Small powder avalanche near Zinal in Switzerland © dahu1 In various geophysical contexts, there are dilute suspensions in which solid particles are transported by a turbulent gas. Examples of this are sandstorms (sand or arena is a loose sedimentary rock consisting of small particles from the decay of other rocks, the dimensions of which are between 0.063 and 2 …), snow avalanches (snow is a form of precipitation that consists of crystallized Ice consists and is agglomerated into flakes that can branch out in endless ways. Since flakes are …) and density flows (The density or relative density of a body is the ratio of its density to the density of a body as a reference. The reference body is .. .) pyroclastic. The properties of these suspensions, such as the speed (we distinguish 🙂 of the flow, the pressure (Pressure is a basic physical term. It can be seen as a force that relates to the surface to which it is applied.) Dynamic (The word “dynamic” is often used to denote or qualify that which relates to movement. It can be used as 🙂 and the distance of movement is largely determined by the concentration of the particles. However, this concentration remains due to the opacity (opacity is the inversion of transparency. This contradicts the passage of light.) Optically difficult to measure. Optics (optics is the branch of physics that deals with light, electromagnetic radiation and their relationship to sight.) Of the medium due to scattering (In common parlance, the term scattering refers to the term “distribution”, “provision” (diffusion ) of a product, of information), even of “evaporation” …) of light (light is the amount of electromagnetic waves that are visible to the human eye, that is, it is contained in wavelengths from 380 nm (violet) to 780 nm …) through the particles, which makes observation difficult (observation is the action of attentive monitoring of phenomena without wanting to modify them, using suitable means for studying and investigating the …) three-dimensional suspensions.
Researchers have perfected a technique (graph) that allows the acoustic method to measure (acoustics is a branch of physics whose aim is the study of noise and mechanical waves. It uses wave phenomena. And vibration mechanics.), The local concentration of solids in turbulent air suspensions (air is the gas mixture that makes up the earth’s atmosphere. It is odorless and colorless. Due to the pressure drop in air with altitude, it is necessary to pressurize aircraft cabins and …) and particles. They observed two important properties of these two-phase mixtures: Gas (A gas is a series of atoms or molecules that are very weakly linked and almost independent. In the gaseous state, matter has no shape or clean volume of its own: a gas tends to …) turbulent (HMS Turbulent (hull no.: S 87) is a Trafalgar class ship of seven nuclear submarines of the Royal Navy.) suspended (Suspending particles In chemistry, suspension refers to a particle dispersion. In geomorphology, suspension is a means of transport …) particles up to a critical (maximum) concentration, and this critical concentration is controlled by the formation of particle clusters, which nevertheless occur in lower concentrations.
These results were obtained by conducting experiments in a rectangular container (in the transport sector, a container (from English), sometimes referred to as a container, is a metal box in the shape of …) in which spheres are rectangular glass (denoted glass in common usage a hard, fragile (brittle) material or an alloy that is transparent to visible radiation. Glass usually consists of …) a diameter (in a circle or a sphere, the diameter is a line segment that runs through the center and is limited by the points of the circle or sphere. The diameter is also the length of …) 77 or 155 micrometers were suspended by a flow (the word flow (from the Latin fluxus, river) generally denotes a series of elements (Information / data, energy, matter, …) that develop in common sense, more precisely the term is used in the areas …) from vertical air (The vertical (rare) or vertical style is a style of musical writing both in clad chords.) ascending. The researchers measured ballistic propagation (ballistics is the science of studying the movement of projectiles.) From ultrasound through the suspension. Then they extracted the particle concentration from the attenuation (loss of intensity and amplitude of a signal …) and from the phase velocity (a wave is a disturbance that moves in a medium. It is possible to combine two wave velocities with it.) Waves ( A wave is the propagation of a disturbance that, when passing through, creates a reversible variation in local physical properties. It transports energy without transporting matter.) Ultrasound continues to form the basis of sound wave diffusion models and the hydrodynamics of a two-phase medium. This project (A project is an irreversible commitment with an uncertain result, which cannot be reproduced a priori identically and which requires the support and integration of a multitude of …) brings a new tool (A tool is a definitive object used by a living being, This increase is used to study the fundamental processes of turbulent mixtures of gases and particles experimentally. This point is particularly important for the understanding of natural phenomena such as pyroclastic density flows, which direct observation is practically impossible.
a) Experimental setup. b) The concentration of the particles (glass beads) is measured by ultrasonic testing using an emitter (D) and a receiver (S). c) Diagram of the air flow with the speed U required to hang the balls. © LMV
Find out more:
Acoustic investigation of particle concentration in turbulent granular suspensions in air – Scientific reports, volume (Volume in science or mathematics is a quantity that measures the extent of an object or part of space.) 16, item number: 16544.
S. van den Wildenberg, X. Jia and O. Roche (Rock from the popular Latin Rocca denotes any material that makes up the earth’s crust. Any material that enters into the composition of the subsurface is formed by an accumulation of minerals, sometimes including …).
– Siet van den Wildenberg – LMV -siet.van_den_wildenberg at uca.fr.
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