Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 19 of 19 for “"downwash"”.
-
Effects of Downwash when Measuring Gas Concentration with UAV-Mounted Gas Sensors
<p>"This research concludes that the downwash region of a rotary-wing unmanned aerial vehicle (UAV) does not produce pressure variations substantial enough to cause significant changes in density-based gas concentration measurements. US regulations evaluate gas concentration as a function of gas …
-
The Near Wake of a European Starling
… Measurements of the wake indicate that downwash is not produced during the upstroke, suggesting that the upstroke does not generate lift. Additional characteristics of the wake are discussed which imply the presence of (secondary) streamwise vortical structures, in addition to the wing …
-
The effect of turboprop propulsion on the aerodynamic benefits of formation flight
… theory of Goldstein and Theodorsen. The downwash velocity field of a B747 during cruise, obtained via the use of the VFM Burnham-Hallock (VFM B-H) model programme, was verified against both the simulation conducted by Ehret and Oertel, in which an integrated Biot-Savart law VFM was …
-
Performance characterization of the multirotor UAS chemical application system
… off-target (up to 50% of droplets) due to downwash outflow, or lost due to meteorological conditions. Droplets in the Medium and Fine spectrum were sensitive to air flow and hence nozzles producing large amounts of these droplets tended to behave less predictably. The more droplets produced …
-
EFFECTS OF WALL PLANE TOPOLOGY ON VORTEX-WALL INTERACTIONS IN A FORCED IMPINGING JET
… landing rotorcraft. In the current work, the downwash of a rotorcraft is simplified using a prototype flow consisting of an acoustically forced impinging jet. The goal of the current investigation is to quantify the effects of disturbances to the ground-plane boundary layer on the …
-
Comparative Evaluation of Propulsive Power Transmission Technologies for High-Speed Vertical Takeoff and Landing (HSVTOL) Cargo Aircraft
… (HSVTOL) cargo aircraft capable of both low downwash velocity hovering and high subsonic speed cruising presents a significant engineering challenge. This challenge, stemming from conflicting design requirements, has been substantially influenced by recent technological advancements, which …
-
Hydrofoil shape optimization by gradient methods
… theory was used to account for induced drag and downwash at the leading edge of the foil. Strip theory was used to extend the two-dimensional wave drag solutions to three dimensions for high aspect ratio foils. A semi-empirical correction was added to account for viscous drag. The drag-to-lift …
-
An Experimental Investigation of Ground Effect on a Quad Tilt Rotor in Hover and Low Speed Forward Flight
… of the bottom of the fuselage were measured. The downwash distributions of the rotors were measured and found to compare well with V-22 rotor measurements. Tuft flow visualization was used to identify the physical processes causing changes in the download and pressure measurements. An uncertainty …
-
Constrained Control of Complex Helicopter Models
… a fully articulated main rotor, main rotor downwash, and blade flapping are also modeled. The modeling process is motivated by the desire to build control oriented, physics based models that directly result in ordinary differential equations (ODE) models which are sufficiently rich in …
-
Aerodynamics of lifting surfaces in propeller slipstreams
… trailing vortices. The trailing vortices caused downwash on the sections within the slipstream flow and upwash on the sections located outside the slipstream which led to an early onset of stall on the outboard sections.
-
Effect of diameter ratios on the flow-sound interaction of the straight circular finned cylinders
… in the near wake is found to be caused by the downwash flow induced by an array of edge vortices that generate at the tip of the fins. The RMS of the fluctuating lift coefficient increases significantly on the surface of the finned cylinders due to a reduction in the vortex formation length and …
-
Unsteady Aerodynamics of Wing–Vortex Gust Encounters
… Küssner functions to incorporate unsteady wake downwash and non-circulatory forces. Both positive and negative vortex gusts are tested at two wing--vortex chord-normal separations and wing incidences between -20º and 20º. The unsteady model yields an average prediction error of 11%, compared to …
-
Effects of Various Shaped Roughness Elements in Two-Dimensional High Reynolds Number Turbulent Boundary Layers
… in front of the element, which induces the downwash of higher momentum fluid toward the wall. This 'sweep' motion not only creates high Reynolds stresses (v^2, w^2, -uv) downstream of the element, but also leads to higher skin-friction drag. Triple products were also found to be very …
-
Large eddy simulations of turbulent flows on graphics processing units: application to film-cooling flows
… was found that the micro-ramp vortices created a downwash effect toward the wall, which helped entrain coolant from the jet and transport it to the wall, resulting in better cooling. Results are reported using two film-cooling configurations, where the primary difference is the way the jet exit …
-
Contributions to the Understanding of Ship Airwakes Using Advanced Flow Diagnostic Techniques
… of the intense zones of unsteady upwash/downwash over the flight deck that are known to affect rotorcraft that operate in the airwake.</p>
-
Fluid dynamics of boundary layer combustion
… the streaks. The troughs are located in a downwash region, where counter-rotating vortices force the flame sheet towards the surface, increasing the surface heat flux. This spanwise redistribution of surface heat flux confirmed that streaks can, at least instantaneously, modify important …
-
Three-Dimensional Unsteady Hydrodynamics of Tidal Turbines
… load response is found to be the unsteady wake downwash, which is divided into contributions from the spanwise and streamwise components of wake vorticity. The former is modelled as extending infinitely in 2D models, while the latter is neglected altogether. URANS modelling and a time-domain …
-
The effect of wing flexibility on ride comfort in formation flight
… spanwise separation of the aircraft, varying the downwash distribution over the wing. The motion of the turbulence in the z-direction merely affected the intensity of the aerodynamic loads caused by the trailing vortices. From these results, it was concluded that an aircraft flying in formation …
-
The effects of micro-vortex generators on normal shock wave/boundary layer interactions
… vortices in addition to an induced upwash/downwash which persists through the normal shock with reduced strength. The microramp flow control also increased the spanwise-averaged skin-friction coefficient and reduced the spanwise-averaged incompressible shape factor, thereby improving the …