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@PHDTHESIS{Ramaswamy:978281,
      author       = {Ramaswamy, Deepak Prem},
      othercontributors = {Schreyer, Anne-Marie and Schröder, Wolfgang and Sandham,
                          Neil},
      title        = {{C}ontrol of shock-induced flow separation with {A}ir-{J}et
                      vortex generators},
      school       = {Rheinisch-Westfälische Technische Hochschule Aachen},
      type         = {Dissertation},
      address      = {Aachen},
      publisher    = {RWTH Aachen University},
      reportid     = {RWTH-2024-01189},
      pages        = {1 Online-Ressource : Illustrationen},
      year         = {2023},
      note         = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
                      University 2024; Dissertation, Rheinisch-Westfälische
                      Technische Hochschule Aachen, 2023},
      abstract     = {Shock-wave/boundary-layer interactions (SWBLIs) are complex
                      flowfields commonly encountered in many high-speed aerospace
                      applications. A strong shock wave imposes a large adverse
                      pressure gradient and can lead to large-scale flow
                      separation. The separated flow and the separation-inducing
                      shock are highly unsteady, causing fluctuating pressure and
                      thermal loads on the surface, inlet instabilities, et
                      cetera; they are generally detrimental to the safe and
                      reliable operation of the vehicle. Hence proper control of
                      the flow is essential. In this thesis, separation control
                      with air-jet vortex generators (AJVGs) is experimentally
                      investigated. Various configurations of a single row of
                      spanwise-inclined AJVGs at 45° are used to control a
                      fully-separated 24° compression-ramp interaction. The
                      results show clear evidence of streamwise vortices induced
                      by the injected jets. Consequently, the 2D separation line
                      of the baseline case is now corrugated. Effectively
                      configured AJVGs can reduce separation length by nearly
                      $25\%,$ the recirculation region area by as much as ~
                      $57\%,$ and alleviate turbulence amplification across the
                      SWBLI. However, these effects strongly depend on various
                      AJVG control parameters, amongst them are jet-to-jet
                      spacing, injection pressure, orifice shape, etc.
                      Investigations of jet/jet spacing show that the jet-induced
                      streamwise vortices incite different control effects based
                      on the degree of interaction between adjacent vortices;
                      AJVGs with intermediate spacing display the most favourable
                      control effects due to the formation of stable, interacting
                      and streamwise-elongated coherent vortical structures
                      downstream of the jet array. A similar mechanism occurs when
                      varying the air-jet injection pressure, where intermediate
                      injection pressures show the best control effectiveness,
                      while both very large and very small injection pressures are
                      ineffective. Furthermore, the results highlight a strong
                      interplay between jet spacing and injection pressure in
                      defining the flow control effectiveness of AJVGs. A more
                      favourable control effect can also be brought about by using
                      non-circular AJVGs, and in-particular, elliptical AJVGs.
                      Measurements of AJVGs with elliptical orifices reveal their
                      improved control effectiveness due to better flow
                      entrainment and higher turbulent mixing, compared to
                      equivalent circular AJVGs. This is attributed to stronger
                      streamwise vortices that penetrate, on average, $25\%$
                      farther into the boundary layer. For all AJVG-controlled
                      cases, the separation bubble and shock exhibit the
                      characteristic low-frequency unsteadiness observed for the
                      baseline case. However, the dynamics of unsteadiness remain
                      largely unaltered by AJVGs. Conditional analysis of the PIV
                      results show that the separated shear-layer dynamics and the
                      separation-bubble motion are dominant, despite the
                      introduced coherent structures and the modification of the
                      incoming boundary layer due to jet-array injection.},
      cin          = {415110},
      ddc          = {620},
      cid          = {$I:(DE-82)415110_20140620$},
      pnm          = {DFG project 326485414 - Ablösebeeinflussung mit
                      Luftstrahl-Wirbelgeneratoren-Arrays in transsonischen und
                      supersonischen Strömungen (326485414)},
      pid          = {G:(GEPRIS)326485414},
      typ          = {PUB:(DE-HGF)11},
      doi          = {10.18154/RWTH-2024-01189},
      url          = {https://publications.rwth-aachen.de/record/978281},
}