Advancing Front Research Articles

Bicameral Mesh Gradation with a Controlled Advancing Front Approach

This paper discusses an approach to controlling two-dimensional local sizing in a bicameral mesh. This concept was introduced in our prior International Meshing Roundtable conference paper, and we expand on it herein. We define bicameral gradation as a mesh size variation of two distinctly different types in two or more separate chambers or subdomains. The first chamber is controlled by constant to local size functions. The second subdomain is governed by a nonlinear sizing function leading to transitioning meshes. A controlled advancing front approach is proposed for both triangular and quadrangular meshes with the singular goal of ensuring a high local quality metric in the first chamber. A modified H-shock sizing scheme governs the second chamber. Virtual mesh topology is constructed at the face boundary both at geometry and node-loop levels to facilitate this type of bicameral meshing. Results clearly indicate the efficacy of the proposed approach leading to both a well-controlled desired size field and high local element quality. • Bicameralism or Bicameral mesh gradation is defined as a mesh size variation of two distinctly different types in two or more separate chambers or subdomains. • There is a “local chamber” where mesh gradation is constant to linear to a specific governing equation and the rest of the area which is called “residual chamber” and where the size varies in a non-linear transition. • Mesher-native virtual topological elements like soft-points and virtual vertices are used to define zonal boundaries. • Local sizes can be applied on (a) vertex, (b) interior of edges and (c) interior of faces. • 2D NodeLoop-segments are used to perform loop-based advancing front meshing in the local chambers with both triangles and quadrangles.

An automatic isotropic/anisotropic hybrid grid generation technique for viscous flow simulations based on an artificial neural network

Based on the author's previous research, a novel hybrid grid generation technique is developed by introducing an Artificial Neural Network (ANN) approach for realistic viscous flow simulations. An initial hybrid grid over a typical geometry with anisotropic quadrilaterals in the boundary layer and isotropic triangles in the off-body region is generated by the classical mesh generation method to train two ANNs on how to predict the advancing direction of the new point and to control the grid size. After inputting the initial discretized fronts, the ANN-based Advancing Layer Method (ALM) is adopted to generate the anisotropic quadrilaterals in boundary layers. When the high aspect ratio of the anisotropic grid reaches a specified value, the ANN-based Advancing Front Method (AFM) is adopted to generate isotropic triangles in the off-body computational domain. The initial isotropic triangles are smoothed to further improve the grid quality. Three typical cases are tested and compared with experimental data to validate the effectiveness of grids generated by the ANN-based hybrid grid generation method. The experimental results show that the two ANNs can predict the advancing direction and the grid size very well, and improve the adaptability of the isotropic/anisotropic hybrid grid generation for viscous flow simulations.

Advancing Front Oxygen Transfer Model for the Design of Microchannel Artificial Lungs.

Microchannel artificial lungs may provide highly efficient, long-term respiratory support, but a robust predictive oxygen transfer (VO2) model is needed to better design them. To meet this need, we first investigated the predictive accuracy of Mikic, Benn, and Drinker's advancing front (AF) oxygen transfer theory by applying it to previous microchannel lung studies. Here, the model that included membrane resistance showed no bias toward overprediction or underprediction of VO2 (median error: -1.13%, interquartile range: [-26.9%, 19.2%]) and matched closely with existing theory. Next, this theory was expanded into a general model for investigating a family of designs. The overall model suggests that, for VO2 = 100 ml/min, fraction of delivered oxygen (FDO2) = 40%, wall shear stress ((Equation is included in full-text article.)) = 30 dyn/cm, and blood channel height = 20-50 μm, a compact design can be achieved with priming volume ((Equation is included in full-text article.)) = 5.8-32 ml; however, manifolding may be challenging to satisfy the rigorous total width ((Equation is included in full-text article.)) requirement ((Equation is included in full-text article.)= 76-475 m). In comparison, 100-200 μm heights would yield larger dimensions ((Equation is included in full-text article.)122-478 ml) but simpler manifolding ((Equation is included in full-text article.)4.75-19.0 m). The device size can be further adjusted by varying FDO2, (Equation is included in full-text article.), or VO2. This model may thus serve as a simple yet useful tool to better design microchannel artificial lungs.

Filling Simple Holes by Using Enhanced Advancing Front Mesh Method (EAFM): Application to a Real Object

Nowadays, the physical object can be constructed in digital representation by reverse engineering process. The process started by collecting the point cloud data point from the surface of 3D object. The non-touch approaches from 3D laser scanner are advantageous because of their high scanning speed, high accuracy, real time application, etc. Object complexity such as glossy surface and shining can lead to deficiencies in the quality of data measure using a 3D scanner which leads to missing data and the formation of holes within the constructed 3D model object. A hole is referred to as simple if it does not have feature vertices except other point which have same connection of data points. This paper utilised the advanced front method (AFM) to create triangle into the simple holes area. The paper then improved the hole filling process for simple holes found on a 3D object or real-world object. In this paper, the enhanced method proposed two new AFM methods to the original method. The method was applied to the 3D object and the problem of finding new point for each triangle creation is solved.

Concentric Advancing Front Corrugations and Multiple Ordered Growth of 2D Mo2C Crystals

Despite a prolific family of transition metal carbides having been obtained via the chemical vapor deposition method into the 2D world looking for large-area ultrathin functional crystals, understa...

Filling Simple Holes of Triangular Mesh by using Enhanced Advancing Front Mesh (EAFM) method

Triangular meshes are extensively used to represent 3D models. Some surfaces cannot be digitised due to various reasons such as inadequacy of the scanner, and this generally occurs for glossy, hollow surfaces and dark-coloured surfaces. This cause triangular meshes to contain holes and it becomes difficult for numerous successive operations such as model prototyping, model rebuilding, and finite element analysis. Hence, it is necessary to fill these holes in a practical manner. In this paper, the Enhanced Advancing Front Mesh (EAFM) method was introduced for recovering missing simple holes in an object. The first step in this research was to extract the feature vertices around a hole on a 3D test data function. Then the Advancing Front Mesh (AFM) method was used to fill the holes. When conflicts occurred during construction of the triangle, the EAFM method was introduced to enhance the method. The results of the study show that the enhanced method is simple, efficient and suitable for dealing with simple hole problems.

Filling Sharp Features on Corner of Triangular Mesh by using Enhanced Advancing Front Mesh (EAFM) method

Repairing an incomplete polygon mesh constitutes a primary difficulty in 3D model construction, especially in the computer graphics area. The objective of hole-filling methods is to keep surfaces smoothly and continually filled at hole boundaries while conforming with the shapes. The Advancing Front Mesh (AFM) method was normally used to fill simple holes. However, there has not been much implementation of AFM in handling sharp features. In this paper, we use an AFM method to fill a holes on sharp features. The Enhanced Advancing Front Mesh (EAFM) method was introduced when there was a conflict during triangle creation. The results of the study show that the presented method can effectively improve the AFM method, while preserving the geometric features and details of the original mesh.

Modified algorithm for generating high volume fraction sphere packings

Advancing front packing algorithms have proven to be very efficient in 2D for obtaining high density sets of particles, especially disks. However, the extension of these algorithms to 3D is not a trivial task. In the present paper, an advancing front algorithm for obtaining highly dense sphere packings is presented. It is simpler than other advancing front packing methods in 3D and can also be used with other types of particles. Comparison with respect to other packing methods have been carried out and a significant improvement in the volume fraction (VF) has been observed. Moreover, the quality of packings was evaluated with indicators other than VF. As additional advantage, the number of generated particles with the algorithm is linear with respect to time.

Recent Advances in Parallel Advancing Front Grid Generation

The quest for scalable, parallel advancing front grid generation techniques now spans more than two decades. A recent innovation has been the use of a so-called domain-defining grid, which has led to a dramatic increase in robustness and speed. The domain-defining grid (DDG) has the same fine surface triangulation as the final mesh desired, but a much coarser interior mesh. The DDG renders the domain to be gridded uniquely defined and allows for a well balanced work distribution among the processors during all stages of grid generation and improvement. In this way, most of the shortcomings of previous techniques are overcome. Timings show that the approach is scalable and able to produce large grids of high quality in a modest amount of clocktime. These recent advances in parallel grid generation have enabled a completely scalable simulation pipeline (grid generation, solvers, post-processing), opening the way for truly large-scale computations using unstructured, body-fitted grids

Mathematical Modeling of Chromium(Ш) Extraction by Emulsion Liquid Membrane

Advancing front model, carrier-facilitated transfer model and reversible reaction model were applied to simulate extracting chromium (Ш) from wastewater by emulsion liquid membrane using di-(2-ethylhexyl) phosphoric acid as carrier and Span-80 as surfactant. Parameters of the mathematic models were gained from the designed experiments, and the reversible reaction model can be used with a reasonably accuracy as estimates of chromium (Ш) permeation. The experimental results demonstrate that the role of reversibility of the chemical reaction between internal phase and membrane phase should be considered, and the diffusion resistance is the primary resistance of the mass transfer process.

926 テンプレートを用いたシンプルで効果的なソリッドメッシュの自動生成(OS18.次世代CAD/CAM/CAE/CG/CSCW/CAT/C-Control (2),ポスターセッションP-2,オーガナイズドセッション)

926 テンプレートを用いたシンプルで効果的なソリッドメッシュの自動生成(OS18.次世代CAD/CAM/CAE/CG/CSCW/CAT/C-Control (2),ポスターセッションP-2,オーガナイズドセッション)

Mathematical modeling of emulsion liquid membrane pertraction of gold (III) from aqueous solutions

Modeling of emulsion liquid membrane pertraction of gold (III) ions from aqueous solutions using MIBK as carrier and LK-80 as emulsifier has been performed. Three models were considered: Advancing front model, diffusion controlled mass transfer inside and outside of globule model and finally, reaction and diffusion controlled mass transfer model. Results showed that the model considered as reaction and diffusion controlled mass transfer model is more compatible with experimental results and the compatibility of the model and the experimental results is more than 90%. This modeling showed that the pH of external phase is the most important parameter for the extraction. The deviation for “Advancing front model”, “diffusion controlled mass transfer model” and “reaction and diffusion controlled mass transfer model” were 82.83, 65.69 and 9.38%, respectively.

349 ハイブリッドアドバンシングフロント法によるソリッドメッシュ自動生成プログラムの開発(次世代CAD/CAM/CAE/CG/CSCW/CAT/C-Control(3),OS22 次世代CAD/CAM/CAE/CG/CSCW/CAT/C-Control)

349 ハイブリッドアドバンシングフロント法によるソリッドメッシュ自動生成プログラムの開発(次世代CAD/CAM/CAE/CG/CSCW/CAT/C-Control(3),OS22 次世代CAD/CAM/CAE/CG/CSCW/CAT/C-Control)

535 テンプレートを用いたハイブリッドフロント法による3次元メッシュの自動生成(S06-1 メッシュ生成 (1),S06 メッシュ生成)

535 テンプレートを用いたハイブリッドフロント法による3次元メッシュの自動生成(S06-1 メッシュ生成 (1),S06 メッシュ生成)

Air-exposed Tissue Culture of Human Middle Ear Epithelium and Meatal Epidermis: a Method to Study the Advancing Front of Cholesteatoma

The suitability of an air-exposed culture model consisting of a collagen matrix was investigated for constructing an advancing front (AF) of human middle ear epithelium (MEE) and meatal epidermis (ME). Three different culture settings were used: ( i ) MEE; ( ii ) ME; and ( iii ) AF (MEE+ME). Small tissue biopsies were placed on a fibroblast-populated collagen matrix and grown at the air-liquid interface. After 3 weeks of culture, the MEE and ME outgrowth was differentiated. Light, scanning electron and transmission electron microscopy showed no visible differences compared to native MEE and ME. Cytokeratin 8 and cytokeratin 10 expressions were comparable to the expression seen in the native MEE and ME tissues. Proliferation, which was demonstrated by the expression of Ki-67, was present in the basal layers of cultured MEE and ME. A double layer of cells in which the ME covered the MEE formed the AF. In the AF, the MEE and ME showed the same morphological and immunohistochemical characteristics as in their native tissues. The results of the study show that this in vitro system is a well-defined model system offering the possibility to study the effects of external stimuli on the different epithelia of the AF involved in the pathogenesis of cholesteatoma.

A comparison of models for 2-chlorophenol recovery from aqueous solutions by emulsion liquid membranes

Advancing front model and three reversible reaction models were applied to describe 2-chlorophenol permeation from aqueous solutions by emulsion liquid membranes. Similar results were obtained in most cases by using either of the reversible reaction models. Also differences between reversible reaction and the advancing front model were shown to be within experimental error in most cases (with the exception of low temperature permeation data) meaning that the role of reversibility of the chemical reaction between internal phase reagent and 2-chlorophenol can be considered negligible. Both advancing front and reversible reaction models can be used with a reasonably accuracy as estimates of 2-chlorophenol permeation for design purposes.

From the Thomas–Windle model to a phenomenological description of Case-II diffusion in polymers

The classic theory of Thomas and Windle has provided a powerful description of the processes involved in Case-II diffusion, in which a sharply defined front of solvent-swollen gel advances into a glassy polymer. We show how some aspects of the Thomas–Windle model can be introduced into a recent formulation by Rossi and coworkers to provide a phenomenological description of the slowing of the advancing front.

Parallel and distributed adaptive quadrilateral mesh generation

A parallel quadrilateral mesh generation using advanced front technology is presented in this paper. An improved quadrilateral mesh generation technology which uses the advancing front technology was introduced by the authors previously. This new quadrilateral mesh generation technique has been developed for use with parallel computing environments. The parallel code has been created by adapting the sequential code using each coarse quadrilateral as a sub-domain for remeshing. A transputer-based parallel system and a heterogeneous network of workstations using the parallel virtual machine system were employed. The use of these parallel environments to improve the efficiency of the proposed mesh generator was investigated. Some pre-processes have been introduced to ensure load balancing during the parallel mesh generation. A post processor has been developed to assist in the assembly of the distributed portions of the mesh. Four examples are presented to demonstrate the robustness and efficiency of this parallel mesh generator. Some nearly linear speed-up curves have been achieved for some large meshes by using up to 11 transputers.

A framework for advancing front techniques of finite element mesh generation

Advancing front techniques are a family of methods for finite element mesh generation that are particularly effective in dealing with complicated boundary geometries. In the first part of this paper, conditions are presented which ensure that any planar aft algorithm that meets these conditions terminates in a finite number of steps with a valid triangulation of the input domain. These conditions are described by specifying a framework of subtasks that can accommodate many aft methods and by prescribing the minimal requirements on each subtask that ensure correctness of an algorithm that conforms to the framework.

Polydispersity and backmixing effects in diffusion controlled mass transfer with irreversible chemical reaction: An analysis of liquid emulsion membrane processes

The effects of polydispersity and backmixing on diffusion-controlled mass transfer with irreversible chemical reaction in liquid emulsion membrane processes have been analysed in terms of the “Advancing Front” model. Separation-of-variables is used to decouple the drop size and axial dependence effects to reduce the problem to a numerically-manageable form. In column-type contactors, it is shown that for constant Sauter mean radius, polydispersity effects arise primarily through the changes in dispersed phase hold-up caused by the distribution in globule rise velocities. For constant hold-up, an increase in Sauter mean radius causes an increase in performance despite a lowered total interfacial area, which can be attributed to the non-linear interaction between the fractional utilization of the internal reagent, the diffusional resistance to transport, and bypassing and segregation phenomena associated with the larger globules. The nonlinear dependence of the transport processes on fractional utilization of internal reagent is also responsible for the development of characteristically convex, rather than concave, concentration profiles in countercurrent operations. Polydispersity effects are evident in batch and mixer-settler operations only at large residence times, although even then they are not significant.