A three-dimensional silicon shadowmask for patterning on trenches with vertical walls

2009 ◽  
Author(s):  
S. Morishita ◽  
J. H. Kim ◽  
F. Marty ◽  
Y. Li ◽  
A. J. Walton ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Vertical Walls

Numerical and experimental investigation for enhancing the energy absorption capacity of the novel three-dimensional printed sandwich structures

2021 ◽  
pp. 146442072199749
Author(s):  
H Geramizadeh ◽  
S Dariushi ◽  
S Jedari Salami
Keyword(s):  
Energy Absorption ◽  
Sandwich Structures ◽  
Three Dimensional ◽  
Absorption Capacity ◽  
The Novel ◽  
Energy Absorption Capacity ◽  
Fused Deposition ◽  
Honeycomb Sandwich ◽  
Out Of Plane ◽  
Vertical Walls

The current study focuses on designing the optimal three-dimensional printed sandwich structures. The main goal is to improve the energy absorption capacity of the out-of-plane honeycomb sandwich beam. The novel Beta VI and Alpha VI were designed in order to achieve this aim. In the Beta VI, the connecting curves (splines) were used instead of the four diagonal walls, while the two vertical walls remained unchanged. The Alpha VI is a step forward on the Beta VI, which was promoted by filleting all angles among the vertical walls, created arcs, and face sheets. The two offered sandwich structures have not hitherto been provided in the literature. All models were designed and simulated by the CATIA and ABAQUS, respectively. The three-dimensional printer fabricated the samples by fused deposition modeling technique. The material properties were determined under tensile, compression, and three-point bending tests. The results are carried out by two methods based on experimental tests and finite element analyses that confirmed each other. The achievements provide novel insights into the determination of the adequate number of unit cells and demonstrate the energy absorption capacity of the Beta VI and Alpha VI are 23.7% and 53.9%, respectively, higher than the out-of-plane honeycomb sandwich structures.

Numerical Study of Three-Dimensional Oscillatory Natural Convection at Low Prandtl Number in Rectangular Enclosures

2000 ◽  
Vol 123 (1) ◽  
pp. 77-83 ◽  
Author(s):  
Shunichi Wakitani
Keyword(s):  
Natural Convection ◽  
Prandtl Number ◽  
Numerical Study ◽  
Three Dimensional ◽  
Width Ratio ◽  
Three Dimensional Flow ◽  
Longitudinal Vortices ◽  
Aspect Ratios ◽  
Vertical Walls ◽  
Prandtl Numbers

Numerical investigations are presented for three-dimensional natural convection at low Prandtl numbers (Pr) from 0 to 0.027 in rectangular enclosures with differentially heated vertical walls. Computations are carried out for the enclosures with aspect ratios (length/height) 2 and 4, and width ratios (width/height) ranging from 0.5 to 4.2. Dependence of the onset of oscillation on the Prandtl number, the aspect ratio, and the width ratio is investigated. Furthermore, oscillatory, three-dimensional flow structure is clarified. The structure is characterized by some longitudinal vortices (rolls) as well as cellular pattern.

scholarly journals Numerical study of three-dimensional natural convection and entropy generation in a cubical cavity with partially active vertical walls

2017 ◽  
Vol 10 ◽  
pp. 100-110 ◽  
Author(s):  
Abdullah A.A.A Al-Rashed ◽  
Lioua Kolsi ◽  
Ahmed Kadhim Hussein ◽  
Walid Hassen ◽  
Mohamed Aichouni ◽  
...  
Keyword(s):  
Natural Convection ◽  
Entropy Generation ◽  
Numerical Study ◽  
Three Dimensional ◽  
Vertical Walls ◽  
Cubical Cavity

Three-Dimensional Natural Convective Flow in a Rectangular Enclosure With a Rectangular Heated Section on One Vertical Wall and With the Other Vertical Walls Cooled

2008 ◽  
Author(s):  
Patrick H. Oosthuizen ◽  
Abdulrahim Kalendar ◽  
Thomas M. Simko
Keyword(s):  
Convective Flow ◽  
Vertical Wall ◽  
Three Dimensional ◽  
The Other ◽  
Heated Wall ◽  
Governing Equations ◽  
Vertical Sidewall ◽  
Rectangular Enclosure ◽  
Wide Range ◽  
Vertical Walls

Three-dimensional natural convective flow in a rectangular enclosure with vertical sidewalls and horizontal top and bottom surfaces has been considered. A heated rectangular element is mounted in the middle of one vertical wall of the enclosure, the remainder of this wall being adiabatic. The remaining vertical walls are cooled to a uniform low temperature. The horizontal top and bottom walls are adiabatic. The flow has been assumed to be steady and laminar. Fluid properties have been assumed constant except for the density change with temperature that gives rise to the buoyancy forces. Radiation effects have been neglected. The numerical solution was obtained using the governing equations written in terms of dimensionless variables. The enclosure height, H′, was used as the characteristic length scale and the difference between the temperatures of the hot wall section and the cooled walls were used as the characteristic temperature scale. The dimensionless governing equations have been solved using FIDAP, a commercial software package that employs the finite element method. The solution has the following parameters: the Rayleigh number, the Prandtl number, the dimensionless height of the heated wall section compared to the overall enclosure height; the dimensionless width of the heated wall section compared to its height; the dimensionless width of the enclosure between the vertical sidewall on which the heated wall section is mounted and the opposite vertical sidewall, and the dimensionless width of the enclosure between the other two vertical sidewalls. Because of the application being considered, results have only been obtained for Pr = 0.7. Attention has been restricted to the case where the dimensionless width of the enclosure between the vertical sidewall on which the heated wall section is mounted and the opposite vertical sidewall is 0.5 and where the dimensionless width of the enclosure between the other two vertical sidewalls is 1.0. A wide range of the other parameters has been considered particular attention having been given to the effect of the dimensionless width of the heated wall section compared to its height on the mean Nusselt number for the heated wall section.

Suppression of Cellular Convection by Lateral Walls

1969 ◽  
Vol 91 (1) ◽  
pp. 145-150 ◽  
Author(s):  
D. K. Edwards
Keyword(s):  
Rayleigh Number ◽  
Cell Size ◽  
Critical Rayleigh Number ◽  
Three Dimensional ◽  
Arbitrary Degree ◽  
Spacing Ratio ◽  
Vertical Walls ◽  
The Stability ◽  
Thermally Conducting ◽  
Lateral Walls

An analysis is presented showing the effect on the critical Rayleigh number of inserting parallel vertical walls into a fluid heated from below. The walls are rigid (nonslippery) and thermally conducting to an arbitrary degree. Three-dimensional cellular convection between the walls is analyzed to determine the most unstable cell size, and the Rayleigh number for this cell size is calculated. It is shown that critical Rayleigh number based on either height or spacing can be made as large as may be desired by decreasing the spacing between vertical walls. At large height-to-spacing ratio with finite conducting walls a new form of the Rayleigh number is found to govern the stability. Experimental measurements are reported and compared to the analytical results.

scholarly journals Regularity and singularity in solutions of the three-dimensional Navier–Stokes equations

2010 ◽  
Vol 466 (2121) ◽  
pp. 2587-2604 ◽  
Author(s):  
J. D. Gibbon
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Acta Math ◽  
Navier Stokes ◽  
Large Initial Data ◽  
Navier Stokes Equations ◽  
Bounded Set ◽  
Junction Points ◽  
Vertical Walls ◽  
Time Averages

Higher moments of the vorticity field Ω m ( t ) in the form of L 2 m -norms ( ) are used to explore the regularity problem for solutions of the three-dimensional incompressible Navier–Stokes equations on the domain . It is found that the set of quantities provide a natural scaling in the problem resulting in a bounded set of time averages 〈 D m 〉 T on a finite interval of time [0,  T ]. The behaviour of D m +1 / D m is studied on what are called ‘good’ and ‘bad’ intervals of [0,  T ], which are interspersed with junction points (neutral) τ i . For large but finite values of m with large initial data ( Ω m (0)≤ ϖ 0 O ( Gr 4 )), it is found that there is an upper bound which is punctured by infinitesimal gaps or windows in the vertical walls between the good/bad intervals through which solutions may escape. While this result is consistent with that of Leray (Leray 1934 Acta Math. 63 , 193–248 ( doi:10.1007/BF02547354 )) and Scheffer (Scheffer 1976 Pacific J. Math. 66 , 535–552),— this estimate for Ω m corresponds to a length scale well below the validity of the Navier–Stokes equations.

A New Way to Form Three-Dimensional Microstructures by Electrochemical Etching of Silicon

2000 ◽  
Vol 638 ◽  
Author(s):  
P. Kleimann ◽  
J. Linnros ◽  
R. Juhasz
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Electrochemical Etching ◽  
Three Dimensional ◽  
Periodic Pattern ◽  
Free Standing ◽  
Vertical Walls ◽  
A New Technique ◽  
Etching Parameters ◽  
Current Lines

AbstractA new technique of bulk micromachining using anodic etching of (100)-oriented n-type silicon is presented. For particular conditions the transition regime between porous silicon formation and electropolishing enables the formation of high aspect ratio microtips which correspond to inverted macropore structures. This unusual property can be explained by the distortion of current lines near the basis of formed structures. The distortion, which prevents the tip dissolution, is due to the electrical field in the space charge region at the silicon-electrolyte interface. The same property can be used to form three-dimensional microstructures. The position and shape of the structures can be defined by forming steps of a few microns depth, prior tothe electrochemical etching. Then the etching parameters (HF concentration, light intensity, etching current density) are adjusted in order to electropolish the sample except where vertical walls are needed. This enables to form microstructures without a periodic pattern. The feasibility of this technique is demonstrated by forming 100μm wide pores, free-standing beams as well as high aspect ratio micro-needles and micro-tubes.

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