The Thermal Instability of Completely Confined Fluids Inside Some Particular Configurations

1963 ◽  
Vol 85 (4) ◽  
pp. 346-354 ◽  
Author(s):  
S. Ostrach ◽  
D. Pnueli
Keyword(s):  
Thermal Stability ◽  
Experimental Investigation ◽  
Rayleigh Number ◽  
Thermal Instability ◽  
Body Force ◽  
Critical Rayleigh Number ◽  
Upper Bounds ◽  
Instability Criterion ◽  
Confined Fluids ◽  
Thermal Stability Of

This paper deals with the thermal stability of completely confined fluids subject to a body force and a temperature gradient which are parallel and oriented in the same direction. It describes a method to obtain upper bounds to the instability criterion (the critical Rayleigh number) for piecewise cylindrical configurations, and demonstrates the use of this method treating some particular practical configurations. These upper bounds are shown to coincide with the critical Rayleigh number under some conditions. An account of experimental investigation of three of the particular configurations is presented and the experimental results compare favorably with the computed upper bounds.

Lower Bounds to Thermal Instability Criteria of Completely Confined Fluids Inside Cylinders of Arbitrary Cross Section

1964 ◽  
Vol 31 (3) ◽  
pp. 376-379 ◽  
Author(s):  
D. Pnueli
Keyword(s):  
Cross Section ◽  
Lower Bounds ◽  
Thermal Instability ◽  
Critical Rayleigh Number ◽  
Arbitrary Cross Section ◽  
The Body ◽  
Instability Criterion ◽  
Confined Fluids ◽  
Force Direction ◽  
Rayleigh Numbers

A method is developed to compute the lower bounds for the thermal instability criterion (the critical Rayleigh number) for fluids completely confined inside cylinders of arbitrary cross section; i.e., Rayleigh numbers below which no spontaneous flow may occur in spite of the density gradient being opposite to the body force direction.

Lower Bounds to the Critical Rayleigh Number in Completely Confined Regions

1967 ◽  
Vol 34 (2) ◽  
pp. 308-312 ◽  
Author(s):  
M. Sherman ◽  
S. Ostrach
Keyword(s):  
Rayleigh Number ◽  
Lower Bounds ◽  
Body Force ◽  
Critical Rayleigh Number ◽  
Convective Motion ◽  
The Body ◽  
Maximum Dimension ◽  
Fixed Temperature ◽  
Boussinesq Fluid ◽  
The Given

A method is presented for estimating lower bounds to the minimum Rayleigh number that will induce a state of convective motion in a quasi-incompressible (Boussinesq) fluid where the temperature gradient is in the direction of the body force. The fluid is completely confined by fixed-temperature, rigid bounding walls. For any arbitrary region, the critical Rayleigh number is greater than 1558(h/D)4 where h is the maximum dimension of the given region in the direction of the body force and D is the diameter of an equal volume sphere. In certain simple geometrical configurations, improved lower-bound estimates are calculated.

Study of the influence of ester orientation on the thermal stability of the smectic C phase: experimental investigation

2008 ◽  
Vol 35 (3) ◽  
pp. 357-364 ◽  
Author(s):  
Richard Vadnais ◽  
Marc‐André Beaudoin ◽  
Alexandre Beaudoin ◽  
Benoît Heinrich ◽  
Armand Soldera
Keyword(s):  
Thermal Stability ◽  
Experimental Investigation ◽  
Smectic C ◽  
Thermal Stability Of

Experimental investigation of the activity and thermal stability of hexaaluminate catalysts for lean methane–air combustion

2003 ◽  
Vol 255 (2) ◽  
pp. 279-288 ◽  
Author(s):  
Roderick W Sidwell ◽  
Huayang Zhu ◽  
Brian A Kibler ◽  
Robert J Kee ◽  
David T Wickham
Keyword(s):  
Thermal Stability ◽  
Experimental Investigation ◽  
Thermal Stability Of ◽  
Hexaaluminate Catalysts

Thermal Stability of Fe Filaments in Deformed Cu-Fe Composites

2010 ◽  
Vol 654-656 ◽  
pp. 2720-2723 ◽  
Author(s):  
En Gang Wang ◽  
Lei Qu ◽  
Xiao Wei Zuo ◽  
Lin Zhang ◽  
Ji Cheng He
Keyword(s):  
Thermal Stability ◽  
Thermal Instability ◽  
Vacuum Induction Furnace ◽  
Drawing Ratio ◽  
Model Calculations ◽  
Instability Modes ◽  
Fe Alloys ◽  
Breakup Time ◽  
Composite Wires ◽  
Thermal Stability Of

The Cu-12.8wt%Fe alloys are prepared in a vacuum induction furnace and then drawn to Cu-Fe composite wires with the drawing ratio of 8.2. The thermal stability of Fe filaments in the deformed Cu-12.8wt% Fe composite wires under different annealed temperature is investigated. The results show that the instability of the Fe filaments in the Cu-Fe composites is controlled by the longitudinal boundary splitting, then the splitting Fe filaments subsequently evolve into the cylinders. The thermal instability of the cylindrical Fe filaments is controlled by the two instability modes of Rayleigh perturbation and two dimensional Ostwald coarsening. The model calculations of two modes indicate that the perturbation breakup of cylindrical Fe filaments firstly occurs at the ones with smaller diameter. The breakup time of cylindrical Fe filaments decreases with the increasing of the annealing temperature. The coarsening diameters of cylindrical Fe filaments increase in linear proportion with the holding time. The smaller is the diameter of cylindrical Fe filaments, the larger is the coarsening rate.

Thermal Stability of Ir-Silicide/SiGe Layers Grown in a Dual Electron Gun Chamber at Ultra-High Vacuum (Extended Abstract)

1994 ◽  
Vol 299 ◽  
Author(s):  
C. K. Chung ◽  
J. Hwang
Keyword(s):  
Thermal Stability ◽  
Thermal Instability ◽  
High Vacuum ◽  
Epitaxial Films ◽  
Ultra High Vacuum ◽  
Electron Gun ◽  
Guard Ring ◽  
X Ray ◽  
Silicide Layer ◽  
Thermal Stability Of

AbstractHeteroepitaxial Ir-silicide/SiGe layers on the top of p-Si(100) have been achieved at a substrate temperature of 450 °C. The co-deposited Ir-silicide layer was determined to be Ir3Si4 with four types of epitaxial modes. Thermal stability of the film was examined by using Auger electron spectroscopy and X-ray diffractometer. The Ir3Si4/SiGe layers were stable as annealed at 550 °C for 20 sec in a rapid thermal annealing furnace, while interdiffusion between Ir3Si4 and SiGe occurs at a temperature of 750 deg;C or higher for 20 sec. The traditional guard-ring fabrication process should be performed before epitaxial films deposition due to this thermal instability.

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