Oscillation responses and wake modes of three staggered rotating cylinders in two- and three-dimensional flows

2018 ◽  
Vol 30 (10) ◽  
pp. 103602 ◽  
Author(s):  
Suresh Behara ◽  
Venu Chandra ◽  
B. Ravikanth ◽  
V. M. Kurshnarao Kotteda
Keyword(s):  
Three Dimensional ◽  
Rotating Cylinders ◽  
Wake Modes

Transient Three-Dimensional Heat Transfer Model of a Solar Thermochemical Reactor for H2O and CO2 Splitting via Nonstoichiometric Ceria Redox Cycling

2013 ◽  
Author(s):  
Justin Lapp ◽  
Wojciech Lipiński
Keyword(s):  
Heat Transfer ◽  
Heat Recovery ◽  
Fuel Efficiency ◽  
Three Dimensional ◽  
Reactor Design ◽  
Heat Transfer Model ◽  
Heat Fluxes ◽  
Transfer Model ◽  
Rotating Cylinders ◽  
Solar Receiver

A transient heat transfer model is developed for a solar reactor prototype for H2O and CO2 splitting via two-step non-stoichiometric ceria cycling. Counter-rotating cylinders of reactive and inert materials cycling between high and low temperature zones permit continuous operation and heat recovery. To guide the reactor design a transient three-dimensional heat transfer model is developed based on transient energy conservation, accounting for conduction, convection, radiation, and chemical reactions. The model domain includes the rotating cylinders, a solar receiver cavity, and insulated reactor body. Radiative heat transfer is analyzed using a combination of the Monte Carlo method, Rosseland diffusion approximation, and the net radiation method. Quasi-steady state distributions of temperatures, heat fluxes, and the non-stoichiometric coefficient are reported. Ceria cycles between temperatures of 1708 K and 1376 K. A heat recovery effectiveness of 28% and solar-to-fuel efficiency of 5.2% are predicted for an unoptimized reactor design.

scholarly journals Flow control with rotating cylinders

2017 ◽  
Vol 825 ◽  
pp. 743-763 ◽  
Author(s):  
James C. Schulmeister ◽  
J. M. Dahl ◽  
G. D. Weymouth ◽  
M. S. Triantafyllou
Keyword(s):  
Reynolds Number ◽  
Flow Control ◽  
Three Dimensional ◽  
Rotating Cylinders ◽  
Piv Measurements ◽  
Rotation Rates ◽  
Image Velocimetry ◽  
The Mean ◽  
Recirculation Length ◽  
Control Cylinder

We study the use of small counter-rotating cylinders to control the streaming flow past a larger main cylinder for drag reduction. In a water tunnel experiment at a Reynolds number of 47 000 with a three-dimensional and turbulent wake, particle image velocimetry (PIV) measurements show that rotating cylinders narrow the mean wake and shorten the recirculation length. The drag of the main cylinder was measured to reduce by up to 45 %. To examine the physical mechanism of the flow control in detail, a series of two-dimensional numerical simulations at a Reynolds number equal to 500 were conducted. These simulations investigated a range of control cylinder diameters in addition to rotation rates and gaps to the main cylinder. Effectively controlled simulated flows present a streamline that separates from the main cylinder, passes around the control cylinder, and reattaches to the main cylinder at a higher pressure. The computed pressure recovery from the separation to reattachment points collapses with respect to a new scaling, which indicates that the control mechanism is viscous.

Three-dimensional elasticity analysis of functionally graded rotating cylinders with variable thickness profile

2011 ◽  
Vol 226 (3) ◽  
pp. 585-594 ◽  
Author(s):  
E Ghafoori ◽  
M Asghari
Keyword(s):  
Variable Thickness ◽  
Three Dimensional ◽  
Functionally Graded ◽  
Numerical Results ◽  
Constant Thickness ◽  
Rotating Cylinders ◽  
Hollow Structures ◽  
Thickness Profile ◽  
Axisymmetric Structure ◽  
Three Dimensional Elasticity

A three-dimensional elasticity solution for the analysis of functionally graded rotating cylinders with variable thickness profile is proposed. The axisymmetric structure has been divided in several divisions in the radial direction. Constant mechanical properties and thickness profile are assumed within each division. The solution is considered for four different thickness profiles, namely constant, linear, concave, and convex. It is shown that the linear, concave, and convex thickness profiles have smaller stress values compared to a constant thickness profile. The effects of various grading indices as well as different boundary conditions, namely solid, free–free hollow and fixed–free hollow structures are discussed. A series of numerical results using zirconia as outer surface ceramic and aluminium as inner surface metal are presented. Parametric study has then been carried out to give a better understanding of how different stress, strain, and displacement components change along radial and axial directions of the rotating structures. Numerical results show that for a given grading index, the structures with a concave thickness profile have the smaller circumferential strain and stress compared to other thickness profiles.

Study on the dynamics of chitosan/cotton fiber in an airflow around two rotating cylinders

2017 ◽  
Vol 88 (18) ◽  
pp. 2035-2043 ◽  
Author(s):  
Hui Fen Guo ◽  
Chenxiao Yang ◽  
Li Li
Keyword(s):  
Cotton Fiber ◽  
Three Dimensional ◽  
Axial Direction ◽  
Simulation Method ◽  
Ring Spinning ◽  
Rotating Cylinders ◽  
Triangle Zone ◽  
Yarn Properties ◽  
Cohesion Force ◽  
Particle Level

To predict chitosan/cotton yarn properties in ring spinning, a particle-level simulation method has been used to simulate the dynamics of the fibers with different initial positions in three-dimensional airflow around counter-rotating cylinders. The results show that the fibers near the cylinder end-face can leave two cylinders’ nip and move around the top cylinder, thus form fly waste. It is good to entangle other fibers as this gives the fiber greater bending energy. Compared with cotton fiber, the axial-direction deflections of the tail-ends of chitosan fibers near the cylinder center are much greater, while their bending energies are much lower, thus forming a wide triangle zone and reduced fiber–fiber cohesion force and yarn strength. To demonstrate the simulation results, a series of spinning experiments are completed, which tally with the predictions.

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