Numerical studies of the advective flow of heptadecane in a horizontal layer with a longitudinal temperature gradient at the lower boundary

Numerical studies of the convective flow of heptadecane in a horizontal layer with a suddenly applied longitudinal temperature gradient at the lower high-thermal conductivity boundary have been carried out by the finite element method. A system of nonstationary dimensionless equations of free convection containing stream function, velocity vortex, and temperature as variables was solved. The calculations were carried out with a free upper boundary with and without taking into account the influence of the thermocapillary effect.

North Atlantic Multidecadal Variability Enhancing Decadal Extratropical Extremes in Boreal Late Summer in the Early Twenty-First Century

In the beginning of the twenty-first century, weather and climate extremes occurred more and more in extratropical summer, linked to the magnified amplitudes of quasi-stationary waves and external forcing. The study analyzes the relations between multidecadal extratropical extremes in boreal late summer and the North Atlantic (NA; 35°–65°N, 40°W–0°) multidecadal variability (NAMV) in the mid- to high latitudes. The results show that multidecadal extratropical extremes link with the intensified NAMV and the related positive–negative–positive (+ − +) zonal mode of sea surface temperature (SST). 1) The SST mode favors the eastward shift of the negative-phase NA oscillation (NNAO), with a latitudinal pattern of cyclone anomalies over the western European coast and anticyclones over Greenland; NNAO is helpful to baroclinic energy transfer and a longitudinal wavelike pattern. 2) The SST mode and the eddy-driven jet of NNAO are conducive to a southeast extension of the NA jet in close conjunction with the Afro-Asian jet, thereby enhancing the jet waveguide and barotropic energy transfer for the maintenance of a low-frequency wave. 3) The effect of the intensified NAMV on warming Europe contributes to the longitudinal temperature gradient–like “cooling ocean and warming land” pattern, which enhances the meridional wind and wave amplitude of the low-frequency wave. Based on these causes, the intensified NAMV and the + − + SST mode favor the enhancement of the low-frequency wave and quasi-resonant probability, which magnifies the amplitude of the quasi-stationary wave and enhances extratropical extremes on the decadal time scale.

Influence of the Thermophysical Properties of a Liquid Coolant on Characteristics of the 3D Flows with Phase Transition

Regimes of the joint flows of the evaporating liquid and gas – vapor mixture induced by the action of a longitudinal temperature gradient in a three-dimensional channel of a rectangular cross-section in the terrestrial gravity field are studied in the present paper. The theoretical investigations are carried out on the basis of the partially invariant solution of rank 2 and defect 3 of the Boussinesq approximation of the Navier – Stokes equations. This solution allows one to correctly describe the two-layer flows with evapora- tion/condensation at the thermocapillary interface and to take into account the effects of thermodiffusion and diffusive thermal conductivity in the gas–vapor phase. The exact solution of governing equations are characterized by dependence of the velocity components on the transverse coordinates only. The functions of pressure, temperature and concentration of vapor linearly depend on the longitudinal coordinate and have the summands which are functions on transverse coordinates. The required functions satisfy the set of differential equations, boundary and interface conditions followed from the original three-dimensional problem statement and are found as a result of numerical technique. The presented solution of the evap- orative convection problem is very contensive. It permits to specify the 3D flow regimes with different topology, thermal and concentration characteristics observed in physical experiments. Differences of flows in the ethanol–nitrogen, HFE-7100 – nitrogen and FC-72 – nitrogen systems are studied. Impact of the thermophysical properties of the working liquids on the basic characteristics of the fluid motions (hydro- dynamical structure, temperature distribution, vapor content in the nitrogen, evaporative mass flow rate) is analyzed

Effect of Longitudinal Temperature Gradient on the Intensity of Two-Way Evaporation in Axisymmetric Capillaries

A two-way evaporation of liquids from conical channels has been studied . The influence of the temperature gradient on the mass transfer process has been considered. An approximation expression for the temperature coefficient of evaporation has been derived and algorithm for calculating the system drainage time is developed. The double-sided vaporization from conical channels at an axial temperature gradient has been investigated in detail. Expressions for temperature coefficient of evaporation has been obtained and a computational algorithm for vaporization velocity has been developed. The obtained results allow estimating the duration of drying for materials with through pores of any type under conditions of uneven heating.