Experiments in Fluids

, Volume 52, Issue 2, pp 273–287 | Cite as

Behaviour of a shock train under the influence of boundary-layer suction by a normal slot

  • A. Weiss
  • H. Olivier
Research Article


The interaction of a shock train with a normal suction slot is presented. It was found that when the pressure in the suction slot is smaller or equal to the static pressure of the incoming supersonic flow, the pressure gradient across the primary shock is sufficient to push some part of the near wall boundary layer through the suction slot. Due to the suction stabilized primary shock foot, the back pressure of the shock train can be increased until the shock train gradually changes into a single normal shock. During the experiments, the total pressure and therewith the Reynolds number of the flow were varied. The structure and pressure recovery within the shock train is analysed by means of Schlieren images and wall pressure measurements. Because the boundary layer is most important for the formation of a shock train, it has been measured by a Pitot probe. Additionally, computational fluid dynamics is used to investigate the shock boundary-layer interaction. Based on the experimental and numerical results, a simplified flow model is derived which explains the phenomenology of the transition of a shock train into a single shock and derives distinct criteria to maintain a suction enhanced normal shock. This flow model also yields the required suction mass flow in order to obtain a single normal shock in a viscous nozzle flow. Furthermore, it allows computation of the total pressure losses across a normal shock under the influence of boundary-layer suction.


Mach Number Normal Shock Total Pressure Loss Schlieren Image Nozzle Wall 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

List of symbols


Speed of sound (m/s)

\( A^{*} \)

Nozzle throat area (mm²)


Half width of the shock-wave reactor (mm)

\( h^{*} \)

Half height of the nozzle throat (mm)


Half duct height (mm)


Thickness of boundary-layer upstream of the suction slot (mm)


Duct height (mm)


Mach number upstream of the suction slot


Mach number downstream of the primary shock


Mach number downstream of reflected shocks at the nozzle centre line

\( \dot{m}_{\text{s}} /\dot{m}_{1} \)

Relative mass flow through suction system


Total pressure (bar)


Static pressure upstream of the shock (bar)


Static pressure downstream of the shock (bar)


Static pressure downstream of the suction slot (bar)


Static pressure in the suction cavity (bar)


Suction mass flow per span (kg/s m)


Specific gas constant (J/kg K)


Slot width (mm)


Total temperature (K)


Distance of suction slot from first nozzle throat (mm)

Greek symbols


Shock-wave angle (°)


Boundary-layer thickness (mm)

\( \delta^{*} \)

Boundary-layer displacement thickness (mm)


Boundary-layer momentum thickness for undisturbed flow (mm)


Deflection angle (°)


Isentropic exponent



The research reported in this paper was funded by the DFG (German research foundation) PAK 75/1. The author also wishes to acknowledge the efforts of Wolfgang Bauer to prepare and carry out the experiments presented herein. Also, thanks to Andreas Grzona for the productive cooperation.


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Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  1. 1.Shock Wave LaboratoryRWTH Aachen UniversityAachenGermany

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