CONVECTING THRESHOLD IN NANOFLUID DRIVEN BY CENTRIFUGAL FORCES IN A ROTATING ANNULAR HELE-SHAW

2017 ◽  
Vol 9 (1) ◽  
pp. 49-62
Author(s):  
K. Souhar ◽  
M. Kriraa ◽  
L. Bammou ◽  
S. Alami ◽  
J. Bouchgl ◽  
...  
Keyword(s):  
Centrifugal Forces

scholarly journals On Population III Star Formation

1983 ◽  
Vol 104 ◽  
pp. 119-120
Author(s):  
A. Kashlinsky ◽  
M. J. Rees
Keyword(s):  
Background Radiation ◽  
Free Fall ◽  
Compact Objects ◽  
Centrifugal Forces ◽  
Tidal Interactions ◽  
Geometrical Cross Section ◽  
Spin Parameter ◽  
Small Density ◽  
Major Factors ◽  
Population Iii

If primordial fluctuations were isothermal their amplitude at recombination would be non-linear on scales Mo ≃ 106÷9 M⊙. Since the Jeans mass after recombination is MJo ≃ 8 × 105 Ω−1/2 M⊙ the clouds of mass Mo would be able to form the first generation of compact objects, the so-called Population III. These clouds would acquire angular momentum via tidal interactions with their neighbours. The importance of rotation can be conveniently characterised by the spin parameter λ = Vrotation/Vfree-fall and tidal interactions lead to a spin λo = 0.07 ± 0.03. As the cloud collapses λ increases as r−1/2. Any fragment forming in a rotating cloud would have the same spin λ as the whole cloud. It could therefore collapse only by ≃ λo2 in radius before centrifugal forces intervened, thus leaving a large geometrical cross-section for coalescence to be important. At radii r ≲ λo8/5 (Mo/MJo)2/15 ro the coalescence time is shorter than the free-fall time and no fragmentation is possible below this radius. In the primordial clouds two major factors prevent fragmentation at larger radii. First, the background radiation is still ‘hot’ and the trapping of it would prevent fragmentation until the whole cloud has collapsed to a radius 10−2 x−2/3 ro. Here x = 10−2(M/107 M⊙)1/3 is the ionization fraction given by the balance between gravitational contraction and recombination cooling. Furthermore, any small density fluctuation would lead to fragmentation only after the paternal cloud had collapsed by a factor (δ/5)2/3 in radius. For these reasons fragmentation is unlikely until centrifugal forces halt the collapse and a disk forms. The disk will be initially at T ≃ 104K but after a small fraction of H2 forms it will cool to T3 ≃ T/103K ≃ 1 and the final fragments mass could be as low as ≃ 0.2(λo/0.07)4 T32(MJo/Mo)1/3 M⊙.

Structural Response of Fiber Composite Fan Blades

1975 ◽  
Author(s):  
C. C. Chamis ◽  
M. D. Minich
Keyword(s):  
Quantitative Data ◽  
Fiber Composite ◽  
Structural Response ◽  
Aerodynamic Heating ◽  
Analysis Method ◽  
Centrifugal Forces ◽  
The Core ◽  
Composite Mechanics ◽  
Composite Blades ◽  
Load Conditions

A fiber composite airfoil, typical for high-tip speed compressor applications, is subjected to load conditions anticipated to be encountered in such applications, and its structural response is theoretically investigated. The analysis method used consists of composite mechanics embedded in pre- and post-processors and coupled with NASTRAN. The load conditions examined include thermal due to aerodynamic heating, pressure due to aerodynamic forces, centrifugal, and combinations of these. The various responses investigated include root reactions due to various load conditions, average composite and ply stresses, ply delaminations, and the fundamental modes and the corresponding reactions. The results show that the thermal and pressure stresses are negligible compared to those caused by the centrifugal forces. Also, the core-shell concept for composite blades is an inefficient design (core plies not highly stressed) and appears to be sensitive to interply delaminations. The results are presented in graphical and tabular forms to illustrate the types and amount of data required for such an analysis, and to provide quantitative data of the various responses which can be helpful in designing such composite blades.

Effect of centrifugal forces on the instability of the thermocapillary flow in partially confined half-zones

2006 ◽  
Vol 18 (3-4) ◽  
pp. 132-136
Author(s):  
Hendrik C. Kuhlmann ◽  
Suguru Shiratori ◽  
Taketoshi Hibiya
Keyword(s):  
Thermocapillary Flow ◽  
Centrifugal Forces

scholarly journals Improved Reliability of Bladed Disks due to Friction Dampers

1997 ◽  
Author(s):  
Walter Sextro ◽  
Karl Popp ◽  
Ivo Wolter
Keyword(s):  
Dry Friction ◽  
Three Dimensional ◽  
Line Contact ◽  
Two Dimensional ◽  
Centrifugal Forces ◽  
Friction Damper ◽  
Blade Vibration ◽  
Friction Dampers ◽  
Bladed Disk ◽  
Bladed Disk Assembly

Friction dampers are installed underneath the blade platforms to improve the reliability. Because of centrifugal forces the dampers are pressed onto the platforms. Due to dry friction and the relative motion between blades and dampers, energy is dissipated, which results in a reduction of blade vibration amplitudes. The geometry of the contact is in many cases like a Hertzian line contact. A three-dimensional motion of the blades results in a two-dimensional motion of one contact line of the friction dampers in the contact plane. An experiment with one friction damper between two blades is used to verify the two-dimensional contact model including microslip. By optimizing the friction dampers masses, the best damping effects are obtained. Finally, different methods are shown to calculate the envelope of a three-dimensional response of a detuned bladed disk assembly (V84.3-4th-stage turbine blade) with friction dampers.

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