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 20 of 22 for “"serrations"”.
-
Aeroacoustic transfer of leading edge serrations from single aerofoils to low-pressure fan applications
Leading edge serrations are well-known for their aeroacoustic potential in reducing aerofoil-turbulence interaction noise and are also associated with certain aerodynamic advantages. To prepare leading edge serrations for industrial application, two obstacles remain to be addressed. First is a …
-
Impact of ground plane serrations on radiation and impedance characteristics of a slot antenna over a conductive back plane
… by treating the edge of the ground plane with serrations. Our primary goal is to show the design trade-offs between bandwidth and thickness for the conductor-backed, serrated slot antenna. In our analysis we use simulations which we validate through measurements. Two bandwidth measures, …
-
Understanding the Impact of a Serrated Trailing Edge on the Unsteady Hydrodynamic Field
… have shown that a trailing edge with sawtooth serrations can reduce trailing edge noise compared to a straight trailing edge, but the mechanism by which sawtooth serrations reduce noise is not fully understood. Previous theoretical models have assumed that the turbulence field convecting past a …
-
Radiation in the genus Amazilia: A comparative approach to understanding the diversification of hummingbirds.
… Then I narrate the discovery of bill serrations among 28 hummingbird genera (Chapter 2), and hypothesized that these structures aid in nectar-robbing of long-tubed corollas. I test this hypothesis and found that the association between nectar-robbing and bill serrations evolved several …
-
Analysis and design of planar slot antennas for RFID applications using characteristic mode theory
… In addition, edge treatment in the form of serrations can be used to improve the bandwidth and radiation properties of thin planar antennas. Although serrations offer a simple technique to improve radiation characteristics of a microstrip antenna, there are no design guidelines or analytical …
-
Modifications of Coherent Structures in Fan Blade Wakes for Broadband Noise Reduction
… of streamwise vorticity. In almost all cases the serrations reduce the spanwise and streamwise turbulence scales. Serrations do not, however, affect the apparent time scale of quasi-periodic structures in the wake, and this appears to limit the potential of this trailing edge treatment to reduce …
-
An embedded IoT antenna for smart pavement monitoring system
… and measurement results show that with serrations on the ground plane, the proposed antenna is able provide broadside gain of 3.4 dB through asphalt pavement.
-
Advanced experimental measurements of heterogeneous strain and temperature change in metals
… Using the microstructure, grain boundary serrations and triple junction strain concentrations were quantitatively identified. There was significant damage in the 900 °C samples and the creep was almost entirely tertiary. In contrast, the 800 °C sample exhibited secondary creep. Using an …
-
Boundary Layer Separation Control on a Salient Back-facing Ramp
… is two-dimensional. Three geometries of serrations: a sharp delta, a double delta and a divergent delta are examined on 15° and 30° deflected, backward-facing ramps. Parameterizing the device spacing and the device-height-to-chord ratio assesses the performance change with different …
-
Small, dual band, placement insensitive antennas
… slot antenna. In this work, we show that edge serrations can reduce the cavity effect in a parallel plate configuration, making a slot antenna with edge treatments a viable design for environment-independent peel-and-stick applications. For this research to be broadly applicable, transmission …
-
Comparative Analysis of Serrated Trailing Edge Designs on Idealized Aircraft Engine Fan Blades for Noise Reduction
… In the wake region, the individual trailing edge serrations tips and valleys could be seen. As the wake convected downstream, the individual tips and valleys became less visible and the wake was more uniform in profile. The tip leakage vortex was only minimally affected by the trailing edge …
-
Statistics of slip avalanches in sheared amorphous materials based on atomistic simulation
… probability distribution of the magnitude of serrations in stress-strain curves. Mesoscale models of amorphous plasticity, depending on assumptions of the interaction between slipped sites, give different predictions of scaling exponents. Atomistic simulation, which does not rely on such …
-
An experimental study on the performance of existing and custom quiet propeller designs for unmanned aircraft systems
… layer trip on the leading edge top surface or serrations to the trailing edge has been shown to reduce the sound radiated by the propeller. In total, 37 quiet propeller designs were created and simulated using SolidWorks Flow Simulation. From the simulation results, the three best performing …
-
Scattering by porous aerofoil adaptations
… through geometric or structural changes: serrations, slits, finlets, and canopies. Each has been shown to have the potential to achieve significant reductions in far-field sound. However, it remains unclear precisely how these reductions are achieved for a number of these designs, …
-
Numerical modelling and design of wideband electromagnetic structures at radio frequencies: Applications in cosmology and digital communications
… Also noted is the impact of the addition of serrations to the edge of a square ground plane, with the replacement of large wavelike chromatic fluctuations with smaller pockmark type deviations. Finally, I describe the implementation of a quantified figure of merit based design method of radio …
-
Modeling the power requirements of a rotary feeding and cutting system
… these concluded that counter-knife sharpness, serrations and bevel angle all had significant effects on the specific energy required by the LSCP RFCS when processing cereal straw and alfalfa. The specific energy required by the LSCP RFCS, while processing cereal straw, increased by 0.35 …
-
Grain boundaries and creep deformation mechanisms in a high performance nickel-based superalloy
… from the testing conditions. Grain boundary serrations promoted the formation of dislocation networks which were linked to both the nucleation of stacking faults and the inhibition of their impingement on opposite grain boundaries. This promoted an homogeneous stress distribution preventing …
-
Phase stability and the Portevin-Le Chatelier effect in Cr-Mn-Fe-Co-Ni High-Entropy Alloys
… testing, the effect is generally associated with serrations in the materials flow curve and the localisation of strain into discrete bands. Serrated flow has been observed in several HEAs but the associated strain localisation behaviour has not yet been reported, so it is uncertain whether this …
-
Bio-Inspired Axial Fan Design, 3D Printing Fabrication and Characterization for Noise and Flow Performance Optimization
… mechanisms of owls, bio-inspired trailing-edge serrations are then investigated as a passive control strategy for noise reduction in airfoil-based configurations relevant to axial fans. A hybrid numerical–experimental methodology, based on Large Eddy Simulations (LES) of the incompressible …
-
Aspects of serrated flow in aluminium alloys
… basis of these observations, the magnitude of serrations and extent of serrated flow in the alloys has been discussed. The extent to which the different alloys were able to undergo dynamic recovery affected both the evolution of the dislocation structure observed in the conventional …
Page 1 of 2