scholarly journals Focusing of Brownian Particles in a Fluid Induced by the Temperature Difference

2021 ◽  
Vol 2097 (1) ◽  
pp. 012025
Author(s):  
Yuxiang Ying ◽  
Kaixuan Zheng ◽  
Deming Nie
Keyword(s):  
Brownian Motion ◽  
Quantitative Analysis ◽  
Low Temperature ◽  
Temperature Difference ◽  
Lattice Boltzmann ◽  
Fluid Temperature ◽  
Two Dimensional ◽  
Temperature Zone ◽  
Brownian Particles ◽  
Boltzmann Method

Abstract In this work the Brownian motion of particles in a two-dimensional channel was numerically studied through a fluctuating-lattice Boltzmann method. The effects of the fluid temperature difference on the biased Brownian motion of particles were examined. It is shown that the particles are likely to move towards and stay at the low temperature zone. More importantly, the focusing of Brownian particles may be realized if the temperature difference is large enough. This paper also provides a quantitative analysis on this issue.

Two-dimensional obstacle avoidance control algorithm for snake-like robot in water based on immersed boundary-lattice Boltzmann method and improved artificial potential field method

2020 ◽  
Vol 42 (10) ◽  
pp. 1840-1857
Author(s):  
Dongfang Li ◽  
Zhenhua Pan ◽  
Hongbin Deng
Keyword(s):  
Flow Field ◽  
Obstacle Avoidance ◽  
Lattice Boltzmann ◽  
Potential Field ◽  
Control Algorithm ◽  
Immersed Boundary ◽  
Artificial Potential Field ◽  
Two Dimensional ◽  
Avoidance Control ◽  
Boltzmann Method

In order to study the adaptability of a multi-redundancy and multi-degree-of-freedom snake-like robot to underwater motion, a two-dimensional (2-D) obstacle avoidance control algorithm for a snake-like robot based on immersed boundary-lattice Boltzmann method (IB-LBM) and improved artificial potential field (APF) is proposed in this paper. Firstly, the non-linear flow field model is established under the framework of LBM, and the IB method is introduced to establish a fluid solid coupling of a 2-D soft snake-like robot. Then, the obstacle avoidance of a snake-like robot in a flow field is realized by optimizing the curvature equation of the serpentine curve and eliminating the local minimum in APF method. Finally, the effects by exerted different control parameters on a snake-like robot’s obstacle avoidance capability are analyzed via MATLAB simulation experiment, by which we can find the optimal parameter of the obstacle avoidance and testify the validity of the proposed control algorithm.

scholarly journals Predicting porosity, permeability, and tortuosity of porous media from images by deep learning

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Krzysztof M. Graczyk ◽  
Maciej Matyka
Keyword(s):  
Neural Networks ◽  
Porous Medium ◽  
Porous Media ◽  
Deep Learning ◽  
Lattice Boltzmann ◽  
Good Accuracy ◽  
Two Dimensional ◽  
Empirical Estimate ◽  
Flow Through ◽  
Boltzmann Method

AbstractConvolutional neural networks (CNN) are utilized to encode the relation between initial configurations of obstacles and three fundamental quantities in porous media: porosity ($$\varphi$$ φ ), permeability (k), and tortuosity (T). The two-dimensional systems with obstacles are considered. The fluid flow through a porous medium is simulated with the lattice Boltzmann method. The analysis has been performed for the systems with $$\varphi \in (0.37,0.99)$$ φ ∈ ( 0.37 , 0.99 ) which covers five orders of magnitude a span for permeability $$k \in (0.78, 2.1\times 10^5)$$ k ∈ ( 0.78 , 2.1 × 10 5 ) and tortuosity $$T \in (1.03,2.74)$$ T ∈ ( 1.03 , 2.74 ) . It is shown that the CNNs can be used to predict the porosity, permeability, and tortuosity with good accuracy. With the usage of the CNN models, the relation between T and $$\varphi$$ φ has been obtained and compared with the empirical estimate.

scholarly journals Erosion of planetesimals by gas flow

2020 ◽  
Vol 639 ◽  
pp. A39 ◽  
Author(s):  
Noemi Schaffer ◽  
Anders Johansen ◽  
Lukas Cedenblad ◽  
Bernhard Mehling ◽  
Dhrubaditya Mitra
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Lattice Boltzmann ◽  
Critical Stress ◽  
Gas Flow ◽  
Protoplanetary Disks ◽  
Two Dimensional ◽  
Eccentric Orbit ◽  
Eccentric Orbits ◽  
Boltzmann Method

The first stages of planet formation take place in protoplanetary disks that are largely made up of gas. Understanding how the gas affects planetesimals in the protoplanetary disk is therefore essential. In this paper, we discuss whether or not gas flow can erode planetesimals. We estimated how much shear stress is exerted onto the planetesimal surface by the gas as a function of disk and planetesimal properties. To determine whether erosion can take place, we compared this with previous measurements of the critical stress that a pebble-pile planetesimal can withstand before erosion begins. If erosion took place, we estimated the erosion time of the affected planetesimals. We also illustrated our estimates with two-dimensional numerical simulations of flows around planetesimals using the lattice Boltzmann method. We find that the wall shear stress can overcome the critical stress of planetesimals in an eccentric orbit within the innermost regions of the disk. The high eccentricities needed to reach erosive stresses could be the result of shepherding by migrating planets. We also find that if a planetesimal erodes, it does so on short timescales. For planetesimals residing outside of 1 au, we find that they are mainly safe from erosion, even in the case of highly eccentric orbits.

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