Fluorescence Visualization of Hypersonic Flow Over Rapid Prototype Wind-Tunnel Models

Journal of Spacecraft and Rockets

Brauckmann

et al. 2009

Planar laser-induced fluorescence was used to visualize the reaction-control system jet flow emanating from the aft body of an Apollo-geometry capsule test article in NASA Langley Research Center's 31 in. Mach 10 Tunnel. The reaction-control system jet was oriented normal to the aft surface of the model and had a nominal Mach number of 2.94. The composition of the jet gas by mass was 95% nitrogen (N 2 ) and 5% nitric oxide (NO). The reaction-control system jet flow rate varied between 0 and 0.5 standard liters per minute, and the angle of attack and tunnel stagnation pressure were also varied. Planar laser-induced fluorescence was used to excite the NO molecules for flow visualization. These flow visualization images were processed to determine the trajectory and to quantify the flapping of the reaction-control system jet. The jet flapping, measured by the standard deviation of the jet centerline position, was as large as 0.9 mm, whereas the jet was 1.5-4 mm in diameter (full width at half-maximum). Schlieren flow visualization images were obtained for comparison with the planar laser-induced fluorescence. Surface pressures were also measured and presented. Virtual diagnostics interface technology, developed at NASA Langley Research Center, was used to superimpose and visualize the data sets. The measurements demonstrate some of the capabilities of the planar laser-induced fluorescence method and provide a test case for computational fluid dynamics validation. Nomenclature C p = pressure coefficient P o = tunnel stagnation pressure P 1 = freestream static pressure q 1 = dynamic pressure

Section: Wind Tunnel Operating Conditions Mass Flow Control Andmentioning

confidence: 93%

Visualization of a Capsule Entry Vehicle Reaction-Control System Thruster

Journal of Spacecraft and Rockets

Brauckmann

et al. 2009

“…For this experiment, ViDI was used primarily for post-test visualization of the PLIF data as in Ref. 6. Figure 2 shows a comparison between two images obtained using the cone nozzle: one with the wind tunnel not operating (tunnel-off) and the other with the wind tunnel operating (tunnel-on).…”

Section: E Virtual Diagnostics Interface (Vidi)mentioning

confidence: 99%

“…In a recent experiment 6 it was demonstrated that hypersonic wind tunnel capsule models could be built rapidly, inexpensively, and with internal plumbing appropriate for seeding NO, using a stereo lithography apparatus (SLA). However, the forebody capsule heating was excessive for the materials used in that test, resulting in model degradation.…”

Section: A Test Articlementioning

confidence: 99%

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Visualization of Flowfield Modification by RCS Jets on a Capsule Entry Vehicle

46th AIAA Aerospace Sciences Meeting and Exhibit

Alderfer

et al. 2008

Self Cite

Nitric-oxide planar laser-induced fluorescence (NO PLIF) was used to visualize the flow on the aft-body of an entry capsule having an activated reaction control system (RCS) jet. A capsule shape representative of the Apollo command module was tested in the NASA Langley Research Center's 31-Inch Mach 10 wind tunnel facility. Two different RCS converging-diverging nozzle designs were used. One nozzle had a conical diverging section while the other had a bell-shaped contoured section followed by a conical section. The two nozzles had area ratios of 13.4 and 22.5 respectively. Both conical nozzle sections had halfangles of 10˚. Low-and high-Reynolds number cases were investigated by changing the tunnel stagnation pressure from 350 psi to 1300 psi, resulting in freestream Reynolds numbers of 0.55 and 1.8 million per foot respectively. For both cases, three different jet plenum pressures were tested (nominally 56, 250 and 500 psi). Images were also acquired for conditions where the jets were issuing into low pressure static gas with the wind tunnel not operating. A single vehicle angle-of-attack of 24˚ was investigated. Visualizations of the flow issuing from the two nozzle shapes were markedly different near the nozzle internal to the RCS jet plume, while relatively similar in structure on the outer edges of the plume. Visualizations produced by seeding pure NO from the vehicle's forebody show that operation of the RCS jet forces the aft shear layer to become turbulent and deflects the shear layer away from the vehicle significantly, with deflection angle increasing with jet pressure.

“…For this experiment, ViDI was used for post-test visualization of the PLIF data as in Ref. 15. All images presented in this paper represent flow conditions along the underbody of the 1/3 scale Hyper-X forebody model.…”

Section: Planar-laser Induced Fluorescence (Plif) System and Imagementioning

confidence: 99%

PLIF Visualization of Active Control of Hypersonic Boundary Layers Using Blowing

Bathel

26th AIAA Aerodynamic Measurement Technology and Ground Testing Conference

et al. 2008

Self Cite

Planar laser-induced fluorescence (PLIF) imaging was used to visualize the boundary layer flow on a 1/3-scale Hyper-X forebody model. The boundary layer was perturbed by blowing out of orifices normal to the model surface. Two blowing orifice configurations were used: a spanwise row of 17-holes spaced at 1/8 inch, with diameters of 0.020 inches and a single-hole orifice with a diameter of 0.010 inches. The purpose of the study was to visualize and identify laminar and turbulent structures in the boundary layer and to make comparisons with previous phosphor thermography measurements of surface heating. Jet penetration and its influence on the boundary layer development was also examined as was the effect of a compression corner on downstream boundary layer transition. Based upon the acquired PLIF images, it was determined that global surface heating measurements obtained using the phosphor thermography technique provide an incomplete indicator of transitional and turbulent behavior of the corresponding boundary layer flow. Additionally, the PLIF images show a significant contribution towards transition from instabilities originating from the underexpanded jets. For this experiment, a nitric oxide/nitrogen mixture was seeded through the orifices, with nitric oxide (NO) serving as the fluorescing gas. The experiment was performed in the 31-inch Mach 10 Air Tunnel at NASA Langley Research Center.