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Hydrostatic equilibrium

About: Hydrostatic equilibrium is a research topic. Over the lifetime, 2451 publications have been published within this topic receiving 62172 citations.


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TL;DR: The effect of hydrostatic scale heights lambda(T) in coronal loops on the determination of the vertical temperature structure of the solar corona is investigated and it is suggested that this effect largely explains the systematic temperature increase in the upper corona reported in recent studies.
Abstract: We investigate the effect of hydrostatic scale heights λ(T) in coronal loops on the determination of the vertical temperature structure T(h) of the solar corona. Every method that determines an average temperature at a particular line of sight from optically thin emission (e.g., in EUV or soft X-ray wavelengths) of a mutlitemperature plasma is subject to the emission measure-weighted contributions dEM(T)/dT from different temperatures. Because most of the coronal structures (along open or closed field lines) are close to hydrostatic equilibrium, the hydrostatic temperature scale height introduces a height-dependent weighting function that causes a systematic bias in the determination of the temperature structure T(h) as function of altitude h. The net effect is that the averaged temperature seems to increase with altitude, dT(h)/dh > 0, even if every coronal loop (of a multitemperature ensemble) is isothermal in itself. We simulate this effect with differential emission measure distributions observed by SERTS for an instrument with a broadband temperature filter such as Yohkoh/Soft X-Ray Telescope and find that the apparent temperature increase due to hydrostatic weighting is of order ΔT ≈ T0h/r☉. We suggest that this effect largely explains the systematic temperature increase in the upper corona reported in recent studies (e.g., by Sturrock et al., Wheatland et al., or Priest et al.), rather than being an intrinsic signature of a coronal heating mechanism.

35 citations

Journal ArticleDOI
TL;DR: In this article, the influence of the tilt and recess shape on the static and dynamic performance characteristics of the hydrostatic thrust pad bearing system having Rabinowitsch fluid model lubricant was numerically analyzed.

35 citations

Journal ArticleDOI
TL;DR: In this article, the development of gravitational instability in an expanding shell having finite thickness was studied analytically, and three models for the radial density profile of the shell were considered: (i) an analytic uniform density model, (ii) a semi-analytic model obtained by numerical solution of the hydrostatic equilibrium equation and (iii) a 3D hydrodynamic simulation.
Abstract: We study analytically the development of gravitational instability in an expanding shell having finite thickness. We consider three models for the radial density profile of the shell: (i) an analytic uniform-density model, (ii) a semi-analytic model obtained by numerical solution of the hydrostatic equilibrium equation and (iii) a 3D hydrodynamic simulation. We show that all three profiles are in close agreement, and this allows us to use the first model to describe fragments in the radial direction of the shell. We then use non-linear equations describing the time-evolution of a uniform oblate spheroid to derive the growth rates of shell fragments having different sizes. This yields a dispersion relation which depends on the shell thickness, and hence on the pressure confining the shell. We compare this dispersion relation with the dispersion relation obtained using the standard thin-shell analysis, and show that, if the confining pressure is low, only large fragments are unstable. On the other hand, if the confining pressure is high, fragments smaller than predicted by the thin-shell analysis become unstable. Finally, we compare the new dispersion relation with the results of 3D hydrodynamic simulations, and show that the two are in good agreement.

35 citations

Journal ArticleDOI
TL;DR: In this article, the effects of the film thickness, the recess pressure, and the geometric configuration on the equivalent stiffness and damping of a hydrostatic journal bearing were investigated using a numerical method.
Abstract: The aim of this research is to study the dynamic characteristics of a hydrostatic journal bearing, with four hydrostatic bearing flat pads fed by diaphragm restrictors and supporting a rotor. We assumed that the fluid flow is incompressible, laminar, isothermal, and steady-state. Linear modeling was performed using a numerical method in order to investigate the effects of the film thickness, the recess pressure, and the geometric configuration on the equivalent stiffness and damping of a hydrostatic journal bearing. In the first step, the variation of equivalent stiffness and damping is studied according to the pressure ratio for different geometric configurations of a hydrostatic bearing at the point of operation. In the second step, the variation of the equivalent stiffness and damping is studied according to the ratio of the film thickness for different geometric configurations of a hydrostatic bearing when one moves away from the point of operation. The results show that the hydrostatic journal bearin...

35 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023282
2022708
202167
202089
201998
201893