Fluorescence imaging and streakline visualization of hypersonic flow over rapid prototype wind-tunnel models

49th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

Bathel

Johansen

et al. 2011

A nonintrusive laser-based measurement system has been applied for the first time in the HYMETS (Hypersonic Materials Environmental Test System) 400 kW arc-heated wind tunnel at NASA Langley Research Center. Planar laser-induced fluorescence of naturally occurring nitric oxide (NO) has been used to obtain instantaneous flow visualization images, and to make both radial and axial velocity measurements. Results are presented at selected facility run conditions, including some in simulated Earth atmosphere (75% nitrogen, 20% oxygen, 5% argon) and others in simulated Martian atmosphere (71% carbon dioxide, 24% nitrogen, 5% argon), for bulk enthalpies ranging from 6.5 MJ/kg to 18.4 MJ/kg. Flow visualization images reveal the presence of large scale unsteady flow structures, and indicate nitric oxide fluorescence signal over more than 70% of the core flow for bulk enthalpies below about 11 MJ/kg, but over less than 10% of the core flow for bulk enthalpies above about 16 MJ/kg. Axial velocimetry was performed using molecular tagging velocimetry (MTV). Axial velocities of about 3 km/s were measured along the centerline. Radial velocimetry was performed by scanning the wavelength of the narrowband laser and analyzing the resulting Doppler shift. Radial velocities of ±0.5km/s were measured.

Section: Image Pre-processingmentioning

confidence: 99%

Nitric Oxide PLIF Measurements in the Hypersonic Materials Environmental Test System (HYMETS)

49th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

Bathel

Johansen

et al. 2011

“…19. When these spatial calibration images were acquired, the dotcard was placed in the plane of the laser sheet.…”

Section: Image Processing and Analysis A Initial Image Processingmentioning

confidence: 99%

Hypersonic Laminar Boundary Layer Velocimetry with Discrete Roughness on a Flat Plate

Bathel

Danehy

40th Fluid Dynamics Conference and Exhibit

et al. 2010

Laminar boundary layer velocity measurements are made on a 10-degree half-angle wedge in a Mach 10 flow. Two types of discrete boundary layer trips were used to perturb the boundary layer gas. The first was a 2-mm tall, 4-mm diameter cylindrical trip. To study the precision of the measurement technique, the angle of attack was varied during one run. Nitric-oxide (NO) molecular tagging velocimetry (MTV) was used to obtain averaged axial velocity values and associated uncertainties. These uncertainties are as low as 20 m/s. An interline, progressive scan CCD camera was used to obtain separate images of the initial reference and shifted NO molecules that had been tagged by the laser. The CCD configuration allowed for sub-microsecond sequential acquisition of both images. The maximum planar spatial resolution achieved for the side-view velocity measurements was 0.07-mm in the wall-normal direction by 1.45-mm in the streamwise direction with a spatial depth of 0.5-mm. For the plan-view measurements, the maximum planar spatial resolution in the spanwise and streamwise directions was 0.69-mm by 1.28-mm, respectively, with a

“…These images were dewarped using a dotcard image-registration process (described in Ref. 14), and imported into the ViDI environment.…”

mentioning

confidence: 99%

High-Speed PLIF Imaging of Hypersonic Transition over Discrete Cylindrical Roughness

Danehy

Ivey

48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

et al. 2010

Transitional flow over cylindrical protuberances attached to a flat plate has been studied in a hypersonic wind tunnel. The tests were performed in the 31-Inch Mach 10 Air Tunnel at NASA Langley Research Center. Cylindrical protuberances with 4-mm diameter and heights of 1, 2, and 4 mm, were attached to the flat plate. The plate angle of attack and tunnel stagnation pressure were varied to achieve desired combinations of boundary layer edge Mach number and the boundary layer thickness. Several different types of flow visualization based on nitric oxide planar laser-induced fluorescence (NO PLIF) were used. A 10-Hz NO PLIF system was used to produce a thin laser sheet. This laser sheet was oriented perpendicular to the flat plate on some runs and parallel to the flat plate on others. A thick laser sheet was also used in some runs to provide visualization of entire flow structures inside the boundary layer. Viewing the PLIF intensity generated with the thick laser sheet using two cameras allowed stereoscopic visualization of the flow. In post processing, these images were combined to produce anaglyphs. Viewing these anaglyphs through blue and red 3D-glasses allows the three-dimensional flow structures to be observed. Another measurement system was a MHz-rate NO PLIF imaging system. Both PLIF measurement systems have better than one microsecond time resolution, which is fast enough to freeze the flow. The MHz system allows subsequent images to be obtained at one or two microsecond time intervals, resulting in movies of the flow. The data reported in this paper show the size, shape, and speed of flow structures in transitional hypersonic boundary layer flows and will provide valuable comparison data for computations of these flows.