scholarly journals Investigation on Computing Method of Martian Dust Fluid Based on the Energy Dissipation Method

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Tianxiang Ding ◽  
Xuyan Hou ◽  
Man Li ◽  
Guangyu Cao ◽  
Jixuan Liu ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Stochastic Model ◽  
Particle Deposition ◽  
Deposition Process ◽  
Dust Particles ◽  
Particle Collision ◽  
Surface Adhesion ◽  
Dissipation Model ◽  
Dust Fluid ◽  
Computing Method

In this paper, an initiative Martian dust fluid simulating research based on the energy dissipation method was developed to simulate the deposition process of Martian dust fluid which was caused by surface adhesion between particles and Martian rovers. Firstly, an energy dissipation model of particles based on the Discrete Element Method (DEM) was established because of the characteristics of Martian dust particles such as tiny size and viscoelasticity. This model is based on the existing DMT model to analyze the collision deposition of dust fluid particles, including particle-spacecraft collision and particle-particle collision. Secondly, this paper analyzed the characteristics of particles after their first collision, then, established the stochastic model of critical wind speed for the particle deposition process. Finally, a series of simulations of the Martian dust fluid particle deposition process were done based on DEM-CFD. The results verified the accuracy of the energy dissipation model and the stochastic model, which could also verify the feasibility and effectiveness of the computing method of Martian dust fluid based on the DEM-CFD technology.

scholarly journals Saharan dust levels in Greece and received inhalation doses

2008 ◽  
Vol 8 (3) ◽  
pp. 11967-11996 ◽  
Author(s):  
C. Mitsakou ◽  
G. Kallos ◽  
N. Papantoniou ◽  
C. Spyrou ◽  
S. Solomos ◽  
...  
Keyword(s):  
Urban Areas ◽  
Particle Deposition ◽  
Mineral Dust ◽  
Weather Conditions ◽  
Pm10 Concentration ◽  
Saharan Dust ◽  
Dust Particles ◽  
Annual Number ◽  
Human Respiratory Tract ◽  
Dust Transport

Abstract. The desert of Sahara is one of the major sources of mineral dust on Earth, producing around 2×108 tons/yr. Under certain weather conditions, dust particles from Saharan desert get transported over the Mediterranean Sea and most of Europe. The limiting values set by the directive EC/30/1999 of European Union can easily be exceeded by the transport of desert dust particles in all south European areas and especially urban. In this study, the effects of dust transport on air quality in several Greek urban areas are quantified. PM10 concentration values from stationary monitoring stations are compared to dust concentrations for the 4-year period 2003–2006. The dust concentration values in the Greek areas were estimated by the SKIRON modelling system coupled with embedded algorithms describing the dust cycle. The mean annual dust contribution to daily-averaged PM10 concentration values was found to be around or even greater than 10% in the urban areas throughout the years examined. Natural dust transport may contribute by much more than 20% to the annual number of exceedances – PM10 values greater than EU limits – depending on the specific monitoring location. In a second stage of the study, the inhaled lung dose received by the residents in various Greek locations is calculated. The particle deposition efficiency of mineral dust at the different parts of the human respiratory tract is determined by applying a lung dosimetry numerical model, which incorporates inhalation dynamics and aerosol physical processes. The inhalation dose from mineral dust particles was greater in the upper respiratory system (extrathoracic region) and less significant in the lungs, especially in the sensitive alveolar region. However, in cases of dust episodes, the amounts of mineral dust deposited along the human lung are comparable to those received during exposure in heavily polluted urban or smoking areas.

Analysis of Buoyancy and Tube Rotation Relative to the Modified Chemical Vapor Deposition Process

1990 ◽  
Vol 112 (4) ◽  
pp. 1063-1069 ◽  
Author(s):  
M. Choi ◽  
Y. T. Lin ◽  
R. Greif
Keyword(s):  
Secondary Flow ◽  
Vapor Deposition ◽  
Particle Deposition ◽  
Three Dimensional ◽  
Chemical Vapor ◽  
Horizontal Tube ◽  
Deposition Process ◽  
Secondary Flows ◽  
Secondary Motion

The secondary flows resulting from buoyancy effects in respect to the MCVD process have been studied in a rotating horizontal tube using a perturbation analysis. The three-dimensional secondary flow fields have been determined at several axial locations in a tube whose temperature varies in both the axial and circumferential directions for different rotational speeds. For small rotational speeds, buoyancy and axial convection are dominant and the secondary flow patterns are different in the regions near and far from the torch. For moderate rotational speeds, the effects of buoyancy, axial and angular convection are all important in the region far from the torch where there is a spiraling secondary flow. For large rotational speeds, only buoyancy and angular convection effects are important and no spiraling secondary motion occurs far downstream. Compared with thermophoresis, the important role of buoyancy in determining particle trajectories in MCVD is presented. As the rotational speed increases, the importance of the secondary flow decreases and the thermophoretic contribution becomes more important. It is noted that thermophoresis is considered to be the main cause of particle deposition in the MCVD process.

scholarly journals Energy Dissipation Characteristics and Parameter Identification of Symmetrically Coated Damping Structure of Pipelines under Different Temperature Environment

Symmetry ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 1283
Author(s):  
Feng Jiang ◽  
Zheyu Ding ◽  
Yiwan Wu ◽  
Hongbai Bai ◽  
Yichuan Shao ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Hysteresis Loop ◽  
Least Square Method ◽  
Least Square ◽  
Test Results ◽  
Restoring Force ◽  
Dissipation Model ◽  
Effects Of Temperature ◽  
Dissipation Test ◽  
Metal Wires

In this paper, a symmetrically coated damping structure for entangled metallic wire materials (EMWM) of pipelines was designed to reduce the vibration of high temperature (300 °C) pipeline. A series of energy dissipation tests were carried out on the symmetrically coated damping structure at 20–300 °C. Based on the energy dissipation test results, the hysteresis loop was drawn. The effects of temperature, vibration amplitude, frequency, and density of EMWM on the energy dissipation characteristics of coated damping structures were investigated. A nonlinear energy dissipation model of the symmetrically coated damping structure with temperature parameters was established through the accurate decomposition of the hysteresis loop. The parameters of the nonlinear model were identified by the least square method. The energy dissipation test results show that the symmetrically coated damping structure for EMWM of pipelines had excellent and stable damping properties, and the established model could well describe the changing law of the restoring force and displacement of the symmetrically coated damping structure with amplitude, frequency, density, and ambient temperature. It is possible to reduce the vibration of pipelines in a wider temperature range by replacing different metal wires.

The Effects of Energy Dissipation of the Closure Bolted Joints Under Vibration Behavior

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Qiang Cheng ◽  
Wenxiang Xu ◽  
Zhifeng Liu ◽  
Congbin Yang ◽  
Ying Li
Keyword(s):  
Energy Dissipation ◽  
Vibration Frequency ◽  
Cyclic Load ◽  
Fractal Theory ◽  
Operator Method ◽  
Bolted Joints ◽  
Bolted Joint ◽  
Modal Shape ◽  
Factors Affecting ◽  
Dissipation Model

Abstract Bolted joints are widely used in mechanical construction due to their ease of disassembly. When the bolting member is subjected to the alternating load, the pretightening force is gradually reduced, which may cause the interface contact performance to decrease, and the surface may be microslipped. Preload relaxation of threaded fasteners is the main factor that influences the joint failure under normal cyclic loading, but it is difficult to monitor the energy dissipation between the interface of the bolted joint. This paper presents an energy dissipation model for the bolted joint based on two-degree-of-freedom vibration differential mathematical model. The parameters of the model is calculated by using the fractal theory and differential operator method. The efficiency of the proposed model is verified by experiments. The results show that the experimental modal shape agrees well with the theoretical modal shape. According to the change of cyclic load and vibration frequency, the vibration response and the law of energy dissipation under different factors can be obtained. The results show that the vibration frequency and cyclic load are the main factors affecting the energy dissipation between interfaces. The energy dissipation of the contact surface of the bolted joints account for the main part of the energy dissipation of the bolted structure. The results provide a theoretical basis for reducing the looseness of the bolt connection and ensuring the reliability of the equipment.

Turbulent Two-Phase Flows and Particle Deposition in a Duct at High Concentrations

2010 ◽  
Author(s):  
Goodarz Ahmadi ◽  
Hojjat Nasr ◽  
John B. McLaughlin
Keyword(s):  
Particle Deposition ◽  
Deposition Velocity ◽  
Particle Collision ◽  
Duct Flow ◽  
Particle Collisions ◽  
Coupling Effects ◽  
Two Phase Flows ◽  
Two Phase ◽  
Mean Velocity ◽  
Navier Stokes Equation

Two-phase flows including particle-particle collisions and two-way coupling in a turbulent duct flow were simulated using a direct simulation approach. The direct numerical simulation (DNS) of the Navier-Stokes equation was performed via a pseudospectral method was extended to cover two-way coupling effects. The effect of particles on the flow was included in the analysis via a feedback force that acted on the fluid on the computational grid points. The point particle equation of motion included the Stokes drag, the Saffman lift, and the gravitational forces. Several simulations for different particle relaxation times and particle mass loading were performed, and the effects of the inter-particle collisions and two-way coupling on the particle deposition velocity, fluid and particle fluctuating velocities, particle normal mean velocity, and particle concentration were determined. It was found that when particle-particle collisions were included in the computation, the particle deposition velocity increased. When the particle collision was neglected but the particle-fluid two-way coupling was accounted for, the particle deposition velocity decreased slightly. When both inter-particle collisions and two-way coupling effects were taken into account in the simulations, the particle deposition velocity increased. Comparisons of the present simulation results with the available experimental data and earlier numerical results are also presented.

Sign in / Sign up

Export Citation Format

Share Document