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Time-resolved investigations of streamtraced inlet restart dynamics.

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Title: Time-resolved investigations of streamtraced inlet restart dynamics.
Authors: Johnson, Ethan C.1 (AUTHOR), Narayanaswamy, Venkateswaran1 (AUTHOR) vnaraya3@ncsu.edu
Source: Experiments in Fluids. Jan2026, Vol. 67 Issue 1, p1-17. 17p.
Subjects: Fluid dynamics, Inlets, Interference (Aerodynamics), Dynamic pressure, Mechanical shock
Abstract: Obtaining reliable restart of hypersonic inlets in the event of accidental unstart remains a key performance metric that constrains the operational boundary of powered hypersonic vehicles. The present work investigates the restart dynamics in a self-starting axisymmetric hypersonic Buseman inlet, which have a strong practical relevance in future platforms. The restart process was triggered by rapidly decreasing the aerodynamic blockage from a high-bandwidth counter injected jet, which allows the examination of the restart dynamics without being masked by the back pressure transience. Two-dimensional time-resolved pressure fields over inlet and isolator surfaces and time-resolved external shock field during the restart process are obtained at 10 kHz repetition rate. Both these measurements revealed a complex unstart shock motions during restart that include small amplitude relatively broadband oscillations prior to restart, a large amplitude periodic oscillation at the early restart phase, and subsequently followed by a dominant downstream shock motion. A complex flow structure within the external contraction portion of the inlet was discernable in the schlieren imagery with shear layer eddies being spilled out of the inlet. The pressure fields further evidenced a strong variation in the streamwise and azimuthal direction reinforcing the occurrence of flow spillage along both directions. Overall, the restart duration was determined to be approximately 11 ms, which is substantially greater than the unstart time scale of 8 ms obtained in the same inlet using the same back pressuring system. The critical process that extends the restart time is the periodic shock oscillations, which is termed as intermediate buzz in prior investigations, that pervade the first half of the restart process. The power spectral density of the unstart shock motions pointed to a shift in the mechanisms that drive the unstart shock motions during restart. [ABSTRACT FROM AUTHOR]
Copyright of Experiments in Fluids is the property of Springer Nature and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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DbLabel: Engineering Source
An: 190888689
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IllustrationInfo
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  Data: Time-resolved investigations of streamtraced inlet restart dynamics.
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  Data: <searchLink fieldCode="AR" term="%22Johnson%2C+Ethan+C%2E%22">Johnson, Ethan C.</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Narayanaswamy%2C+Venkateswaran%22">Narayanaswamy, Venkateswaran</searchLink><relatesTo>1</relatesTo> (AUTHOR)<i> vnaraya3@ncsu.edu</i>
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  Data: <searchLink fieldCode="JN" term="%22Experiments+in+Fluids%22">Experiments in Fluids</searchLink>. Jan2026, Vol. 67 Issue 1, p1-17. 17p.
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  Data: <searchLink fieldCode="DE" term="%22Fluid+dynamics%22">Fluid dynamics</searchLink><br /><searchLink fieldCode="DE" term="%22Inlets%22">Inlets</searchLink><br /><searchLink fieldCode="DE" term="%22Interference+%28Aerodynamics%29%22">Interference (Aerodynamics)</searchLink><br /><searchLink fieldCode="DE" term="%22Dynamic+pressure%22">Dynamic pressure</searchLink><br /><searchLink fieldCode="DE" term="%22Mechanical+shock%22">Mechanical shock</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: Obtaining reliable restart of hypersonic inlets in the event of accidental unstart remains a key performance metric that constrains the operational boundary of powered hypersonic vehicles. The present work investigates the restart dynamics in a self-starting axisymmetric hypersonic Buseman inlet, which have a strong practical relevance in future platforms. The restart process was triggered by rapidly decreasing the aerodynamic blockage from a high-bandwidth counter injected jet, which allows the examination of the restart dynamics without being masked by the back pressure transience. Two-dimensional time-resolved pressure fields over inlet and isolator surfaces and time-resolved external shock field during the restart process are obtained at 10 kHz repetition rate. Both these measurements revealed a complex unstart shock motions during restart that include small amplitude relatively broadband oscillations prior to restart, a large amplitude periodic oscillation at the early restart phase, and subsequently followed by a dominant downstream shock motion. A complex flow structure within the external contraction portion of the inlet was discernable in the schlieren imagery with shear layer eddies being spilled out of the inlet. The pressure fields further evidenced a strong variation in the streamwise and azimuthal direction reinforcing the occurrence of flow spillage along both directions. Overall, the restart duration was determined to be approximately 11 ms, which is substantially greater than the unstart time scale of 8 ms obtained in the same inlet using the same back pressuring system. The critical process that extends the restart time is the periodic shock oscillations, which is termed as intermediate buzz in prior investigations, that pervade the first half of the restart process. The power spectral density of the unstart shock motions pointed to a shift in the mechanisms that drive the unstart shock motions during restart. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Experiments in Fluids is the property of Springer Nature and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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        Value: 10.1007/s00348-025-04156-0
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      – Code: eng
        Text: English
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        PageCount: 17
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      – SubjectFull: Fluid dynamics
        Type: general
      – SubjectFull: Inlets
        Type: general
      – SubjectFull: Interference (Aerodynamics)
        Type: general
      – SubjectFull: Dynamic pressure
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      – SubjectFull: Mechanical shock
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      – TitleFull: Time-resolved investigations of streamtraced inlet restart dynamics.
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              Text: Jan2026
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              Y: 2026
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