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Gas Giants: Jupiter and Saturn
Published in Thomas Hockey, Jennifer Lynn Bartlett, Daniel C. Boice, Solar System, 2021
Thomas Hockey, Jennifer Lynn Bartlett, Daniel C. Boice
Now, with Jupiter so massive and sizeable, you might assume that it has the right to spin slowly on its axis, that is, until you consider the large amount of matter that has contracted to form the planet—pulling its ‘arms’ in like the skater. Jupiter rotates in approximately 9 hours, 55 minutes, the fastest rotation period among the planets. (The measured rotation rate at the jovian equator differs from that near the poles by 6 minutes: While this sounds peculiar, remember that Jupiter is a fluid world.) It is this rapid rotation that helps whip up Jupiter's magnetic field at the core/metallic-hydrogen boundary. This field is the strongest of any planet in the Solar System—40,000 times stronger than the Earth's. It is intense enough to produce radio noise that astronomers can pick up on the Earth (Figure 10.6).
Incident Radiation
Published in Robert P. Bukata, John H. Jerome, Kirill Ya. Kondratyev, Dimitry V. Pozdnyakov, of Inland and Coastal Waters, 2018
Robert P. Bukata, John H. Jerome, Kirill Ya. Kondratyev, Dimitry V. Pozdnyakov
The sun is a relatively small, faint, cool star about which the Earth rotates yearly at an average distance (center of gravity to center of gravity) of 1.497 × 1011 m (1 astronomical unit). The mass of the sun is ∼333,400 times that of the Earth or 1.989 × 1030 kg. The rotation period of the sun about its own axis of rotation is a function of solar latitude, varying from about 26 days at the solar equator to about 34 days at the solar poles. An effective solar rotation period of 27 days is usually adequate for assessing and predicting recurring solar occurrences (such as sunspots and magnetic plage regions) that may affect the Earth’s atmosphere.
Introduction
Published in Fang Lin Luo, Hong Ye, Renewable Energy Systems, 2013
The Earth’s rotation period relative to the fixed stars, called its stellar day by the International Earth Rotation and Reference Systems Service (IERS), is 86164.098903691 s of mean solar time (UT1) or 23 h 56 m 4.098903691 s. The Earth’s rotation period relative to the precessing or moving mean vernal equinox, misnamed its sidereal day, is 86,164.09053083288 s of mean solar time (UT1) (23 h 56 m 4.09053083288 s). Thus, the sidereal day is shorter than the stellar day by about 8.4 ms. The length of the mean solar day in seconds is available from the IERS for the periods 1623–2005 and 1962–2005.
Modulation effect on rotor-stator interaction subjected to fluctuating rotation speed in a centrifugal pump
Published in Engineering Applications of Computational Fluid Mechanics, 2023
Shiwei Ni, Guofeng Zhao, Yuxuan Chen, Haifeng Cao, Chenxing Jiang, Wei Zhou, Tao Yu, Zhijun Shuai
The pressure pulsation at the pump outlet is decomposed using the VMD. In Figure 15, the signal (SIG) is decomposed into a number of IMFs and a residual part. T is the impeller rotation period. The center frequencies corresponding to IMF1-IMF3 are the BPF and its harmonics. The central frequency of IMF4 is the FF. It is worth noting that the instantaneous amplitude variations of IMF1-IMF3 at fluctuating rotation speed are more significant than those at stationary rotation speed.
Nonlinear response of rotor system with bearing dynamic misalignment
Published in Mechanics Based Design of Structures and Machines, 2023
Pengfei Wang, Hongyang Xu, Hui Ma, Yang Yang, Qingkai Han, Bangchun Wen, Xiaopeng Li
Assuming that the rotor is in complete balance, the simulation working condition is: the rotor speed is 3000 r/min, the misalignment angles of Cases 2–4 are all 0.2°. The bearing parameters of left and right are: radial clearance cr = 8 μm, the ball number Nb = 9, the coefficient of the curvature radius of raceway fi/o = 0.515, and the radial load Fr = 0 kN. The effect of bearing dynamic misalignment phase difference on system dynamic response is analyzed, and the results are shown in Figure 5. Due to the rotor gravity, the rotor orbit is in the negative direction of the y-axis. It can be found through the spectrum diagram and time-domain waveform that when there is no misalignment of the bearing, the time-domain waveform shows a periodic excitation dominated by bearing varying compliance (VC) vibration. Only VC frequency (fvc) and 2fvc with lower amplitudes are present in the spectrum. This indicates that in the balance state, the rotor system only has the bearing VC excitation, but this excitation is relatively weak. Once the dynamic bearing misalignment occurs, according to Figure 5b–d, the system amplitude raises significantly, and the system vibration is dominated by two times the rotating frequency excitation (2fr). In addition, there are some combination frequency components of rotating frequency and bearing frequency with lower amplitude, such as fvc–2fr and 6fr–fvc. The time domain waveform is dominated by twice the rotor rotation period. The characteristic frequency of bearing dynamic misalignment is 2fr. In addition, under the condition of bearing dynamic misalignment, the rotor vibration characteristics of Cases 2–4 at the current speed have little difference (see Figure 5b–d).
Effects of anisotropic diffusion on onset of rotating magnetoconvection in plane layer; stationary modes
Published in Geophysical & Astrophysical Fluid Dynamics, 2019
E. Filippi, J. Brestenský, T. Šoltis
In case of partial anisotropy we have the following main dimensionless linearised equations with anisotropic Laplacians and defined in (10)–(13) and (9). Here, the non-dimensional quantities are related to their dimensional counterparts by and the dimensionless numbers are The parameters in (6) are is the modified Rossby number, a ratio of rotation period to magnetic diffusion time (the classical Rossby number, , is a ratio of rotation period to the time d/U).Λ is the Elsasser number, namely a ratio of magnetic force to Coriolis force. is the Ekman number1, a ratio of viscous forces to Coriolis force.R is the modified Rayleigh number (the classical Rayleigh number is ); it is a ratio between effective buoyancy force and Coriolis force, where is thermal expansion coefficient. is the Roberts number, the ratio of magnetic to thermal diffusion time scales.