A direct method to investigate the stability of flow in a narrow gap between two rotating cylinders

1999 ◽  
Vol 40 (4) ◽  
pp. 459-466 ◽  
Author(s):  
Basem S. Attili
Keyword(s):  
Direct Method ◽  
Narrow Gap ◽  
Rotating Cylinders ◽  
The Stability ◽  
A Direct Method

ONSET OF INSTABILITY IN HYDROMAGNETIC COUETTE FLOW

2004 ◽  
Vol 02 (02) ◽  
pp. 145-159 ◽  
Author(s):  
ISOM H. HERRON
Keyword(s):  
Magnetic Field ◽  
Prandtl Number ◽  
Boundary Conditions ◽  
Viscous Flow ◽  
Couette Flow ◽  
Axial Magnetic Field ◽  
Narrow Gap ◽  
Rotating Cylinders ◽  
Magnetic Prandtl Number ◽  
The Stability

The stability of viscous flow between rotating cylinders in the presence of a constant axial magnetic field is considered. The boundary conditions for general conductivities are examined. It is proved that the Principle of Exchange of Stabilities holds at zero magnetic Prandtl number, for all Chandrasekhar numbers, when the cylinders rotate in the same direction, the circulation decreases outwards, and the cylinders have insulating walls. The result holds for both the finite gap and the narrow gap approximation.

A Study of the Influence of Initial Shape Imperfections on the Stability of Lattice Shells by Direct and Shell Analogy Methods

1987 ◽  
Vol 2 (4) ◽  
pp. 223-230 ◽  
Author(s):  
Jozef Sumec ◽  
Antonino E. Zingali
Keyword(s):  
Mathematical Model ◽  
Direct Method ◽  
Initial Shape ◽  
Analogy Method ◽  
General Stability ◽  
Reduction Coefficient ◽  
The Stability ◽  
Comparison Of The Results ◽  
A Direct Method ◽  
Lattice Shells

This paper describes the influence of initial shape imperfections of lattice shells on their general stability. An adequate mathematical model for the analysis of the shell instability by using a direct method (FEM) and a shell analogy method is presented. The reduction coefficient k for calculation of the critical load is derived. An illustrative example is used for comparison of the results calculated by the two numerical methods.

scholarly journals Plastic waste to fuels by hydrocracking at mild conditions

2021 ◽  
Vol 7 (17) ◽  
pp. eabf8283
Author(s):  
Sibao Liu ◽  
Pavel A. Kots ◽  
Brandon C. Vance ◽  
Andrew Danielson ◽  
Dionisios G. Vlachos
Keyword(s):  
Direct Method ◽  
Acid Sites ◽  
Liquid Fuels ◽  
High Yield ◽  
Tandem Catalysis ◽  
Hy Zeolite ◽  
Environmental Threat ◽  
Single Use ◽  
Initial Activation ◽  
A Direct Method

Single-use plastics impose an enormous environmental threat, but their recycling, especially of polyolefins, has been proven challenging. We report a direct method to selectively convert polyolefins to branched, liquid fuels including diesel, jet, and gasoline-range hydrocarbons, with high yield up to 85% over Pt/WO3/ZrO2 and HY zeolite in hydrogen at temperatures as low as 225°C. The process proceeds via tandem catalysis with initial activation of the polymer primarily over Pt, with subsequent cracking over the acid sites of WO3/ZrO2 and HY zeolite, isomerization over WO3/ZrO2 sites, and hydrogenation of olefin intermediates over Pt. The process can be tuned to convert different common plastic wastes, including low- and high-density polyethylene, polypropylene, polystyrene, everyday polyethylene bottles and bags, and composite plastics to desirable fuels and light lubricants.

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