Effect of Leading Edge Protuberance on Thrust Production of a Dynamically Pitching Aerofoil

The paper presents a computational analysis of the characteristics of a NACA 634-021 aerofoil modified by incorporating sinusoidal leading-edge protuberances at Re = 14,000. The protuberances are from the tubercles of the humpback whale flipper with leading edge acting as passive-flow control devices that improve performance and manoeuvrability of the flipper. They are characterized by an amplitude and wavelength of 12% and 50% of the aerofoil chord length respectively. Three-dimensional CFD on the modified aerofoil oscillating about a point located on the centreline at quarter-chord has been performed with the frequency and amplitude of oscillation being 4Hz and 10 deg respectively. In addition to the lift and thrust coefficients, near wall flow visualisations and the shedding of vortices during oscillations are presented to illustrate the unsteady flow features on the performance of the oscillating flipper. The results show an improvement in the thrust production when compared to previous studies on similar symmetric aerofoil without the leading edge modifications

Role of carbon dioxide and ion transport in the formation of sub-embryonic fluid by the blastoderm of the Japanese quail

1. The explanted blastoderm of the Japanese quail was used to explore the role of ions and carbon dioxide in determining the rate of sub-embryonic fluid (SEF) production between 54 and 72 h of incubation. 2. Amiloride, an inhibitor of Na+/H+ exchange, at concentrations of 10-3 to 10-6 M substantially decreased the rate of SEF production when added to the albumen culture medium. N-ethylmaleimide, an inhibitor of V type H+ ATPase, also decreased this rate but only to a small extent at the highest dose applied, 10-3 M. Both inhibitors had no effect on SEF production when added to the SEF. 3. The inhibitors of cellular bicarbonate and chloride exchange, 4-acetamido-4-'isothiocyano-2, 2-'disulphonic acid (SITS) and 4,4'diisothiocyanostilbene-2,2-'disulphonic acid (DIDS), had no effect upon SEF production. 4. Ouabain, an inhibitor of Na+/K+ ATPase, decreased SEF production substantially at all concentrations added to the SEF (10-3 to 10-6 M). Three sulphonamide inhibitors of carbonic anhydrase, acetazolamide, ethoxzolamide and benzolamide, decreased SEF production when added to the SEF at concentrations of 10-3 to 10-6 M. Benzolamide was by far the most potent. Neither ouabain nor the sulphonamides altered SEF production when added to the albumen culture medium. 5. Using a cobalt precipitation method, carbonic anhydrase activity was localised to the endodermal cells of the area vasculosa. The carbonic anhydrase activity was primarily associated with the lateral plasma membranes, which together with the potent inhibitory effect of benzolamide, suggests the carbonic anhydrase of these cells is the membrane-associated form, CA IV. 6. The changes in SEF composition produced by inhibitors were consistent with the production of SEF by local osmotic gradients. 7. It is concluded that a Na+/K+ ATPase is located on the basolateral membranes of the endodermal cells of the area vasculosa , and that a sodium ion/hydrogen ion exchanger is located on their apical surfaces. Protons for this exchanger would be provided by the hydration of CO2 catalysed by the membrane-associated carbonic anhydrase. Furthermore, it is proposed that the prime function of the endodermal cells of the area vasculosa is the production of SEF

Revised Program. New England Intercollegiate Geological Excursion: Montreal, 1931

Program includes visits to St. Helen Island, Mount Royal, Pre-Cambrian of the Laurentians, and the Appalachia front in the vicinity of Phillipsburg, Que

Qualitätsmanagementsysteme und ihre Anwendung auf Serviceeinrichtungen der WGL

"Der Arbeitsbericht gibt einen Überblick über häufig verwendete Begriffe und Konzepte im Bereich von Qualitätsmanagementsystemen. Neben der Normenfamilie ISO 9000 - 9004 sowie Total Quality Management (TQM) werden spezielle Maßnahmen wie Benchmarking und Re-Engineering angesprochen sowie Probleme der Anwendung dieser Systeme im Bereich von Forschungs- und Serviceeinrichtungen diskutiert. Auf die Evaluation und die geplanten Maßnahmen zur Qualitätssicherung im Rahmen der Institute der Wissenschaftsgemeinschaft Gottfried Wilhelm Leibniz (WGL) und die Besonderheiten von Serviceeinrichtungen wird eingegangen." (Autorenreferat

A Numerical Study on the Effects of Leading-Edge Modifications Upon Propeller Flow Characteristics

This paper reports upon a numerical investigation into the implementation of tubercles in marine propellers. Although they have been mooted as a possible flow control solution in propeller designs, their exact implementation and performances have so far been virtually non-existent. In this work, global performance of a tubercle-modified propeller in terms of thrust and torque are determined from numerical simulations. These quantities are taken across various advance ratio values as well. Results show that implementation of tubercles on the propeller is able to improve thrust by up to 1.5%, specifically at lower advance ratio values. However, decreases in propeller efficiency are also observed. In particular, propeller efficiency only shows improvements above the baseline values when the advance ratio is 0.85 and beyond. Lastly, wall streamlines and surface pressure results are presented to shed light upon the influences exerted by the tubercles upon the propeller blade flow fields

Effects of cross-stream radial injections on a round jet

10.1080/14685240600847466Journal of Turbulence71-2

Effects of circumferential microjets on the near-field behaviour of a round jet

AIAA Paper11651-1166

Tubercle Modifications in Marine Propeller Blades

Tubercles are essentially sinusoidal serrations that are present in the fins of humpback whales. They have been widely postulated as a form of passive flow control device for aerodynamic surfaces. Studies pertaining the implementation of tubercles into aerofoils and turbine blades are widely present, while efforts in incorporating these tubercles onto marine propeller blades and how their presence alters the original propeller blade flow behaviour are comparatively less well understood. In this study, tubercle modifications are investigated in marine propellers through the use of high-fidelity Computational Fluid Dynamics (CFD). The results indicate that while there is a substantial increase in thrust generation of up to 10%, there is also a 5% decrease in propeller efficiency. The results indicate that the particular design and implementation of leading-edge tubercles here confer selected favourable flow effects upon propeller performance by varying the pressure and velocity distributions of the propeller blades

Effects of indeterminate-origin collars on self-excited collared-jets

10.1080/14685248.2010.490220Journal of Turbulence111-2