On the Necessity of Species-specific Internal Energy Resolution in Hypersonic Aerothermoelasticity

On the Necessity of Species-specific Internal Energy Resolution in Hypersonic Aerothermoelasticity | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article On the Necessity of Species-specific Internal Energy Resolution in Hypersonic Aerothermoelasticity Sai Siddharth S This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6888696/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Hypersonic flight yields extreme temperatures that drive high-temperature air into complex chemical and thermal processes. Using NASA’s Chemical Equilibrium with Applications (CEA) code for a five-species air model (N2, O2, NO, N, O), we first assume equilibrium to characterize gas behavior at hypersonic conditions. Notably, different species respond very differently, for example, at ∼5000 K and 1 atm, oxygen is almost fully dissociated while nitrogen remains ∼99% intact, indicating essentially uncoupled behavior[1]. In general, translational and rotational modes equilibrate much faster than internal energy excitation or chemical reactions, which relax on much longer timescales[2] . Conventional CFD often simplifies such flows by assuming instantaneous equilibration (effectively an infinite Damköhler number), so that the gas composition adjusts immediately to flow changes[3] . However, in a hypersonic aeroelastic regime, where vehicle structures can dynamically interact with unsteady aerodynamic loads, these differing relaxation times become critical. A lag in each gas species or energy mode reaching equilibrium means the flow cannot respond uniformly to rapid structural motions, introducing phase lags and nonlinear coupling. Such thermochemical nonequilibrium effects can induce unexpected, highly nonlinear behavior in aeroelastic responses, potentially destabilizing the structure or leading to catastrophic failures if ignored. Our findings highlight that relaxation times, rooted in molecular energy transition kinetics, must be accounted for in hypersonic aeroelastic modeling. Capturing these effects may require high-fidelity models (informed by quantum-level energy state considerations[2]) beyond the standard equilibrium approach. Ultimately, this work underlines the necessity of incorporating species-specific and mode-specific relaxation processes to reliably predict hypersonic aerothermoelastic phenomena. Aeronautics and Astronautics Hypersonics Quantum Chemistry Hard-sphere mechanics Full Text Additional Declarations The authors declare no competing interests. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6888696","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":470948015,"identity":"bc208724-ec6b-4d3a-a491-c4f4bc937309","order_by":0,"name":"Sai Siddharth S","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABHUlEQVRIiWNgGAWjYFACxgaGBDbmBCCLjeEDSOAAQs6AgBZmNsYZIEUHwEL4tIAAVAszDzFa5NsPN394UGadxz/7/LHHNn/+JPYd7z3+gPGHnRwDe/M2CSxaDM4ktkkknEsvljiXzG6c22aQOPPMuUSgLcnGDDzHyrBqYUhsA6LDiQ1nmNmkcxsMEjfcyDEEajmQ2CCRY4ZNi3z/w+YPIC3zQVos/gC13H8D1lLfIP8GqxaGG0DTQFo2gLQwsIFs4QFrSWCQ4MGqxeDGQ7BfEjeeYTaT7G0zNp55JsdwRkJasmEbT1qxBVaHpT/++KPMOnHeGcZnEj/+yMn2HT9j8OGDjZ08P/vhjTewOQw7SGAAJYZRMApGwSgYBeQCAEscaizi9xvpAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0009-0004-4150-2821","institution":"Thiagarajar College of Engineering","correspondingAuthor":true,"prefix":"","firstName":"Sai","middleName":"Siddharth","lastName":"S","suffix":""}],"badges":[],"createdAt":"2025-06-13 13:38:14","currentVersionCode":1,"declarations":{"humanSubjects":false,"vertebrateSubjects":false,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":false,"humanSubjectConsent":false,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":false},"doi":"10.21203/rs.3.rs-6888696/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6888696/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":84662429,"identity":"9f1be4bf-48ed-4759-8a93-1003d47fd699","added_by":"auto","created_at":"2025-06-16 04:59:06","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":311347,"visible":true,"origin":"","legend":"","description":"","filename":"HypersonicAerothermoelasticity.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6888696/v1_covered_e3dc9044-d0fa-4c8a-91e3-ae6cd407b194.pdf"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003eOn the Necessity of Species-specific Internal Energy Resolution in Hypersonic Aerothermoelasticity\u003c/p\u003e","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"Thiagarajar College of Engineering","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Hypersonics, Quantum Chemistry, Hard-sphere mechanics","lastPublishedDoi":"10.21203/rs.3.rs-6888696/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6888696/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eHypersonic flight yields extreme temperatures that drive high-temperature air into complex chemical and thermal processes. 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