Constructal Trees of Convective Fins

1999 ◽  
Vol 121 (3) ◽  
pp. 675-682 ◽  
Author(s):  
A. Bejan ◽  
N. Dan
Keyword(s):  
Finite Size ◽  
Constructal Theory ◽  
Self Organization ◽  
Design Parameters ◽  
Tree Structures ◽  
Source Sink ◽  
A Current ◽  
Geometric Detail ◽  
Uniform Stream ◽  
Volume Size

This paper extends to the field of convective heat transfer the constructal theory of optimizing the access of a current that flows between one point and a finite-size volume, when the volume size is constrained. The volume is bathed by a uniform stream. A small amount of high-conductivity fin material is distributed optimally through the volume, and makes the connection between the volume and one point (fin root) on its boundary. The optimization proceeds in a series of volume subsystems of increasing sizes (elemental volume, first construct, second construct). The shape of the volume and the relative thicknesses of the fins are optimized at each level of assembly. The optimized structure emerges as a tree of fins in which every geometric detail is a result of minimizing the thermal resistance between the finite-size volume and the root point (source, sink). Convection occurs in the interstitial spaces of the tree. The paper shows that several of the geometric details of the optimized structure are robust, i.e., relatively insensitive to changes in other design parameters. The paper concludes with a discussion of constructal theory and the relevance of the optimized tree structures to predicting natural self-organization and self-optimization.

scholarly journals Constructal theory of design in engineering and nature

2006 ◽  
Vol 10 (1) ◽  
pp. 9-18 ◽  
Author(s):  
Adrian Bejan
Keyword(s):  
Body Size ◽  
Honey Bees ◽  
Finite Size ◽  
The Body ◽  
Constructal Theory ◽  
Flow Structures ◽  
Engineering Theory ◽  
Heart Beating ◽  
Size Constraints ◽  
Source Sink

This is a brief introduction to an engineering theory on the origin and generation of geometric form in all flow systems: the animate, the in animate and the engineered. The theory is named constructal, and is based on the thought that it is natural for cur rents to construct for them selves in time paths of greater flow access. It is shown that this process of flow path optimization can be reasoned on the basis of principle: the maximization of global performance subject to finite-size constraints. One example is the generation of tree-shaped flow pat terns, as paths of least resistance between one point (source, sink) and an infinity of points (area, volume), as in the circulatory, respiratory and nervous systems. Another is the generation of regular spacing's in heat generating volumes, such as swarms of honey - bees. The optimized tree-flow geometries ac count for allometric laws, e. g., the relation ship between the total tube contact area and the body size, the proportionality between metabolic rate and body size raised to the power 3/4, the proportionality between breathing and heart beating times and body size raised to the power 1/4, and the proportionality between the cruising speed of flying bodies (in sects, birds, air planes) and body mass raised to the power 1/6. The optimized flow structures constitute robust designs, and robustness improves as the complexity of the system increases. Flow architectures that are more efficient look more natural.

scholarly journals CONSTRUCTAL THEORY APPLIED TO THE GEOMETRIC OPTIMIZATION OF ELLIPTICAL CAVITIES INTO A SOLID CONDUCTING WALL

2008 ◽  
Vol 7 (2) ◽  
pp. 81
Author(s):  
L. A. O. Rocha ◽  
C. Biserni ◽  
E. Lorenzini
Keyword(s):  
Solid Wall ◽  
Thermal Conditions ◽  
Geometric Optimization ◽  
Constructal Theory ◽  
Design Parameters ◽  
Cavity Volume ◽  
Cavity Shape ◽  
Elliptical Cavity ◽  
Conducting Wall ◽  
Geometrical Shapes

This work reports, according to Bejan’s Constructal theory, the geometric optimization of an elliptical cavity that intrudes into a solid conducting wall. The objective is to minimize the global thermal resistance between the solid and the cavity. There is uniform heat generation on the solid wall. The cavity is optimized for two sets of thermal conditions: isothermal cavity and cavity bathed by a steady stream of fluid. The solid conducting wall is isolated on the external perimeter. The total volume and the elliptical cavity volume are fixed while the geometry of the cavity is free to vary. The results show that the optimized geometrical shapes are relatively robust, i.e., insensitive to changes in some of the design parameters: the cavity shape is optimal when penetrates the conducting wall almost completely.

Feeding System of a High-Frequency Accelerating Cavities of the Novosibirsk Microtron-Recovery Unit for The Fel. Divider of a High CW Power on the Basis of a Rectangular Waveguide

2013 ◽  
Vol 8 (1) ◽  
pp. 32-43
Author(s):  
Vladimir Arbuzov ◽  
Eduard Gorniker ◽  
Evgeny Kozyrev ◽  
Alexey Kondakov ◽  
Viktor Petrov ◽  
...  
Keyword(s):  
Rectangular Waveguide ◽  
Current Source ◽  
Coaxial Line ◽  
Design Parameters ◽  
Thz Radiation ◽  
Recovery Unit ◽  
Accelerating Cavities ◽  
Continuous Power ◽  
A Current ◽  
Frequency Power

The article is devoted to the system of the Radio Frequency power transfer and distribution between accelerating cavities of the ERL for FEL of the Siberian center of SR and THz Radiation, SB RAS, Novosibirsk. The system of dividing is built on the basis of a rectangular waveguide, associated with each cavity of a coaxial line by the coaxial-to-waveguide adapter (CWA). It is shown that under a certain choice of waveguide sizes and CWA, the equivalent circuit of the CWA can be represented by a current source. The analysis of the properties of such a system has been carried out and shown its advantages. Also it is discussed the experimental results and the experience of the operation of the device. The article presents the basic design parameters of a waveguide divider 600 kW of continuous power, running at a frequency of 180.4 MHz

scholarly journals Theory of Vibrations of Sugar Beet Leaf Harvester Front-Mounted on Universal Tractor

2017 ◽  
Vol 20 (4) ◽  
pp. 96-103 ◽  
Author(s):  
Volodymyr Bulgakov ◽  
Valerii Adamchuk ◽  
Ladislav Nozdrovický ◽  
Yevhen Ihnatiev
Keyword(s):  
Sugar Beet ◽  
System Development ◽  
Vertical Plane ◽  
Equation System ◽  
Design Parameters ◽  
Differential Equation System ◽  
Current Task ◽  
Leaf Cutting ◽  
Linear Differential ◽  
A Current

Abstract The harvest and transport of sugar beet leaves during harvesting can be considered a current task in the area of sugar beet growing system development. A rotary sugar beet leaf cutting mechanism is used for achieving the significant increase in the harvester forward speed during harvest. This leads to intensive vibrations of the topping mechanism in the longitudinal vertical plane causing the decrease of harvest quality. Therefore, it is necessary to analytically determine the effect of kinematic and design parameters of the sugar beet topping mechanism front-mounted on the tractor and to discover the value of the amplitude of oscillations in the longitudinal vertical plane of its sugar beet topping mechanism. We have constructed a mathematical model of the estimated motion of this machine by means of dynamics equations in Lagrange II-kind form. A system consisting of two non-linear differential equations was obtained by developing the equivalent scheme of selected generalized coordinates and by performing the necessary mathematical transformations. This system describes the vibrations of the sugar beet topping mechanism in the longitudinal vertical plane. The optimal design and kinematic parameters of the sugar beet topper mechanism front-mounted on the tractor were determined by means of our own software and numerical solution of the differential equation system, which allows the reduction of mentioned vibrations.

scholarly journals Physically-Accurate Synthetic Images for Machine Vision Design

1999 ◽  
Vol 121 (4) ◽  
pp. 763-770 ◽  
Author(s):  
J. M. Parker ◽  
Kok-Meng Lee
Keyword(s):  
Machine Vision ◽  
Vision System ◽  
Finite Size ◽  
Image Synthesis ◽  
Design Parameters ◽  
Synthesis Methods ◽  
Ambient Lighting ◽  
Wide Range ◽  
Synthetic Images ◽  
Synthesis Methodology

In machine vision applications, accuracy of the image far outweighs image appearance. This paper presents physically-accurate image synthesis as a flexible, practical tool for examining a large number of hardware/software configuration combinations for a wide range of parts. Synthetic images can efficiently be used to study the effects of vision system design parameters on image accuracy, providing insight into the accuracy and efficiency of image-processing algorithms in determining part location and orientation for specific applications, as well as reducing the number of hardware prototype configurations to be built and evaluated. We present results illustrating that physically accurate, rather than photo-realistic, synthesis methods are necessary to sufficiently simulate captured image gray-scale values. The usefulness of physically-accurate synthetic images in evaluating the effect of conditions in the manufacturing environment on captured images is also investigated. The prevalent factors investigated in this study are the effects of illumination, the sensor non-linearity and the finite-size pinhole on the captured image of retroreflective vision sensing and, therefore, on camera calibration was shown; if not fully understood, these effects can introduce apparent error in calibration results. While synthetic images cannot fully compensate for the real environment, they can be efficiently used to study the effects of ambient lighting and other important parameters, such as true part and environment reflectance, on image accuracy. We conclude with an evaluation of results and recommendations for improving the accuracy of the synthesis methodology.

scholarly journals Sound Insulation of Corrugated-Core Sandwich Panels: Modeling, Optimization and Experiment

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7785
Author(s):  
Longlong Ren ◽  
Haosen Yang ◽  
Lei Liu ◽  
Chuanlong Zhai ◽  
Yuepeng Song
Keyword(s):  
High Frequency ◽  
Sandwich Panel ◽  
Transmission Loss ◽  
Finite Size ◽  
Sandwich Panels ◽  
Sound Transmission ◽  
Coefficient Of Determination ◽  
Design Parameters ◽  
Sound Insulation ◽  
Vast Number

With the extension of the applications of sandwich panels with corrugated core, sound insulation performance has been a great concern for acoustic comfort design in many industrial fields. This paper presents a numerical and experimental study on the vibro-acoustic optimization of a finite size sandwich panel with corrugated core for maximizing the sound transmission loss. The numerical model is established by using the wave-based method, which shows a great improvement in the computational efficiency comparing to the finite element method. Constrained by the fundamental frequency and total mass, the optimization is performed by using a genetic algorithm in three different frequency bands. According to the optimization results, the frequency averaged sound transmission of the optimized models in the low, middle, and high-frequency ranges has increased, respectively, by 7.6 dB, 7.9 dB, and 11.7 dB compared to the baseline model. Benefiting from the vast number of the evolution samples, the correlation between the structural design parameters and the sound transmission characteristics is analyzed by introducing the coefficient of determination, which gives the variation of the importance of each design parameter in different frequency ranges. Finally, for validation purposes, a sound insulation test is conducted to validate the optimization results in the high-frequency range, which proves the feasibility of the optimization method in the practical engineering design of the sandwich panel.

scholarly journals Self-Organization of Tree Structures

1992 ◽  
Vol 88 (6) ◽  
pp. 1225-1230
Author(s):  
H. Sakaguchi
Keyword(s):  
Self Organization ◽  
Tree Structures
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