{"id":{"repo_id":"cambridge","oai_identifier":"oai:www.repository.cam.ac.uk:1810/381857"},"canonical_url":"https://search.dev.ndltd.org/etd/cambridge/oai:www.repository.cam.ac.uk:1810/381857","repository":{"repo_id":"cambridge","name":"Cambridge University","base_url":"https://api.repository.cam.ac.uk/server/oai/request"},"display":{"title":"The relationship between surface geometry and transonic intake performance during off-design climb","abstract":"The design of slimmer, shorter gas-turbine nacelles supports lower emissions in civil aviation. However, these designs often have a stronger shock on the windward front-lip of the intake during off-design climb, producing a severe shock wave--boundary-layer interaction (SBLI) that greatly increases the ingested incompressible boundary-layer displacement thickness, \\(\\delta_i^*\\), and shape factor, \\(H_i\\). Simulating these conditions without validation is challenging, and poor optical access has inhibited observations of how intake surface geometry influences the SBLI. This thesis investigates the relationships between intake surface geometry, the impact of the transonic SBLI, and intake performance during off-design climb with a quasi-two-dimensional (Q2D) experiment that represents flow over the lower-lip of a civil intake. Design of Experiments was applied to create a \\(2^4\\) factorial investigation of highlight curvature, surface-curvature distribution, diffuser shape, and mass flow rate. The facility supports high-speed schlieren imaging, pressure-sensitive paint, laser Doppler velocimetry and oil-flow visualisation. A Q2D transonic SBLI formed on the intake front-lip in each test-case, and the test-cases have shock strengths in the range of \\(M_s = 1.14 - 1.64\\) and an order of magnitude range in \\(\\delta_i^*\\). Importantly, this shows that intake surface geometry influences performance as significantly as other studies conclude for changes in overall intake geometry. Intakes with large highlight curvature had minimal \\(\\delta_i^*\\) and little sensitivity to changes in mass flow rate or the surface-curvature distribution, which demonstrates that highlight curvature is the key geometric parameter in determining intake performance at off-design climb. Once the front-lip shape is optimised to a small nose-radius (equivalent to large highlight curvature) and generally thin profile, the diffuser shape becomes an important consideration. An \"s-shaped\" diffuser with a large peak surface angle promotes minimal \\(\\delta_i^*\\). Intake performance generally remains favourable provided that \\(M_s<1.45\\), which corresponds to the onset of well-established separation, and worsens non-linearly as shock strength exceeds this threshold. Further analysis identified two key parameters that together characterise the impact of the SBLI on intake performance, \\(APG\\), which is the pressure gradient between the end of the shock jump and the measurement of \\(\\delta_i^*\\), and a newly-defined parameter, \\(L^*\\), which is similar to the supersonic length-scale in an attached transonic SBLI. Plotting \\(APG\\) and \\(L^*\\), or \\(APG\\) and \\(\\delta^*_i\\), collapses the test-cases onto linear trends, where intake performance scales continuously between the smallest and largest values of \\(L^*\\). The intake performs with minimal \\(\\delta^*_i\\) when the SBLI is effectively-separated, \\(M_s=1.32\\), because these interactions have minimum \\(L^*\\), while weaker or stronger interactions worsen this performance. This analysis is supported by validated multivariate response surfaces that model the relationships between intake surface geometry, the SBLI and intake performance. Overall, the models and conclusions in this thesis guide the design of an intake surface that maintains fan-intake compatibility, which supports the development of shorter and slimmer nacelles. Further work should consider other off-design conditions, such as high-power crosswind.","abstract_html":"The design of slimmer, shorter gas-turbine nacelles supports lower emissions in civil aviation. However, these designs often have a stronger shock on the windward front-lip of the intake during off-design climb, producing a severe shock wave--boundary-layer interaction (SBLI) that greatly increases the ingested incompressible boundary-layer displacement thickness, <span class=\"etd-inline-math\">&delta;<sub>i</sub><sup>*</sup></span>, and shape factor, <span class=\"etd-inline-math\">H<sub>i</sub></span>. Simulating these conditions without validation is challenging, and poor optical access has inhibited observations of how intake surface geometry influences the SBLI. This thesis investigates the relationships between intake surface geometry, the impact of the transonic SBLI, and intake performance during off-design climb with a quasi-two-dimensional (Q2D) experiment that represents flow over the lower-lip of a civil intake. Design of Experiments was applied to create a <span class=\"etd-inline-math\">2<sup>4</sup></span> factorial investigation of highlight curvature, surface-curvature distribution, diffuser shape, and mass flow rate. The facility supports high-speed schlieren imaging, pressure-sensitive paint, laser Doppler velocimetry and oil-flow visualisation. A Q2D transonic SBLI formed on the intake front-lip in each test-case, and the test-cases have shock strengths in the range of <span class=\"etd-inline-math\">M<sub>s</sub> = 1.14 - 1.64</span> and an order of magnitude range in <span class=\"etd-inline-math\">&delta;<sub>i</sub><sup>*</sup></span>. Importantly, this shows that intake surface geometry influences performance as significantly as other studies conclude for changes in overall intake geometry. Intakes with large highlight curvature had minimal <span class=\"etd-inline-math\">&delta;<sub>i</sub><sup>*</sup></span> and little sensitivity to changes in mass flow rate or the surface-curvature distribution, which demonstrates that highlight curvature is the key geometric parameter in determining intake performance at off-design climb. Once the front-lip shape is optimised to a small nose-radius (equivalent to large highlight curvature) and generally thin profile, the diffuser shape becomes an important consideration. An &quot;s-shaped&quot; diffuser with a large peak surface angle promotes minimal <span class=\"etd-inline-math\">&delta;<sub>i</sub><sup>*</sup></span>. Intake performance generally remains favourable provided that <span class=\"etd-inline-math\">M<sub>s</sub>&lt;1.45</span>, which corresponds to the onset of well-established separation, and worsens non-linearly as shock strength exceeds this threshold. Further analysis identified two key parameters that together characterise the impact of the SBLI on intake performance, \\(APG\\), which is the pressure gradient between the end of the shock jump and the measurement of <span class=\"etd-inline-math\">&delta;<sub>i</sub><sup>*</sup></span>, and a newly-defined parameter, <span class=\"etd-inline-math\">L<sup>*</sup></span>, which is similar to the supersonic length-scale in an attached transonic SBLI. Plotting \\(APG\\) and <span class=\"etd-inline-math\">L<sup>*</sup></span>, or \\(APG\\) and <span class=\"etd-inline-math\">&delta;<sup>*</sup><sub>i</sub></span>, collapses the test-cases onto linear trends, where intake performance scales continuously between the smallest and largest values of <span class=\"etd-inline-math\">L<sup>*</sup></span>. The intake performs with minimal <span class=\"etd-inline-math\">&delta;<sup>*</sup><sub>i</sub></span> when the SBLI is effectively-separated, <span class=\"etd-inline-math\">M<sub>s</sub>=1.32</span>, because these interactions have minimum <span class=\"etd-inline-math\">L<sup>*</sup></span>, while weaker or stronger interactions worsen this performance. This analysis is supported by validated multivariate response surfaces that model the relationships between intake surface geometry, the SBLI and intake performance. Overall, the models and conclusions in this thesis guide the design of an intake surface that maintains fan-intake compatibility, which supports the development of shorter and slimmer nacelles. Further work should consider other off-design conditions, such as high-power crosswind.","abstract_has_math":true,"creators":["O'Pray, Connor"],"institution":"University of Cambridge","degree_name":"Doctor of Philosophy (PhD)","degree_level":"Doctoral","degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Babinsky, Holger"],"committee_chairs":[],"committee_members":[],"year":2024,"date_issued":"2024-09-26","date_published":"2024-09-26","updated_at":"2026-07-22T22:24:13Z","subjects":["SBLI","shock wave--boundary-layer interaction","Intake performance","Gas turbine aerodynamics","Experimental","Design of Experiments","Schlieren","Pressure sensitive paint","Laser Doppler velocimetry","Oil flow visualisation","Transonic","Boundary-layer displacement thickness","Highlight curvature","Leading-edge radius","Diffuser","Intake design"],"languages":["eng"],"rights":[],"rights_urls":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/5acf7ff2-2fc0-47b8-a566-ffe5ceecc27b/download","http://purl.org/NET/rdflicense/allrightsreserved"],"identifier_entries":[{"key":"dc:creator.authoridentifier","label":"Author Identifier","values":["0000000167482460"],"render_values":[{"text":"0000-0001-6748-2460","href":"https://orcid.org/0000-0001-6748-2460","code":true}]}]},"links":{"outbound_url":"https://doi.org/10.17863/CAM.116901","outbound_label":"DOI","outbound_source":"dc:identifier.doi"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Babinsky, Holger"]},{"key":"dc:contributor.sponsor","label":"Sponsor","values":["UKRI EPSRC; Rolls-Royce."]},{"key":"dc:creator","label":"Author","values":["O'Pray, Connor"]},{"key":"dc:creator.authoridentifier","label":"Author Identifier","values":["0000000167482460"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.issued","label":"Date","values":["2024-09-26"]},{"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/1810/381857"]},{"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":["SBLI","shock wave--boundary-layer interaction","Intake performance","Gas turbine aerodynamics","Experimental","Design of Experiments","Schlieren","Pressure sensitive paint","Laser Doppler velocimetry","Oil flow visualisation","Transonic","Boundary-layer displacement thickness","Highlight curvature","Leading-edge radius","Diffuser","Intake design"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/5acf7ff2-2fc0-47b8-a566-ffe5ceecc27b/download","http://purl.org/NET/rdflicense/allrightsreserved"]},{"key":"dc:rights.embargodate","label":"Dc Rights Embargodate","values":["2026-03-25"]},{"key":"dc:rights.embargotype","label":"Dc Rights Embargotype","values":["embargo"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.doi","label":"DOI","values":["https://doi.org/10.17863/CAM.116901"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/94c4adb7-f875-4e38-9c4f-126589477fdb/download"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["The design of slimmer, shorter gas-turbine nacelles supports lower emissions in civil aviation. However, these designs often have a stronger shock on the windward front-lip of the intake during off-design climb, producing a severe shock wave--boundary-layer interaction (SBLI) that greatly increases the ingested incompressible boundary-layer displacement thickness, \\(\\delta_i^*\\), and shape factor, \\(H_i\\). Simulating these conditions without validation is challenging, and poor optical access has inhibited observations of how intake surface geometry influences the SBLI. This thesis investigates the relationships between intake surface geometry, the impact of the transonic SBLI, and intake performance during off-design climb with a quasi-two-dimensional (Q2D) experiment that represents flow over the lower-lip of a civil intake. Design of Experiments was applied to create a \\(2^4\\) factorial investigation of highlight curvature, surface-curvature distribution, diffuser shape, and mass flow rate. The facility supports high-speed schlieren imaging, pressure-sensitive paint, laser Doppler velocimetry and oil-flow visualisation. A Q2D transonic SBLI formed on the intake front-lip in each test-case, and the test-cases have shock strengths in the range of \\(M_s = 1.14 - 1.64\\) and an order of magnitude range in \\(\\delta_i^*\\). Importantly, this shows that intake surface geometry influences performance as significantly as other studies conclude for changes in overall intake geometry. Intakes with large highlight curvature had minimal \\(\\delta_i^*\\) and little sensitivity to changes in mass flow rate or the surface-curvature distribution, which demonstrates that highlight curvature is the key geometric parameter in determining intake performance at off-design climb. Once the front-lip shape is optimised to a small nose-radius (equivalent to large highlight curvature) and generally thin profile, the diffuser shape becomes an important consideration. An \"s-shaped\" diffuser with a large peak surface angle promotes minimal \\(\\delta_i^*\\). Intake performance generally remains favourable provided that \\(M_s<1.45\\), which corresponds to the onset of well-established separation, and worsens non-linearly as shock strength exceeds this threshold. Further analysis identified two key parameters that together characterise the impact of the SBLI on intake performance, \\(APG\\), which is the pressure gradient between the end of the shock jump and the measurement of \\(\\delta_i^*\\), and a newly-defined parameter, \\(L^*\\), which is similar to the supersonic length-scale in an attached transonic SBLI. Plotting \\(APG\\) and \\(L^*\\), or \\(APG\\) and \\(\\delta^*_i\\), collapses the test-cases onto linear trends, where intake performance scales continuously between the smallest and largest values of \\(L^*\\). The intake performs with minimal \\(\\delta^*_i\\) when the SBLI is effectively-separated, \\(M_s=1.32\\), because these interactions have minimum \\(L^*\\), while weaker or stronger interactions worsen this performance. This analysis is supported by validated multivariate response surfaces that model the relationships between intake surface geometry, the SBLI and intake performance. Overall, the models and conclusions in this thesis guide the design of an intake surface that maintains fan-intake compatibility, which supports the development of shorter and slimmer nacelles. Further work should consider other off-design conditions, such as high-power crosswind."]},{"key":"dc:format.checksum.md5","label":"Dc Format Checksum Md5","values":["e4ab72151b4120a2ec5cf04bebb7b186","87eda9de84448d1f82354d60eee3eb5f"]},{"key":"dc:title","label":"Title","values":["The relationship between surface geometry and transonic intake performance during off-design climb"]}]}],"canonical_facts":{"dc:contributor.advisor":["Babinsky, Holger"],"dc:contributor.sponsor":["UKRI EPSRC; Rolls-Royce."],"dc:creator":["O'Pray, Connor"],"dc:creator.authoridentifier":["0000000167482460"],"dc:date.issued":["2024-09-26"],"dc:description.abstract":["The design of slimmer, shorter gas-turbine nacelles supports lower emissions in civil aviation. However, these designs often have a stronger shock on the windward front-lip of the intake during off-design climb, producing a severe shock wave--boundary-layer interaction (SBLI) that greatly increases the ingested incompressible boundary-layer displacement thickness, \\(\\delta_i^*\\), and shape factor, \\(H_i\\). Simulating these conditions without validation is challenging, and poor optical access has inhibited observations of how intake surface geometry influences the SBLI. This thesis investigates the relationships between intake surface geometry, the impact of the transonic SBLI, and intake performance during off-design climb with a quasi-two-dimensional (Q2D) experiment that represents flow over the lower-lip of a civil intake. Design of Experiments was applied to create a \\(2^4\\) factorial investigation of highlight curvature, surface-curvature distribution, diffuser shape, and mass flow rate. The facility supports high-speed schlieren imaging, pressure-sensitive paint, laser Doppler velocimetry and oil-flow visualisation. A Q2D transonic SBLI formed on the intake front-lip in each test-case, and the test-cases have shock strengths in the range of \\(M_s = 1.14 - 1.64\\) and an order of magnitude range in \\(\\delta_i^*\\). Importantly, this shows that intake surface geometry influences performance as significantly as other studies conclude for changes in overall intake geometry. Intakes with large highlight curvature had minimal \\(\\delta_i^*\\) and little sensitivity to changes in mass flow rate or the surface-curvature distribution, which demonstrates that highlight curvature is the key geometric parameter in determining intake performance at off-design climb. Once the front-lip shape is optimised to a small nose-radius (equivalent to large highlight curvature) and generally thin profile, the diffuser shape becomes an important consideration. An \"s-shaped\" diffuser with a large peak surface angle promotes minimal \\(\\delta_i^*\\). Intake performance generally remains favourable provided that \\(M_s<1.45\\), which corresponds to the onset of well-established separation, and worsens non-linearly as shock strength exceeds this threshold. Further analysis identified two key parameters that together characterise the impact of the SBLI on intake performance, \\(APG\\), which is the pressure gradient between the end of the shock jump and the measurement of \\(\\delta_i^*\\), and a newly-defined parameter, \\(L^*\\), which is similar to the supersonic length-scale in an attached transonic SBLI. Plotting \\(APG\\) and \\(L^*\\), or \\(APG\\) and \\(\\delta^*_i\\), collapses the test-cases onto linear trends, where intake performance scales continuously between the smallest and largest values of \\(L^*\\). The intake performs with minimal \\(\\delta^*_i\\) when the SBLI is effectively-separated, \\(M_s=1.32\\), because these interactions have minimum \\(L^*\\), while weaker or stronger interactions worsen this performance. This analysis is supported by validated multivariate response surfaces that model the relationships between intake surface geometry, the SBLI and intake performance. Overall, the models and conclusions in this thesis guide the design of an intake surface that maintains fan-intake compatibility, which supports the development of shorter and slimmer nacelles. Further work should consider other off-design conditions, such as high-power crosswind."],"dc:format.checksum.md5":["e4ab72151b4120a2ec5cf04bebb7b186","87eda9de84448d1f82354d60eee3eb5f"],"dc:identifier.doi":["https://doi.org/10.17863/CAM.116901"],"dc:identifier.uri":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/94c4adb7-f875-4e38-9c4f-126589477fdb/download"],"dc:language":["eng"],"dc:publisher.institution":["University of Cambridge"],"dc:relation.isreferencedby.uri":["https://www.repository.cam.ac.uk/handle/1810/381857"],"dc:rights":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/5acf7ff2-2fc0-47b8-a566-ffe5ceecc27b/download","http://purl.org/NET/rdflicense/allrightsreserved"],"dc:rights.embargodate":["2026-03-25"],"dc:rights.embargotype":["embargo"],"dc:subject":["SBLI","shock wave--boundary-layer interaction","Intake performance","Gas turbine aerodynamics","Experimental","Design of Experiments","Schlieren","Pressure sensitive paint","Laser Doppler velocimetry","Oil flow visualisation","Transonic","Boundary-layer displacement thickness","Highlight curvature","Leading-edge radius","Diffuser","Intake design"],"dc:title":["The relationship between surface geometry and transonic intake performance during off-design climb"],"dc:type":["Thesis"],"dc:type.qualificationlevel":["Doctoral"],"dc:type.qualificationname":["Doctor of Philosophy (PhD)"]},"updated_at":"2026-07-22T22:24:13Z"}