Hydrostatic equilibrium

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

Three-Dimensional Hydrostatic Curved Channel Flow Simulations Using Non-Staggered Triangular Grids

Abstract: Non-staggered triangular grids have many advantages in performing river or ocean modeling with the finite-volume method. However, horizontal divergence errors may occur, especially in large-scale hydrostatic calculations with centrifugal acceleration. This paper proposes an unstructured finite-volume method with a filtered scheme to mitigate the divergence noise and avoid further influencing the velocities and water elevation. In hydrostatic pressure calculations, we apply the proposed method to three-dimensional curved channel flows. Approximations reduce the numerical errors after filtering the horizontal divergence operator, and the approximation is second-order accurate. Numerical results for the channel flow accurately calculate the velocity profile and surface elevation at different Froude numbers. Moreover, secondary flow features such as the vortex pattern and its movement along the channel sections are also well captured.

EPR Spectrometer for Studying Crystals under High Hydrostatic Pressure

Abstract: A spectrometer for studying the effect of hydrostatic pressure to 10 kbar on the electron paramagnetic resonance spectra of crystals is described. A two‐sample comparison method is used which greatly simplifies both the experimental procedure and the analysis. The pressure is purely hydrostatic, and the cavity coupling is readily adjustable from outside the pressure vessel.

Gravity Waves Driven by Diurnal Fluctuations in Mesoscale Heating

Abstract: Observed convective systems, such as mesoscale convective complexes (MCCs), often undergo repeated cycles of nocturnal growth and daytime decay especially during the summer. The gravity wave response to these pulsations is poorly understood. The motivation for this study is to understand this response and especially its sensitivity to environmental factors such as horizontal wind and static stability. A semianalytical approach is used that focuses on the roles of singularities in a complex horizontal wavenumber space. The model is linear, Boussinesq, hydrostatic, and rotating with uniform ambient conditions. Prescribed, 2D, pulsating, upright, convective heating drives the waves. The Fourier transform technique is used to unravel the response into a discrete and continuous horizontal spectrum. Many features of the response depend on a Froude number, F 5 pU/(DN) where U 5 background wind, D 5 depth of source region, and N 5 buoyancy frequency. The most efficient forcing of the gravity wave field occurs near criticality (F 5 1). For typical values of U and D associated with midlatitude convective systems, the critical value of N is about one-fourth of average tropospheric values. The resulting enhanced loss of energy from the convective system due to gravity waves could limit the intensity of convective systems near criticality. At subcriticality (F , 1), the pulsating upstream response is dominated by unbalanced ageostrophic propagating modes upstream of the source region and by a balanced geostrophic mode downstream of the source. The latter advances with a speed equal to the background flow. No far-upstream response occurs for supercriticality ( F . 1). The downstream response for F . 1 is dominated by the geostrophic mode in the pressure, temperature, and source-parallel wind. In addition, a vigorous ageostrophic mode advances downstream from the subcritical source region giving rise to alternating regions of rising motion and subsidence. It is hypothesized that the latter could trigger new lines of convection in the downstream subcrticial Froude number regime. Mature MCCs often develop low-level cooling in response to evaporative cooling. This cooling primarily triggers the advective inertial gravity wave mode, which propagates downstream at the background wind speed. It is shown that subcritical flows ( F , 1; weak ambient flow and/or strong static stability) are tuned to strongly respond to this mode. It is suggested that the development of new convection might be suppressed near the system under subcritical conditions. Low-level cooling has little effect on the supercritical response.

The Classical Stellar Atmosphere Problem

Abstract: We introduce the classical stellar atmosphere problem and describe in detail its numerical solution. The problem consists of the solution of the radiation transfer equations under the constraints of hydrostatic, radiative and statistical equilibrium (non-LTE). We outline the basic idea of the Accelerated Lambda Iteration (ALI) technique and statistical methods which finally allow the construction of non-LTE model atmospheres considering the influence of millions of metal absorption lines. Some applications of the new models are presented.