Conventional Grid Method Research Articles

Particle Flow Simulation Based on Hybrid IMB-DEM-LBM Approach with New Solid Fraction Calculation Scheme

A new coupling method, immersed moving boundary–discrete element method–lattice Boltzmann method (IMB-DEM-LBM), is proposed to simulate particle flow for application in soil mechanics or coastal engineering. In this study, LBM fluid is simulated on the regular Eulerian grid and Lagrangian particle motion is governed by DEM while IMB couples the two algorithms. The new method is promising and robust as it resolves numerical instability near the particle boundary caused by mesh distortion in the conventional grid method. In IMB, the interface lattice solid fraction determines the distribution function ratio of non-equilibrium bounce back and Bhatnagar-Gross-Krook (BGK) collision. The non-equilibrium bounce back at moving boundary results in the fluid momentum change and contributes to the hydrodynamic force on particle. For numerical stability, this paper introduces the hydrodynamic force calculation concept from IB (immersed boundary method) to IMB, and at the same time, proposes a new solid fraction calculation method for sphere that divides the intersection into simple sector and triangle, as well as calculates the intersection area by vector. With this method, approximate inaccuracy is overcome while complicated integration is avoided.

Digital image correlation utilization in measuring displacement and strain during plastic film blowing process: A feasibility study

This research work explores on Digital Image Correlation (DIC) technique as a potential tool for measuring displacement and strain in film blowing extrusion process. A feasibility study on the surface patterning technique, validation of the DIC analysis and selection of DIC parameters were investigated. Understanding on the effects of these factors on the analysis of DIC in film blowing process is crucial as the film moves vertically at a relative speed while being stretched and deformed. Results showed that ink application was the best practice for surface pattern creation. The DIC was validated as a reliable method as the results obtained with the ink procedure were comparable to the conventional grid method. Subset size of 11 pixels and 21 pixels were preferred for small and large pattern, respectively. Regardless of pattern size, subset space of 1 pixel and strain radius of 5 pixels was chosen for yielding accurate result without any distortion in spatial resolution.

A grid-free particle tracking simulation for tracer dispersion in porous reservoir model

Tracer test is a useful method to investigate various phenomena in geological porous media including groundwater contaminant transport, sweep efficiency and retention time in oil reservoir, reservoir characterization, fractures orientation assessment, as well as geothermal reservoir evaluation. Numerical methods are powerful tools in interpreting tracer test results. However, they are limited by computational restrictions which include finer grid requirements and small calculation steps. In this study, an analog model of a quarter five-spot porous reservoir was simulated by using random walk particle tracking method. This scheme used ‘method of images’ with pairs of injector–producer potential flow to generate the velocity vectors instead of conventionally solving Darcy’s equation to obtain grid velocities. Simulated breakthrough concentration profiles and flow visualization were compared with both experimental results and Eulerian-grid based finite volume simulation. The predicted breakthrough curves of tracer concentration were found to agree with experimental data sets. In addition to be free from numerical errors as often encountered in grid-based simulation, the proposed particle tracking model showed a faster computational time. Unlike the conventional grid method, this technique provides inherently smooth and continuous flow field at arbitrary position within the reservoir model.

Optical Measurement of Forming Limit and Formability of Cu/Al Clad Metals

A digital image deformation measurement and analysis control system (XJTUDIC 8.0) was employed to measure the forming limit strain for Cu/Al clad metals produced via explosive welding technique. A contrast test between the digital image correlation (DIC) method and the conventional grid method was also implemented using the SPCC sheet metal forming limit test. The effect of heat treatment and contact status on forming limit was discussed based on the forming limit strain of Cu/Al clad metals. The interfacial and fracture structures were analyzed using scanning electron microscopy. The fracture site was predicted by finite element method. Results demonstrate that the forming limit curve of Cu/Al clad metals through DIC is more likely to reflect the formability of SPCC accurately. The forming limit of the clad with Al in the inner layer is higher than that of the clad with Cu in the inner layer. The formability of the annealed clads is superior to that of the non-annealed clads. The local interface failure induces the microcracks in Cu/Al clad metals during the forming process, which could be the main failure mode. With the finite element method, the fracture location of Cu/Al clad metals caused by uniaxial tensile during the forming limit test using DIC method is predicted accurately.

Three‐dimensional Displacement and Shape Measurement with a Diffraction‐assisted Grid Method

ABSTRACTThe grid method is a full‐field optical technique for computing surface displacements and strains of a material by analyzing the phase of grid lines patterned on the specimen. To date, most experiments using the grid method have measured only two‐dimensional in‐plane deformations. Here, the grid method is extended to three dimensions by using a crossed grid pattern and a diffraction grating which enables acquiring images from multiple viewing angles on a single camera. In‐plane displacements and strains are computed using the conventional grid method, and the corresponding three‐dimensional (3D) displacements—including out‐of‐plane displacements or shapes—are computed by analyzing the images collected at different viewing angles. The technique is demonstrated by measuring 3D rigid body motion, the 3D displacements of a membrane in a pressure‐bulge experiment, and the out‐of‐plane curvature of a cylindrical specimen.

New method: calculation of magnification factor from an intracardiac marker.

In order to calculate a magnification factor (MF), an intracardiac marker (pigtail catheter with markers) was evaluated using a new formula and correlated with the conventional grid method. By applying the Pythagorean theorem and trigonometry, a new formula was developed, which is (formula; see text) In an experimental study, MF by the intracardiac markers was 0.71 +/- 0.15 (M +/- SD) and one by the grid method was 0.72 +/- 0.15, with a correlation coefficient of 0.96. In patients study, MF by the intracardiac markers was 0.77 +/- 0.06 and one by the grid method was 0.77 +/- 0.05. We conclude that this new method is simple and the results were comparable to the conventional grid method at mid-chest level.

Numerical Solution of Parabolic Partial Differential Equations With Two-Point Boundary Conditions by Use of the Method of Lines

The Method of Lines, a numerical technique commonly used for solving partial differential equations on analog computers, is used to attain digital computer solutions of such equations. An extensive theoretical development is presented that establishes convergence and stability for one-dimensional parabolic equations with Dirichlet boundary conditions. A new modification of the method, using noncentral differences, is shown to be much faster, in terms of computer time, than conventional grid methods, for two examples.