Department of Aerospace and Ocean Engineering

Permanent URI for this community

https://hdl.handle.net/10919/11363

Browse

Browsing Department of Aerospace and Ocean Engineering by Title

Now showing 1 - 20 of 168
  • Thumbnail Image
    50-kHz-rate 2D imaging of temperature and H2O concentration at the exhaust plane of a J85 engine using hyperspectral tomography
    Ma, Lin; Li, Xuesong; Sanders, Scott T.; Caswell, Andrew W.; Roy, Sukesh; Plemmons, David H.; Gord, James R. (Optical Society of America, 2013-01-01)
    This paper describes a novel laser diagnostic and its demonstration in a practical aero-propulsion engine (General Electric J85). The diagnostic technique, named hyperspectral tomography (HT), enables simultaneous 2-dimensional (2D) imaging of temperature and water-vapor concentration at 225 spatial grid points with a temporal response up to 50 kHz. To our knowledge, this is the first time that such sensing capabilities have been reported. This paper introduces the principles of the HT techniques, reports its operation and application in a J85 engine, and discusses its perspective for the study of high-speed reactive flows. (C) 2013 Optical Society of America
  • Thumbnail Image
    5th International Symposium on Focused Ultrasound
    Abounader, Roger; Abraham, Christopher; Adema, Gosse; Agrawal, Punit; Airan, Raag; Aleman, Dionne; Alexander, Phillip; Alkins, Ryan; Alnazeer, Moez; Altman, Michael; Aly, Amirah; Amaral, Joao G.; Amrahli, Maral; Amraoui, Sana; Andarawewa, Kumari; Andriyakhina, Yulia; Angstadt, Mary; Ankou, Bénédicte; Arias, Ana C.; Arvanitis, Costas; Asadnia, Kiana; Aubert, Isabelle; Aubry, Jean-Francois; Aubry, Jean-Francois; Aurup, Christian; Bader, Kenneth; Badr, Lena; Baek, Hongchae; Barbato, Gaetano; Beccaria, Kevin; Bellorofonte, Carlo; Benson, Lee; Bernus, Olivier; Berriet, Rémi; Bertolina, Jim; Beskin, Viktoriya; Bessière, Francis; Bethune, Allison; Bezzi, Mario; Bond, Aaron; Bonomo, Guido; Borowsky, Alexander; Borys, Nicolas; Böttcher, Joachim; Bouley, Donna; Bour, Pierre; Bourekas, Eric; Brenin, David; Brokman, Omer; Brosh, Inbar; Buckner, Andrew; Bullock, Timothy; Cafarelli, Andrea; Cahill, Jessica; Camarena, Francisco; Camelo-Piragua, Sandra; Campbell, Benjamin; Campbell, Fiona; Cannata, Jon; Canney, Michael; Carlson, Roy; Carneiro, Antonio; Carpentier, Alexandre; Catheline, Stefan; Cavin, Ian; Cesana, Claudio; Chabok, Hamid R.; Chamanara, Marzieh; Chang, Jin H.; Chang, Won S.; Changizi, Barbara; Chapelon, Jean Y.; Chaplin, Vandiver; Chapman, Martin; Chaudhary, Neeraj; Chaussy, Christian; Chen, Cherry; Chen, Johnny; Chen, Wohsing; Chen, Xiaoming; Chevalier, Philippe; Chiou, George; Chisholm, Alexander; Christofferson, Ivy; Chung, Hyun H.; Ciuti, Gastone; Clement, Gregory; Cooper, Mark; Corea, Joseph; Corso, Cristiano; Cosman, Josh; Coughlin, Dezba; Crake, Calum; Cunitz, Bryan; Curiel, Laura; Curley, Colleen T.; Czarnota, Gregory; Dababou, Susan; Dallapiazza, Robert; de Bever, Joshua; de Jager, Bram; de Ruiter, Joost; de Senneville, Baudouin D.; Deckers, Roel; Delattre, Jean-Yves; den Brok, Martijn; Dhanaliwala, Ali; Diodato, Alessandro; Dixon, Adam; Donner, Elizabeth; Downs, Matthew; Du, Zhongmin; Dubois, Rémi; Dupre, Aurelien; Eikelenboom, Dylan; Elias, W. J.; Ellens, Nicholas; Endre, Ruby; Eran, Ayelet; Erasmus, Hans-Peter; Everstine, Ashli; Farahani, Keyvan; Farrer, Alexis; Farry, Justin; Federau, Christian; Feng, Xue; Ferrer, Cyril; Ferrera, Vincent; Fishman, Paul; Foley, Jessica; Frenkel, Victor; Fütterer, Jurgen; Gach, H. M.; Gandhi, Dheeraj; Gertner, Michael; Goldsher, Dorit; Gorgone, Alessandro; Greillier, Paul; Griesenauer, Rebekah; Grissom, William; Grondin, Julien; Guha, Chandan; Gulati, Amitabh; Gullapalli, Rao; Guo, Sijia; Gupta, Samit; Gurm, Hitinder; Gwinn, Ryder; Hadley, Rock; Haïssaguerre, Michel; Hammoud, Dima; Hananel, Arik; Hargrove, Amelia; Hatch, Robert; Haworth, Kevin; Hazan, Eilon; He, Ye; Heemels, Maurice; Heerschap, Arend; Hilas, Elaine; Hoang-Xuan, Khe; Hocini, Mélèze; Hodaie, Mojgan; Hofmann, Denis; Holland, Christy; Hoogenboom, Martijn; Hopyan, Sevan; Hossack, John; Houdouin, Alexandre; Hsu, Po-Hung; Hu, Jim; Hurwitz, Mark; Huss, Diane; Hwang, Chang-il; Hwang, Joo H.; Idbaih, Ahmed; Ikeuchi, Masahiko; Ingham, Elizabeth; Ives, Kimberly; Izumi, Masashi; Jackson-Lewis, Vernice; Janát-Amsbury, Margit; Jang, Kee W.; Jedruszczuk, Kathleen; Jiménez-Gambín, Sergio; Jiménez, Noé; Johnson, Sara; Jonathan, Sumeeth; Joy, Joyce; Jung, Hyun H.; Jung, Na Y.; Kahn, Itamar; Kamimura, Hermes; Kamrava, Seyed K.; Kang, Jeeun; Kang, Kook J.; Kang, Soo Y.; Kao, Yi-tzu; Katti, Prateek; Kawasaki, Motohiro; Kaye, Elena; Keupp, Jochen; Kim, AeRang; Kim, Harry; Kim, Hyun-Chul; Kim, Hyuncheol; Kim, Hyungmin; Kim, Min S.; Kim, Namho; Kiyasu, Katsuhito; Kneepkens, Esther; Knopp, Michael; Kobus, Thiele; Koral, Korgun; Kreider, Wayne; Krishna, Vibhor; Krug, Roland; Krupa, Steve; Kuo, Chia-Chun; Kwiecinski, Wojciech; Lacoste, Romain; Lam, Heather; Lamberti-Pasculli, Maria; Lang, Brian; Larner, James; Larrabee, Zachary; Leach, J. K.; LeBlang, Suzanne; Leclercq, Delphine; Lee, Hak J.; Lee, Jong-Hwan; Lehericy, Stéphane; Leighton, Wan; Leung, Steven; Lewis, Bobbi; Lewis, Matthew; Li, Dawei; Linn, Sabine; Lipsman, Nir; Liu, Hao-Li; Liu, Jingfei; Lopes, M. B.; Lotz, Jeff; Lu, Xin; Lundt, Jonathan; Luo, Xi; Lustgarten, Lior; Lustig, Micheal; Macoskey, Jonathan; Madore, Bruno; Maev, Roman; Magat, Julie; Maimbourg, Guillaume; Maimon, Noam; Mainprize, Todd; Malayer, Jerry; Maples, Danny; Marquet, Fabrice; Marrocchio, Cristina; Marx, Mike; Mastorakos, Panagiotis; Mauri, Giovanni; McLean, Hailey; McMichael, John; Mead, Brian P.; Melodelima, David; Melot-Dusseau, Sandrine; Menciassi, Arianna; Merrill, Robb; Meyer, Joshua; Midiri, Massimo; Miga, Michael; Migliore, Ilaria G.; Miller, Eric; Minalga, Emilee; Moon, Hyungwon; Moore, David; Mourad, Pierre; Mouratidis, Petros; Mueller, Michael; Mugler, John; Muller, Sébastien; Namba, Hirofumi; Naor, Omer; Nassar, Maria; Nazai, Navid; Negron, Karina; Negussie, Ayele; Nguyen, Thai-Son; Nicolay, Klaas; Nikolaeva, Anastasia V.; Oetgen, Matthew; Olive, Kenneth; Olumolade, Oluyemi; Orsi, Franco; Owens, Gabe; Ozilgen, Arda; Padegimas, Linas; Palermo, Carmine; Pan, Chia-Hsin; Pandey, Aditya; Papadakis, Georgios; Park, Chang K.; Park, Sang M.; Parker, Jonathon; Parvizi, Mohammad H.; Pascal-Tenorio, Aurea; Patel, Janish; Patz, Sam; Payen, Thomas; Perich, Eloi; Pernot, Mathieu; Perol, David; Perry, James; Pillarisetty, Venu; Pioche, Mathieu; Pizzuto, Matthew; Plaksin, Michael; Plata, Juan; Price, Karl; Prince, Jessica; Przedborski, Serge; Quinones-Hinojosa, Alfredo; Ramachandran, Akhilesh; Ranjan, Ashish; Ravikumar, Vinod; Reichenbach, Juergen; Repasky, Elizabeth; Rezai, Ali; Ritter, Philippe; Rivoire, Michel; Rochman, Carrie; Rosenberg, Jarrett; Rosnitskiy, Pavel B.; Ruiz, Antonio; Sahgal, Arjun; Samiotaki, Gesthimani; Sanghvi, Narendra; Santin, Mathieu D.; Santos, Domiciano; Sasaki, Noboru; Sastra, Steve; Schade, George; Schall, Jeffrey; Schlesinger, Ilana; Schmitt, Paul; Schwaab, Julia; Scionti, Stephen; Scipione, Roberto; Scoarughi, Gian L.; Scott, Serena; Sebeke, Lukas; Seifabadi, Reza; Seo, Jai; Sesenoglu-Laird, Ozge; Shah, Binit; Shahriari, Kian; Shaikh, Sumbul; Shea, Jill; Shi, Jiaqi; Shim, Jenny; Shinkov, Alexander; Shuman, Jillian; Silvestrini, Matthew; Sim, Changbeom; Sin, Vivian; Sinai, Alon; Singh, Manoj; Sinilshchikov, Ilya; Skalina, Karin; Slingluff, Craig; So, Po-Wah; Solomon, Stephen; Son, Keon H.; Sperling, Scott; Stein, Ruben; Stein, Sherman; Stevens, Aaron; Stimec, Jennifer; Storm, Gert; Straube, William; Suelmann, Britt; Sutton, Jonathan; Svedin, Bryant; Takemasa, Ryuichi; Takiguchi, Mitsuyoshi; Tam, Emily; Tan, Jeremy; Tang, Xinyan; Tanter, Mickael; Tebebi, Pamela; Tehrani, Seruz; Temple, Michael; Teofilovic, Dejan; ter Haar, Gail; Terzi, Marina E.; Thueroff, Stefan; Timbie, Kelsie; Tognarelli, Selene; Tretbar, Steffen; Trudeau, Maureen; Tsai, Yi-Chieh; Tsysar, Sergey A.; Tucci, Samantha; Tuveson, David; Ushida, Takahiro; Vaessen, Paul; Vaillant, Fanny; Van Arsdell, Glen; van Breugel, Johanna; Van der Jeugd, Anneke; Van der Jeugd, Anneke; Van der Wall, Elsken; van Diest, Paul; van Stralen, Marijn; Varano, Gianluca; Velat, Manuela; Vidal-Jove, Joan; Vigna, Paolo D.; Vignot, Alexandre; Vincenot, Jeremy; Vykhodtseva, Natalia; Wang, Bin; Wang, Han; Wang, Kevin; Wang, Qi; Wang, Qingguo; Wang, Shengping; Wang, Yak-Nam; Wang, Zhaorui; Wardlow, Rachel; Warren, Amy; Waszczak, Barbara; Watson, Katherine; Webb, Taylor; Wei-Bin, Shen; Wei, Kuo-Chen; Weiss, Steffen; Weissler, Yoni; Werner, Beat; Wesseling, Pieter; Williams, Noelle; Wilson, Emmanuel; Wintermark, Max; Witkamp, Arjen; Wong, Carlos; Wu, Jing-Fu; Wydra, Adrian; Xu, Alexis; Xu, Doudou; Xu, Su; Yang, Georgiana; Yang, Nai-Yi; Yao, Chen; Yarowsky, Paul; Ye, Patrick P.; Yuldashev, Petr; Zaaroor, Menashe; Zachiu, Cornel; Zahos, Peter; Zangos, Stephan; Zhang, Dandan; Zhang, Hua; Zhang, Jimin; Zhang, Junhai; Zhang, Xi; Zhao, Li; Zhong, Pei; Zhuo, Jiachen; Zidowitz, Stephan; Zinke, Wolf; Zorgani, Ali (2016-11-21)
  • Thumbnail Image
    Acoustic Inversion for Uncertainty Reduction in Reynolds-Averaged Navier-Stokes-Based Jet Noise Prediction
    Zhang, Xin-Lei; Xiao, Heng; Wu, Ting; He, Guowei (American Institute of Aeronautics and Astronautics, 2021-12-13)
    The Reynolds-averaged Navier–Stokes (RANS)-based method is a practical tool to provide rapid assessment of jet noise-reduction concepts. However, the RANS-based method requires modeling assumptions to represent noise generation and propagation, which often reduces the predictive accuracy due to the model-form uncertainties. In this work, the ensemble Kalman filter-based acoustic inversion method is introduced to reduce uncertainties in the turbulent kinetic energy and dissipation rate based on the far-field noise and the axial centerline velocity data. The results show that jet noise data are more effective from which to infer turbulent kinetic energy and dissipation rate compared to velocity data. Moreover, the inferred noise source is able to improve the estimation of the turbulent flowfield and the far-field noise at unobserved locations. Further, the noise model parameters are also considered uncertain quantities, demonstrating the ability of the proposed framework to reduce uncertainties in both the RANS and noise models. Finally, one realistic case with experimental data is investigated to show the practicality of the proposed framework. The method opens up the possibility for the inverse modeling of jet noise sources by incorporating far-field noise data that are relatively straightforward to be measured compared to the velocity field.
  • Thumbnail Image
    Advanced Boundary Simulations of an Aeroacoustic and Aerodynamic Wind Tunnel
    Szőke, Máté; Devenport, William J.; Borgoltz, Aurelien; Roy, Christopher J.; Lowe, K. Todd (2021-05-25)
    This study presents the first 3D two-way coupled fluid structure interaction (FSI) simulation of a hybrid anechoic wind tunnel (HAWT) test section with modeling all important effects, such as turbulence, Kevlar wall porosity and deflection, and reveals for the first time the complete 3D flow structure associated with a lifting model placed into a HAWT. The Kevlar deflections are captured using finite element analysis (FEA) with shell elements operated under a membrane condition. Three-dimensional RANS CFD simulations are used to resolve the flow field. Aerodynamic experimental results are available and are compared against the FSI results. Quantitatively, the pressure coefficients on the airfoil are in good agreement with experimental results. The lift coefficient was slightly underpredicted while the drag was overpredicted by the CFD simulations. The flow structure downstream of the airfoil showed good agreement with the experiments, particularly over the wind tunnel walls where the Kevlar windows interact with the flow field. A discrepancy between previous experimental observations and juncture flow-induced vortices at the ends of the airfoil is found to stem from the limited ability of turbulence models. The qualitative behavior of the flow, including airfoil pressures and cross-sectional flow structure is well captured in the CFD. From the structural side, the behavior of the Kevlar windows and the flow developing over them is closely related to the aerodynamic pressure field induced by the airfoil. The Kevlar displacement and the transpiration velocity across the material is dominated by flow blockage effects, generated aerodynamic lift, and the wake of the airfoil. The airfoil wake increases the Kevlar window displacement, which was previously not resolved by two-dimensional panel-method simulations. The static pressure distribution over the Kevlar windows is symmetrical about the tunnel mid-height, confirming a dominantly two-dimensional flow field.
  • Thumbnail Image
    ALMO: Active Learning-Based Multi-Objective Optimization for Accelerating Constrained Evolutionary Algorithms
    Singh, Karanpreet; Kapania, Rakesh K. (MDPI, 2024-10-31)
    In multi-objective optimization, standard evolutionary algorithms, such as NSGA-II, are computationally expensive, particularly when handling complex constraints. Constraint evaluations, often the bottleneck, require substantial resources. Pre-trained surrogate models have been used to improve computational efficiency, but they often rely heavily on the model’s accuracy and require large datasets. In this study, we use active learning to accelerate multi-objective optimization. Active learning is a machine learning approach that selects the most informative data points to reduce the computational cost of labeling data. It is employed in this study to reduce the number of constraint evaluations during optimization by dynamically querying new data points only when the model is uncertain. Incorporating machine learning into this framework allows the optimization process to focus on critical areas of the search space adaptively, leveraging predictive models to guide the algorithm. This reduces computational overhead and marks a significant advancement in using machine learning to enhance the efficiency and scalability of multi-objective optimization tasks. This method is applied to six challenging benchmark problems and demonstrates more than a 50% reduction in constraint evaluations, with varying savings across different problems. This adaptive approach significantly enhances the computational efficiency of multi-objective optimization without requiring pre-trained models.
  • Thumbnail Image
    Analytic Costate Initialization from Rough State-Trajectory Estimates
    Skamangas, Emmanuel E.; Lawton, John A.; Black, Jonathan T. (American Institute of Aeronautics and Astronautics, 2021-09-07)
  • Thumbnail Image
    Anisotropic RANS Turbulence Modeling for Wakes in an Active Ocean Environment
    Wall, Dylan; Paterson, Eric G. (MDPI, 2020-12-18)
    The problem of simulating wakes in a stratified oceanic environment with active background turbulence is considered. Anisotropic RANS turbulence models are tested against laboratory and eddy-resolving models of the problem. An important aspect of our work is to acknowledge that the environment is not quiescent; therefore, additional sources are included in the models to provide a non-zero background turbulence. The RANS models are found to reproduce some key features from the eddy-resolving and laboratory descriptions of the problem. Tests using the freestream sources show the intuitive result that background turbulence causes more rapid wake growth and decay.
  • Thumbnail Image
    Application of the Spectral Element Method in a Surface Ship Far-Field UNDEX Problem
    Lu, Zhaokuan; Brown, Alan J. (Hindawi, 2019-07-25)
    The prediction of surface ship response to a far-field underwater explosion (UNDEX) requires the simulation of shock wave propagation in the fluid, cavitation, fluid-structure interaction, and structural response. Effective approaches to model the fluid include cavitating acoustic finite element (CAFE) and cavitating acoustic spectral element (CASE) methods. Although the spectral element method offers the potential for greater accuracy at lower computational cost, it also generates more spurious oscillations around discontinuities which are difficult to avoid in shock-related problems. Thus, the advantage of CASE remains unproven. In this paper, we present a 3D-partitioned FSI framework and investigate the application of CAFE and CASE to a surface ship early-time far-field UNDEX problem to determine which method has the best computational efficiency for this problem. We also associate the accuracy of the structural response with the modeling of cavitation distribution. A further contribution of this work is the examination of different nonmatching mesh information exchange schemes to demonstrate how they affect the structural response and improve the CAFE/CASE methodologies.
  • Thumbnail Image
    An Approach for Computing Parameters for a Lagrangian Nonlinear Maneuvering and Seakeeping Model of Submerged Vessel Motion
    Jung, Seyong; Brizzolara, Stefano; Woolsey, Craig A. (IEEE, 2021-07-01)
    In this study, hydrodynamic forces on a submerged vessel maneuvering near a free surface are determined using a reformulated Lagrangian nonlinear maneuvering and seakeeping model derived using Lagrangian mechanics under ideal flow assumptions. A Lagrangian mechanics maneuvering model is first reformulated to simplify the computation of parameters; then, incident wave effects are incorporated into the reformulation; finally, the parameters are computed using a medium-fidelity time-domain potential-flow panel code. Predictions from the reformulated Lagrangian nonlinear maneuvering and seakeeping model, whose parameters are computed using the methods described here, are compared with direct numerical computations in two steps for a prolate spheroid maneuvering in the longitudinal plane near the free surface. First, the hydrodynamic force and moment predicted by the model are compared with solutions from the panel code for sinusoidal motion in surge, heave, and pitch in calm water. Second, the hydrodynamic force and moment are investigated for cases where the spheroid maneuvers to approach the surface in calm water and in plane progressive waves. To conclude, a physically intuitive formulation of the Lagrangian nonlinear maneuvering and seakeeping model is presented for control applications and simulations.
  • Thumbnail Image
    An Approach for Computing Parameters for a Lagrangian Nonlinear Maneuvering and Seakeeping Model of Submerged Vessel Motion
    Jung, Seyong; Brizzolara, Stefano; Woolsey, Craig A. (IEEE, 2021-03)
    In this study, hydrodynamic forces on a submerged vessel maneuvering near a free surface are determined using a reformulated Lagrangian nonlinear maneuvering and seakeeping model derived using Lagrangian mechanics under ideal flow assumptions. A Lagrangian mechanics maneuvering model is first reformulated to simplify the computation of parameters; then, incident wave effects are incorporated into the reformulation; finally, the parameters are computed using a medium-fidelity time-domain potential-flow panel code. Predictions from the reformulated Lagrangian nonlinear maneuvering and seakeeping model, whose parameters are computed using the methods described here, are compared with direct numerical computations in two steps for a prolate spheroid maneuvering in the longitudinal plane near the free surface. First, the hydrodynamic force and moment predicted by the model are compared with solutions from the panel code for sinusoidal motion in surge, heave, and pitch in calm water. Second, the hydrodynamic force and moment are investigated for cases where the spheroid maneuvers to approach the surface in calm water and in plane progressive waves. To conclude, a physically intuitive formulation of the Lagrangian nonlinear maneuvering and seakeeping model is presented for control applications and simulations.
  • Thumbnail Image
    A Beacon in the Galaxy: Updated Arecibo Message for Potential FAST and SETI Projects
    Jiang, Jonathan H.; Li, Hanjie; Chong, Matthew; Jin, Qitian; Rosen, Philip E.; Jiang, Xiaoming; Fahy, Kristen A.; Taylor, Stuart F.; Kong, Zhihui; Hah, Jamilah; Zhu, Zong-Hong (MDPI, 2022-03-25)
    An updated, binary-coded message has been developed for transmission to extraterrestrial intelligences in the Milky Way galaxy. The proposed message includes basic mathematical and physical concepts to establish a universal means of communication followed by information on the biochemical composition of life on Earth, the Solar System’s time-stamped position in the Milky Way relative to known globular clusters, as well as digitized depictions of the Solar System, and Earth’s surface. The message concludes with digitized images of the human form, along with an invitation for any receiving intelligences to respond. Calculation of the optimal timing during a given calendar year is specified for potential future transmission from both the Five-hundred-meter Aperture Spherical radio Telescope in China and the SETI Institute’s Allen Telescope Array in northern California to a selected region of the Milky Way which has been proposed as the most likely location for life to have developed. These powerful new beacons, the successors to the Arecibo radio telescope which transmitted the 1974 message upon which this expanded communication is in part based, can carry forward Arecibo’s legacy into the 21st century with this equally well-constructed communication from Earth’s technological civilization.
  • Thumbnail Image
    A Brief History of Aerospace Engineering at the Virginia Polytechnic Institute and State University
    Walters, Robert W.; Johnston, Jane Echols (American Institute of Aeronautics and Astronautics, 2004)
    This book chapter provides an historical of Aerospace Engineering at Virginia Tech, covering 1913-2004.
  • Thumbnail Image
    Buckling Analysis and Optimization of Stiffened Variable Angle Tow Laminates with a Cutout Considering Manufacturing Constraints
    Zhao, Wei; Kapania, Rakesh K. (MDPI, 2022-03-04)
    Variable angle tow laminates (VAT) and stiffeners are known to redistribute the in-plane load distribution and tailor the buckling mode shapes, respectively, for improving structural performance. To leverage the benefits of using VAT laminates in the practical applications, in the present paper, we discuss buckling load maximization conducted for a stiffened VAT laminated plate with a central cutout considering VAT laminate manufacturing constraints. Three representative boundary conditions as seen in the aerospace structures are considered: in-plane axial displacement, in-plane pure shear, and in-plane pure bending displacements. Two common manufacturing constraints, the one on the automatic fiber placement (AFP) manufacturing head turning radius and the other on the tow gap/overlap, while fabricating VAT laminates are considered in the laminate design. These two manufacturing constraints are modeled by controlling the fiber path radius of curvature and tape parallelism in optimizing the fiber path orientations for the VAT laminates. Stiffener layout and fiber path angle for the VAT laminated plates are both considered in the buckling load maximization study. To avoid using a fine mesh in modeling the stiffened VAT laminates with a cutout when employing the finite element analysis during the optimization, the VAT laminated plate and the stiffeners are modeled independently. The displacement compatibility is enforced at the stiffener–plate interfaces to ensure that the stiffeners move with the plate. Particle swarm optimization is used as the optimization algorithm for the buckling load maximization study. Optimization results show that, without considering AFP manufacturing constraints, the VAT laminates can increase the buckling loads by 21.2% and 12.4%, respectively, comparing to the commonly used quasi-isotropic laminates and traditionally straight fiber path laminates for the structure under the in-plane axial displacement case, 19.7% and 12.5%, respectively, for the in-plane shear displacement case, and 62.1% and 26.6%, respectively, for the in-plane bending displacement case. The AFP manufacturing constraints are found to have different impacts on the buckling responses for the VAT laminates, which cause the maximum buckling load to be 9.3–10.1%, 3.0–3.2%, and 23.2–29.8% less than those obtained without considering AFP manufacturing constraints, respectively, for the present studied model under in-plane axial, shear, and bending displacements.
  • Thumbnail Image
    Calculating and Analyzing Angular Head Jerk in Augmented and Virtual Reality: Effect of AR Cue Design on Angular Jerk
    Van Dam, Jared; Tanous, Kyle; Werner, Matt; Gabbard, Joseph L. (MDPI, 2021-10-28)
    In this work, we propose a convenient method for evaluating levels of angular jerk in augmented reality (AR) and virtual reality (VR). Jerk is a rarely analyzed metric in usability studies, although it can be measured and calculated easily with most head-worn displays and can yield highly relevant information to designers. Here, we developed and implemented a system capable of calculating and analyzing jerk in real-time based on orientation data from an off-the-shelf head-worn display. An experiment was then carried out to determine whether the presence of AR user interface annotations results in changes to users’ angular head jerk when conducting a time-pressured visual search task. Analysis of the data indicates that a decrease in jerk is significantly associated with the use of AR augmentations. As noted in the limitations section, however, the conclusions drawn from this work should be limited, as this analysis method is novel in the VR/AR space and because of methodological limitations that limited the reliability of the jerk data. The work presented herein considerably facilitates the use of jerk as a quick component measure of usability and serves as an initial point off which future research involving jerk in VR and AR can be performed.
  • Thumbnail Image
    Closed-form approximations and series representations for partially saturated ocean acoustic processes
    Perakis, Anastassios N.; Nikolaidis, Efstratios; Katzouros, Emmanuel (Acoustical Society of America, 1988-04-01)
    An approximate, closed-form expression for the value of the integral encountered in the calculation of the probability density function (PDF) of the envelope of a partially saturated ocean acoustic process is obtained. Furthermore, an expression of this PDF as a series of modified Bessel functions is presented. The results may also be directly applied to the evaluation of the PDF encountered in the structural reliability analysis of rotating machinery components. Numerical applications show that the closed-form expression is always within 1-2% of the exact result. The required computational effort is substantially lower than that required by direct numerical integration. Copyright 1988 Acoustical Society of America
  • Thumbnail Image
    A closed-form method for calculating the angular distribution of multiply scattered photons through isotropic turbid slabs
    Sun, Xueqiang; Li, Xuesong; Ma, Lin (Optical Society of America, 2011-11-01)
    This paper develops a method for calculating the angular distribution (AD) of multiply scattered photons through isotropic turbid slabs. Extension to anisotropic scattering is also discussed. Previous studies have recognized that the AD of multiply scattered photons is critical for many applications, such as the design of imaging optics and estimation of image quality. This paper therefore develops a closed-from method that can accurately calculate the AD over a wide range of conditions. Other virtues of the method include its simplicity in implementation and its prospective for extension to anisotropic scattering. (C) 2011 Optical Society of America
  • Thumbnail Image
    Combined Analysis of Hydrogen and Oxygen 102.6 nm Emission at Mars
    Chaffin, Michael S.; Deighan, Justin; Jain, Sonal; Holsclaw, Greg; AlMazmi, Hoor; Chirakkil, Krishnaprasad; Correira, John; England, Scott L.; Evans, J. Scott; Fillingim, Matt; Lillis, Rob; Lootah, Fatma; Raghuram, Susarla; Eparvier, Frank; Thiemann, Ed; Curry, Shannon; AlMatroushi, Hessa (American Geophysical Union, 2022-08)
    Water is lost from the Mars upper atmosphere to space as hydrogen and oxygen, both of which can be observed in scattered ultraviolet sunlight at 102.6 nm. We present Emirates Mars Mission Emirates Mars Ultraviolet Spectrometer (EMM/EMUS) insertion orbit observations of this airglow, resolving the independent altitude contributions of H and O for the first time. We present the first airglow modeling of the complete H and O 102.6 nm system and the first 3D azimuthally symmetric modeling of the O emission, retrieving temperatures and densities typical of northern spring. Our model reproduces the emission well above 200 km, but does not incorporate partial frequency redistribution needed to reproduce the observed O brightness at lower altitudes and on the disk. These results support future EMM/EMUS science orbit retrievals of H loss and the use of 102.6 nm observations to constrain planetary atmospheres across the solar system.
  • Thumbnail Image
    Comparative Assessment of Sound Generated Using Laser-Induced Plasma
    Szőke, Máté; Bahr, Christopher; Cattafesta, Louis; Rossignol, Karl-Stéphane; Ura, Hiroki; Zhang, Yang; Zigunov, Fernando (2021-08-10)
  • Thumbnail Image
    Computational Micromechanics Investigation of Percolation and Effective Electro-Mechanical Properties of Carbon Nanotube/Polymer Nanocomposites using Stochastically Generated Realizations: Effects of Orientation and Waviness
    Talamadupula, Krishna Kiran; Seidel, Gary (MDPI, 2022-11-23)
    The electrical and mechanical properties of carbon nanotube/polymer nanocomposites depend strongly upon several factors such as CNT volume fraction, CNT alignment, CNT dispersion and CNT waviness among others. This work focuses on obtaining estimates and distribution for the effective electrical conductivity, elastic constants and piezoresistive properties as a function of these factors using a stochastic approach with numerous CNT/polymer realizations coupled with parallel computation. Additionally, electrical percolation volume fraction and percolation transitional behavior is also studied. The effective estimates and percolation values were found to be in good agreement with experimental works in the literature. It was found that with increasing CNT volume fraction, the mechanical properties improved. However, due to the interaction of CNTs with one another through electrical tunneling, the conductivity and piezoresistivity properties evolved in a more complex manner. While the degree of alignment played a strong role in the effective properties making them anisotropic, the effect of waviness was found to be insubstantial.
  • Thumbnail Image
    Corrosion Fatigue Characteristics of 316L Stainless Steel Fabricated by Laser Powder Bed Fusion
    Gnanasekaran, Balachander; Song, Jie; Vasudevan, Vijay; Fu, Yao (MDPI, 2021-06-29)
    Laser powder bed fusion (LPBF) has been increasingly used in the fabrication of dense metallic structures. However, the corrosion related properties of LPBF alloys, in particular environment-assisted cracking, such as corrosion fatigue properties, are not well understood. In this study, the corrosion and corrosion fatigue characteristics of LPBF 316L stainless steels (SS) in 3.5 wt.% NaCl solution have been investigated using an electrochemical method, high cycle fatigue, and fatigue crack propagation testing. The LPBF 316L SSs demonstrated significantly improved corrosion properties compared to conventionally manufactured 316L, as reflected by the increased pitting and repassivation potentials, as well as retarded crack initiation. However, the printing parameters did not strongly affect the pitting potentials. LPBF samples also demonstrated enhanced capabilities of repassivation during the fatigue crack propagation. The unique microstructural features introduced during the printing process are discussed. The improved corrosion and corrosion fatigue properties are attributed to the presence of columnar/cellular subgrains formed by dislocation networks that serve as high diffusion paths to transport anti-corrosion elements.