Draft:Original research/Particle fountain

A particle fountain consists of a narrow transmission tube that usually transports particles from one location to another. Once the desired location is reached the particles shower outward from the projected direction like a fountain.

The diagram at the right conceptualizes a particle fountain as a model for individual storm cell development.

Theoretical particle fountains
The "ensemble of hydrometeor trajectories associated with a buoyant updraft element [is] a ‘‘particle fountain.’’ In the convective stage of a storm, the buoyant parcels carry ice particles to the middle and upper levels of the storm and spread them laterally before they fall, just as jets of water in a fountain shoot up and spread out before falling to the ground in a gravitationally sorted pattern. As a convective region dies out and the precipitation takes on a stratiform character, the ice particles left aloft by the old spreading buoyant elements (the upper portion of old particle fountains) are local maxima in ice particle concentrations. These concentrated particles gradually fall out through the region of weak stratiform ascent. The concentrated particles likely aggregate, melt into large drops, and manifest themselves as fallstreaks below the 0°C level."

"Conceptual model of the kinematic, microphysical, and radar echo structure of a convective line with trailing‐stratiform precipitation viewed in a vertical cross section oriented perpendicular to the convective line (and generally parallel to its motion) [is on the right]. Intermediate and strong radar reflectivity is indicated by medium and dark shading, respectively. H and L indicate centers of positive and negative pressure perturbations, respectively. Dashed‐line arrows indicate fallout trajectories of ice particles passing through the melting layer."

Atmospheres
"Individual cells can be described in terms of a single particle fountain. ... in multicellular storms, the ensemble of particle fountains rapidly evolves toward microphysical characteristics indicative of dominant vapor depositional growth, characteristic of stratiform regions, even when strong updrafts are present. [...] in contrast to the ensemble of particle fountains, for individual particle fountains the kinematic and microphysical evolution are more closely coupled in time and that vapor depositional growth does not dominate in the individual cell until the updraft associated with the cell has weakened. [...] A particle fountain is associated with a single cell, and consists of a buoyant updraft element and its accompanying precipitation particles and pressure-gradient-forced downdrafts required by mass continuity."

Volcanic eruptions
"In explosive volcanic eruptions, two-phase fountains develop when a dense mixture of particles and gas issues from the volcano (Woods 2010). Although theoretical models have been developed to describe the dynamics of such volcanic fountains, these models are often based on the assumption of single-phase flow, and in many cases they focus on the potential reversal of buoyancy as air is entrained and heated by the ash."

Materials
"In this modification of a fluidized bed, a single entry spout (fuel plus air) penetrates a cylindrical bed of inert (sand) particles [from below and up along a central vertical tube or slightly conical tube with the larger diameter on top]. The particles displaced by the spout create a particle fountain, but gravity returns them to the annulus."

Fountain tubes
"The fountain tube serves as an additional spray coating zone, a zone to introduce heat for drying and a means for controlling the height of the particle fountain issuing from the draft tube."

Fluidized bed granulations
"In fluidized bed granulation, either surface layering or agglomeration may lead to granule growth. Agglomeration will occur if a wet particle collides with another particle and is bound by a liquid bridge which becomes solidified during the subsequent drying period. In the case of a two-fluid-nozzle spraying upwards into the fluidized bed, wetted particles may be transported pneumatically by the nozzle air above the bed plenum and dry before they fall down in the outer regions of the bed."

"As a result, less particles will agglomerate if the nozzle gas flow rate is increased. At first sight, this is reasonable as the height of the particle fountain and hence, the residence time in the drying region above the bed increases."

Hypotheses

 * 1) A particle accelerator designed to function as a particle fountain may be able to initiate cumulus cell growth with resulting precipitation locally.