Download or read book Numerical and Experimental Investigation of Turbulent Transport Control Via Shaping of Radial Plasma Flow Profiles written by and published by . This book was released on 2017 with total page 73 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulence, and turbulence-driven transport are ubiquitous in magnetically confined plasmas, where there is an intimate relationship between turbulence, transport, instability driving mechanisms (such as gradients), plasma flows, and flow shear. Though many of the detailed physics of the interrelationship between turbulence, transport, drive mechanisms, and flow remain unclear, there have been many demonstrations that transport and/or turbulence can be suppressed or reduced via manipulations of plasma flow profiles. This is well known in magnetic fusion plasmas [e.g., high confinement mode (H-mode) and internal transport barriers (ITB's)], and has also been demonstrated in laboratory plasmas. However, it may be that the levels of particle transport obtained in such cases [e.g. H-mode, ITB's] are actually lower than is desirable for a practical fusion device. Ideally, one would be able to actively feedback control the turbulent transport, via manipulation of the flow profiles. The purpose of this research was to investigate the feasibility of using both advanced model-based control algorithms, as well as non-model-based algorithms, to control cross-field turbulence-driven particle transport through appropriate manipulation of radial plasma flow profiles. The University of New Mexico was responsible for the experimental portion of the project, while our collaborators at the University of Montana provided plasma transport modeling, and collaborators at Lehigh University developed and explored control methods.
Download or read book Final Technical Report written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The strong coupling between the different physical variables involved in the plasma transport phenomenon and the high complexity of its dynamics call for a model-based, multivariable approach to profile control where those predictive models could be exploited. The overall objective of this project has been to extend the existing body of work by investigating numerically and experimentally active control of unstable fluctuations, including fully developed turbulence and the associated cross-field particle transport, via manipulation of flow profiles in a magnetized laboratory plasma device. Fluctuations and particle transport can be monitored by an array of electrostatic probes, and Ex B flow profiles can be controlled via a set of biased concentric ring electrodes that terminate the plasma column. The goals of the proposed research have been threefold: i- to develop a predictive code to simulate plasma transport in the linear HELCAT (HELicon-CAThode) plasma device at the University of New Mexico (UNM), where the experimental component of the proposed research has been carried out; ii- to establish the feasibility of using advanced model-based control algorithms to control cross-field turbulence-driven particle transport through appropriate manipulation of radial plasma flow profiles, iii- to investigate the fundamental nonlinear dynamics of turbulence and transport physics. Lehigh University (LU), including Prof. Eugenio Schuster and one full-time graduate student, has been primarily responsible for control-oriented modeling and model-based control design. Undergraduate students have also participated in this project through the National Science Foundation Research Experience for Undergraduate (REU) program. The main goal of the LU Plasma Control Group has been to study the feasibility of controlling turbulence-driven transport by shaping the radial poloidal flow profile (i.e., by controlling flow shear) via biased concentric ring electrodes.
Download or read book Experimental Investigation of Dynamical Coupling Between Turbulent Transport and Parallel Flows in the JET Plasma Boundary Region written by C. Hidalgo and published by . This book was released on 2004* with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Study of Flow Turbulence and Transport on the Large Plasma Device written by David Andrew Schaffner and published by . This book was released on 2013 with total page 247 pages. Available in PDF, EPUB and Kindle. Book excerpt: The relationships amongst azimuthal flow, radial particle transport and turbulence on the Large Plasma Device (LAPD) are explored through the use of biasable limiters which continuously modify the rotation of the plasma column. Four quarter annulus plates serve as an iris-like boundary between the cathode source and the main plasma chamber. Application of a voltage to the plates using a capacitor bank drives cross-field current which rotates the plasma azimuthally in the electron diamagnetic direction (EDD). With the limiters inserted, a spontaneous rotation in the ion diamagnetic direction is observed; thus, increasing biasing tends to first slow rotation, null it out, then reverse it. This experiment builds on previous LAPD biasing experiments which used the chamber wall as the biasing electrode rather than inserted limiter plates. The use of inserted limiter biasing rather than chamber wall biasing allows for better cross-field current penetration between the plasma source and the electrodes which in turn allow for a finer variation of applied torque on the plasma. The modification of plasma parameter profiles, turbulent characteristics, and radial transport are tracked through these varying flow states. Azimuthal flow radial profiles are peaked at the limiter edge. Consequently, the variation in flow states also results in variation of sheared flow. Improved radial particle confinement is observed in states with sheared flow regardless of the direction of rotation. This improvement is indicated by both steepened density profiles and decreased radial particle flux. Conversely, a confinement degradation is seen in the minimum sheared flow state. Comparison of density fluctuation power and crossphase between density and radial velocity fluctuations show that both quantities are suppressed by sheared flow, but that the density fluctuation suppression is dominant and contributes most to the decrease in radial particle flux. Also, some observed changes to density and flux profiles suggest disagreement with a purely local model of transport including the formation of a hollow density profile at state of high flow (high bias) and regions where the direction of measured flux is opposite to that predicted by the direction of density gradient. Changes in flux and density gradient with bias are correlated but in a way that is inconsistent with a Fick's Law like model. Changes in turbulent spectra and features are observed with modification of the rotation state. Log-linear spectra with rotation in either azimuthal direction tends to exhibit a linear slope for power versus frequency and versus wavenumber, while spectra curves in the null flow case have an upward concave shape. Time traces corresponding to these spectra indicate a clear presence of Lorentzian structures in flow states but not in the null flow state. Spectral density histograms, showing the distribution of density fluctuation power in both frequency and wavenumber space, indicate that the modes tend to propagate azimuthally in the same direction as the flow. This suggests a large contribution of rotational interchange instability to the plasma turbulence. Regions with significant flow exhibit spectral density distributions which follow narrow curves in frequency and wavenumber space, much like a dispersion relation line. Regions without flow (either the null flow state or the plasma core) have broader, more diffuse distributions. A pair of coherent modes develop with rotation in the EDD direction. The mode fluctuation power peaks at the limiter edge; since maximum flow is observed at the limiter edge, the modes are most likely flow driven. Comparison with a linear Braginskii-fluid model eigenfunction solver supports this conclusion. The lower frequency mode---first observed at about 1-2kHz---is identified as a pure interchange mode while the higher frequency mode---first observed at about 5-6kHz---is determined to be a coupled drift-wave interchange mode. The frequency of these modes increases with flow velocity; the appearance of sideband modes in the frequency spectra also suggests that these mode begin to interact.
Download or read book Computational Fluid Dynamics written by Takeo Kajishima and published by Springer. This book was released on 2016-10-01 with total page 364 pages. Available in PDF, EPUB and Kindle. Book excerpt: This textbook presents numerical solution techniques for incompressible turbulent flows that occur in a variety of scientific and engineering settings including aerodynamics of ground-based vehicles and low-speed aircraft, fluid flows in energy systems, atmospheric flows, and biological flows. This book encompasses fluid mechanics, partial differential equations, numerical methods, and turbulence models, and emphasizes the foundation on how the governing partial differential equations for incompressible fluid flow can be solved numerically in an accurate and efficient manner. Extensive discussions on incompressible flow solvers and turbulence modeling are also offered. This text is an ideal instructional resource and reference for students, research scientists, and professional engineers interested in analyzing fluid flows using numerical simulations for fundamental research and industrial applications.
Download or read book Applied mechanics reviews written by and published by . This book was released on 1948 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2009 with total page 840 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Japanese Science and Technology written by and published by . This book was released on 1986 with total page 724 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 702 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Plasma Boundary of Magnetic Fusion Devices written by P.C Stangeby and published by CRC Press. This book was released on 2000-01-01 with total page 738 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Plasma Boundary of Magnetic Fusion Devices introduces the physics of the plasma boundary region, including plasma-surface interactions, with an emphasis on those occurring in magnetically confined fusion plasmas. The book covers plasma-surface interaction, Debye sheaths, sputtering, scrape-off layers, plasma impurities, recycling and control, 1D and 2D fluid and kinetic modeling of particle transport, plasma properties at the edge, diverter and limiter physics, and control of the plasma boundary. Divided into three parts, the book begins with Part 1, an introduction to the plasma boundary. The derivations are heuristic and worked problems help crystallize physical intuition, which is emphasized throughout. Part 2 provides an introduction to methods of modeling the plasma edge region and for interpreting computer code results. Part 3 presents a collection of essays on currently active research hot topics. With an extensive bibliography and index, this book is an invaluable first port-of-call for researchers interested in plasma-surface interactions.
Download or read book Documentation of Plasma Physics Pt 1 Experimental Plasma Physics and Theoretical Plasma Physics written by and published by . This book was released on 1980 with total page 570 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Japanese Science and Technology 1983 1984 written by United States. National Aeronautics and Space Administration. Scientific and Technical Information Branch and published by . This book was released on 1985 with total page 1080 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Conference Papers Index written by and published by . This book was released on 1987 with total page 950 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Energy a Continuing Bibliography with Indexes written by and published by . This book was released on 1979 with total page 666 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Plasma Physics Index written by and published by . This book was released on 1982 with total page 936 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Physics Briefs written by and published by . This book was released on 1993 with total page 1212 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Indexes to Publications written by American Society of Mechanical Engineers and published by . This book was released on 1981 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt: Contains indexes to all ASME papers and publications. Periodical indexed are : Mechanical engineering, Journal of engineering for power, Journal of engineering for industry, Journal of heat transfer, Journal of basic engineering, Journal of applied mechanics, Journal of lubrication technology, Applied mechanics reviews, Mechanical Engineers' and product directory.
