Secondary convective motions in a plane inclined layer

1978 ◽  
Vol 12 (3) ◽  
pp. 347-352
Author(s):  
A. A. Nepomnyashchii
Keyword(s):  
Inclined Layer ◽  
Convective Motions

Spatial Distribution of Pre-Warm Front Rainfall in the Mediterranean Area

1988 ◽  
Vol 19 (1) ◽  
pp. 53-64 ◽  
Author(s):  
C. Corradini ◽  
F. Melone
Keyword(s):  
Mediterranean Area ◽  
Compact Structure ◽  
Large Variability ◽  
Air Mass ◽  
Orographic Effects ◽  
Warm Front ◽  
Average Rainfall ◽  
Convective Motions ◽  
Rainfall Type ◽  
The Mediterranean

Evidence is given of the distribution of pre-warm front rainfall at the meso-γ scale, together with a discussion of the main mechanisms producing this variability. An inland region in the Mediterranean area is considered. The selected rainfall type is commonly considered the most regular inasmuch as it is usually unaffected by extended convective motions. Despite this, within a storm a large variability in space was observed. For 90% of measurements, the typical deviations from the area-average total depth ranged from - 40 to 60 % and the storm ensemble-average rainfall rate over an hilly zone was 60 % greater than that in a contiguous low-land zone generally placed upwind. This variability is largely explained in terms of forced uplift of air mass over an envelope type orography. For a few storms smaller orographic effects were found in locations influenced by an orography with higher slopes and elevations. This feature is ascribed to the compact structure of these mountains which probably determines a deflection of air mass in the boundary layer. The importance of this type of analysis in the hydrological practice is also emphasized.

Turbulent convective flows in the solar photospheric plasma

2015 ◽  
Vol 81 (5) ◽  
Author(s):  
A. Caroli ◽  
F. Giannattasio ◽  
M. Fanfoni ◽  
D. Del Moro ◽  
G. Consolini ◽  
...  
Keyword(s):  
Mean Square Displacement ◽  
Small Scale ◽  
Solar Photosphere ◽  
Distribution Analysis ◽  
Pixel Resolution ◽  
Convective Flows ◽  
Magnetic Elements ◽  
Highly Nonlinear ◽  
Convective Motions ◽  
Short Time

The origin of the 22-year solar magnetic cycle lies below the photosphere where multiscale plasma motions, due to turbulent convection, produce magnetic fields. The most powerful intensity and velocity signals are associated with convection cells, called granules, with a scale of typically 1 Mm and a lifetime of a few minutes. Small-scale magnetic elements (SMEs), ubiquitous on the solar photosphere, are passively transported by associated plasma flows. This advection makes their traces very suitable for defining the convective regime of the photosphere. Therefore the solar photosphere offers an exceptional opportunity to investigate convective motions, associated with compressible, stratified, magnetic, rotating and large Rayleigh number stellar plasmas. The magnetograms used here come from a Hinode/SOT uninterrupted 25-hour sequence of spectropolarimetric images. The mean-square displacement of SMEs has been modelled with a power law with spectral index ${\it\gamma}$. We found ${\it\gamma}=1.34\pm 0.02$ for times up to ${\sim}2000~\text{s}$ and ${\it\gamma}=1.20\pm 0.05$ for times up to ${\sim}10\,000~\text{s}$. An alternative way to investigate the advective–diffusive motion of SMEs is to look at the evolution of the two-dimensional probability distribution function (PDF) for the displacements. Although at very short time scales the PDFs are affected by pixel resolution, for times shorter than ${\sim}2000~\text{s}$ the PDFs seem to broaden symmetrically with time. In contrast, at longer times a multi-peaked feature of the PDFs emerges, which suggests the non-trivial nature of the diffusion–advection process of magnetic elements. A Voronoi distribution analysis shows that the observed small-scale distribution of SMEs involves the complex details of highly nonlinear small-scale interactions of turbulent convective flows detected in solar photospheric plasma.

scholarly journals An experimental investigation of convection in a fluid that exhibits phase change

1981 ◽  
Vol 102 ◽  
pp. 85-100 ◽  
Author(s):  
D. E. Fitzjarrald
Keyword(s):  
Thin Layer ◽  
Phase Change ◽  
Latent Heat ◽  
Thermal Gradient ◽  
Lower Boundary ◽  
Working Fluid ◽  
Heavy Fluid ◽  
Convective Motions ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

Convection flows have been systematically observed in a layer of fluid between two isothermal horizontal boundaries. The working fluid was a nematic liquid crystal, which exhibits a liquid–liquid phase change at which latent heat is released and the density changed. In addition to ordinary Rayleigh–Bénard convection when either phase is present alone, there exist two distinct types of convective motions initiated by the unstable density difference. When a thin layer of heavy fluid is present near the top boundary, hexagons with downgoing centres exist with no imposed thermal gradient. When a thin layer of light fluid is brought on near the lower boundary, the hexagons have upshooting centres. In both cases, the motions are kept going once they are initiated by the instability due to release of latent heat. Relation of the results to applicable theories is discussed.

scholarly journals Large-scale vortices in rapidly rotating Rayleigh–Bénard convection

2014 ◽  
Vol 758 ◽  
pp. 407-435 ◽  
Author(s):  
Céline Guervilly ◽  
David W. Hughes ◽  
Chris A. Jones
Keyword(s):  
Large Scale ◽  
Reynolds Numbers ◽  
Spectral Space ◽  
Small Scale ◽  
Convective Velocity ◽  
Onset Of Convection ◽  
Convective Structures ◽  
Convective Scale ◽  
Domain Of Existence ◽  
Convective Motions

AbstractUsing numerical simulations of rapidly rotating Boussinesq convection in a Cartesian box, we study the formation of long-lived, large-scale, depth-invariant coherent structures. These structures, which consist of concentrated cyclones, grow to the horizontal scale of the box, with velocities significantly larger than the convective motions. We vary the rotation rate, the thermal driving and the aspect ratio in order to determine the domain of existence of these large-scale vortices (LSV). We find that two conditions are required for their formation. First, the Rayleigh number, a measure of the thermal driving, must be several times its value at the linear onset of convection; this corresponds to Reynolds numbers, based on the convective velocity and the box depth, $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}{\gtrsim }100$. Second, the rotational constraint on the convective structures must be strong. This requires that the local Rossby number, based on the convective velocity and the horizontal convective scale, ${\lesssim }0.15$. Simulations in which certain wavenumbers are artificially suppressed in spectral space suggest that the LSV are produced by the interactions of small-scale, depth-dependent convective motions. The presence of LSV significantly reduces the efficiency of the convective heat transport.

Supercritical convective motions in a short horizontal cylinder

1981 ◽  
Vol 15 (4) ◽  
pp. 585-590
Author(s):  
G. P. Bogatyrev ◽  
V. G. GiLev
Keyword(s):  
Horizontal Cylinder ◽  
Convective Motions

Convective motions in a porous ring sector

2011 ◽  
Vol 52 (3) ◽  
pp. 427-435 ◽  
Author(s):  
A. V. Trofimova ◽  
B. G. Tsibulin
Keyword(s):  
Convective Motions

Convective motions in the Earth's fluid core

1994 ◽  
Vol 21 (18) ◽  
pp. 1939-1942 ◽  
Author(s):  
K. Zhang ◽  
C. A. Jones
Keyword(s):  
Fluid Core ◽  
Convective Motions

scholarly journals A numerical study for convection in a cylindrical model with continuously varying viscosity

1996 ◽  
Vol 39 (3) ◽  
Author(s):  
F. Fanucci ◽  
A. Megna ◽  
S. Santini ◽  
F. Vetrano
Keyword(s):  
Viscosity Solutions ◽  
Numerical Study ◽  
Viscosity Coefficient ◽  
Cylindrical Symmetry ◽  
The Earth ◽  
Realistic Representation ◽  
Convective Motions ◽  
Constant Viscosity ◽  
Varying Viscosity ◽  
Better Than

In the framework of a cylindrical symmetry model for convective motions in the asthenosphere, a new profile for the viscosity coefficient depending on depth is suggested here. The numerical elaboration of the above mentioned model leads to interesting results which fit well with experimental observations. In particular these continuously varying viscosity solutions probably describe the convective motions within the Earth better than simple constant viscosity solutions. Consequently the temperature values seem to be a realistic representation of the possible thermal behaviour in the upper mantle.

Sign in / Sign up

Export Citation Format

Share Document