Numerical Study on Aeolian Sand Ripples Forming and Moving Process in Desert Highway

2011 ◽  
Vol 462-463 ◽  
pp. 1032-1037 ◽  
Author(s):  
Abdurahman Ablimit ◽  
Mamtimin Gheni ◽  
Zhong Hua Xu ◽  
Mamatjan Tursun ◽  
Xamxinur Abdikerem
Keyword(s):  
Flow Field ◽  
Numerical Study ◽  
Numerical Models ◽  
Flow Direction ◽  
Sand Particle ◽  
Forming Process ◽  
Sand Surface ◽  
Airflow Field ◽  
Sand Flow ◽  
Desert Highway

In this paper, the sand break into highway problem in desert, which is caused by the sand flow blown by wind, is studied. The mathematical models are introduced by considering the fixed, semi-fixed and free sand desert fields based on the fluid dynamics and the sand particle dynamics. Different kinds of numerical models are made by changing the desert highway height, wind flow direction and its uniformity. The weak coupling method is used due to spatial relationships between air flow field and the sand flow field. Finally, by coupling the airflow field and sand flow field with desert highway, the numerical simulations of sand forming process on desert highway are conducted. The numerical results shown, that the wind blown sand breaks into highway easier when wind direction perpendicular highway and if the highway height higher than the range size of the sand surface the wind blown sand break into highway is more difficult.

scholarly journals Numerical Modeling and Simulation of Wind Blown Sand Morphology under Complex Wind-Flow Field

2014 ◽  
Vol 2014 ◽  
pp. 1-10
Author(s):  
Xamxinur Abdikerem ◽  
Lei Wang ◽  
Afang Jin ◽  
Mamtimin Geni
Keyword(s):  
Flow Field ◽  
Numerical Models ◽  
Air Flow ◽  
Local Area ◽  
Flow Fields ◽  
The Road ◽  
Sand Surface ◽  
Airflow Field ◽  
Sand Flow ◽  
Desert Highway

The flow field and the sand flow field constitutive equations are analyzed at first, then the different desert highway numerical models are established by considering the crossroad and by changing the road surface height and air stream flow field, then three kinds of different models with different complex air flow fields are made for simulating the sand ripple formation process by weak coupling of air and sand flow field, and finally the numerical simulations of these models are conducted and the affect process of sand morphology under complex air flow fields are discussed. The results show that under the uniform airflow field, the straight parallel ripple formed and the flared ripple formed in the middle region of the crossroad, and the wavelength of the ripples on the desert highway is bigger than that of the ripples around the road when the road height is higher than that of the sand surface height. Under the nonuniform complex airflow field, the complex curved ripples are formed, and some of the local area, where the whirlwind exits, no ripples are formed.

Effects of a flow mode transition on natural convection heat transfer in a heat tracing enclosure

2018 ◽  
Vol 233 (3) ◽  
pp. 489-499 ◽  
Author(s):  
CJ Ho ◽  
GN Sou ◽  
CM Lai
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Flow Field ◽  
Numerical Study ◽  
Flow Direction ◽  
Convection Heat Transfer ◽  
Flow Mode ◽  
Mode Transition ◽  
Flow And Heat Transfer ◽  
Lower Variation

This paper presents a numerical study of transient buoyancy-induced fluid flow and heat transfer between two horizontal, differentially heated pipelines inside a circular, air-filled enclosure. Numerical simulations based on the finite difference method were conducted to investigate the flow mode transition of the buoyant airflow and its effects on the heat transfer characteristics of the pipelines. The results indicate that the fluid flow complexity and the heat transfer of air between the pipelines are strongly affected by the Rayleigh number. When Ra = 6 × 105 and 1.2 × 106, both the flow field and the temperature distribution exhibit periodic variations with different patterns. The former ( Ra = 6 × 105) is a complete alteration of the flow direction from clockwise to counterclockwise, whereas the latter is a variation in the flow field strength that varies between strong and weak. The latter has a lower variation frequency than that of the former.

Numerical Modeling for Sand Desert Morphology and Forming Process in Fixed, Semi-Fixed and Free Desert Field

2008 ◽  
Vol 33-37 ◽  
pp. 1055-1062 ◽  
Author(s):  
Xamxinur Abdikerem ◽  
Zhong Hua Xu ◽  
Mamtimin Gheni
Keyword(s):  
Numerical Simulation ◽  
Mathematical Model ◽  
Numerical Modeling ◽  
Numerical Model ◽  
Flow Field ◽  
Stream Flow ◽  
Forming Process ◽  
Flow Process ◽  
Sand Movement ◽  
Sand Flow

In this study, to conduct numerical simulation of desert physiognomy forming process in fixed, semi-fixed and free sand desert field by considering the sand flow process by wind, the numerical model based on the hydrodynamics and sand grains kinemics are proposed. For analyze the actual characteristic of sand movement phenomenon, the stream flow field and desert flow field are introduced and mathematical model for numerical analysis are established by considering the sand shape, size and mass in order to describe the fixed, semi-fixed and fully free sand desert physiographical process. Then according to the real fixed, semi-fixed and free sand flow field by coupling with stream flow field, several models are made and numerical simulations are conducted.

Numerical Simulation of Sand Ripple Formation with Periodically Uniform and Non-Uniform Stream Field

2008 ◽  
Vol 33-37 ◽  
pp. 1063-1068 ◽  
Author(s):  
Abudoukelimu Abudoureheman ◽  
Xamxinur Abdikerem ◽  
Mamtimin Gheni
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Stream Flow ◽  
Simulation Models ◽  
Forming Process ◽  
Sand Ripple ◽  
Ripple Formation ◽  
Sand Flow ◽  
Moving Process ◽  
Uniform Stream

In this study, for the numerical simulation of the sand ripple’s forming process which caused by the sand flow, the simulation models based on the fluid dynamics and the sand flow field by the wind are analyzed. Due to sand field’s characteristics is very complex, the establishing process of stream flow field constitutive equations analyzed at first, and then the implication relations and independency between stream flow field and the sand flow field analyzed. Finally, the sand ripple forming and moving process simulated in uniform and non-uniform stream flow field.

scholarly journals 3D Direct Numerical Simulation on the Emergence and Development of Aeolian Sand Ripples

2021 ◽  
Vol 9 ◽  
Author(s):  
Xinghui Huo ◽  
Hongchao Dun ◽  
Ning Huang ◽  
Jie Zhang
Keyword(s):  
Particle Size ◽  
Wind Field ◽  
Numerical Models ◽  
Sand Particle ◽  
Particle Dynamic ◽  
Aeolian Sand ◽  
Holistic View ◽  
Sand Ripples ◽  
Sand Surface

A sand surface subjected to a continuous wind field exhibits a regular ripple surface. These aeolian sand ripples emerge and develop under the coupling effect between the wind field, bed surface topology, and sand particle transportation. Lots of theoretical and numerical models have been established to study the aeolian sand ripples since the last century, but none of them has the capability to directly reproduce the 3D long-term development of them. In this work, a novel numerical model with wind-blow sand and dynamic bedform is established. The emergence and long-term development of sand ripples can be obtained directly. The statistical results extracted from this model tally with those deduced from wind tunnel experiments and field observations. A simplified bed surface particle size description procedure is used in this model, which shows that the particle size distribution makes a very important contribution to sand ripples’ final steady state. This 3D bedform provides a more holistic view on the merging of small bumps before regular ripples’ formation. Analyzing the wind field results reveals an ignored development on the particle dynamic threshold during the bedform deformation.

Numerical Study on the Comparison of Deformation Characteristics during the Fine Blanking Process of Spur Gears and Helical Gear

2015 ◽  
Vol 639 ◽  
pp. 559-566 ◽  
Author(s):  
Wen Ting Xia ◽  
Hua Jie Mao ◽  
Lin Hua ◽  
Yan Xiong Liu
Keyword(s):  
Production Efficiency ◽  
Numerical Study ◽  
Numerical Models ◽  
Spur Gears ◽  
Deformation Characteristics ◽  
Forming Process ◽  
Rigid Plastic ◽  
Fine Blanking ◽  
Helical Gears ◽  
Blanking Process

As important transmission components, helical gears have been widely applied to mechanical and automotive fields. The traditional manufacturing process for helical gears is machining, which is time-consuming and result in the high cost of gears. In order to improve the production efficiency and product quality of helical gears, a novel forming process principle for the fine blanking of helical gears was developed. In this study, reliable three-dimensional (3D) rigid-plastic finite element (FE) models of single tooth and complete gears were set up and investigated using the software Deform-3D, the deformation characteristics of fine blanking of spur gears and helical gears were compared. Based on the valid numerical models, variation tendency of different field variables such as damage material flow velocity, and mean stress were obtained, as well as the feature of the tooth section, which provides a better understanding of the deformation mechanism of rotational fine blanking process.

scholarly journals Numerical study on the flow characteristics of centrifugal compressor impeller with crack damage

2021 ◽  
Vol 13 (7) ◽  
pp. 168781402110346
Author(s):  
Zhaoyu Liang ◽  
Longhao Xiang ◽  
Xuesong Wei ◽  
Songying Chen ◽  
Jingting Liu ◽  
...  
Keyword(s):  
Flow Field ◽  
Entropy Production ◽  
Numerical Study ◽  
Flow Direction ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Maximum Pressure ◽  
Corrosion Propagation ◽  
Maximum Value ◽  
Compressor Impeller

The distribution and characteristics of internal flow field of the impeller with crack damage in service environment was investigated via numerical simulation with RNG k-ε turbulence model. The diffuser and volute are added based on the original impeller to simulate the internal flow field comprehensively. It was found that along the flow direction, the pressure, velocity, and temperature of the fluid increase continuously, and the maximum value appears near the outlet of the impeller. The maximum pressure and velocity in the crack area are distributed around the middle section and the trailing edge of the crack. Entropy production theory was applied in the study of internal flow, which reveals that the entropy production becomes larger around the crack. The further propagation of the crack is promoted by the opening force perpendicular to the entrance direction of the middle crack, the corrosion propagation at the rear edge of the crack, and the thermal deformation of the blade. The accelerated crack process will finally lead to the blade fracture accident.

Dynamics and Numerical Modeling of Sandy Desert Morphology Caused by Aeolian Transport of Sand Particles

2011 ◽  
Vol 462-463 ◽  
pp. 1038-1043 ◽  
Author(s):  
Xamxinur Abdikerem ◽  
Mamtimin Gheni ◽  
Abdurahman Ablimit ◽  
A Fang Jin
Keyword(s):  
Numerical Modeling ◽  
Flow Field ◽  
Stream Flow ◽  
Sand Particle ◽  
Threshold Condition ◽  
Sandy Desert ◽  
Aeolian Transport ◽  
Significant Information ◽  
Sand Flow ◽  
Sand Particles

Wind caused the much sediment fluxes leading to both erosion and deposits in the sandy desertification area, and the much kind of beautiful sandy desert morphologies are formed. This is really crucial to the development of the dynamic behaviour of aeolian transport of sand particles. The sand desert morphologies are representing significant information archives for understanding the desertification problem. Dynamics and numerical modeling provides an essential tool for studying the aeolian transport of sand particle and morphology of sand desert such as ripple and dune. In this study, the mathematical models based on the dynamics are analyzed by considering the several keys as saltation, creep, suspension, avalanche and its threshold condition etc. for sand morphology forming processes. Then due to sand flow field real characteristics, the establishing process of stream flow field are analyzed, and the implication relationships as well as the coupling process between uniform stream flow field and the sand flow field are analyzed. Finally, the sand flow field models is discretized, and different kinds of sandy desert morphology are simulated by considering the sand particle size and mass in fixed, semi-fixed and free sand flow field area.

Numerical Study of the Combined Free-Forced Convection and Mass Transfer Flow Past a Vertical Porous Plate in a Porous Medium with Heat Generation and Thermal Diffusion

2006 ◽  
Vol 11 (4) ◽  
pp. 331-343 ◽  
Author(s):  
M. S. Alam ◽  
M. M. Rahman ◽  
M. A. Samad
Keyword(s):  
Mass Transfer ◽  
Flow Field ◽  
Differential Equations ◽  
Forced Convection ◽  
Heat Generation ◽  
Numerical Study ◽  
Porous Plate ◽  
Integration Scheme ◽  
Suction Parameter ◽  
Transfer Flow

The problem of combined free-forced convection and mass transfer flow over a vertical porous flat plate, in presence of heat generation and thermaldiffusion, is studied numerically. The non-linear partial differential equations and their boundary conditions, describing the problem under consideration, are transformed into a system of ordinary differential equations by using usual similarity transformations. This system is solved numerically by applying Nachtsheim-Swigert shooting iteration technique together with Runge-Kutta sixth order integration scheme. The effects of suction parameter, heat generation parameter and Soret number are examined on the flow field of a hydrogen-air mixture as a non-chemical reacting fluid pair. The analysis of the obtained results showed that the flow field is significantly influenced by these parameters.

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