{"id":478,"date":"2026-09-29T13:05:02","date_gmt":"2026-09-29T13:05:02","guid":{"rendered":"https:\/\/www.auriga.polimi.it\/index.php\/lab\/bubble-swarm-column\/"},"modified":"2026-09-30T11:39:04","modified_gmt":"2026-09-30T11:39:04","slug":"bubble-swarm-column","status":"publish","type":"page","link":"https:\/\/www.auriga.polimi.it\/index.php\/lab\/bubble-swarm-column\/","title":{"rendered":"Bubble-swarm column"},"content":{"rendered":"\n<p class=\"is-style-eyebrow wp-block-paragraph\">Small scale \u00b7 Work package b and c<\/p>\n\n\n\n<div class=\"wp-block-group facility-flow\"><div class=\"wp-block-group__inner-container is-layout-flow wp-block-group-is-layout-flow\">\n<figure class=\"wp-block-image size-full rig-drawing\"><img loading=\"lazy\" decoding=\"async\" width=\"186\" height=\"810\" src=\"https:\/\/www.auriga.polimi.it\/wp-content\/uploads\/2026\/09\/rig-bubble-swarm.png\" alt=\"CAD elevation of the rectangular bubble-swarm column\" class=\"wp-image-343\" srcset=\"https:\/\/www.auriga.polimi.it\/wp-content\/uploads\/2026\/09\/rig-bubble-swarm.png 186w, https:\/\/www.auriga.polimi.it\/wp-content\/uploads\/2026\/09\/rig-bubble-swarm-69x300.png 69w\" sizes=\"auto, (max-width: 186px) 100vw, 186px\" \/><\/figure>\n\n\n\n<p class=\"is-style-lede wp-block-paragraph\">The Bubble Swarm Rig is a rectangular bubble column made of transparent plexiglass (150 \u00d7 40 mm cross-section, 1 m high). It supports the study of bubble swarms and their column-scale behaviour, as part of our goal of understanding the multiscale connection between small and large scales in multiphase flows.<\/p>\n\n\n\n<p class=\"is-style-prose wp-block-paragraph\">The column is filled with the liquid under study to a height of 63 cm, an aspect ratio of 10 with respect to its hydraulic diameter of 6.3 cm. Bi-distilled water is the baseline for comparison and the base for preparing the ionic liquid mixtures, all of which are studied. Compressed air is regulated by a pressure reducer and metered by two rotameters (0\u2013500 and 0\u20131000 nl\/h, \u00b12% full scale), which set the superficial gas velocity. It enters a gas chamber at the base and is distributed through one of three interchangeable perforated plates with a triangular hole layout: \u00d80.5 mm (97 holes), \u00d81.0 mm (97 holes) and \u00d81.5 mm (43 holes).<\/p>\n\n\n\n<p class=\"is-style-prose wp-block-paragraph\"><strong>Continuous phase.<\/strong> Liquid velocity fields are measured with Particle Shadow Velocimetry (PSV). Volumetric LED backlighting and a shallow depth of field give sharp tracer-particle shadows without the lateral bubble shadows and light scattering that limit conventional PIV in bubbly flows. From the velocity fields we derive vorticity, strain and turbulence parameters. Images are recorded with a Phantom Miro C321 high-speed camera.<\/p>\n\n\n\n<p class=\"is-style-prose wp-block-paragraph\"><strong>Dispersed phase.<\/strong> AI-based detection identifies individual bubbles even when their projections overlap, giving bubble size distributions and shapes. A deep-learning, graph-based tracker follows the bubbles through occlusions over long time spans, giving bubble velocities and trajectories.<\/p>\n\n\n\n<p class=\"is-style-prose wp-block-paragraph\"><strong>Local and global measurements.<\/strong> Optical Doppler probes on the column give local gas holdup, bubble size distribution and bubble velocity. Pressure transducers give the global gas holdup, which, analysed within the flow-regime framework developed by Besagni (2021), is used to identify flow regimes and their transitions.<\/p>\n\n\n\n<p class=\"is-style-prose wp-block-paragraph\"><strong>Computing.<\/strong> The image-analysis pipeline of the experimental data runs on an NVIDIA H200 GPU, which turns the recordings into bubble statistics for the whole swarm.<\/p>\n<\/div><\/div>\n\n\n\n<p class=\"is-style-eyebrow facility-figures-label wp-block-paragraph\">Measurement set-up<\/p>\n\n\n\n<div class=\"wp-block-group facility-figures is-single\"><div class=\"wp-block-group__inner-container is-layout-flow wp-block-group-is-layout-flow\">\n<figure class=\"wp-block-image size-full fig-diagram\"><a href=\"https:\/\/www.auriga.polimi.it\/wp-content\/uploads\/2026\/09\/bubble-swarm-rig-diagram.png\"><img loading=\"lazy\" decoding=\"async\" width=\"2560\" height=\"1297\" src=\"https:\/\/www.auriga.polimi.it\/wp-content\/uploads\/2026\/09\/bubble-swarm-rig-diagram-scaled.png\" alt=\"Diagram of the bubble-swarm rig: air supply, pressure reducer and two rotameters feeding the gas chamber, the column with optical Doppler probes and pressure transducers, the imaging set-up seen from above, and what each technique measures\" class=\"wp-image-500\" srcset=\"https:\/\/www.auriga.polimi.it\/wp-content\/uploads\/2026\/09\/bubble-swarm-rig-diagram-scaled.png 2560w, https:\/\/www.auriga.polimi.it\/wp-content\/uploads\/2026\/09\/bubble-swarm-rig-diagram-300x152.png 300w, https:\/\/www.auriga.polimi.it\/wp-content\/uploads\/2026\/09\/bubble-swarm-rig-diagram-1024x519.png 1024w, https:\/\/www.auriga.polimi.it\/wp-content\/uploads\/2026\/09\/bubble-swarm-rig-diagram-768x389.png 768w, https:\/\/www.auriga.polimi.it\/wp-content\/uploads\/2026\/09\/bubble-swarm-rig-diagram-1536x778.png 1536w, https:\/\/www.auriga.polimi.it\/wp-content\/uploads\/2026\/09\/bubble-swarm-rig-diagram-2048x1038.png 2048w\" sizes=\"auto, (max-width: 2560px) 100vw, 2560px\" \/><\/a><figcaption class=\"wp-element-caption\">Open the diagram at full size<\/figcaption><\/figure>\n<\/div><\/div>\n\n\n\n<nav class=\"facility-nav\" aria-label=\"Other facilities\"><p class=\"is-style-eyebrow\">Other facilities<\/p><ul><li><a href=\"https:\/\/www.auriga.polimi.it\/?page_id=477\">Single-bubble column<\/a><\/li><li><a href=\"https:\/\/www.auriga.polimi.it\/?page_id=479\">Circular bubble-swarm column<\/a><\/li><li><a href=\"https:\/\/www.auriga.polimi.it\/?page_id=480\">Coalescence cell<\/a><\/li><li><a href=\"https:\/\/www.auriga.polimi.it\/?page_id=481\">CFD-grade column<\/a><\/li><li><a href=\"https:\/\/www.auriga.polimi.it\/?page_id=482\">Mass-transfer column<\/a><\/li><li><a href=\"https:\/\/www.auriga.polimi.it\/?page_id=499\">Large-diameter bubble column<\/a><\/li><\/ul><\/nav>\n\n\n\n<p class=\"is-style-back wp-block-paragraph\"><a href=\"https:\/\/www.auriga.polimi.it\/?page_id=13\">\u2190 Back to Lab<\/a><\/p>\n\n","protected":false},"excerpt":{"rendered":"<p>Small scale \u00b7 Work package b and c The Bubble Swarm Rig is a rectangular bubble column made of transparent plexiglass (150 \u00d7 40 mm cross-section, 1 m high). It supports the study of bubble swarms and their column-scale behaviour, as part of our goal of understanding the multiscale connection between small and large scales [&hellip;]<\/p>\n","protected":false},"author":6,"featured_media":0,"parent":13,"menu_order":2,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_monsterinsights_skip_tracking":false,"footnotes":""},"class_list":["post-478","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.auriga.polimi.it\/index.php\/wp-json\/wp\/v2\/pages\/478","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.auriga.polimi.it\/index.php\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.auriga.polimi.it\/index.php\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.auriga.polimi.it\/index.php\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/www.auriga.polimi.it\/index.php\/wp-json\/wp\/v2\/comments?post=478"}],"version-history":[{"count":0,"href":"https:\/\/www.auriga.polimi.it\/index.php\/wp-json\/wp\/v2\/pages\/478\/revisions"}],"up":[{"embeddable":true,"href":"https:\/\/www.auriga.polimi.it\/index.php\/wp-json\/wp\/v2\/pages\/13"}],"wp:attachment":[{"href":"https:\/\/www.auriga.polimi.it\/index.php\/wp-json\/wp\/v2\/media?parent=478"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}