Ground vortex flow field investigation

Flow field investigations were conducted at the NASA Ames-Dryden Flow Visualization Facility (water tunnel) to investigate the ground effect produced by the impingement of jets from aircraft nozzles on a ground board in a STOL operation. Effects on the overall flow field with both a stationary and a moving ground board were photographed and compared with similar data found in other references. Nozzle jet impingement angles, nozzle and inlet interaction, side-by-side nozzles, nozzles in tandem, and nozzles and inlets mounted on a flat plate model were investigated. Results show that the wall jet that generates the ground effect is unsteady and the boundary between the ground vortex flow field and the free-stream flow is unsteady. Additionally, the forward projection of the ground vortex flow field with a moving ground board is one-third less than that measured over a fixed ground board. Results also showed that inlets did not alter the ground vortex flow field

Upper extremity pain and overuse injuries in fly-fishing: A North American cross-sectional survey and implications for injury prevention

Background: Fly-fishing requires rhythmic, coordinated movements to successfully cast a fly line. Previous studies have shown that the biomechanical demands of fly-casting may cause some individuals to develop upper extremity pain or injuries. Purpose: To report the rates, trends, and contributing factors of upper extremity pain and overuse injuries in a sample of North American recreational fly-fishers. Study Design: Descriptive epidemiology study. Methods: Participants were reached via 3 popular online fly-fishing forums in April 2019. Each consenting North American participant over 18 years of age was given a link to a unique survey that recorded his or her demographic and orthopaedic histories, fly-fishing experience, equipment, casting techniques, upper extremity pain after fly-fishing, and chronic outcomes. Results: The 162 fly-fishers included were 63.3 (± 11.5) years of age, and 95.1% were men. In total, 59 (36.4%) reported experiencing upper extremity pain immediately after fly-fishing. Pain was rated a 4.0 (interquartile range, 3.0-6.0) on a 10-point Likert scale, commonly lasting less than 1 day (45.0%) or between 1 day and 1 week (45.0%). The majority (62.7%) reported not needing to see a medical provider for their pain/soreness. Those who did most commonly received diagnoses of elbow or rotator cuff tendinitis. Pain/soreness was associated with casting in an elliptical/sidearm fashion, compared with overhead or 2-handed casting ( Conclusion: In this sample of recreational fly-fishers, no aspects of fly-fishing were associated with long-term upper extremity disability, and only a little more than a third reported having transient pain immediately after fishing. Casting style, using weighted lines or added weight, and grip style were all associated with pain. These are modifiable risk factors that can be adjusted to reduce the risk of upper extremity pain immediately after fly-fishing

Investigation of the Aerodynamic Characteristics of a Model Wing-Propeller Combination and of the Wing and Propeller Separately at Angles of Attack up to 90 Degrees

This report presents the results of an investigation conducted in the Langley 300 mph 7- by 10-foot wind tunnel for the purpose of determining the aerodynamic characteristics of a model wing-propeller combination, and of the wing and propeller separately at angles of attack up to 90 degrees. The tests covered thrust coefficients corresponding to free-stream velocities from zero forward speed to the normal range of cruising speeds. The results indicate that increasing the thrust coefficient increases the angle of attack for maximum lift and greatly diminishes the usual reduction in lift above the angle of attack for maximum lift

The Role of Source Coherence in Atom Interferometery

The role of source cloud spatial coherence in a Mach-Zehnder type atom interferometer is experimentally investigated. The visibility and contrast of a Bose-Einstein condensate (BEC) and three thermal sources with varying spatial coherence are compared as a function of interferometer time. At short times, the fringe visibility of a BEC source approaches 100 % nearly independent of pi pulse efficiency, while thermal sources have fringe visibilities limited to the mirror efficiency. More importantly for precision measurement systems, the BEC source maintains interference at interferometer times significantly beyond the thermal source

80hk Momentum Separation with Bloch Oscillations in an Optically Guided Atom Interferometer

We demonstrate phase sensitivity in a horizontally guided, acceleration-sensitive atom interferometer with a momentum separation of 80hk between its arms. A fringe visibility of 7% is observed. Our coherent pulse sequence accelerates the cold cloud in an optical waveguide, an inherently scalable route to large momentum separation and high sensitivity. We maintain coherence at high momentum separation due to both the transverse confinement provided by the guide, and our use of optical delta-kick cooling on our cold-atom cloud. We also construct a horizontal interferometric gradiometer to measure the longitudinal curvature of our optical waveguide.Comment: 6 pages, 6 figure