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激波数值稳定的低耗散修正HLLEM格式与应用
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作者 胡立军 李斌 黄泓兴 《计算力学学报》 CAS CSCD 北大核心 2024年第5期921-928,共8页
在航空航天领域,含强激波的可压缩流动问题的数值模拟具有重要的科学工程意义。许多流行的数值通量格式(如CFD工业软件中普遍使用的Roe格式)在计算强激波时会出现不同形式的数值不稳定现象,这些非物理现象极大影响了模拟结果的可靠性。... 在航空航天领域,含强激波的可压缩流动问题的数值模拟具有重要的科学工程意义。许多流行的数值通量格式(如CFD工业软件中普遍使用的Roe格式)在计算强激波时会出现不同形式的数值不稳定现象,这些非物理现象极大影响了模拟结果的可靠性。本文采用平衡对流耗散与声耗散的方法来增强格式的激波数值稳定性,通过简单修改波速的计算将其应用到HLLEM通量格式上。不同于传统上通过增加数值耗散的方法来消除格式的激波数值不稳定性,本文采用的策略不仅简单而且还能局部减少格式对非线性波的数值耗散。此外,采用THINC重构结合BVD算法来进一步减少数值耗散项中网格界面两侧的密度差,从而提高格式对于线性波的分辨率。稳定性分析证明了平衡对流耗散与声耗散可以有效地消除激波数值失稳现象。一系列经典的数值实验验证了构造的激波捕捉格式的高分辨率和强稳定性。 展开更多
关键词 三维欧拉方程组 HLLEM格式 激波数值不稳定性 声耗散 高分辨率
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水中孤立气泡对声波的耗散作用 被引量:8
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作者 黄景泉 李福新 《应用数学和力学》 EI CSCD 北大核心 1994年第6期549-554,共6页
本文从气泡壁面线性运动方程出发,对水中孤立气泡的声耗散机理进行了分析.结果表明:气泡对声波具有明显的耗散作用;耗散作用由声散射和声吸收两部份组成;热传导在气泡对声波的耗散作用中起决定性作用;气泡处于谐振时,对声波具有... 本文从气泡壁面线性运动方程出发,对水中孤立气泡的声耗散机理进行了分析.结果表明:气泡对声波具有明显的耗散作用;耗散作用由声散射和声吸收两部份组成;热传导在气泡对声波的耗散作用中起决定性作用;气泡处于谐振时,对声波具有最大的耗散作用. 展开更多
关键词 气泡 吸收 声耗散
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Phonon Excitation and Energy Redistribution in Phonon Space for Energy Dissipation and Transport in Lattice Structure with Nonlinear Dispersion
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作者 徐志杰 《Communications in Theoretical Physics》 SCIE CAS CSCD 2015年第1期101-108,共8页
We first propose fundamental solutions of wave propagation in dispersive chain subject to a localized initial perturbation in the displacement. Analytical solutions are obtained for both second order nonlinear dispers... We first propose fundamental solutions of wave propagation in dispersive chain subject to a localized initial perturbation in the displacement. Analytical solutions are obtained for both second order nonlinear dispersive chain and homogenous harmonic chain using stationary phase approximation. Solution is also compared with numerical results from molecular dynamics (MD) simulations. Locally dominant phonon modes (k-space) are introduced based on these solutions. These locally defined spatially and temporally varying phonon modes k(x, t) are critical to the concept of the local thermodynamic equilibrium (LTE). Wave propagation accompanying with the nonequilibrium dynamics leads to the excitation of these locally defined phonon modes. It is found that the system energy is gradually redistributed among these excited phonons modes (k-space). This redistribution process is only possible with nonlinear dispersion and requires a finite amount of time to achieve a steady state distribution. This time scale is dependent on the spatial distribution (or frequency content) of the initial perturbation and the dispersion relation. Sharper and more concentrated perturbation leads to a faster energy redistribution and dissipation. This energy redistribution generates localized phonons with various frequencies that can be important for phonon-phonon interaction and energy dissipation in nonlinear systems. Depending on the initial perturbation and temperature, the time scale associated with this energy distribution can be critical for energy dissipation compared to the Umklapp scattering process. Ballistic type of heat transport along the harmonic chain reveals that at any given position, the lowest mode (k = O) is excited first and gradually expanding to the highest mode (km^(x,t)), where km^(x,t) can only asymptotically approach the maximum mode kB of the first Brillouin zone (kmax(x,t) --~ kB). NO energy distributed into modes with k_max(x,t) 〈 k 〈 k^B demonstrates that the local thermodynamic equilibrium cannot be established in harmonic chain. Energy is shown to be uniformly distributed in all available phonon modes k ≤ _max(x, t) at any position with heat transfer along the harmonic chain. The energy flux along the chain is shown to be a constant with time and proportional to the sound speed (ballistic transport). Comparison with the Fourier's law leads to a time-dependent thermal conductivity that diverges with time. 展开更多
关键词 dispersion energy dissipation energy distribution phonon modes heat transport local thermo-dynamic equilibrium nonequilibrium statistical mechanics
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Nonlinear Dust Acoustic Waves in Dissipative Space Dusty Plasmas with Superthermal Electrons and Nonextensive Ions
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作者 A.M.El-Hanbaly E.K.El-Shewy +1 位作者 M.Sallah H.F.Darweesh 《Communications in Theoretical Physics》 SCIE CAS CSCD 2016年第5期606-612,共7页
The nonlinear characteristics of the dust acoustic(DA)waves are studied in a homogeneous,collisionless,unmagnetized,and dissipative dusty plasma composed of negatively charged dusty grains,superthermal electrons,and n... The nonlinear characteristics of the dust acoustic(DA)waves are studied in a homogeneous,collisionless,unmagnetized,and dissipative dusty plasma composed of negatively charged dusty grains,superthermal electrons,and nonextensive ions.Sagdeev pseudopotential technique has been employed to study the large amplitude DA waves.It(Sagdeev pseudopotential)has an evidence for the existence of compressive and rarefractive solitons.The global features of the phase portrait are investigated to understand the possible types of solutions of the Sagdeev form.On the other hand,the reductive perturbation technique has been used to study small amplitude DA waves and yields the Korteweg-de Vries-Burgers(Kd V-Burgers)equation that exhibits both soliton and shock waves.The behavior of the obtained results of both large and small amplitude is investigated graphically in terms of the plasma parameters like dust kinematic viscosity,superthermal and nonextensive parameters. 展开更多
关键词 Sagdeev pseudopotential KdV-Burgers equation soliton and shock waves reductive perturbation dust kinematic viscosity
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