates understanding of complex mathematical flow models and the governing parameters of granular flow. Further, the practical work can be used for an introduction into image-based evaluation and analysis techniques and to illustrate scientific methodologies. At a broader public audience, especially children up to the age of 14 seem attracted by the use of a familiar toy system but also for adults the flexibility of the design has been found useful for demonstrations. In this work, the chosen experimental design, its benefits and drawbacks, and its scientific quality are presented.

How to cite: Heinze, T.: Demonstrating granular flow characteristics easily using LEGO bricks, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4204, https://doi.org/10.5194/egusphere-egu2020-4204, 2020.

On the south flank of Kilauea volcano in Hawaii Island, we will find glass fibers called “Pele’s hair” in the volcanic products of lava fountains and explosions. It is named after Pele, who is the Hawaiian goddess of volcanos. “Pele’s hairs” are highly stretched volcanic glass products, which are formed by breakup, stretching, and cooling of molten magma during their eruption. The texture of the glass fibers (thickness and length of fibers) depend on many parameters such as rheological properties of the volcanic glass, cooling rate, ejection speed, wind velocity, and so on. In order to consider the formation process of “Pele’s hair” in classroom experiments, we developed a handmade cotton candy maker. We used a commercial stirrer which could control the rotating speed. At the edge of the stirrer, we attached a rotating dish, which was made of thin steel and had small outlets along its periphery. To make fibers of sugars (threads of cotton candy), crystal sugar (“Za-ra-me” in Japanese, coarse sugar) was added to the dish and rotated at a constant speed. The melted sugar was formed after heating the rotating disk and ejected through the outlets. We measured the temperature of the melted sugar by a commercial radiation thermometer and the flow behavior of the melted sugar jet was captured by a high-speed video camera, which helped us to understand the formation process. By controlling the rotating speed, heating temperature and diameter of the outlets, we have succeeded in producing a variety of analog “Pele’s hair” and Pele’s tear”. We carefully examined the texture of the analogue Pele’s products and discussed the role of these controlling parameters on their formation process. In this presentation, we will also discuss the similarity of the texture of Pele’s hairs, which were sampled from volcanic products in Hawaii Islands, with the analog Pele’s hairs of cotton candy using a commercial digital microscope.

How to cite: Kumagai, I. and Yamada, M.: Fluid dynamic analog experiments on “Pele’s hair” using a handmade cotton candy machine, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8151, https://doi.org/10.5194/egusphere-egu2020-8151, 2020.

Even in the eon of supercomputers, I would claim that laboratory experiments remain an invaluable tool to investigate new phenomena and old problems, for at least 6 reasons:  (1) Since they let nature solve the equations, they can explore new phenomena for which such equations do not yet exist. (2) You usually can turn around them and have a good look at their three-dimensional structure. (3) You can observe their evolution through time. (4) you can simplify the system until you understand something ! (5) On the other hand, experiments can explore ranges of parameters, or geometries, where the equations are too challenging to be solved analytically or even numerically. (6) They are at the same time fun and thought-provoking. So yes, laboratory experiments are crucial for exploring new physics, testing theories and computer codes, and show your students, colleagues and family « how it works ». 
Mantle dynamics, and thermal convection, is a good example.  The emergence of mantle convection models was dictated by the failure of static, conductive, and/or radiative thermal history models to account for the mantle temperature regime, the Earth’s energy budget, and the Earth’s lateral surface motions. Convection, which transports heat by material flow, is the only other physical mechanism capable of explaining these observations. The force driving flow is gravity, whereby material lighter than its environment rises, while denser material sinks. Such density anomalies can be produced by differences in composition and/or temperature. Then, the flow patterns produced by convection also strongly depend on the way the material deforms when submitted to a force: cold surface rocks break (typical of a solid) on short time scale and distances, while hot mantle rocks creep (typical of a liquid !) on geological time scales. This dual nature of a solid and a liquid is the main source of complexity, and debate, in mantle dynamics. Modern physics calls these solid-liquid materials « soft matter », and we use plenty of them in the everyday life and in the kitchen. I will show how differently mantle plumes and lithospheric plates form in honey syrup, hair gel, milk and cake. And how marble cake can help us understand mantle mixing.

How to cite: Davaille, A.: Mantle flow in planets: lessons from sugar syrup, hair gel, milk skin and marble cake., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11190, https://doi.org/10.5194/egusphere-egu2020-11190, 2020.