{"id":{"repo_id":"cambridge","oai_identifier":"oai:www.repository.cam.ac.uk:1810/287478"},"canonical_url":"https://search.dev.ndltd.org/etd/cambridge/oai:www.repository.cam.ac.uk:1810/287478","repository":{"repo_id":"cambridge","name":"Cambridge University","base_url":"https://api.repository.cam.ac.uk/server/oai/request"},"display":{"title":"The development of turbulent slender open-core annular jets","abstract":"The very first study of the development of the turbulent isothermal and incompressible air jet which issues at a constant velocity from a slender annular slot, circumnavigating an open core, into an otherwise quiescent and unbounded environment of the same density, is presented. The geometry of this source is defined by three diameters: the outer diameter of the slot $D_o$; the inner diameter of the slot $D_i$; and the diameter of the (circular) open core $D_v$. `Slender' refers to a slot for which the inner and outer diameters are approximately equal, i.e. $D_i/D_o\\approx 1$. Our focus lies in understanding the development of the time-averaged flow with distance downstream and the influence of the source geometry on the development of the jet. Given the absence of information on jets issuing from the sources of interest, the investigation follows an approach reminiscent of the classic investigations into round jets. That is, it begins with the development of a nozzle and experimental set-up which are suitable for studying the slender open-core annular jet. In addition to the experimental measurements, a complementary mathematical model was developed to describe the unique near-field behaviour of the open-core jet. Measurements were acquired using flow visualisation and Particle Image Velocimetry. On examining the streamwise development of the flow, the slender almost fully open-core jet was delineated into four key regions and the characteristic scalings identified. The regions were as follows: a bounded induced-flow region; a near-source planar-jet region; a transitional region; and a far-field round-jet region. Fluid induced through the open core of the nozzle and subsequently entrained into the jet significantly enhanced the near-field dilution of the jet. Following on from this, the influence of the diameter ratio $D_i/D_o$ and ventilation ratio $D_v/D_i$ on jet coalescence was examined. Over the range of diameter ratios examined ($0.845 \\leq D_i/D_o\\leq 0.981$), experimental measurements and the predictions from mathematical modelling indicated that $D_i/D_o$ significantly influenced the volume flux induced through the core while the coalescing behaviour of the jet and the far-field region remained largely unchanged. Over the range of ventilation ratios examined ($0 \\leq D_v/D_i\\leq 0.90$), experimental measurements demonstrated that $D_v/D_i$ controlled the restriction experienced by fluid induced through the open core and significantly influenced the far-field behaviour of the jet. Our findings suggest that jet of interest is then uniquely characterised by the momentum flux $M_0$, the diameter ratio $D_i/D_o$, and the ventilation ratio $D_v/D_i$.","abstract_html":"The very first study of the development of the turbulent isothermal and incompressible air jet which issues at a constant velocity from a slender annular slot, circumnavigating an open core, into an otherwise quiescent and unbounded environment of the same density, is presented. The geometry of this source is defined by three diameters: the outer diameter of the slot <span class=\"etd-inline-math\">D<sub>o</sub></span>; the inner diameter of the slot <span class=\"etd-inline-math\">D<sub>i</sub></span>; and the diameter of the (circular) open core <span class=\"etd-inline-math\">D<sub>v</sub></span>. `Slender&#x27; refers to a slot for which the inner and outer diameters are approximately equal, i.e. <span class=\"etd-inline-math\">D<sub>i</sub>/D<sub>o</sub>\\approx 1</span>. Our focus lies in understanding the development of the time-averaged flow with distance downstream and the influence of the source geometry on the development of the jet. Given the absence of information on jets issuing from the sources of interest, the investigation follows an approach reminiscent of the classic investigations into round jets. That is, it begins with the development of a nozzle and experimental set-up which are suitable for studying the slender open-core annular jet. In addition to the experimental measurements, a complementary mathematical model was developed to describe the unique near-field behaviour of the open-core jet. Measurements were acquired using flow visualisation and Particle Image Velocimetry. On examining the streamwise development of the flow, the slender almost fully open-core jet was delineated into four key regions and the characteristic scalings identified. The regions were as follows: a bounded induced-flow region; a near-source planar-jet region; a transitional region; and a far-field round-jet region. Fluid induced through the open core of the nozzle and subsequently entrained into the jet significantly enhanced the near-field dilution of the jet. Following on from this, the influence of the diameter ratio <span class=\"etd-inline-math\">D<sub>i</sub>/D<sub>o</sub></span> and ventilation ratio <span class=\"etd-inline-math\">D<sub>v</sub>/D<sub>i</sub></span> on jet coalescence was examined. Over the range of diameter ratios examined (<span class=\"etd-inline-math\">0.845 \\leq D<sub>i</sub>/D<sub>o</sub>\\leq 0.981</span>), experimental measurements and the predictions from mathematical modelling indicated that <span class=\"etd-inline-math\">D<sub>i</sub>/D<sub>o</sub></span> significantly influenced the volume flux induced through the core while the coalescing behaviour of the jet and the far-field region remained largely unchanged. Over the range of ventilation ratios examined (<span class=\"etd-inline-math\">0 \\leq D<sub>v</sub>/D<sub>i</sub>\\leq 0.90</span>), experimental measurements demonstrated that <span class=\"etd-inline-math\">D<sub>v</sub>/D<sub>i</sub></span> controlled the restriction experienced by fluid induced through the open core and significantly influenced the far-field behaviour of the jet. Our findings suggest that jet of interest is then uniquely characterised by the momentum flux <span class=\"etd-inline-math\">M<sub>0</sub></span>, the diameter ratio <span class=\"etd-inline-math\">D<sub>i</sub>/D<sub>o</sub></span>, and the ventilation ratio <span class=\"etd-inline-math\">D<sub>v</sub>/D<sub>i</sub></span>.","abstract_has_math":true,"creators":["Padhani, Shahid Anwar"],"institution":"University of Cambridge","degree_name":"Doctor of Philosophy (PhD)","degree_level":"Doctoral","degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Hunt, Gary R."],"committee_chairs":[],"committee_members":[],"year":2019,"date_issued":"2019-02-23","date_published":"2019-02-23","updated_at":"2026-07-22T22:24:10Z","subjects":["Jets","Annular Jets","Particle Image Velocimetry","Turbulent Mixing"],"languages":["en"],"rights":[],"rights_urls":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/6d060e49-16ce-47ac-9129-5770bbef1aef/download","https://www.rioxx.net/licenses/all-rights-reserved/"],"identifier_entries":[]},"links":{"outbound_url":"https://doi.org/10.17863/CAM.34783","outbound_label":"DOI","outbound_source":"dc:identifier.doi"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Hunt, Gary R."]},{"key":"dc:contributor.sponsor","label":"Sponsor","values":["EPSRC Industrial CASE award - Dyson Ltd."]},{"key":"dc:creator","label":"Author","values":["Padhani, Shahid Anwar"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.issued","label":"Date","values":["2019-02-23"]},{"key":"dc:publisher.institution","label":"Dc Publisher Institution","values":["University of Cambridge"]},{"key":"dc:relation.isreferencedby.uri","label":"Dc Relation Isreferencedby URI","values":["https://www.repository.cam.ac.uk/handle/1810/287478"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"dc:type.qualificationlevel","label":"Dc Type Qualificationlevel","values":["Doctoral"]},{"key":"dc:type.qualificationname","label":"Dc Type Qualificationname","values":["Doctor of Philosophy (PhD)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Jets","Annular Jets","Particle Image Velocimetry","Turbulent Mixing"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/6d060e49-16ce-47ac-9129-5770bbef1aef/download","https://www.rioxx.net/licenses/all-rights-reserved/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.doi","label":"DOI","values":["10.17863/CAM.34783"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/1ecd4f4a-7ed3-4077-89d7-a0be5be2b442/download"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["The very first study of the development of the turbulent isothermal and incompressible air jet which issues at a constant velocity from a slender annular slot, circumnavigating an open core, into an otherwise quiescent and unbounded environment of the same density, is presented. The geometry of this source is defined by three diameters: the outer diameter of the slot $D_o$; the inner diameter of the slot $D_i$; and the diameter of the (circular) open core $D_v$. `Slender' refers to a slot for which the inner and outer diameters are approximately equal, i.e. $D_i/D_o\\approx 1$. Our focus lies in understanding the development of the time-averaged flow with distance downstream and the influence of the source geometry on the development of the jet. Given the absence of information on jets issuing from the sources of interest, the investigation follows an approach reminiscent of the classic investigations into round jets. That is, it begins with the development of a nozzle and experimental set-up which are suitable for studying the slender open-core annular jet. In addition to the experimental measurements, a complementary mathematical model was developed to describe the unique near-field behaviour of the open-core jet. Measurements were acquired using flow visualisation and Particle Image Velocimetry. On examining the streamwise development of the flow, the slender almost fully open-core jet was delineated into four key regions and the characteristic scalings identified. The regions were as follows: a bounded induced-flow region; a near-source planar-jet region; a transitional region; and a far-field round-jet region. Fluid induced through the open core of the nozzle and subsequently entrained into the jet significantly enhanced the near-field dilution of the jet. Following on from this, the influence of the diameter ratio $D_i/D_o$ and ventilation ratio $D_v/D_i$ on jet coalescence was examined. Over the range of diameter ratios examined ($0.845 \\leq D_i/D_o\\leq 0.981$), experimental measurements and the predictions from mathematical modelling indicated that $D_i/D_o$ significantly influenced the volume flux induced through the core while the coalescing behaviour of the jet and the far-field region remained largely unchanged. Over the range of ventilation ratios examined ($0 \\leq D_v/D_i\\leq 0.90$), experimental measurements demonstrated that $D_v/D_i$ controlled the restriction experienced by fluid induced through the open core and significantly influenced the far-field behaviour of the jet. Our findings suggest that jet of interest is then uniquely characterised by the momentum flux $M_0$, the diameter ratio $D_i/D_o$, and the ventilation ratio $D_v/D_i$."]},{"key":"dc:format.checksum.md5","label":"Dc Format Checksum Md5","values":["3dcd029a83261e15ec6576571e42c29b","87eda9de84448d1f82354d60eee3eb5f"]},{"key":"dc:title","label":"Title","values":["The development of turbulent slender open-core annular jets"]}]}],"canonical_facts":{"dc:contributor.advisor":["Hunt, Gary R."],"dc:contributor.sponsor":["EPSRC Industrial CASE award - Dyson Ltd."],"dc:creator":["Padhani, Shahid Anwar"],"dc:date.issued":["2019-02-23"],"dc:description.abstract":["The very first study of the development of the turbulent isothermal and incompressible air jet which issues at a constant velocity from a slender annular slot, circumnavigating an open core, into an otherwise quiescent and unbounded environment of the same density, is presented. The geometry of this source is defined by three diameters: the outer diameter of the slot $D_o$; the inner diameter of the slot $D_i$; and the diameter of the (circular) open core $D_v$. `Slender' refers to a slot for which the inner and outer diameters are approximately equal, i.e. $D_i/D_o\\approx 1$. Our focus lies in understanding the development of the time-averaged flow with distance downstream and the influence of the source geometry on the development of the jet. Given the absence of information on jets issuing from the sources of interest, the investigation follows an approach reminiscent of the classic investigations into round jets. That is, it begins with the development of a nozzle and experimental set-up which are suitable for studying the slender open-core annular jet. In addition to the experimental measurements, a complementary mathematical model was developed to describe the unique near-field behaviour of the open-core jet. Measurements were acquired using flow visualisation and Particle Image Velocimetry. On examining the streamwise development of the flow, the slender almost fully open-core jet was delineated into four key regions and the characteristic scalings identified. The regions were as follows: a bounded induced-flow region; a near-source planar-jet region; a transitional region; and a far-field round-jet region. Fluid induced through the open core of the nozzle and subsequently entrained into the jet significantly enhanced the near-field dilution of the jet. Following on from this, the influence of the diameter ratio $D_i/D_o$ and ventilation ratio $D_v/D_i$ on jet coalescence was examined. Over the range of diameter ratios examined ($0.845 \\leq D_i/D_o\\leq 0.981$), experimental measurements and the predictions from mathematical modelling indicated that $D_i/D_o$ significantly influenced the volume flux induced through the core while the coalescing behaviour of the jet and the far-field region remained largely unchanged. Over the range of ventilation ratios examined ($0 \\leq D_v/D_i\\leq 0.90$), experimental measurements demonstrated that $D_v/D_i$ controlled the restriction experienced by fluid induced through the open core and significantly influenced the far-field behaviour of the jet. Our findings suggest that jet of interest is then uniquely characterised by the momentum flux $M_0$, the diameter ratio $D_i/D_o$, and the ventilation ratio $D_v/D_i$."],"dc:format.checksum.md5":["3dcd029a83261e15ec6576571e42c29b","87eda9de84448d1f82354d60eee3eb5f"],"dc:identifier.doi":["10.17863/CAM.34783"],"dc:identifier.uri":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/1ecd4f4a-7ed3-4077-89d7-a0be5be2b442/download"],"dc:language":["en"],"dc:publisher.institution":["University of Cambridge"],"dc:relation.isreferencedby.uri":["https://www.repository.cam.ac.uk/handle/1810/287478"],"dc:rights":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/6d060e49-16ce-47ac-9129-5770bbef1aef/download","https://www.rioxx.net/licenses/all-rights-reserved/"],"dc:subject":["Jets","Annular Jets","Particle Image Velocimetry","Turbulent Mixing"],"dc:title":["The development of turbulent slender open-core annular jets"],"dc:type":["Thesis"],"dc:type.qualificationlevel":["Doctoral"],"dc:type.qualificationname":["Doctor of Philosophy (PhD)"]},"updated_at":"2026-07-22T22:24:10Z"}