The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Vincent L. Y. Loke - One of the best experts on this subject based on the ideXlab platform.
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discrete dipole approximation with Surface Interaction computational toolbox for matlab
Journal of Quantitative Spectroscopy & Radiative Transfer, 2011Co-Authors: Pinar M Menguc, Vincent L. Y. Loke, Timo A NieminenAbstract:We describe a MATLAB toolbox that utilizes the discrete-dipole approximation (DDA) method for modelling light Interaction with arbitrarily-shape scatterers in free space as well with planar Surface Interaction (DDA-SI). The range of applicable models range from optical micromanipulation, plamonics, nano-antennae, near-field coupling and general light Interaction with scatterers ranging from a few nanometers to several microns in size.
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Surface waves and atomic force microscope probe particle near field coupling discrete dipole approximation with Surface Interaction
Journal of The Optical Society of America A-optics Image Science and Vision, 2010Co-Authors: Vincent L. Y. Loke, Pinar M MengucAbstract:Evanescent waves on a Surface form due to the collective motion of charges within the medium. They do not carry any energy away from the Surface and decay exponentially as a function of the distance. However, if there is any object within the evanescent field, electromagnetic energy within the medium is tunneled away and either absorbed or scattered. In this case, the absorption is localized, and potentially it can be used for selective diagnosis or nanopatterning applications. On the other hand, scattering of evanescent waves can be employed for characterization of nanoscale structures and particles on the Surface. In this paper we present a numerical methodology to study the physics of such absorption and scattering mechanisms. We developed a MATLAB implementation of discrete dipole approximation with Surface Interaction (DDA-SI) in combination with evanescent wave illumination to investigate the near-field coupling between particles on the Surface and a probe. This method can be used to explore the effects of a number of physical, geometrical, and material properties for problems involving nanostructures on or in the proximity of a substrate under arbitrary illumination.
Clifford A Brown - One of the best experts on this subject based on the ideXlab platform.
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including finite Surface span effects in empirical jet Surface Interaction noise models
54th AIAA Aerospace Sciences Meeting, 2016Co-Authors: Clifford A BrownAbstract:The effect of finite span on the jet-Surface Interaction noise source and the jet mixing noise shielding and reflection effects is considered using recently acquired experimental data. First, the experimental setup and resulting data are presented with particular attention to the role of Surface span on far-field noise. These effects are then included in existing empirical models that have previously assumed that all Surfaces are semi-infinite. This extended abstract briefly describes the experimental setup and data leaving the empirical modeling aspects for the final paper.
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an empirical jet Surface Interaction noise model with temperature and nozzle aspect ratio effects
53rd AIAA Aerospace Sciences Meeting, 2015Co-Authors: Clifford A BrownAbstract:An empirical model for jet-Surface Interaction (JSI) noise produced by a round jet near a flat plate is described and the resulting model evaluated. The model covers unheated and hot jet conditions (1 ≤ TT,R ≤ 2.7) in the subsonic range (0.5 ≤ Ma ≤ 0.9), Surface lengths 0.6 ≤ x TE /Dj ≤ 10, and Surface standoff distances (0 ≤ h TE /x TE ≤ 1) using only second-order polynomials to provide predictable behavior. The JSI noise model is combined with an existing jet mixing noise model to produce exhaust noise predictions. Fit quality metrics and comparisons to between the predicted and experimental data indicate that the model is suitable for many system level studies. A first-order correction to the JSI source model that accounts for the effect of nozzle aspect ratio is also explored. This correction is based on changes to the potential core length and frequency scaling associated with rectangular nozzles up to 8:1 aspect ratio. However, more work is needed to refine these findings into a formal model.
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jet Surface Interaction test flow measurements results
AIAA CEAS Aeroacoustics Conference, 2014Co-Authors: Clifford A Brown, Mark P WernetAbstract:Modern aircraft design often puts the engine exhaust in close proximity to the airframe Surfaces. Aircraft noise prediction tools must continue to develop in order to meet the challenges these aircraft present. The Jet-Surface Interaction Tests have been conducted to provide a comprehensive quality set of experimental data suitable for development and validation of these exhaust noise prediction methods. Flow measurements have been acquired using streamwise and cross-stream particle image velocimetry (PIV) and fluctuating Surface pressure data acquired using flush mounted pressure transducers near the Surface trailing edge. These data combined with previously reported far-field and phased array noise measurements represent the first step toward the experimental data base. These flow data are particularly applicable to development of noise prediction methods which rely on computational fluid dynamics to uncover the flow physics. A representative sample of the large flow data set acquired is presented here to show how a Surface near a jet affects the turbulent kinetic energy in the plume, the spatial relationship between the jet plume and Surface needed to generate Surface trailing-edge noise, and differences between heated and unheated jet flows with respect to Surfaces.
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jet Surface Interaction test far field noise results
Volume 1: Aircraft Engine; Ceramics; Coal Biomass and Alternative Fuels; Controls Diagnostics and Instrumentation, 2012Co-Authors: Clifford A BrownAbstract:Many configurations proposed for the next generation of aircraft rely on the wing or other aircraft Surfaces to shield the engine noise from the observers on the ground. However, the ability to predict the shielding effect and any new noise sources that arise from the high-speed jet flow interacting with a hard Surface is currently limited. Furthermore, quality experimental data from jets with Surfaces nearby suitable for developing and validating noise prediction methods are usually tied to a particular vehicle concept and, therefore, very complicated. The Jet/Surface Interaction Test was intended to supply a high quality set of data covering a wide range of Surface geometries and positions and jet flows to researchers developing aircraft noise prediction tools. During phase one, the goal was to measure the noise of a jet near a simple planar Surface while varying the Surface length and location in order to: (1) validate noise prediction schemes when the Surface is acting only as a jet noise shield and when the jet/Surface Interaction is creating additional noise, and (2) determine regions of interest for more detailed tests in phase two. To meet these phase one objectives, a flat plate was mounted on a two-axis traverse in two distinct configurations: (1) as a shield between the jet and the observer (microphone array) and (2) as a reflecting Surface on the opposite side of the jet from the observer. The Surface was moved through axial positions 2 ≤ xTE/Dj ≤ 20 (measured at the Surface trailing edge, xTE, and normalized by the jet diameter, Dj) and radial positions 1 ≤ h/Dj ≤ 20. Far-field and phased array noise data were acquired at each combination of axial and radial Surface location using two nozzles and at 8 different jet exit conditions across several flow regimes (subsonic cold, subsonic hot, underexpanded, ideally expanded, and overexpanded supersonic cold). The far-field noise results, discussed here, show where the Surface shields some of the jet noise and, depending on the location of the Surface and the observer, where scrubbing and trailing edge noise sources are created as a Surface extends downstream and approaches the jet plume.
Patrick Jenny - One of the best experts on this subject based on the ideXlab platform.
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a gas Surface Interaction kernel for diatomic rarefied gas flows based on the cercignani lampis lord model
Physics of Fluids, 2014Co-Authors: Hossein Miladi Gorji, Patrick JennyAbstract:This work presents a kinetic wall boundary model for diatomic gas molecules. The model is derived by generalizing the Cercignani-Lampis-Lord gas-Surface Interaction kernel in order to account for the gas internal degrees of freedom. Here, opposed to the extensions by Lord [“Some extensions to the Cercignani-Lampis gas-Surface scattering kernel,” Phys. Fluids 3, 706–710 (1991)], energy exchange between different molecular modes is honored and thus, different physical phenomena arising from inelastic gas–Surface collisions can be described. For practical implementations of the model, a Monte–Carlo algorithm was devised, which significantly reduces the computational cost associated with sampling. Comparisons of model predictions with experimental and molecular dynamics data exhibit good agreement. Moreover, simulation studies are performed to demonstrate how energy transfers between different modes due to wall collisions can be exploited for gas separation.
Timo A Nieminen - One of the best experts on this subject based on the ideXlab platform.
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discrete dipole approximation with Surface Interaction computational toolbox for matlab
Journal of Quantitative Spectroscopy & Radiative Transfer, 2011Co-Authors: Pinar M Menguc, Vincent L. Y. Loke, Timo A NieminenAbstract:We describe a MATLAB toolbox that utilizes the discrete-dipole approximation (DDA) method for modelling light Interaction with arbitrarily-shape scatterers in free space as well with planar Surface Interaction (DDA-SI). The range of applicable models range from optical micromanipulation, plamonics, nano-antennae, near-field coupling and general light Interaction with scatterers ranging from a few nanometers to several microns in size.
Hossein Miladi Gorji - One of the best experts on this subject based on the ideXlab platform.
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a gas Surface Interaction kernel for diatomic rarefied gas flows based on the cercignani lampis lord model
Physics of Fluids, 2014Co-Authors: Hossein Miladi Gorji, Patrick JennyAbstract:This work presents a kinetic wall boundary model for diatomic gas molecules. The model is derived by generalizing the Cercignani-Lampis-Lord gas-Surface Interaction kernel in order to account for the gas internal degrees of freedom. Here, opposed to the extensions by Lord [“Some extensions to the Cercignani-Lampis gas-Surface scattering kernel,” Phys. Fluids 3, 706–710 (1991)], energy exchange between different molecular modes is honored and thus, different physical phenomena arising from inelastic gas–Surface collisions can be described. For practical implementations of the model, a Monte–Carlo algorithm was devised, which significantly reduces the computational cost associated with sampling. Comparisons of model predictions with experimental and molecular dynamics data exhibit good agreement. Moreover, simulation studies are performed to demonstrate how energy transfers between different modes due to wall collisions can be exploited for gas separation.
