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Abstract

In the presented paper, two different meshing strategies are compared to show the accuracy advantage of properly constructed mesh. For this purpose, it was necessary to automatize simulation process, in order to perform a number of calculations without the necessity of user interaction. Later, a method of results extrapolation as well as a way of judging mesh quality are introduced for more throughout comparison of presented discretization strategies. The latter method, called grid convergence index, is also used to calculate probability range of accurate result. To conclude, outcomes of this study are in agreement with general opinon on pracitces for an accurate CFD result. Structured O-type mesh with refinement at wall boundaries (often referred to as “inflation layers”) performs better than simple free mesh.
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Authors and Affiliations

Adam Tater
1
ORCID: ORCID
Pavel Mačák
1
Patrik Kovář
1

  1. Center of Aviation and Space Research, Faculty of Mechanical Engineering, Czech Technical University in Prague, Jugoslávských partyzán˚u1580/3, 16000, Prague 6, Czech Republic
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Abstract

A global path-planning algorithm for robots is proposed based on the critical-node diffusion binary tree (CDBT), which solves the problems of large memory consumption, long computing time, and many path inflection points of the traditional methods. First of all, the concept of Quad-connected, Tri-connected, Bi-connected nodes, and critical nodes are defined, and the mathematical models of diverse types of nodes are established. Second, the CDBT algorithm is proposed, in which different planning directions are determined due to the critical node as the diffusion object. Furthermore, the optimization indices of several types of nodes are evaluated in real-time. Third, a path optimization algorithm based on reverse searching is designed, in which the redundant nodes are eliminated, and the constraints of the robot are considered to provide the final optimized path. Finally, on one hand, the proposed algorithm is compared with the A* and RRT methods in the ROS system, in which four types of indicators in the eight maps are analysed. On the other hand, an experiment with an actual robot is conducted based on the proposed algorithm. The simulation and experiment verify that the new method can reduce the number of nodes in the path and the planning time and is suitable for the motion constraints of an actual robot.
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Authors and Affiliations

Zhiyong Yang
1
ORCID: ORCID
Lipeng Wang
1
ORCID: ORCID
Zejun Cao
1
Zhi Zhang
1
Zhuang Xu
1

  1. College of Intelligent Systems Science and Engineering, Harbin Engineering University, Harbin, 150001, China
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Abstract

This paper presents a numerical analysis of the thermal-flow characteristics for a laminar flow inside a rectangular microchannel. The flow of water through channels with thin obstacles mounted on opposite walls was analyzed. The studies were conducted with a low Reynolds number (from 20 to 200). Different heights of rectangular obstacles were analyzed to see if geometrical factors influence fluid flow and heat exchange in the microchannel. Despite of the fact that the use of thin obstacles in the microchannels leads to an increase in the pressure drop, the increase in the height of the obstacles favors a significant intensification of heat exchange with the maximum thermal gain factor of 1.9 for the obstacle height coefficient h/H=0.5, which could be acceptable for practical application.
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Authors and Affiliations

Małgorzata Kmiotek
1
ORCID: ORCID
Robert Smusz
1
ORCID: ORCID

  1. Rzeszow University of Technology, The Faculty of Mechanical Engineering and Aeronautics, Rzeszow, Poland

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