The Experts below are selected from a list of 44322 Experts worldwide ranked by ideXlab platform
Tang Huazhong - One of the best experts on this subject based on the ideXlab platform.
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High-order accurate physical-constraints-preserving finite difference WENO schemes for special Relativistic hydrodynamics
'Elsevier BV', 2015Co-Authors: Wu Kailiang, Tang HuazhongAbstract:The paper develops high-order accurate physical-constraints-preserving finite difference WENO schemes for special Relativistic hydrodynamical (RHD) equations, built on the local Lax-Friedrich splitting, the WENO reconstruction, the physical-constraints-preserving flux limiter, and the high-order strong stability preserving time discretization. They are extensions of the positivity-preserving finite difference WENO schemes for the non-Relativistic Euler equations. However, developing physical-constraints-preserving methods for the RHD system becomes much more difficult than the non-Relativistic Case because of the strongly coupling between the RHD equations, no explicit expressions of the primitive variables and the flux vectors, in terms of the conservative vector, and one more physical constraint for the fluid velocity in addition to the positivity of the rest-mass density and the pressure. The key is to prove the convexity and other properties of the admissible state set and discover a concave function with respect to the conservative vector replacing the pressure which is an important ingredient to enforce the positivity-preserving property for the non-Relativistic Case. Several one- and two-dimensional numerical examples are used to demonstrate accuracy, robustness, and effectiveness of the proposed physical-constraints-preserving schemes in solving RHD problems with large Lorentz factor, or strong discontinuities, or low rest-mass density or pressure etc.Comment: 39 pages, 13 figure
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High-order accurate physical-constraints-preserving finite difference WENO schemes for special Relativistic hydrodynamics
JOURNAL OF COMPUTATIONAL PHYSICS, 2015Co-Authors: Wu Kailiang, Tang HuazhongAbstract:The paper develops high-order accurate physical-constraints-preserving finite difference WENO schemes for special Relativistic hydrodynamical (RHD) equations, built on the local Lax-Friedrichs splitting, the WENO reconstruction, the physical-constraints-preserving flux limiter, and the high-order strong stability preserving time discretization. They are extensions of the positivity-preserving finite difference WENO schemes for the non-Relativistic Euler equations [20]. However, developing physical-constraints-preserving methods for the RHD system becomes much more difficult than the non-Relativistic Case because of the strongly coupling between the RHD equations, no explicit formulas of the primitive variables and the flux vectors with respect to the conservative vector, and one more physical constraint for the fluid velocity in addition to the positivity of the rest-mass density and the pressure. The key is to prove the convexity and other properties of the admissible state set and discover a concave function with respect to the conservative vector instead of the pressure which is an important ingredient to enforce the positivity-preserving property for the non-Relativistic Case. Several one-and two-dimensional numerical examples are used to demonstrate accuracy, robustness, and effectiveness of the proposed physical-constraints-preserving schemes in solving RHD problems with large Lorentz factor, or strong discontinuities, or low rest-mass density or pressure etc. (C) 2015 Elsevier Inc. All rights reserved.National Natural Science Foundation of China [91330205, 11421101]SCI(E)ARTICLEwukl@pku.edu.cn; hztang@math.pku.edu.cn539-56429
P B Makhalov - One of the best experts on this subject based on the ideXlab platform.
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high frequency devices with weakly Relativistic hollow thin wall electron beams
International Conference on Plasma Science, 2012Co-Authors: V L Bratman, A E Fedotov, P B MakhalovAbstract:Summary form only given. The medium-power millimeter-wave sources are widely used in radars, space telecommunications, and spectroscopy. For microwave generation with power level from tens of watts to several kilowatts, slow-wave devices such as traveling-wave tubes (TWTs) and backward-wave oscillators (BWOs) are widely used. Traditionally, these radiation sources are based on utilizing thin rectilinear electron beams guided through thin cylindrical channel in slow-wave structures of helical, folded-waveguide, or coupled-cavity types. For millimeter or shorter wavelengths, a very thin electron beam with very high energy density is needed, which hinders the guiding of the beam in a proximity of the slow-wave structure wall, especially in CW regime. In order to mitigate the described difficulty, a new concept of medium-power slow-wave devices of the millimeter-wavelength range is proposed.1 This concept is based on the usage of azimuthally-symmetric or helically corrugated operating waveguides and hollow rectilinear thin-wall electron beams instead of pencil-like beams. It should be noticed, that slow-wave devices with Relativistic hollow electron beams are widely used.2 In the weakly-Relativistic Case, the exploit of hollow beams permits a significant increase in the diameter of the beam channel and, simultaneously, a drastic decrease in the required current density and heat load at the interaction structure wall in comparison with the conventional devices with pencil-like beams.
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high frequency devices with weakly Relativistic hollow thin wall electron beams
Physics of Plasmas, 2012Co-Authors: V L Bratman, A E Fedotov, P B MakhalovAbstract:Slow-wave devices with hollow electron beams and azimuthally symmetric corrugated operating waveguides can be very effective not only for Relativistic but also weakly Relativistic particle energies. In the weakly Relativistic Case, the use of hollow beams permits a significant increase in the diameter of the beam channel and, simultaneously, a drastic decrease in the required current density and heat load at the interaction structure wall in comparison with the conventional devices, which basically exploit thin pencil-like beams. Advantages of the hollow beams in the achievement of continuous wave (CW) and long-pulse generation can manifest themselves in a wide range from gigahertz to terahertz frequencies. As an example of the concept, a W-band oscillator (orotron) with kilowatt output power in CW regime is discussed in detail. Modification of the microwave system makes it possible to implement high-power frequency-tunable BWOs, klystron or TWT amplifiers, and many types of hybrid devices.
Wu Kailiang - One of the best experts on this subject based on the ideXlab platform.
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High-order accurate physical-constraints-preserving finite difference WENO schemes for special Relativistic hydrodynamics
'Elsevier BV', 2015Co-Authors: Wu Kailiang, Tang HuazhongAbstract:The paper develops high-order accurate physical-constraints-preserving finite difference WENO schemes for special Relativistic hydrodynamical (RHD) equations, built on the local Lax-Friedrich splitting, the WENO reconstruction, the physical-constraints-preserving flux limiter, and the high-order strong stability preserving time discretization. They are extensions of the positivity-preserving finite difference WENO schemes for the non-Relativistic Euler equations. However, developing physical-constraints-preserving methods for the RHD system becomes much more difficult than the non-Relativistic Case because of the strongly coupling between the RHD equations, no explicit expressions of the primitive variables and the flux vectors, in terms of the conservative vector, and one more physical constraint for the fluid velocity in addition to the positivity of the rest-mass density and the pressure. The key is to prove the convexity and other properties of the admissible state set and discover a concave function with respect to the conservative vector replacing the pressure which is an important ingredient to enforce the positivity-preserving property for the non-Relativistic Case. Several one- and two-dimensional numerical examples are used to demonstrate accuracy, robustness, and effectiveness of the proposed physical-constraints-preserving schemes in solving RHD problems with large Lorentz factor, or strong discontinuities, or low rest-mass density or pressure etc.Comment: 39 pages, 13 figure
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High-order accurate physical-constraints-preserving finite difference WENO schemes for special Relativistic hydrodynamics
JOURNAL OF COMPUTATIONAL PHYSICS, 2015Co-Authors: Wu Kailiang, Tang HuazhongAbstract:The paper develops high-order accurate physical-constraints-preserving finite difference WENO schemes for special Relativistic hydrodynamical (RHD) equations, built on the local Lax-Friedrichs splitting, the WENO reconstruction, the physical-constraints-preserving flux limiter, and the high-order strong stability preserving time discretization. They are extensions of the positivity-preserving finite difference WENO schemes for the non-Relativistic Euler equations [20]. However, developing physical-constraints-preserving methods for the RHD system becomes much more difficult than the non-Relativistic Case because of the strongly coupling between the RHD equations, no explicit formulas of the primitive variables and the flux vectors with respect to the conservative vector, and one more physical constraint for the fluid velocity in addition to the positivity of the rest-mass density and the pressure. The key is to prove the convexity and other properties of the admissible state set and discover a concave function with respect to the conservative vector instead of the pressure which is an important ingredient to enforce the positivity-preserving property for the non-Relativistic Case. Several one-and two-dimensional numerical examples are used to demonstrate accuracy, robustness, and effectiveness of the proposed physical-constraints-preserving schemes in solving RHD problems with large Lorentz factor, or strong discontinuities, or low rest-mass density or pressure etc. (C) 2015 Elsevier Inc. All rights reserved.National Natural Science Foundation of China [91330205, 11421101]SCI(E)ARTICLEwukl@pku.edu.cn; hztang@math.pku.edu.cn539-56429
V L Bratman - One of the best experts on this subject based on the ideXlab platform.
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high frequency devices with weakly Relativistic hollow thin wall electron beams
International Conference on Plasma Science, 2012Co-Authors: V L Bratman, A E Fedotov, P B MakhalovAbstract:Summary form only given. The medium-power millimeter-wave sources are widely used in radars, space telecommunications, and spectroscopy. For microwave generation with power level from tens of watts to several kilowatts, slow-wave devices such as traveling-wave tubes (TWTs) and backward-wave oscillators (BWOs) are widely used. Traditionally, these radiation sources are based on utilizing thin rectilinear electron beams guided through thin cylindrical channel in slow-wave structures of helical, folded-waveguide, or coupled-cavity types. For millimeter or shorter wavelengths, a very thin electron beam with very high energy density is needed, which hinders the guiding of the beam in a proximity of the slow-wave structure wall, especially in CW regime. In order to mitigate the described difficulty, a new concept of medium-power slow-wave devices of the millimeter-wavelength range is proposed.1 This concept is based on the usage of azimuthally-symmetric or helically corrugated operating waveguides and hollow rectilinear thin-wall electron beams instead of pencil-like beams. It should be noticed, that slow-wave devices with Relativistic hollow electron beams are widely used.2 In the weakly-Relativistic Case, the exploit of hollow beams permits a significant increase in the diameter of the beam channel and, simultaneously, a drastic decrease in the required current density and heat load at the interaction structure wall in comparison with the conventional devices with pencil-like beams.
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high frequency devices with weakly Relativistic hollow thin wall electron beams
Physics of Plasmas, 2012Co-Authors: V L Bratman, A E Fedotov, P B MakhalovAbstract:Slow-wave devices with hollow electron beams and azimuthally symmetric corrugated operating waveguides can be very effective not only for Relativistic but also weakly Relativistic particle energies. In the weakly Relativistic Case, the use of hollow beams permits a significant increase in the diameter of the beam channel and, simultaneously, a drastic decrease in the required current density and heat load at the interaction structure wall in comparison with the conventional devices, which basically exploit thin pencil-like beams. Advantages of the hollow beams in the achievement of continuous wave (CW) and long-pulse generation can manifest themselves in a wide range from gigahertz to terahertz frequencies. As an example of the concept, a W-band oscillator (orotron) with kilowatt output power in CW regime is discussed in detail. Modification of the microwave system makes it possible to implement high-power frequency-tunable BWOs, klystron or TWT amplifiers, and many types of hybrid devices.
A E Fedotov - One of the best experts on this subject based on the ideXlab platform.
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high frequency devices with weakly Relativistic hollow thin wall electron beams
International Conference on Plasma Science, 2012Co-Authors: V L Bratman, A E Fedotov, P B MakhalovAbstract:Summary form only given. The medium-power millimeter-wave sources are widely used in radars, space telecommunications, and spectroscopy. For microwave generation with power level from tens of watts to several kilowatts, slow-wave devices such as traveling-wave tubes (TWTs) and backward-wave oscillators (BWOs) are widely used. Traditionally, these radiation sources are based on utilizing thin rectilinear electron beams guided through thin cylindrical channel in slow-wave structures of helical, folded-waveguide, or coupled-cavity types. For millimeter or shorter wavelengths, a very thin electron beam with very high energy density is needed, which hinders the guiding of the beam in a proximity of the slow-wave structure wall, especially in CW regime. In order to mitigate the described difficulty, a new concept of medium-power slow-wave devices of the millimeter-wavelength range is proposed.1 This concept is based on the usage of azimuthally-symmetric or helically corrugated operating waveguides and hollow rectilinear thin-wall electron beams instead of pencil-like beams. It should be noticed, that slow-wave devices with Relativistic hollow electron beams are widely used.2 In the weakly-Relativistic Case, the exploit of hollow beams permits a significant increase in the diameter of the beam channel and, simultaneously, a drastic decrease in the required current density and heat load at the interaction structure wall in comparison with the conventional devices with pencil-like beams.
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high frequency devices with weakly Relativistic hollow thin wall electron beams
Physics of Plasmas, 2012Co-Authors: V L Bratman, A E Fedotov, P B MakhalovAbstract:Slow-wave devices with hollow electron beams and azimuthally symmetric corrugated operating waveguides can be very effective not only for Relativistic but also weakly Relativistic particle energies. In the weakly Relativistic Case, the use of hollow beams permits a significant increase in the diameter of the beam channel and, simultaneously, a drastic decrease in the required current density and heat load at the interaction structure wall in comparison with the conventional devices, which basically exploit thin pencil-like beams. Advantages of the hollow beams in the achievement of continuous wave (CW) and long-pulse generation can manifest themselves in a wide range from gigahertz to terahertz frequencies. As an example of the concept, a W-band oscillator (orotron) with kilowatt output power in CW regime is discussed in detail. Modification of the microwave system makes it possible to implement high-power frequency-tunable BWOs, klystron or TWT amplifiers, and many types of hybrid devices.
