3D Temporal Model Research Articles

Spiral Thermal Plumes in Water under Conventional Heating: Numerical Results on the Effect of Rotation

In this paper, we study numerically the effect of rotation within a sample of water in a cylindrical container subject to rotation which is heated with a constant temperature at the bottom and lateral wall. We analyze the temporal behavior of temperature and flow velocity of the solvent. The thermal plumes developed at lower levels, already observed in the case without rotation, begin to spiral spreading outwards by the effect of rotation, increasing the azimuthal velocity of the fluid. No significant increases in the radial and vertical velocity components are observed which do not favor the mixture of hotter and colder flows in the sample and a faster heating of the solvent. In the rotation range studied, the state loses the axisymmetry and becomes fully 3D earlier in time as the rotation rate increases. To perform simulations, we use a 3D temporal model that couples momentum and heat equations and is based on spectral element methods.

Thermal plumes in water under conventional heating: In silico experiments

In this paper we study numerically the behavior of water in a cylindrical container within a constant and maintained temperature at the bottom and lateral wall. We study the temporal behavior of the flow velocity and temperature in the sample, highlighting the development of thermal plumes close to the lower boundary. The regime is laminar for the range of parameters studied and the flow evolves to a stationary state with a homogenous temperature in the cell. We analyze the effect of the bath temperature in the character of the flow developed and determine the temperature threshold at which fully 3D flows (non-axisymmetric) are found, for which thermal plumes grow more abundantly and in a more disorganized way. We use a 3D temporal model coupling heat and momentum equations based on spectral element methods. Results are of interest as they permit a full understanding of this conventional way of heating and the effect of the variation of external temperature conditions on the temperature and fluid flow distribution in the sample.

Variability of the hydrogen in the martian upper atmosphere as simulated by a 3D atmosphere–exosphere coupling

We present the temporal variability of the atomic and molecular hydrogen density derived from a 3D General Circulation Model describing the martian atmosphere from the surface to the exobase. A kinetic exospheric model is used to compute the hydrogen density above the exobase. We use these models to study the diurnal and seasonal variations of the hydrogen density and the Jeans escape rate as well as their variations with solar activity, assuming a classic dust scenario. We find that the diurnal variations of the hydrogen density are important with a peak in the dawn region during equinoxes and a peak on the nightside during solstices. These features result from the dynamics of the martian upper atmosphere. The variations of the atomic hydrogen Jeans escape with seasons and solar activity are in the range 1.3×1025s−1–4.4×1026s−1. A factor ∼8 is due to the seasonal variations with a maximum during the winter solstice in the northern hemisphere and a minimum during the summer solstice in the northern hemisphere that we attribute to the variation of the Mars–Sun distance. A factor ∼5 is due to the solar cycle with a maximum escape rate at high solar activity. The variations of the molecular hydrogen Jeans escape with seasons and solar activity are in the range 3×1022s−1–6×1024s−1. A factor ∼10 is due to the seasonal variations with a maximum during the winter solstice in the northern hemisphere and a minimum during the summer solstice in the northern hemisphere. A factor ∼20 is due to the solar cycle with a maximum escape rate at high solar activity. If Jeans escape is the major escape channel for hydrogen, the hydrogen escape is never limited by diffusion. The hydrogen density above 10,000km presents seasonal and solar cycle variations similar to the Jeans escape rate at all latitudes and local times. This 3D temporal model of the hydrogen thermosphere/exosphere will be useful to interpret future MAVEN observations and the consequences of the hydrogen corona variability on the martian plasma environment.