Blade Tip Pressure Measurements Using Pressure Sensitive Paint

This paper discusses the application of pressure sensitive paint using laser-based excitation for measurement of the upper surface pressure distribution on the tips of rotor blades in hover and simulated forward flight. The testing was conducted in the Rotor Test Cell and the 14- by 22-ft Subsonic Tunnel at the NASA Langley Research Center on the General Rotor Model System (GRMS) test stand. The Mach-scaled rotor contained three chordwise rows of dynamic pressure transducers for comparison with PSP measurements. The rotor had an 11 ft 1 in. diameter, 5.45 in. main chord and a swept, tapered tip. Three thrust conditions were examined in hover, C(sub T) = 0.004, 0.006 and 0.008. In forward flight, an additional thrust condition, C(sub T) = 0.010 was also examined. All four thrust conditions in forward flight were conducted at an advance ratio of 0.35

Deployment of a Pressure Sensitive Paint System for Measuring Global Surface Pressures on Rotorcraft Blades in Simulated Forward Flight

This paper will present details of a Pressure Sensitive Paint (PSP) system for measuring global surface pressures on the tips of rotorcraft blades in simulated forward flight at the 14- x 22-Foot Subsonic Tunnel at the NASA Langley Research Center. The system was designed to use a pulsed laser as an excitation source and PSP data was collected using the lifetime-based approach. With the higher intensity of the laser, this allowed PSP images to be acquired during a single laser pulse, resulting in the collection of crisp images that can be used to determine blade pressure at a specific instant in time. This is extremely important in rotorcraft applications as the blades experience dramatically different flow fields depending on their position in the rotor disk. Testing of the system was performed using the U.S. Army General Rotor Model System equipped with four identical blades. Two of the blades were instrumented with pressure transducers to allow for comparison of the results obtained from the PSP. Preliminary results show that the PSP agrees both qualitatively and quantitatively with both the expected results as well as with the pressure taps. Several areas of improvement have been indentified and are currently being developed

Deployment of a Pressure Sensitive Paint System for Measuring Global Surface Pressures on Rotorcraft Blades in Simulated Forward Flight: Preliminary PSP Results from Test 581 in the 14- by 22-Foot Subsonic Tunnel

This report will present details of a Pressure Sensitive Paint (PSP) system for measuring global surface pressures on the tips of rotorcraft blades in simulated forward flight at the 14- x 22-Foot Subsonic Tunnel. The system was designed to use a pulsed laser as an excitation source and PSP data was collected using the lifetime-based approach. With the higher intensity of the laser, this allowed PSP images to be acquired during a single laser pulse, resulting in the collection of crisp images that can be used to determine blade pressure at a specific instant in time. This is extremely important in rotorcraft applications as the blades experience dramatically different flow fields depending on their position in the rotor disk. Testing of the system was performed using the U.S. Army General Rotor Model System equipped with four identical blades. Two of the blades were instrumented with pressure transducers to allow for comparison of the results obtained from the PSP. This report will also detail possible improvements to the system

Laser Initiated Chain Reactions: The Kinetics of the Chlorine/Cyclohexane/Oxygen Chain System

The combination of laser photolysis with infrared chemiluminescence detection has proven an effective technique for determining the propagation rate coefficients of halogen + RH chain reactions. This thesis will extend the technique to cyclic alkanes by determining the propagation rate coefficients of the Cl2/ cyclohexane chain system as well as the rate coefficient for the primary chain termination mechanism, R + O2 → RO2. The following reaction scheme is supported by the kinetic analysis: Cl2 → 2Cl Laser Photolysis Cl + RH → HCl(v) + R First Propagation Step (k1) R + Cl2 → RCl + Cl Second Propagation Step (k2) where RH = cyclohexane, R = cyclohexyl radical, and RCl = cyclohexyl chloride. The addition of a radical scavenger such as oxygen will terminate the chain reaction by the following mechanisms: Cl + O2 + M → ClO2 + M (k3) R + O2 → RO2 (k4) Laser photolysis/ chemiluminescence experiments were performed under first-order conditions on slowly flowing mixtures of cyclohexane, chlorine, oxygen, diluted in argon at reduced pressures (5 to 50 Torr). Chlorine is photolyzed by a Nd:YAG laser emitting a pulse of third harmonic (355 nm) light to initiate the chain reaction. The first propagation step is sufficiently exothermic as to generate HCl in the v = 1 vibrational energy level which subsequently returns to the ground state by fluorescence emission at 3.5 μm which is monitored via a bandpass filter with a cryogenically cooled (77 K) mercury-cadmium-telluride (HgCdTe) detector. This technique requires observation of HCl(v) only under the appropriate experimental conditions to determine the rate coefficients k1, k2, kv, and k4. Signal-to-noise challenges limit the technique from determining k3, the scavenging of Cl atom by oxygen, because of the necessity of a third-body collision for this reaction. A detailed derivation of the equations describing the time-dependent concentrations in this kinetic scheme under pseudo first-order conditions is included. Computer simulations were used to model the fluorescence intensity profile in an effort to determine the experimental parameters that best serves this study. Nonlinear least-squares fits of the fluorescence intensity profiles yields values for the rate coefficients when using the expression for [HCl(v)]. The values for the rate coefficients determined by this study were: k1 = (1.8 ± 0.2) x 10-10 cc·molecule-1·sec-1, k2 = (3.1 ± 0.2) x 10-11 cc·molecule-1·sec-1, kv = (1.7 ± 0.5) x 10-11 cc·molecule-1·sec-1, and k4 = (1.2 ± 0.3) x 10-11 cc·molecule-1·sec-1. A comparison with literature values for these rate coefficients will be made followed by a discussion of the success and challenge of this technique. This technique is useful for studying reactions of the halogen + hydrocarbon type where intermediates other than HCl(v) are difficult to monitor. Improvements in detector design could allow this technique in theory to perform real-time kinetic analysis and thus provide a better understanding of these chain systems

Support for Multi-User, Multi-Touch Applications

DiamondTouch is a multi-touch input technology that supports multiple, simultaneous users; it can distinguish who is touching where. We present the DiamondTouch SDK; it provides support for the development of applications that utilize DiamondTouch s capabilities to implement computer-supported collaboration and rich input modalities (such as gestures). Our first demo illustrates the basic utilities and functionality of our system. Our second demo, a multi-user map application, highlights DiamondTouch s ability to sup-port input from multiple, simultaneous users and exploits Di-amondTouch s ability to identify the owner of each touch. Our third demo illustrates DiamondTouch s ability to run with existing applications by providing a mouse emulation mode. DiamondTouch is well-suited to shared-display applications. It is suitable for front-projected video of the computer display, which facilitates direct manipulation of user interface elements and provides a shared focus of attention for collab-orating users. Possible applications include command-and-control command posts, control rooms, business or technical meetings, and a variety of casual applications in the home, at schools, and in retail settings

Multi-user, multi-display interaction with a single-user, single-display geospatial application

www.merl.com In this paper, we discuss our adaptation of a single-display, single-user commercial application for use in a multidevice, multi-user environment. We wrap Google Earth, a popular geospatial application, in a manner that allows for synchronized coordinated views among multiple instances running on different machines in the same co-located environment. The environment includes a touch-sensitive tabletop display, three vertical wall displays, and a TabletPC. A set of interaction techniques that allow a group to manage and exploit this collection of devices is presented. ACM Classification: H5.2 [Information interfaces an

Rapid Serial Visual Presentation Techniques for Consumer Digital Video Devices

In this paper we propose a new model for a class of rapid serial visual presentation (RSVP) interfaces [16] in the context of consumer video devices. The basic spatial layout explodes a sequence of image frames into a 3D trail in order to provide more context for a spatial/temporal presentation. As the user plays forward or back, the trail advances or recedes while the image in the foreground focus position is replaced. The design is able to incorporate a variety of methods for analyzing or highlighting images in the trail. Our hypotheses are that users can navigate more quickly and precisely to points of interest when compared to conventional consumer-based browsing, channel flipping, or fast-forwarding techniques. We report on an experiment testing our hypotheses in which we found that subjects were more accurate but not faster in browsing to a target of interest in recorded television content with a TV remote