ALE Method Research Articles

An enhancement of the back region forced convection heat transfer rates of a reciprocating curved channel with a rib by the ALE method

An enhancement of the back region forced convection heat transfer rates of a reciprocating curved channel with a rib by the ALE method is investigated numerically. In order to avoid damage caused by a huge difference of heat transfer rates between the front and back regions of a reciprocating curved channel, a rib is selected and installed at an appropriate location to enhance the heat transfer rate of the back region. In the ALE method, the generalized minimal residual method preconditioned by the mesh free pressure convection–diffusion in which the pressure terms are arranged in a finite element linearized matrix system is used to solve governing equations. The results show that the heat transfer rate of the back region is indeed enhanced by the installation of the rib at an appropriate location.

Towards a complete numerical description of lubricant film dynamics in ball bearings

In this article, we propose a framework for a detailed finite element analysis of elastohydrodynamic lubrication in ball bearings. Our contribution to this field is twofold. First, we present a fully monolithic ALE method for the treatment of fluid---structure interaction. For the lubricant, we use the full Navier---Stokes equations in combination with a pressure-dependent viscosity law and include thermal effects. Second, we introduce a novel method for a fully implicit treatment of the evolution of the lubricants' free surface using Nitsches method. This allows for arbitrarily large time steps independent of the spatial discretization. Despite the variety of numerical challenges present in this application, such as anisotropy and extreme values of pressure, our approach for the first time shows robustness up to high rotational speeds as required in industrial applications. We describe the numerical ingredients we use in detail and present numerical results that validate our approaches and demonstrate its capabilities.

A Numerical Simulation of Parachute Opening Process Based on ALE Method

In this paper, the parachute opening process of finite mass situation was simulated based on ALE method. The results of structure change, the flow field change and some important aerodynamic data were obtained. Compared with the experiment, it can be found that the opening process was same with the actual opening. This method was useful in parachute designing and performance analyzing.

Study on the Simulation of Anti-Flood Spiral Pile-Driven Process

Pile-driven operation is the essential means of flood control and river harnessing. Anti-flood Spiral Pile is an innovative flood fighting and rescue equipment. Based on the experiment, established the spiral pile finite element model in FEM method and constructed the soil model with SPH smooth particles, set the keywords and parameters by using LS-DYNA softwares own processor, and then, the large deformation (soil extrusion and shearing status, etc.) and stress conditions be simulated truthfully. With reference to the experiment, the simulation results of SPH method with ALE method was contrasted, which could provide a reliable reference and scientific basis for the subsequent analysis and design of the spiral pile.

Modeling of Blast-Induced Craters by Multi-Material ALE Method

Multi-material ALE method combines the advantages of Lagrangian and Eulerian methods, avoids mesh distortion of the Lagrangian method, and eliminates moving boundary problems of the Euler method. A numerical simulation of blast-induced craters in geotechnical medium was performed within the frame of LS-DYNA by multi-material ALE method. The simulated crater which coincides with the empirical data from CONWEP was observed in post processing by the flow of material. This demonstrates that the multi-material ALE method is an effective way to simulate blast-induced craters in geotechnical medium.

Coordinate Based Meta-Analysis of Functional Neuroimaging Data; False Discovery Control and Diagnostics

Coordinate based meta-analysis (CBMA) is widely used to find regions of consistent activation across fMRI studies that have been selected for their functional relevance to a given hypothesis. Only reported coordinates (foci), and a model of their spatial uncertainty, are used in the analysis. Results are clusters of foci where multiple studies have reported in the same spatial region, indicating functional relevance. There are several published methods that perform the analysis in a voxel-wise manner, resulting in around 105 statistical tests, and considerable emphasis placed on controlling the risk of type 1 statistical error. Here we address this issue by dramatically reducing the number of tests, and by introducing a new false discovery rate control: the false cluster discovery rate (FCDR). FCDR is particularly interpretable and relevant to the results of CBMA, controlling the type 1 error by limiting the proportion of clusters that are expected under the null hypothesis. We also introduce a data diagnostic scheme to help ensure quality of the analysis, and demonstrate its use in the example studies. We show that we control the false clusters better than the widely used ALE method by performing numerical experiments, and that our clustering scheme results in more complete reporting of structures relevant to the functional task.

On a robust ALE method with discrete primary and secondary conservation

On a robust ALE method with discrete primary and secondary conservation

Simulation of 2D wedge impacts on water using the SPH–ALE method

Prediction of the forces on pitching boat hulls is a subtle issue, since the underlying phenomena are highly dynamic and unsteady. The solution of a full 3D model of the hull is possible, but comes with a high computational cost; alternatively, it might be simpler to assume the hull as consecutive 2D slices. The traditional CFD approach, with mesh-based algorithms, introduces additional complexity due to mesh motion and interface tracking. By adopting a Lagrangian point of view, the computational algorithm would be substantially simpler, since free surface and moving geometries would be handled easily. In the current work, the smoothed particle hydrodynamics meshless method is used within an arbitrary Lagrangian–Eulerian framework (SPH–ALE), in order to predict the force and motion of a wedge during high-velocity water entry. Various impacts have been simulated, using wedges of different shapes and masses. Two methods of particle refinement have also been examined, in order to increase the accuracy near the point of impact. Results of the method are compared with experimental and numerical results from literature, showing good agreement.

缓冲气囊研究方法进展

缓冲气囊具有重量轻、可折叠和成本低廉等优点，被广泛应用在交通工具乘员安全、货物空投、无人机回收及深空探测等领域。本文首先介绍了各类缓冲气囊并总结了缓冲气囊的研究方法，包括实验分析、物理模型分析以及有限元仿真。然后对比分析了有限元仿真中的CV法和ALE法，并指出了两种方法的优缺点。 The buffering airbag is lightweight, collapsible and low cost, which is widely used in the field of transport safety of the crew, cargo airdrop, UAV recovery and deep space exploration. Firstly this article presents the various kinds of buffering airbags and summarizes the research methods of the buffering airbags, which include laboratory analysis, physical model analysis and finite element simulation. Secondly the CV method and the ALE method are compared in this article, and the advantages and the disadvantages of the two methods are pointed out.

An effective integration of methods for second-order three-dimensional multi-material ALE method on unstructured hexahedral meshes using MOF interface reconstruction

This paper presents an effective second-order three-dimensional unstructured multi-material arbitrary Lagrangian–Eulerian (MMALE) method for compressible fluid dynamics. This is an integration work. The MMALE method utilizes Moment of Fluid (MOF) capability with interface reconstruction for multi-material modeling of immiscible fluids. It is of the explicit time-marching Lagrange plus remap type. In the Lagrangian phase, the staggered compatible discretization for Lagrangian gas dynamics is used also with Tipton’s pressure relaxation model for the closure of mixed cells. For the remapping phase, an improved second-order cell-intersection-based method for three-dimensional unstructured mesh is presented. It is conservative for remapping cell-centered variables such as density and internal energy. It is suitable for remapping between two meshes with different topology. By using this remapping method, the new material centroid position in the rezoned cells can be geometrically computed. This enables it to be combined with the MOF algorithm for constructing a second-order MMALE method. The MMALE method can be implemented on three-dimensional unstructured hexahedral meshes. Numerical results have proved the accuracy and robustness of the MMALE method.

A swept‐intersection‐based remapping method in a ReALE framework

SUMMARYA complete reconnection‐based arbitrary Lagrangian–Eulerian (ReALE) strategy devoted to the computation of hydrodynamic applications for compressible fluid flows is presented here. In ReALE, we replace the rezoning phase of classical ALE method by a rezoning where we allow the connectivity between cells of the mesh to change. This leads to a polygonal mesh that recovers the Lagrangian features in order to follow more efficiently the flow. Those reconnections allow to deal with complex geometries and high vorticity problems contrary to ALE method. For optimizing the remapping phase, we have modified the idea of swept‐integration‐based. The new method is called swept‐intersection‐based remapping method. We demonstrate that our method can be applied to several numerical examples representative of hydrodynamic experiments.Copyright © 2012 John Wiley & Sons, Ltd.

A Coupled Fluid-Structure Simulation for Variable Displacement Pump Used in Vehicle

The defects of constant displacement pumps hinder the modern vehicle to achieve its energy saving goals. Variable displacement pump is becoming the focus of research and development. In the paper, the displacement adjusting mechanism in the pump is treated as a rigid, and its motion leads to a continuously deforming and moving fluid domain. ALE method is used in CFD to overcome the difficulties of the fluid-structure interaction exists in the variable displacement pump. The moving regularity of computing grid and the boundary conditions of the ALE method are reasonably specified, to minimize the computing complexity in the coupled analysis. Experiments on prototype prove the performance of the pump in flow rate and energy saving. The results of analysis agree well with the experimental data, and the motion of the displacement adjusting mechanism is analyzed accurately.

A remapping-free, efficient Riemann-solvers based, ALE method for multi-material fluids with general EOS

Based on an efficient Riemann solver, a remapping-free ALE method (RALE) for multi-material fluids with general equations of state is proposed. The basic idea of constructing the RALE is to couple the Lagrangian method with a remapping-free ALE-type method. In order to keep the sharpness of a material interface, the Lagrangian formulation is employed for tracking the material interface, where the Lagrangian velocity of nodes and Lagrangian fluxes are designed. In single material regions, the numerical fluxes are constructed on moving meshes which move nodes to the regions with large gradients to increase the numerical accuracy, and the explicit remapping stage is avoided because of the new discrete scheme. The inverse Hermite interpolation argument is employed in solving the Riemann problem with general EOS, consequently, reducing iteration steps greatly and resulting in an efficient and robust Riemann solver. A number of numerical examples are presented.

Study on Finite Element Algorithm of Jointed Rock Mass in Tunnel in Blasting and Model Building

It is a kind of effective way to study blasting to joint rock mass using the finite element method, in which the key is algorithm and model building. Comparing the relationship of explosive and blasting structure simulated by adopting Lagrange method and ALE method, the paper considers that Lagrange method is more close to practice, and could finish numerical simulation analysis of the intact rock blasting.

On the numerical approach for simulating reactor thermal hydraulics under seismic conditions

The motions of bubbles and free interfaces in oscillating two-phase flow fields are simulated numerically to assess the methodology for simulating reactor thermal hydraulics under seismic conditions. Two numerical methods are compared: one is to model the oscillating flow filed directly using the moving grid of the ALE method, and the other is to simulate the effect of oscillation using an external force acting on the fluid in a stationary grid. The two-phase flow field is simulated by the level set method. The theoretical back ground and the limitation of the two methods are discussed, and the calculated results using the external force are shown to coincide with those using the moving grid. It is found that the interfacial area between liquid and gas phases, which is one of the most important parameters for the nuclear reactor safety analysis, is affected largely by the oscillation.

Study of a novel cathode tool structure for improving heat removal in electrochemical micro-machining

In this paper, the effects of a hollow structure of cathode tool and radial flow of electrolyte on heat removal are studied using COMSOL software. A multi-physics (electrical field, flow field and heat transfer) model, which implement the bilateral interactions with customized PDE, is proposed to simulate the EMM process with a moving cathode tool. The ALE method is used to track the moving interface. The simulations show that the electrolyte flow rate and flushing time are the most important factors for the heat removal. A hollow structure of the cathode tool is proposed to improve the stability of flow rate, which will remove the heat generated during the EMM process effectively.

Experimental and Numerical Studies on the Reinforced Concrete Frames Subjected to Blast Loads

Terrorist bombing attacks will endanger and may even destroy the target building structures, resulting in economic loss and casualties. Typical columns and floor slab systems are not designed to resist the complex blast loading. So, in recent years, the effects of blast on conventional public buildings are focused on. In this paper,a two-bay,one-story reinforced concrete frame structure which is used to model a portion of a typical reinforced concrete frame structural system is used to investigate the blast response. The experiments are conducted on two models, allowing a variation in explosives standoff and explosives charge. In each experiment,the blast pressure values are recorded and the degree of damage of the frames are studied. According to the two kinds of experiments, two numerical models are established. ALE method which considers the interaction of the explosive, the air, and the structure is applied.Structure response analyses are performed using the large deformation finite-element computer code, LS-DYNA. The numerical results are compared with the experiment results, and a good agreement is obtained. The calculating results also demonstrate that some experimental value is unreasonable.

Fluid Structure Interaction for Hydraulic Problems

Fluid Structure interaction plays an important role in engineering applications. Physical phenomena such as flow induced vibration in nuclear industry, fuel sloshing tank in automotive industry or rotor stator interaction in turbo machinery, can lead to structure deformation and sometimes to failure.In order to solve fluid structure interaction problems, the majority of numerical tests consists in using two different codes to separately solve pressure of the fluid and structural displacements. In this paper, a unique code with an ALE formulation approach is used to implicitly calculate the pressure of an incompressible fluid applied to the structure. The development of the ALE method as well as the coupling in a computational structural dynamic code, allows to solve more large industrial problems related to fluid structure coupling.

Extension of ALE methodology to unstructured conical meshes

We propose a bi-dimensional finite volume extension of a continuous ALE method on unstructured cells whose edges are parameterized by rational quadratic Bezier curves. For each edge, the control point possess a weight that permits to represent any conic (see for example [LIGACH]) and thanks to [WAGUSEDE,WAGU], we are able to compute the exact area of our cells. We then give an extension of scheme for remapping step based on volume fluxing [MARSHA] and self-intersection flux [ALE2DHAL]. For the rezoning phase, we propose a three step process based on moving nodes, followed by control point and weight re-adjustment. Finally, for the hydrodynamic step, we present the GLACE scheme [GLACE] extension (at first-order) on conic cell using the same formalism. We only propose some preliminary first-order simulations for each steps: Remap, Pure Lagrangian and finally ALE (rezoning and remapping).

Kinetic Analysis of Hydraulic Mount of Vehicular Engine Based on Fluid-Structure Interaction

A fluid-solid interaction FEM of entire hydraulic mount of vehicular engine are presented. The dynamic response of the hydraulic mount is simulated. By means of the simulated result of the mount transient response in time domain, the dynamic performance and transmissibility of the hydraulic mounts are calculated. the ALE method transforming reference frames is used to resolve the problem the reference frame of hydro-dynamical questions is different from the reference frame of structural questions.