Beeinflussung des laminar-turbulenten Grenzschichtumschlags durch kontrollierte Anregung stationärer Querströmungsinstabilitäten

Peter, Barth Hans

doi:10.53846/goediss-8718

Cited by 1 publication

(3 citation statements)

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“…The turbulence level of the flow in the empty short test section is in the order of 0.2% at 20 m s −1 in the frequency range of 10 Hz to 10 4 Hz [ 23 ]. Measurements with the long open test section and the SPECTRA-B configuration showed a similar turbulence level of 0.18% for typical flow conditions [ 24 ]. For the test, the long open test section with a length of

m is installed.…”

Section: Methodsmentioning

confidence: 99%

“…The experiment was first reestablished with different pressure distributions and boundary-layer stability characteristics suitable for the investigation of a transition control technique called upstream flow deformation [ 25 ]. In that configuration, it is named SPECTRA-B [ 10 , 24 ]. For both SPECTRA-A and SPECTRA-B , the boundary layer under study is stable with respect to all typical primary instabilities in a swept configuration, except for cross-flow instabilities.…”

Section: Methodsmentioning

confidence: 99%

“…Contoured side walls and the nozzle adapter make it possible to approximate infinite swept wing flow in the experiment despite the configuration’s high blockage [ 24 ]. The contoured side walls are shaped like the streamline at the upper boundary-layer edge as derived from numerical calculations.…”

Section: Methodsmentioning

confidence: 99%

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Miniaturization and Model-Integration of the Optical Measurement System for Temperature-Sensitive Paint Investigations

Lemarechal

Dimond

Barth

et al. 2023

Sensors

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The temperature-sensitive paint (TSP) method, an optical measurement technique, is used for qualitative skin friction visualizations in a wide variety of aerodynamic applications. One such application is the visualization of the laminar–turbulent boundary-layer transition. Optical access to the surface of interest is mandatory for the measurement system, which consists of scientific cameras and LEDs. But the optical access to the area of interest is often impeded by the available windows of the wind tunnel and the wind tunnel model itself, reducing the field of view and the spatial resolution. In some cases, it is of interest to increase the flexibility of the installation of the optical measurement system by reducing its physical dimensions and placing the installation inside the plenum. The DLR Swept flat PlatE Cross-flow TRAnsition (SPECTRA-A) configuration was selected to investigate the influence of two-dimensional steps on the cross-flow-induced boundary layer transition by means of TSP, as part of the EU project Clean Sky 2. The SPECTRA-A configuration consists of two main elements: a flat plate and a displacement body mounted within a very close distance of each other, creating a narrow gap between the two elements. The surface of interest is the area on the flat plate facing the displacement body. The narrow gap limits the utilization of an external camera setup due to poor optical access. A new optical setup consisting of four miniature CMOS machine-vision cameras and five miniature high-power LEDs was integrated into the displacement body. The characteristics of the camera system were analyzed in laboratory tests, establishing that the miniature CMOS machine-vision cameras are suitable for qualitative TSP skin friction visualizations. This was confirmed by successfully measuring the laminar–turbulent boundary-layer transition on the SPECTRA-A configuration. The integrated TSP system is capable of resolving even small variations of the transition location caused by changing the amplitude of the stationary cross-flow instability. The quality of the TSP visualization with the integrated optical system allows for the measurement of the transition location and the wavelength of the stationary cross-flow instability. Overall, a cost-effective TSP visualization system with small space requirements was developed and tested for future applications in wind tunnel models, model support, or side walls of wind tunnels.

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m is installed.…”

Section: Methodsmentioning

confidence: 99%