Turbulence and its Sources Below the Convective Zone

2003 ◽  
pp. 23-32 ◽  
Author(s):  
K. Petrovay
Keyword(s):  
Convective Zone

Mathematical Description of the Influence of the Bunker Outlet on the Grain Motion in the Microwave Convective Area

2020 ◽  
pp. 73-80
Author(s):  
Aleksey N. Vasil’yev ◽  
Andrey A. Tsymbal ◽  
Aleksey A. Vasil’yev
Keyword(s):  
Mathematical Description ◽  
Microwave Field ◽  
Convective Zone ◽  
Research Purpose ◽  
Field Zone ◽  
Flow Process ◽  
Grain Processing ◽  
Grain Flow ◽  
The Right ◽  
Processing Zone

One of the environmentaly friendly methods of drying and decontamination of grain is its processing in microwave-convective installations. The efficiency of using the microwave field depends on the uniformity of its distribution in the grain processing zone. This is provided by the design features of the microwave core and waveguides. The uniformity of grain movement in the microwave field zone is important. It is important that the grain is moved in the microwave convective zone by hydraulic movement. In this case, the grain passes through zones with different intensity of the microwave field sequentially and the grain processing is uniform. (Research purpose) The research purpose is in making a mathematical dependence of parameters of the hopper outlet on the movement of grain in the microwave convective zone. (Materials and methods) The article presents the parameters of the outlet that ensure the grain flow without forming static arches in accordance with the method of calculating outlet bins. Fluctuations in humidity for different crops of processed grain will not lead to a violation of the grain flow process. The resulting equation for changing the height of the dynamic arch, depending on its location in the height of the hopper, allows to determine the uneven flow of grain from the hopper outlet. (Results and discussion) When unloading grain, there is an uneven flow in the right and left halves of the hopper, relative to the central axis. When only one hopper is unloaded, 0.84 kilograms more wheat is unloaded from its left half than from the right. This difference leads to uneven and reduced efficiency of grain processing in the microwave-convective zone. (Conclusions) To ensure the uniformity of grain processing in the microwave convective zone, it is necessary to improve the mechanism of grain flow from the outlet of the hopper.

Study of surface convective zone behavior of solar pond in laboratory

1994 ◽  
Vol 4 (1) ◽  
pp. 47-51 ◽  
Author(s):  
Renyuan Zhang ◽  
C.E. Nielsen
Keyword(s):  
Convective Zone ◽  
Solar Pond

Assessing the Maximum Stability of the Nonconvective Zone in a Salinity-Gradient Solar Pond

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
A. A. Abdullah ◽  
K. A. Lindsay
Keyword(s):  
Salinity Gradient ◽  
Fluid Velocity ◽  
Weather Conditions ◽  
Convective Zone ◽  
Heat Extraction ◽  
Solar Pond ◽  
Maximum Stability ◽  
Storage Zone ◽  
The Stability

The quality of the stability of the nonconvective zone of a salinity-gradient solar pond (SGSP) is investigated for an operating protocol in which the flushing procedure exactly compensates for evaporation losses from the solar pond and its associated evaporation pond. The mathematical model of the pond uses simplified, but accurate, constitutive expressions for the physical properties of aqueous sodium chloride. Also, realistic boundary conditions are used for the behaviors of the upper and lower convective zones (LCZs). The performance of a salinity-gradient solar pond is investigated in the context of the weather conditions at Makkah, Saudi Arabia, for several thickness of upper convective zone (UCZ) and operating temperature of the storage zone. Spectral collocation based on Chebyshev polynomials is used to assess the quality of the stability of the pond throughout the year in terms of the time scale for the restoration of disturbances in temperature, salinity, and fluid velocity underlying the critical eigenstate. The critical eigenvalue is found to be real and negative at all times of year indicating that the steady-state configuration of the pond is always stable, and suggesting that stationary instability would be the anticipated mechanism of instability. Annual profiles of surface temperature, salinity, and heat extraction are constructed for various combinations for the thickness of the upper convective zone and storage zone temperature.

scholarly journals Low-Mass AGB Stellar Models for 0.003 ≤ Z ≤ 0.02: Basic Formulae for Nucleosynthesis Calculations

2003 ◽  
Vol 20 (4) ◽  
pp. 389-392 ◽  
Author(s):  
O. Straniero ◽  
I. Domínguez ◽  
S. Cristallo ◽  
R. Gallino
Keyword(s):  
Effective Temperature ◽  
Convective Instability ◽  
Convective Zone ◽  
Maximum Temperature ◽  
Core Mass ◽  
Convective Envelope ◽  
Appropriate Treatment ◽  
Low Mass ◽  
Thermal Pulses ◽  
Radiative Opacity

AbstractWe have extended our published set of low-mass AGB stellar modelsto lower metallicities. Different mass-loss rates have been explored. We provide interpolation formulae for the luminosity, effective temperature, core mass, mass of dredge up material and maximum temperature in the convective zone generated by thermal pulses. Finally, we discuss the resultant modification of these quantities when we use an appropriate treatment of the inward propagation of the convective instability, as caused by the steeprise in radiative opacity when the convective envelope penetratesthe H-depleted region.

scholarly journals Helioseismic inferences

2009 ◽  
Vol 5 (S264) ◽  
pp. 33-38
Author(s):  
Hiromoto Shibahashi
Keyword(s):  
Solar Activity ◽  
Linear Approximation ◽  
Activity Cycle ◽  
Solar Activity Cycle ◽  
Convective Zone ◽  
Dynamo Model ◽  
Kinematic Dynamo ◽  
Wide Range ◽  
Dynamo Mechanism ◽  
Solar Type

AbstractThe brilliant outcome of some 30 years of helioseismology spreads over a wide range of topics. Some highlights relevant to the cause of the solar activity cycle are listed up. The rotation profile in the solar convective zone is discussed as an important source of the dynamo mechanism. The kinematic dynamo model is described in the linear approximation, and the condition for the solar type dynamo is derived. It is shown that comparison of this condition with the rotation profile determined from helioseismology is useful to identify the possible seats of the dynamo.

scholarly journals Variability in the solar output

1990 ◽  
Vol 330 (1615) ◽  
pp. 641-643 ◽  
Keyword(s):  
Solar Cycle ◽  
Solar Neutrino ◽  
Neutrino Flux ◽  
Convective Zone ◽  
Solar Oscillation ◽  
Dynamo Action ◽  
Solar Neutrino Flux ◽  
Oscillation Frequencies

Evidence for variability in the solar output is briefly discussed. If the solar neutrino flux and the solar oscillation frequencies vary over a solar cycle this could indicate that the solar cycle has its origin in the solar core rather than be due to dynamo action in the solar convective zone.

scholarly journals Convectively Generated Turbulent Pressure: A Possible Cause for η Car - Type Shell Ejections

1991 ◽  
Vol 143 ◽  
pp. 549-549
Author(s):  
M. Kiriakidis ◽  
N. Langer ◽  
K.J. Fricke
Keyword(s):  
Massive Star ◽  
Energy Transport ◽  
Convection Zone ◽  
Hydrostatic Equilibrium ◽  
Convective Zone ◽  
Contraction Phase ◽  
Hydrodynamic Calculation ◽  
Turbulent Pressure ◽  
Possible Cause ◽  
Η Car

A selfconsistent hydrodynamic calculation of a very massive star (MZAMS = 2OOM⊙) including turbulent pressure and energy has been performed. In the contraction phase after core hydrogen exhaustion, the star moves towards cool surface temperatures in the HR diagram (cf. Fig. 1). Consequently, (at Teff ⋍ 8000K) an envelope convection zone developes, and its inner boundery moves inwards with time. First, the envelope remains in hydrostatic equilibrium, with radiation pressure correspondingly decreasing as turbulent pressure increases (gas pressure is small). However, due to the fact, that the gradient of the turbulent pressure is directed inwards at the bottom of the convective zone, this part of the star rapidly contracts. Due to the released contraction energy, the luminosity locally exceeds the Eddington-luminosity. It cannot be transported outwards by convection in the upper part of the convection zone, where convective energy transport is inefficient (▽c ⋍ ▽r) . Thus, the local super-Eddington luminosity leads to the ejection of the overlying layers.

scholarly journals The Small-Scale Photospheric Magnetic Field as an Indicator of the Dynamo

1993 ◽  
Vol 141 ◽  
pp. 143-146
Author(s):  
K. Petrovay ◽  
G. Szakály
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Observational Data ◽  
Convective Zone ◽  
Small Scale ◽  
Dynamo Theory ◽  
Flux Tubes ◽  
Magnetic Flux Tubes ◽  
Surface Fields

AbstractThe presently widely accepted view that the solar dynamo operates near the base of the convective zone makes it difficult to relate the magnetic fields observed in the solar atmosphere to the fields in the dynamo layer. The large amount of observational data concerning photospheric magnetic fields could in principle be used to impose constraints on dynamo theory, but in order to infer these constraints the above mentioned “missing link” between the dynamo and surface fields should be found. This paper proposes such a link by modeling the passive vertical transport of thin magnetic flux tubes through the convective zone.

scholarly journals The Generation of Internal Waves

1993 ◽  
Vol 137 ◽  
pp. 278-280
Author(s):  
Josefina Montalbán
Keyword(s):  
Equilibrium State ◽  
Internal Waves ◽  
Deep Ocean ◽  
Stable Stratification ◽  
Convective Zone ◽  
Earth Atmosphere ◽  
Fluid Element ◽  
Turbulent Fluid ◽  
The Earth ◽  
Zero Momentum

The generation of internal waves in the radiatively stable stellar region by the turbulent motion at the boundary of the overlaying convective zone is similar to the same case in the deep ocean or in the earth atmosphere (Townsend, 1965), and can be described in a simple way as following: When an turbulent fluid element arrives at the boundary of the convective region with a non-zero momentum, it beats and it deforms the interface between both regions. This disturbance of the equilibrium state excites a train of internal waves propagating below the convective zone in the horizontal and vertical directions for the frequencies lower than the characteristic one for the stable stratification (Brunt-Väisälä frequency).

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