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Particle-based Simulations of Flows with Free Surfaces Using Hyperbolic-typeWeighting Functions
Get PDFIn this paper, we present the application of the particle-based simulations to complicated fluid flow problem with free surfaces. The particle approach is based on the MPS (Moving Particle Simulation) method using hyperbolic-type weighting function to stabilize the spurious oscillatory solutions for solving the Poisson equation with respect to the pressure fields. The hyperbolic-type weighting function is constructed by differentiating the characteristic function based on neural network framework. The weighting function proposed herein is collaterally applied to the kernel function in the SPH-framework. Numerical results demonstrate the workability and validity of the present MPS approach through the dambreaking flow problem
Research on Band Structure of One-dimensional Phononic Crystals Based on Wavelet Finite Element Method
Get PDFA wavelet finite element method (WFEM) is developed to analyze the dispersion relation for one-dimensional phononic crystals (1DPCs). In order to calculate the band gaps (BGs) of 1DPCs, the wavelet finite element model is constructed using a slender beam element based on B-spline wavelet on the interval (BSWI). Combining with the Bloch-Floquet theorem and ω(k) technique, the model will be simplified as a simple eigenproblem. The performance of the proposed method has been numerically verified by one numerical example
Geometrical Modeling of Cell Division and Cell Remodeling Based on Voronoi Tessellation Method
Get PDFThe Voronoi tessellation is employed to describe cellular patterns and to simulate cell division and cell remodeling in epithelial tissue. First, Halton sequence is utilized to generate the random generators of Voronoi cell points. The centroidal Voronoi cell center is obtained by probabilistic Lloyd's method and polygonal structure of cell distribution is modeled. Based on the polygonal shape of cells, the instantaneous mechanism of cell division is applied to simulate the cell proliferation and remodeling. Four kinds of single-cell division algorithms are designed with the consideration of cleavage angle. From these simulations, we find that cell topological structure varies case by case, but the cell cycle time is almost the same. With respect to double-cell proliferation, the cycle time is shorter than single-cell division for the same number of replicated cells, but this doesn’t imply the direct linear relationship between cycle time and the total number of cell divisions. The current study provides a novel numerical tool for cell division simulation and may open a door for more realistic and more accurate modeling of the features of morphogenesis emerging from the complex interactions between geometric and biomechanical properties of epithelial tissues
A Coupled Finite Difference Material Point Method and Its Application in Explosion Simulation
Get PDFThe material point method (MPM) discretizes the material domain by a set of particles, and has showed advantages over the mesh-based methods for many challenging problems associated with large deformation. However, at the same time, it requires more computational resource and has difficulties to construct high order scheme when simulating the fluid in high explosive (HE) explosion problems. A coupled finite difference material point (CFDMP) method is proposed through a bridge region to combine the advantages of the finite difference method (FDM) and MPM. It solves a 3D HE explosion and its interaction with the surrounding structures by dividing the problem domain into FDM region and MPM region in space. FDM is employed to simulate the region where the detonation products disperse into the surrounding air, while the FSI region is simulated by MPM. A bridging region is employed to exchange the information. In the bridge region, MPM provides the boundary condition for FDM region by mapping the variables from MPM background grid nodes to FDM fictitious points, while FDM provides the boundary condition for MPM region by mapping the variables from FDM cell-centre points to MPM interface grid nodes. The transportation between the two computational regions is implemented by moving particles in the bridge region. Numerical results are in good agreement with those of theoretical solutions, empirical formula and experiments. No obvious interface effect are observed in the bridge region in numerical tests
An LGDAE Method to Solve Nonlinear Cauchy Problem Without Initial Temperature
Get PDFWe recover an unknown initial temperature for a nonlinear heat conduction equation ut(x,t) = uxx(x,t) + H(x,t,u,ux), under the Cauchy boundary conditions specified on the left-boundary. The method in the present paper transforms the Cauchy problem into an inverse heat source problem to find F(x) in Tt(x,t) = Txx(x,t) + H + F(x). By using the GL(N,R) Lie-group differential algebraic equations (LGDAE) algorithm to integrate the numerical method of lines discretized equations from sideways heat equation, we can fast recover the initial temperature and two boundary conditions on the right-boundary. The accuracy and efficiency are confirmed by comparing the exact solutions with the recovered results, where a large noisy disturbance is imposed on the Cauchy data
Additive Manufacturing of Anatomical Models from Computed Tomography Scan Data
Get PDFThe purpose of the study presented here was to investigate the manufacturability of human anatomical models from Computed Tomography (CT) scan data via a 3D desktop printer which uses fused deposition modelling (FDM) technology. First, Digital Imaging and Communications in Medicine (DICOM) CT scan data were converted to 3D Standard Triangle Language (STL) format by using InVaselius digital imaging program. Once this STL file is obtained, a 3D physical version of the anatomical model can be fabricated by a desktop 3D FDM printer. As a case study, a patient’s skull CT scan data was considered, and a tangible version of the skull was manufactured by a 3D FDM desktop printer. During the 3D printing process, the skull was built using acrylonitrile-butadiene-styrene (ABS) co-polymer plastic. The printed model showed that the 3D FDM printing technology is able to fabricate anatomical models with high accuracy. As a result, the skull model can be used for preoperative surgical planning, medical training activities, implant design and simulation to show the potential of the FDM technology in medical field. It will also improve communication between medical stuff and patients. Current result indicates that a 3D desktop printer which uses FDM technology can be used to obtain accurate anatomical models
Simulation of Hydrogen Absorption in a Magnesium Hydride Tank
Get PDFThis paper summarizes the outcomes of a numerical study about the phenomenon of hydrogen absorption in an axisymmetric tank geometry containing magnesium hydride heated to 300˚C and at moderate storage pressure 1 MPa. The governing equations are solved with a fully implicit finite volume numerical scheme (as implemented in the commercial software FLUENT). Different kinetic reaction equations modeling hydrogen absorption are considered and the related numerical simulations are compared with experimental results. Spatial and temporal profiles of temperature and concentration in hydride bed are plotted
Effects of Non-Newtonian Micropolar Fluids on the Dynamic Characteristics of Wide Tapered-Land Slider Bearings
Get PDFWe investigate the influence of non-Newtonian micropolar fluids on the dynamic characteristics of wide tapered-land slider bearings. The study is carried out on the basis of the micro-continuum theory originally developed by Eringen (1966). Analytical expressions for the linear dynamic coefficients are provided and compared with earlier results in the literature. In particular, direct comparison with the Newtonian fluid-lubricated tapered-land bearings by Lin et al. (2006) indicates that the use of non-Newtonian micropolar fluids can lead to a significant increase in the values of stiffness and damping coefficients. Such improvements are found to be even more pronounced for larger values of the non-Newtonian parameters. Moreover, comparison with the non-Newtonian micropolar fluid-lubricated bearings with an inclined plane film by Naduvinamani and Marali (2007), leads to the conclusion that tapered-land bearings with large geometric parameters have higher dynamic stiffness coefficients. Furthermore, such bearings can provide better damping characteristics with respect to the case of inclined-plane bearings
Low Reynolds Numbers LDA-Experimental Analysis of the Near-Field of an Isothermal Laminar Round Free Jet
Get PDFJet transition towards a turbulent state is an interesting topic requiring a detailed analysis of the process leading to the onset and amplification of small flow disturbances. Here we examine experimentally the transition process for an isothermal laminar round free jet at low values of the Reynolds number. Close to the inlet nozzle, the turbulence intensity is assumed to be small enough so that the initial shear layer can be considered laminar and the velocity profile uniform. Experimental data are obtained using a Laser Doppler Anemometry (LDA) technique at various longitudinal and transversal coordinates, (x,y). Spectral analysis of the instantaneous streamwise velocity component u(y,t), at fixed stations x measured from the nozzle exit, reveals that the entrainment physical mechanism, which occurs by engulfment, is caused by the presence of coherent structures. However, in proximity to the jet center, the energy spectrum of the u(x,y = 0, t) velocity component proves the existence of a preferred mode (most unstable mode) of instability that has a convective nature. Our results compare well with those obtained using another experimental method based on laser tomography
MHD Effect on Relative Motion of Two Immiscible Liquid Spheres
Get PDFWe examine the motion of the two concentric immiscible liquid spheres with different viscosities in an electrically conducting fluid in the presence of transverse magnetic field. The inner sphere is assumed to move at a constant velocity. The Stoke’s equation along with the Lorentz force is considered to model the resulting fluid flow, analytical solutions being obtained by the similarity solution method in terms of modified Bessel’s functions. Streamlines related to the fluid circulation in the annulus between the two liquid spheres and inside the inner liquid sphere are presented for different combinations of the governing non-dimensional parameters