Nitric oxide (NO) planar laser-induced fluorescence (PLIF) has been use to investigate the hypersonic flow over a flat plate with and without a 2-mm (0.08-in) radius hemispherical trip. In the absence of the trip, for all angles of attack and two different Reynolds numbers, the flow was observed to be laminar and mostly steady. Boundary layer thicknesses based on the observed PLIF intensity were measured and compared with a CFD computation, showing agreement. The PLIF boundary layer thickness remained constant while the NO flowrate was varied by a factor of 3, indicating non-perturbative seeding of NO. With the hemispherical trip in place, the flow was observed to be laminar but unsteady at the shallowest angle of attack and lowest Reynolds number and appeared vigorously turbulent at the steepest angle of attack and highest Reynolds number. Laminar corkscrew-shaped vortices oriented in the streamwise direction were frequently observed to transition the flow to more turbulent structures.

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Nitric-oxide planar laser-induced fluorescence (NO PLIF) was used to perform velocity measurements in hypersonic flows by generating multiple tagged lines which fluoresce as they convect downstream. For each laser pulse, a single interline, progressive scan intensified CCD camera was used to obtain separate images of the initial undelayed and delayed NO molecules that had been tagged by the laser. The CCD configuration allowed for sub-microsecond acquisition of both images, resulting in sub-microsecond temporal resolution as well as sub-mm spatial resolution (0.5-mm x 0.7-mm). Determination of axial velocity was made by application of a cross-correlation analysis of the horizontal shift of individual tagged lines.Quantification of systematic errors, the contribution of gating/exposure duration errors, and influence of collision rate on fluorescence to temporal uncertainty were made. Quantification of the spatial uncertainty depended upon the analysis technique and signal-to-noise of the acquired profiles. This investigation focused on two hypersonic flow experiments: (1) a reaction control system (RCS) jet on an Orion Crew Exploration Vehicle (CEV) wind tunnel model and (2) a 10-degree half-angle wedge containing a 2-mm tall, 4-mm wide cylindrical boundary layer trip. The experiments were performed at the NASA Langley Research Center's 31-inch Mach 10 wind tunnel.

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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

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.

Femtosecond laser electronic excitation tagging (FLEET) is an optical measurement technique that permits quantitative velocimetry of unseeded air or nitrogen using a single laser and a single camera. In this paper, we seek to determine the fundamental precision of the FLEET technique using high-speed complementary metal-oxide semiconductor (CMOS) cameras. Also, we compare the performance of several different high-speed CMOS camera systems for acquiring FLEET velocimetry data in air and nitrogen free-jet flows. The precision was defined as the standard deviation of a set of several hundred single-shot velocity measurements. Methods of enhancing the precision of the measurement were explored such as digital binning (similar in concept to on-sensor binning, but done in postprocessing), row-wise digital binning of the signal in adjacent pixels and increasing the time delay between successive exposures. These techniques generally improved precision; however, binning provided the greatest improvement to the un-intensified camera systems which had low signal-to-noise ratio. When binning row-wise by 8 pixels (about the thickness of the tagged region) and using an inter-frame delay of 65 µs, precisions of 0.5 m/s in air and 0.2 m/s in nitrogen were achieved. The camera comparison included a pco.dimax HD, a LaVision Imager scientific CMOS (sCMOS) and a Photron FASTCAM SA-X2, along with a two-stage LaVision HighSpeed IRO intensifier. Excluding the LaVision Imager sCMOS, the cameras were tested with and without intensification and with both short and long interframe delays. Use of intensification and longer inter-frame delay generally improved precision. Overall, the Photron FASTCAM SA-X2 exhibited the best performance in terms of greatest precision and highest signal-to-noise ratio primarily because it had the largest pixels. Nomenclature= number of binned pixels = root mean square signal noise = signal intensity = time delay

The extent of MPA incorporation was determined upon analysis of 1 H NMR spectra by integration of backbone and side-group peaks, with the following complication. For PB functionalization with MPA, we expect two peaks between 2.85 and 2.55 ppm corresponding to HO 2 CCH 2 CH 2 S-protons and HO 2 CCH 2 CH 2 S-, with one or more additional peaks (depending on whether cyclic structures are formed or not) around 2.55 ppm, corresponding to HO 2 CCH 2 CH 2 SCH 2 -protons. Experimental results consistentlyshowed two large, partially overlapping peaks between 2.825 and 2.575 ppm, and a much smaller, broad overlapping shoulder below 2.575 ppm, extending in some cases down to 2.4 ppm (for instance, for 510kPB4.7A polymer that shoulder peak was about 1/3 of the size of the first two). These observations indicate that the signal for HO 2 CCH 2 CH 2 SCH 2 -is broad, with significant overlap with the middle peak, and that for simplicity the 2.85-2.4 ppm range should be integrated as a whole, accounting for 6 protons for each functionalized monomer. The complication is that the integration of the small shoulder region between 2.55 and 2.4 ppm was found to be completely unreliable (due both to its small size at the very low extents of functionalization investigated, and apparently to the presence of the very large neighboring PB backbone peak): in many cases, the softwarecomputed integral was a physically nonsensical negative number. As a result, extents of MPA functionalization were approximated instead in all cases by integrating between 2.825 and 2.575 ppm and estimating that that integral accounted for 5 protons for each functionalized monomer. A.1.2 Extensional Viscosity ResultsFigure A.1 below reports apparent extensional viscosity for the solutions whose capillary breakup behavior is shown in Figure 13.A-1 A.2 Numerical Approach for Chain Statistics of Self-Associating Chains atInfinite Dilution in θ-Solvent A.2.1 Model DescriptionOur objective is to determine the size of a linear chain of N monomers, f of which are modified to act as stickers capable of forming pair-wise only, physical associations. The stickers are assumed to be equidistantly spaced l monomers apart along the chain, and the energy of association is εkT. We will assume Gaussian chain statistics for any segment of the chain whose configuration is unrestrained by reversible crosslinks.To calculate the size of the chain in the very dilute regime (all associations are intramolecular), we define a semi-Markov process X(t), t > 0 such that each state i is fully specified by identifying which pairs of stickers form bonds. (Note here that a given state has an infinite number of chain configurations.) The chain goes from one state to the next by either breaking or forming a bond, as illustrated in Figure A. Assume the polymer chain enters state i at time t. Clearly, the state it enters next is determined by which bond is broken or formed first; and the time spent in the present state is the time it took for that bond-breaking or bond-forming event to take place.B...