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水下载体和磁力仪的匹配是水下地磁导航的关键技术之一.为了完成匹配实验,首先要选择地磁场平缓的局部区域,基于这一目的进行了局域地磁场的测量,并通过克里金插值法构建地磁图,给出基于克里金插值的局部二维和三维地磁图.从地磁图上可以找到磁异常区域和地磁平缓区域,并在地磁平缓区域进行有无水下载体的地磁空间测量.由于载体主要由铁磁物质组成,安装在载体上的传感器所测量的磁场除了地磁场以外,还有载体硬磁材料产生的固有磁场以及载体内机电设备产生的磁场.因此,如何从复杂的磁场环境中提取地磁场信息是实时测量的一大难题.基于载体的空间磁测,利用传感器测量值构建载体磁场的数学模型,分析了水下载体对周围磁场的影响,为水下载体与磁力仪的匹配和水下磁测提供了理论和实验依据. 相似文献
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讨论了由于纵向磁场不均匀引起的磁约束等离子体的变形,在表面电流分布与体电流分布情形下分别求得磁面变形与各参数之间的关系,给出了等离子体平衡对于不均匀磁场参数相应的限制。 相似文献
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《中国惯性技术学报》2019,(5)
针对低频交变磁场定位中,螺线管磁场分布的单磁偶极子模型在近场误差较大,定位精度差的问题,提出了一种基于双磁偶极子的螺线管磁场分布建模方法。首先通过分析磁偶极子在空间中的磁场分布规律,将螺线管等效为两个对称的磁偶极子阵列的叠加,建立了螺线管的磁偶极子阵列模型。然后引入模型误差的目标函数,利用模拟退火算法计算最优模型参数。最后根据磁场分布模型,将磁偶极子阵列简化为磁偶极子,在保证定位精度的同时,简化了模型,便于定位解算。实验结果表明,在近场条件下,双磁偶极子模型的最大误差仅为0.003m,相对传统的单磁偶极子模型,最大定位误差下降了90.26%,在远场条件下,单磁偶极子模型与双磁偶极子模型的最大误差近似。 相似文献
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磁场系统作为磁光阱的重要组成部分,在高精度冷原子陀螺仪中占有极其重要的地位。随着陀螺体积的不断减小和集成度的不断提高,磁场系统的制造和装调误差对陀螺性能的影响不断增大。这些误差会引起磁场零点漂移和磁场梯度变化,降低捕获效率和原子团的质量,从而影响陀螺性能。从三维磁光阱磁场分布的理论分析出发,结合数学建模和计算机仿真,对三维磁场系统的主要制造和装调误差对磁场的影响进行了分析和比较,并基于预设阈值利用试验设计和数学回归对关键制造和装调参数设计了合理的容差限,为小型化冷原子陀螺仪三维磁场系统的设计和制造提供了理论依据。 相似文献
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为研究平面入射激波与磁化R22重质圆形气柱的作用过程,首先通过数值方法得到了不同初始条件下激波诱导R22气柱的Kelvin-Helmholtz (KH)及Richtmyer-Meshkov (RM)不稳定性导致的重气柱变形过程,并详细讨论了不同情况下透射激波在气柱内聚焦诱导射流的过程;然后在加入磁场的情况下,采用CTU+CT算法进行数值模拟,以保证数值结果满足任意时刻磁场的散度为零。计算结果表明:磁场对激波诱导R22气柱不稳定性具有抑制作用;法向磁场和流向磁场都可以很好地抑制RM不稳定性;对于KH不稳定性,法向磁场的控制效果更好,不仅可以抑制界面上涡串的卷起,还可以阻止主涡的发展,而流向磁场做不到后者;磁场对射流影响不大,射流处的磁能量可以一定程度上抑制射流的衰减,同时法向磁场可以减小聚焦时压力及速度峰值。 相似文献
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为提高磁致伸缩导波换能器的激励效能,本文研究了磁场结构参数对偏置磁场空间分布的影响。基于COMSOL有限元仿真平台,对磁致伸缩换能器磁场分布特性进行了数值计算,研究了磁路结构形式、磁路和永磁铁数量等对偏置磁场分布的影响,最后优化出适合纵向导波激励的磁场结构参数。检测实验结果表明,随着偏置磁场磁路数量的增加,偏置磁场强度增大,磁场径向均匀性更好,磁致伸缩换能器的效能也相应提高;在相同磁路数量的条件下,永磁体数量的改变对换能器效能影响较小,四磁路偏置磁场最优;轭铁中部增加永磁铁后的磁路结构的偏置磁场的轴向均匀性更高,其激励效能更好。 相似文献
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为掌握轴向脉冲磁场对金属射流的作用规律,基于破甲弹金属射流对目标的作用原理及磁场与金属射流之间的相互作用关系,设计了励磁线圈对破甲弹金属射流作用的试验系统,并开展了相关实弹试验,突破了金属射流形成和励磁线圈脉冲电流产生之间时序匹配的关键技术,得出了使金属射流发生有效变形的合理储能电容器组电参数和励磁线圈结构参数。试验结果表明,当电容器电压为5 kV、电容为1 200 μF、励磁线圈长度为50 mm时,破甲弹金属射流对目标靶板的侵彻穿深增量最大,破甲效果最佳;各因素对破甲弹金属射流侵彻穿深能力影响程度由大到小分别是电容器组充电电压、电容器组电容、线圈长度。研究成果为破甲弹威力电磁增强技术可行性论证、原理试验及励磁线圈结构设计提供了重要的理论和技术支撑。 相似文献
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《Comptes Rendus Mecanique》2007,335(9-10):665-678
The Boussinesq approximation provides a convenient framework to describe the dynamics of stably-stratified fluids. A fundamental motion in these fluids consists of internal gravity waves, whatever the strength of the stratification. These waves may be unstable through parametric instability, which results in turbulence and mixing. After a brief review of the main properties of internal gravity waves, we show how the parametric instability of a monochromatic internal gravity wave organizes itself in space and time, using energetics arguments and a simple kinematic model. We provide an example, in the deep ocean, where such instability is likely to occur, as estimates of mixing from in situ measurements suggest. We eventually discuss the fundamental role of internal gravity wave mixing in the maintenance of the abyssal thermal stratification. To cite this article: C. Staquet, C. R. Mecanique 335 (2007). 相似文献
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Paolo Boccotti 《Meccanica》1982,17(1):16-19
Summary Mean shape characteristics of ocean waves with high crests are predicted through analysis of the gaussian model of a sea state and then tested against data.
Sommario Il profilo caratteristico delle onde di mare con le creste più alte, viene previsto at traverso l'analisi del modello gaussiano di uno stato di mare e quindi confrontato con dati di misurazioni effettuate nel Golfo del Messico.相似文献
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The formulation of stationary, plane, and self-similar problems is considered when the flow parameters depend only on the polar angle, and the magnetic field lies in the flow plane. The case in which the magnetic field is perpendicular to the flow plane has been examined in [1]. The conditions are found under which the solution depends on an arbitrary parameter and the reasons for this nonuniqueness are explained. Self-similar solutions are constructed to describe the flow around an insulating wedge and a wall. 相似文献
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E. A. Pushkar' 《Fluid Dynamics》1976,11(5):755-762
One component of the solution to the problem of flow around a corner within the scope of magnetohydrodynamics, with the interception or stationary reflection of magnetohydrodynamic shock waves, and also steady-state problems comprising an ionizing shock wave, is the steady-state solution of the equations of magnetohydrodynamics, independent of length but depending on a combination of space variables, for example, on the angle. The flows described by these solutions are called stationary simple waves; they were considered for the first time in [1], where the behavior of the flow was investigated in stationary rotary simple waves, in which no change of density occurs. For a magnetic wave, of parallel velocity, the first integrals were found and the solution was reduced to a quadrature. The investigations and the applications of the solutions obtained for a qualitative construction of the problems of streamline flow were continued in [2–8]. In particular, problems were solved concerning flow around thin bodies of a conducting ideal gas. The general solution of the problem of streamline flow or the intersection of shock waves was not found because stationary simple waves with the magnetic field not parallel to the flow velocity were not investigated. The necessity for the calculation of such a flow may arise during the interpretation of the experimental results [9] in relation to the flow of an ionized gas. In the present paper, we consider stationary simple waves with the magnetic field not parallel to the flow velocity. A system of three nonlinear differential equations, describing fast and slow simple waves, is investigated qualitatively. On the basis of the pattern constructed of the behavior of the integral curves, the change of density, magnetic field, and velocity are found and a classification of the waves is undertaken, according to the nature of the change in their physical quantities. The relation between waves with outgoing and incoming characteristics is explained. A qualitative difference is discovered for the flow investigated from the flow in a magnetic field parallel to the flow velocity.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 130–138, September–October, 1976.The author thanks A. A. Barmin and A. G. Kulikovskii for constant interest in the work and for valuable advice. 相似文献
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This paper gives a solution of the problem of the propagation of weak shock waves in an inhomogeneous conducting medium in the presence of a magnetic field. The width of the perturbed region is taken to be small compared with the characteristic dimensions of the problem. The magnetic Reynolds number is also assumed small, which allows one to neglect the induced magnetic field. The method of solution employed is similar to that used in [1–3],The author is grateful to B. I. Zaslavskii for useful advice and for discussing the paper. 相似文献
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Michael Yanowitch 《Wave Motion》1979,1(2):123-125
The problem considered is that of vertically propagating hydromagnetic waves of small amplitude and frequency 2π/ω in a horizontally stratified, perfectly conducing, isothermal atmosphere with a horizontal magnetic field. In an ideal fluid the boundary value problem for such waves is not well determined. However, the presence of small viscosity is sufficient to determine a unique solution. The resulting differential equation can be solved in terms of hypergeometric functions. The solution shows that the acoustic-gravity waves are modified by the effects of the viscosity and of the magnetic field in such a way as to be partly reflected downward. 相似文献
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The influence of magnetic field on the generation of a localized wave in a nonlinearly elastic conducting medium is considered. The evolution equation for describing the wave beam propagation in the medium is derived. It is shown that the wave beam parameters depend on the value of the external magnetic field and on the field orientation in space. 相似文献