Fluted Films Caused by Gravity Driven Water Drainage from Vertical Tubes

When a stationary mass of water in a vertical tube is suddenly released, it creates a variety of artistic shapes and behaviors as it escapes the tube exit. As the descending water accelerates in the tube, friction along the tube wall slows the outer radius, resulting in a moving film entrained on the tube that trails the main body of water. When this film exits the tube, surface tension, gravity, and inertia interact to cause the film to create a wide variety of shapes, including jets, tubes, water bells, champagne glasses, and bubbles; rich forms that appear in other natural realizations of thin film dynamics. Despite the seeming simplicity and ubiquity of a water column exiting a vertical tube, this transient and beautiful phenomenon has never been described or studied. Here we show how and why the varied shapes trailing the column arise using both experimental data and theoretical modelling. We found that the forms observed are the result of a highly variable exiting film, which arises from the interaction of several distinct phenomena occurring inside the tube. These include the accelerating draining film and the development of waves on the film over time, both of which lead to a very variable exiting film. Theoretical predictions that are in agreement with experiments reveal how the ultimate shape, size and breakup point of the exiting film depend on the film thickness and velocity profile at the tube outlet. We anticipate that our research will provide a foundation for future studies involving the dynamics of falling water columns and films over a large range of physical scales and fluid properties. Furthermore, our results demonstrate how multiple known natural phenomena can interact unexpectedly to form artistically beautiful results. In this way, our work connects scientific and artistic fields, lending understanding to appreciate or create beautiful liquid shapes for fountains and other works of art

EXPERIMENTAL AND COMPUTATIONAL ANALYSIS OF ADVANCED CASING TREATMENTS IN A TRANSONIC COMPRESSOR

Turbo-fan engines seek to achieve the highest compression ratios possible with the minimum number of parts by driving compressor stages to the extremes of their operating limits, which can risk compressor stall. This study expands on previous work by combining experimental and computational methods to evaluate the effectiveness of advanced transonic compressor casing treatments at increasing stall margin while minimizing losses. The NPS Turbopropulsion Lab Transonic Compressor Rig was used to characterize the performance of an advanced transonic compressor in the stage and stage-and-a-half configurations; additionally, inlet guide vanes were installed and evaluated. After characterization of the base performance, s-shaped axial endwall grooves were added to improve stall margin of the compressor stage. Experimental results proved the casing treatments were successful only in the subsonic regime. Stall margin increases of at least 286% were seen in low speed tests with 117% observed in high speed operation. Computational analysis simulated advanced casing treatments and effects of inlet whirl and was correlated to experimental data to shed light on the recirculation mechanisms active in casing treatments. The simulations provided insight for further development of novel self-recirculating endwall treatments and associated technologies.Office of Naval Research, Arlington, VA, 22217Outstanding ThesisEnsign, United States NavyApproved for public release. Distribution is unlimited

Capturing the "Whole Tale" of Computational Research: Reproducibility in Computing Environments

We present an overview of the recently funded "Merging Science and Cyberinfrastructure Pathways: The Whole Tale" project (NSF award #1541450). Our approach has two nested goals: 1) deliver an environment that enables researchers to create a complete narrative of the research process including exposure of the data-to-publication lifecycle, and 2) systematically and persistently link research publications to their associated digital scholarly objects such as the data, code, and workflows. To enable this, Whole Tale will create an environment where researchers can collaborate on data, workspaces, and workflows and then publish them for future adoption or modification. Published data and applications will be consumed either directly by users using the Whole Tale environment or can be integrated into existing or future domain Science Gateways

Halo detection via large-scale Bayesian inference

We present a proof-of-concept of a novel and fully Bayesian methodology designed to detect halos of different masses in cosmological observations subject to noise and systematic uncertainties. Our methodology combines the previously published Bayesian large-scale structure inference algorithm, HADES, and a Bayesian chain rule (the Blackwell-Rao Estimator), which we use to connect the inferred density field to the properties of dark matter halos. To demonstrate the capability of our approach we construct a realistic galaxy mock catalogue emulating the wide-area 6-degree Field Galaxy Survey, which has a median redshift of approximately 0.05. Application of HADES to the catalogue provides us with accurately inferred three-dimensional density fields and corresponding quantification of uncertainties inherent to any cosmological observation. We then use a cosmological simulation to relate the amplitude of the density field to the probability of detecting a halo with mass above a specified threshold. With this information we can sum over the HADES density field realisations to construct maps of detection probabilities and demonstrate the validity of this approach within our mock scenario. We find that the probability of successful of detection of halos in the mock catalogue increases as a function of the signal-to-noise of the local galaxy observations. Our proposed methodology can easily be extended to account for more complex scientific questions and is a promising novel tool to analyse the cosmic large-scale structure in observations.Comment: 17 pages, 13 figures. Accepted for publication in MNRAS following moderate correction

NASA Manned Launch Vehicle Lightning Protection Development

Historically, the National Aeronautics and Space Administration (NASA) relied heavily on lightning avoidance to protect launch vehicles and crew from lightning effects. As NASA transitions from the Space Shuttle to the new Constellation family of launch vehicles and spacecraft, NASA engineers are imposing design and construction standards on the spacecraft and launch vehicles to withstand both the direct and indirect effects of lightning. A review of current Space Shuttle lightning constraints and protection methodology will be presented, as well as a historical review of Space Shuttle lightning requirements and design. The Space Shuttle lightning requirements document, NSTS 07636, Lightning Protection, Test and Analysis Requirements, (originally published as document number JSC 07636, Lightning Protection Criteria Document) was developed in response to the Apollo 12 lightning event and other experiences with NASA and the Department of Defense launch vehicles. This document defined the lightning environment, vehicle protection requirements, and design guidelines for meeting the requirements. The criteria developed in JSC 07636 were a precursor to the Society of Automotive Engineers (SAE) lightning standards. These SAE standards, along with Radio Technical Commission for Aeronautics (RTCA) DO-160, Environmental Conditions and Test Procedures for Airborne Equipment, are the basis for the current Constellation lightning design requirements. The development and derivation of these requirements will be presented. As budget and schedule constraints hampered lightning protection design and verification efforts, the Space Shuttle elements waived the design requirements and relied on lightning avoidance in the form of launch commit criteria (LCC) constraints and a catenary wire system for lightning protection at the launch pads. A better understanding of the lightning environment has highlighted the vulnerability of the protection schemes and associated risk to the vehicle, which has resulted in lost launch opportunities and increased expenditures in manpower to assess Space Shuttle vehicle health and safety after lightning events at the launch pad. Because of high-percentage launch availability and long-term on-pad requirements, LCC constraints are no longer considered feasible. The Constellation vehicles must be designed to withstand direct and indirect effects of lightning. A review of the vehicle design and potential concerns will be presented as well as the new catenary lightning protection system for the launch pad. This system is required to protect the Constellation vehicles during launch processing when vehicle lightning effects protection might be compromised by such items as umbilical connections and open access hatches

Spectral Absorption Coefficient of Additive Manufacturing Polymers

As NASA turns to additive manufacturing processes, there is a need to ensure that the parts they produce are reliable. This is especially true when creating parts in space, where resources are limited and failure could result in catastrophe. Active thermography has shown potential as a non-destructive quality assurance technique for additive manufacturing processes. Heat transfer models used in active thermography techniques require accurate material property measurements in order to extract useful information about the system, including defect location. The spectral absorption coefficient, which determines the depth at which radiative power is absorbed into a surface, is a material property necessary for performing active thermography on AM polymers. This paper presents measurements of spectral absorption coefficients of polymers commonly used in additive manufacturing. Spectral absorption coefficients for fully dense PLA, ABS, and Nylon 12 samples are reported. Future work is needed to measure the spectral absorption coefficients of different materials and colored filaments commonly used in additive manufacturing

Surfactant-free poly(lactide-co-glycolide) honeycomb films for tissue engineering: relating solvent, monomer ratio and humidity to scaffold structure

International audienceOne-step surfactant-free, water-droplet templating has been developed as a fabrication method for a poly(lactide-co-glycolide) (PLGA) film that can be used as a model to investigate the relationship between solvent, monomer ratio, polymer concentration and humidity on its structure. The resulting material is a honeycomb-structured film. Formation of this structure was highly sensitive to solvent, monomer ratio, polymer concentration and humidity. Surfactant-free, water-droplet templating thus allows investigation of fabrication parameters and that PLGA monomer ratio selection is important for scaffold structure but not for MG63 cell attachment and proliferation

Searching for gravitational waves from the Crab pulsar - the problem of timing noise

Of the current known pulsars, the Crab pulsar (B0531+21) is one of the most promising sources of gravitational waves. The relatively large timing noise of the Crab causes its phase evolution to depart from a simple spin-down model. This effect needs to be taken in to account when performing time domain searches for the Crab pulsar in order to avoid severely degrading the search efficiency. The Jodrell Bank Crab pulsar ephemeris is examined to see if it can be used for tracking the phase evolution of any gravitational wave signal from the pulsar, and we present a method of heterodyning the data that takes account of the phase wander. The possibility of obtaining physical information about the pulsar from comparisons of the electromagnetically and a gravitationally observed timing noise is discussed. Finally, additional problems caused by pulsar glitches are discussed.Comment: 5 pages, 1 figure, Proceedings of the 5th Amaldi Conference on Gravitational Waves, Pisa, Italy, 6-11 July 200