Generalized periodic surface model and its application in designing fibrous porous media

2015 ◽  
Vol 32 (1) ◽  
pp. 7-36 ◽  
Author(s):  
Wei Huang ◽  
Sima Didari ◽  
Yan Wang ◽  
Tequila A.L. Harris
Keyword(s):  
Porous Media ◽  
Geometric Modeling ◽  
Cfd Simulation ◽  
Three Dimensional ◽  
Field Method ◽  
Surface Model ◽  
Periodic Surface ◽  
Content Type ◽  
Modeling Methods ◽  
Fibrous Porous Media

Purpose – Fibrous porous media have a wide variety of applications in insulation, filtration, acoustics, sensing, and actuation. To design such materials, computational modeling methods are needed to engineer the properties systematically. There is a lack of efficient approaches to build and modify those complex structures in computers. The paper aims to discuss these issues. Design/methodology/approach – In this paper, the authors generalize a previously developed periodic surface (PS) model so that the detailed shapes of fibers in porous media can be modeled. Because of its periodic and implicit nature, the generalized PS model is able to efficiently construct the three-dimensional representative volume element (RVE) of randomly distributed fibers. A physics-based empirical force field method is also developed to model the fiber bending and deformation. Findings – Integrated with computational fluid dynamics (CFD) analysis tools, the proposed approach enables simulation-based design of fibrous porous media. Research limitations/implications – In the future, the authors will investigate robust approaches to export meshes of PS models directly to CFD simulation tools and develop geometric modeling methods for composite materials that include both fibers and resin. Originality/value – The proposed geometric modeling method with implicit surfaces to represent fibers is unique in its capability of modeling bent and deformed fibers in a RVE and supporting design parameter-based modification for global configuration change for the purpose of macroscopic transport property analysis.

The simulation of single wraparound fin on a semi-cylindrical missile body

2020 ◽  
Vol 92 (3) ◽  
pp. 418-427 ◽  
Author(s):  
Nayhel Sharma ◽  
Rakesh Kumar
Keyword(s):  
Research Study ◽  
Cfd Simulation ◽  
Three Dimensional ◽  
Future Research ◽  
Aerodynamic Coefficients ◽  
Content Type ◽  
Computational Fluid Dynamics Cfd ◽  
Predicted Values ◽  
Characteristic Trend ◽  
Practical Implications

Purpose The purpose of this paper is to establish a freestream computational fluid dynamics (CFD) model of a three-dimensional non-spinning semi-cylindrical missile model with a single wrap around fin in Mach 2.70-3.00M range and 0° angle of attack, and ultimately establishing itself for future research study. Design/methodology/approach In this study, the behaviour of flow around the fin was investigated using a κ-ϵ turbulence model of second-order of discretization. This was done using a highly structured mesh. Additionally, an inviscid CFD simulation involving the same boundary conditions have also been carried out for comparison. Findings The obtained values of aerodynamic coefficients and pressure contours visualizations are compared against their experimental and computational counterparts. A typical missile aerodynamic characteristic trend can be seen in the current CFD. Practical implications The predicted values of the aerodynamic coefficients of this single fin model have also been compared to those of the full missile body comprising of four fins from the previous research studies, and a similar aerodynamic trend can be seen. Originality/value This study explores the possibility of the use of turbulence modelling in a single fin model of a missile and provides a basic computational model for further understanding the flow behaviour near the fin.

Enhanced understanding of leakage in mechanical seals with elliptical dimples based on CFD simulation

2019 ◽  
Vol 72 (1) ◽  
pp. 24-30
Author(s):  
Sen Jiang ◽  
Hua Ji ◽  
Tianhao Wang ◽  
Donglin Feng ◽  
Qian Li
Keyword(s):  
Cfd Simulation ◽  
Three Dimensional ◽  
Leakage Rate ◽  
Geometric Feature ◽  
Maximum Pressure ◽  
Mechanical Seals ◽  
Ansys Fluent ◽  
Content Type ◽  
Surface Textures ◽  
Influencing Mechanism

Purpose The shapes of surface textures have been designed to control the leakage of mechanical seals in recent years. The purpose of this paper is to demonstrate the influence of geometric properties of elliptical dimples on the leakage rate. Design/methodology/approach A new geometric feature point is expressed using an analytical solution to locate the high-pressure zones. Furthermore, a numerical model of the three-dimensional flow field for the mechanical seal with elliptical dimples is developed using ANSYS Fluent to demonstrate the influencing mechanism. Findings The location of the proposed geometric converging point coincides with the maximum pressure point under different orientation angles. An inward flow on the leakage section observed from the simulation results is responsible for decreasing the leakage rate. Originality/value The influencing mechanism of the elliptical dimple on the leakage rate is demonstrated, which can facilitate the design of surface textures.

On the forced convective flow inside thermal collectors enhanced by porous media: from macro to micro-channels

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Maziar Dehghan ◽  
Zahra Azari Nesaz ◽  
Abolfazl Pourrajabian ◽  
Saman Rashidi
Keyword(s):  
Porous Media ◽  
Velocity Distribution ◽  
General Model ◽  
Convective Flow ◽  
Three Dimensional ◽  
Momentum Equation ◽  
Distribution Profile ◽  
Content Type ◽  
Forced Convective Flow ◽  
Drag Term

Purpose Aiming at finding the velocity distribution profile and other flow characteristic parameters such as the Poiseuille (Po) number, this study aims to focus on the three-dimensional forced convective flow inside rectangular ducts filled with porous media commonly used in air-based solar thermal collectors to enhance the thermal performance. The most general model for the fluid flow (i.e. the non-linear Darcy–Brinkman–Forchheimer partial differential equation subjected to slip and no-slip boundary conditions) is considered. Design/methodology/approach The general governing equations are solved analytically based on the perturbation technique and the results are validated against numerical simulation study based on a finite-difference solution over a non-uniform but structured grid. Findings The analytical velocity distribution profile based on exponential functions for the above-mentioned general case is obtained, and accordingly, expressions for the Po are introduced. It is found that the velocity distribution tends to be uniform by increasing the aspect ratio of the duct. Moreover, a criterion for considering/neglecting the nonlinear drag term in the momentum equation (i.e. the Forchheimer term) is proposed. According to the sensitivity analysis, results show that the nonlinear drag term effects on the Nusselt number are important only in porous media with high Darcy numbers. Originality/value A general analytic solution for three-dimensional forced convection flows through rectangular ducts filled with porous media for the general model of Darcy–Brinkman–Forchheimer and the general boundary condition including both no-slip and slip-flow regimes is obtained. An analytic expression to calculate Po number is obtained which can be practical for engineering estimations and a basis for validation of numerical simulations. A criterion for considering/neglecting the nonlinear drag term in the momentum equation is also introduced.

Numerical simulation of methane spreading in porous media after leaking from an underground pipe

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ji Wang ◽  
Yuting Yan ◽  
Junming Li
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Numerical Model ◽  
Natural Gas ◽  
Three Dimensional ◽  
Ground Surface ◽  
Air Transportation ◽  
Water Evaporation ◽  
Content Type ◽  
Gas Leak

Purpose Natural gas leak from underground pipelines could lead to serious damage and global warming, whose spreading in soil should be systematically investigated. This paper aims to propose a three-dimensional numerical model to analyze the methane–air transportation in soil. The results could help understand the diffusion process of natural gas in soil, which is essential for locating leak source and reducing damage after leak accident. Design/methodology/approach A numerical model using finite element method is proposed to simulate the methane spreading process in porous media after leaking from an underground pipe. Physical models, including fluids transportation in porous media, water evaporation and heat transfer, are taken into account. The numerical results are compared with experimental data to validate the reliability of the simulation model. The effects of methane leaking direction, non-uniform soil porosity, leaking pressure and convective mass transfer coefficient on ground surface are analyzed. Findings The methane mole fraction distribution in soil is significantly affected by the leaking direction. Horizontally and vertically non-uniform soil porosity has a stronger effect. Increasing leaking pressure causes increasing methane mole flux and flow rate on the ground surface. Originality/value Most existing gas diffusion models in porous media are for one- or two-dimensional simulation, which is not enough for predicting three-dimensional diffusion process after natural gas leak in soil. The heat transfer between gas and soil was also neglected by most researchers, which is very important for predicting the gas-spreading process affected by the soil moisture variation because of water evaporation. In this paper, a three-dimensional numerical model is proposed to further analyze the methane–air transportation in soil using finite element method, with the presence of water evaporation and heat transfer in soil.

The Numerical Simulation Study of the Cone Hindered Settling Hydro-Sizer Based on CFD

2013 ◽  
Vol 807-809 ◽  
pp. 2340-2344
Author(s):  
Fei Yue Wang ◽  
Yi Shun Zhang ◽  
Chang Liang Shi ◽  
Yuan Yang Liu ◽  
Ling Zhang
Keyword(s):  
Numerical Simulation ◽  
Geometric Modeling ◽  
Flow Model ◽  
Cfd Simulation ◽  
Three Dimensional ◽  
Internal Flow ◽  
Two Phase ◽  
Hindered Settling ◽  
Flow Field Characteristics ◽  
Fluent Software

This paper use CFD software for geometric modeling and structural mesh for the Cone Hindered Settling Hydro-sizer and then apply the Fluent software for three-dimensional CFD simulation. Using RNG K-ε two-equation turbulence model and Swirl Dominated Flow model respectively, and the top speed of different feeding liquid two-phase flow of water under medium CFD numerical simulation results grader internal flow field characteristics.

Research on the surface of multilayer weft knitted fabrics using computer simulation

2015 ◽  
Vol 27 (4) ◽  
pp. 561-572 ◽  
Author(s):  
Lanming Jin ◽  
Gaoming Jiang
Keyword(s):  
Computer Simulation ◽  
Large Scale ◽  
Structural Parameters ◽  
Three Dimensional ◽  
Surface Model ◽  
Knitted Fabric ◽  
Loop Model ◽  
Knitted Fabrics ◽  
Content Type ◽  
3D Effect

Purpose – Multilayer weft knitted fabrics possess many advantages, such as strongly stereoscopic patterns, soft handling and adjustable thickness of apparel and home textiles use. However, it is difficult to predict the final visual effects before the productive process because of the three-dimensional (3D) effect caused by the connecting yarn of the fabric. The purpose of this paper is to realize a realistic simulation of the fabric. Design/methodology/approach – The authors applied to the curve and surface model to simulate the knitted fabric, instead of previous single loop model by NURBS. Macro simulation is more suitable for the fabric with the 3D effect because of the quick, real and convenient simulation. This research includes experiments on the structural parameters concerning the regular sag of multilayer weft knitted fabrics, and analysis of parameter data and the simulation process with the aim of realizing a computer simulation of the fabric, especially with a sense of reality. The Digital Elevation Model was also applied to build a simulated 3D model. Findings – To obtain the values for the change rules, different samples were used and the outputs of the model were found to be close to the experimental results. The thickest and thinnest lengths and the changing curves between them were established. Patterned simple multilayer weft knitted fabric could be simulated through the results of the research. It is possible to simulate different real fabrics using their materials and expected effects. The authors are going to improve the model to simulate the complicate large-scale jacquard fabrics in further research. Practical implications – The results will be useful for establishing a computer surface simulation system for stereo perception of fabrics. Originality/value – The authors put forward the concept of surface warpage degree (R). It is an important factor affecting the fabric stereo feeling. The larger the value of R, the stronger the stereo sense of the fabric. It could be applied to most 3D fabric. A thickness difference testing method was proposed to characterize the stereo perception of fabrics. It is possible to simulate different real fabrics quickly without the model of the woven loop.

Three-Dimensional Bobsled Turning Dynamics

1989 ◽  
Vol 5 (2) ◽  
pp. 222-237 ◽  
Author(s):  
Mont Hubbard ◽  
Michael Kallay ◽  
Payam Rowhani
Keyword(s):  
Geometric Modeling ◽  
Control Strategies ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
Quantitative Information ◽  
Surface Model ◽  
Approximation Techniques ◽  
Driver Performance ◽  
Track Surface ◽  
Cross Track

We have developed a mathematical model and computer simulation of three-dimensional bobsled turning. It is based on accurate descriptions of existing or hypothetical tracks and on dynamic equations of motion including gravitational, normal, lift, drag, ice friction, and steering forces. The three-dimensional track surface model uses cubic spline geometric modeling and approximation techniques. The position of the sled on the track is specified by the two variables α and β in the along-track and cross-track directions, differential equations for which govern the possible motions of the sled. The model can be used for studies involving (a) track design, (b) calculation of optimal driver control strategies, and (c) as the basis for a real-time bobsled simulator. It can provide detailed quantitative information (e.g., splits for individual turns) that is not available in runs at actual tracks. The model also allows for comparison of driver performance with the numerically computed optimum performance, and for safe experimentation with risky driving strategies.

Permeability of three-dimensional models of fibrous porous media

1996 ◽  
Vol 308 ◽  
pp. 341-361 ◽  
Author(s):  
J. J. L. Higdon ◽  
G. D. Ford
Keyword(s):  
Porous Media ◽  
Numerical Solutions ◽  
Volume Fraction ◽  
Three Dimensional ◽  
Slender Body Theory ◽  
Permeable Media ◽  
Fibrous Porous Media ◽  
Periodic Models ◽  
Dimensional Models ◽  
Three Dimensional Models

Viscous flow through three-dimensional models of fibrous porous media is analysed. The periodic models are based on ordered networks of cylindrical fibres on regular cubic lattices. Numerical solutions are obtained using the spectral boundary element method introduced by Muldowney & Higdon (1995). Results are presented for solid volume fractions ranging from extreme dilution to near the maximum volume fraction for permeable media. Theoretical estimates are derived using slender-body theory and lubrication approximations in the appropriate asymptotic regimes. Comparisons are made with model predictions based on properties of two-dimensional media (Jackson & James 1986), and with results for disordered dispersions of prolate spheroids (Claeys & Brady 1993b).

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