Blow molded plastic liners (BMPLs) for on-board Type IV compressed gaseous hydrogen (CGH2) storage tanks consist of a high-molecular-weight polymer wall that serves as a permeation layer for hydrogen gas. This paper presents the latest numerical model integrated in the Blow View software for predicting the hydrogen permeation in a BMPL. The prediction model is based on Fick's solution-diffusion laws, with pressure and temperature dependent transport properties, for steady/unsteady state permeation regimes through a polymeric wall. An overview of key simulation results for an industrial BMPL for a CGH2 tank, as well as the adopted methodology addressing the challenge to optimize the wall thickness for light weighting and permeability performance, are also presented.

The nonlinear relationship between the input process parameters and in-flight particle characteristics of the atmospheric plasma spray (APS) is of paramount importance for coating properties design and quality. It is also known that the ageing of torch electrodes affects this relationship. In recent years, machine learning algorithms have proven to be able to take into account such complex nonlinear interactions. This work illustrates the application of ensemble methods to predict the in-flight particle temperature and velocity during an APS process considering torch electrodes ageing. Experiments were performed to record simultaneously the input process parameters, the in-flight powder particle characteristics and the electrodes usage time. Random Forest (RF) and Gradient Boosting (GB) were used to rank and select the features for the APS process data recorded as the electrodes aged and the corresponding predictive models were compared. The time series aspect of the multivariate APS in-flight particle characteristics data is explored. Two strategies of time series embedding are considered. The first one simply embeds the attributes and the targets from the previous n time segments considered without any modification; whereas the second strategy first performs differencing to make the time series stationary before embedding. For the present application, RF is found to be more suitable than GB since RF can predict both the in-flight particle velocity and temperature simultaneously, properly considering the interactions between the two targets. On the other hand, GB can only predict these two targets one at a time. The superior performance of both embedded predictive models and the feature rankings of them suggest that it is better to consider the APS data as time series for the in-flight particle characteristic prediction. In particular, it is demonstrated that it is advantageous to first make the time series stationary using the traditional differencing technique, even when modeling using RF.

•Novel 3D electrochemical model with heat generation, gives thermal field in prismatic cells.•investigated Ice plates (flush with cell face) and Cold plates (bottom surface of cell)•Thermal profiles found as function of drive cycle, cooling regime and battery case material.•Ice plates give thermal rises 5–8 K less than Cold plate, and provide narrower ΔT range•among battery case materials tested, Cold plate cooling is best with thick aluminum

This study combined a simple two-dimensional (2D) finite volume model (Kim model), which employs Ohm's law along with charge conservation over the electrodes and Butler–Volmer charge transfer kinetics for prismatic battery cells coupled with the single particle model (SPM) in order to model the thermal state of automotive battery packs. The objective here was to determine the effects of liquid cooling applied to the packs under standard driving cycles. A model developed by Kim provided a means for determining a nonuniform current distribution over the surface of the current collectors. The Kim model is based on the application of Ohm's law over a conducting medium, with empirical source terms representing current flowing into or out of an adjacent electrode layer. Here, a modeling advance is presented where empirical source terms in the Kim model were replaced with ones based on the chemistry and physics occurring inside the battery. As such, fundamental battery function was imparted to the model by integrating the SPM into the 2D finite volume Kim model. The 2D procedure described above was carried out on electrode sheets at different positions inside the cell, and determined thermal generation values that were mapped volumetrically into a heat transfer simulation, which, in turn, updated the electrochemical simulation. Capacity fade kinetics were determined by fitting experimental data to simulated results. With time-temperature profiles produced as described above for different pack cooling levels and varying degrees of cell degradation, a basic SPM simulation was then used with thermal overlays to estimate automotive cell life under various driving scenarios and various cooling levels. With these simulations, scenarios representing different thermal management regimes along with driving behavior were able to show the combined impact on automotive battery pack lifetimes.

The Journal of Thermal Spray Technology could not exist without the ongoing contributions of guest editors and reviewers, which ensure the highest quality of our journal. Manuscripts are reviewed for technical excellence, quality, and relevance by competent reviewers. The editors identify and select reviewers based on their demonstrable and recognized research expertise, professional experience, critical judgment and foresight, and forward thinking in their field of expertise. We express our deepest appreciation to these guest editors who have created special topical issues of JTST published in 2013, and to these reviewers, all of whom have completed manuscript reviews during 2013. Thank you all for giving generously of your valuable time and expertise.

Numerical solutions are shown for the natural convection flow inside a cold square enclosure with a hot rosette-shaped cylinder inside. Solutions are obtained using an immersed-boundary finite element method. The study investigates the effect of the rosette-shape factor on the heat transfer and fluid flow for Rayleigh numbers between 10(3) and 10(7). Results indicate the formation of recirculation cells of number, size, and location depending strongly on the shape of the cylinder and on the Rayleigh number. All solutions reach a steady state, except when the rosette-shape factor is 0.6 at Ra=10(6), for which a periodic transient solution is obtained.

Solving the flow around objects with complex shapes may involve extensive meshing work that has to be repeated each time a change in the geometry is needed. The same problem arises if one need to solve the heat transfer involving multiple materials whose interface is complex or changes with time. Time consuming meshing can be avoided when the solution algorithm can tackle grids that do not fit the shape of the interface between different materials. This work presents the extension of a recently proposed immersed boundary-body conformal enrichment (IB-BCE) method to the solution of the heat transfer. The method produces solutions of the temperature field satisfying accurately the continuity of the normal heat flux at interfaces between materials with different thermal properties. As for the isothermal flow problems, the fluid/solid interface is defined using a level-set function and the finite element discretization of interface elements is enriched with additional degrees of freedom which are eliminated at element level. The method is first validated in the case of heat conduction in two solids with different thermal properties. Then, solutions are shown for the more complex conjugate heat transfer between water and aluminum for two configurations: steady state flow inside a channel obstructed by a heated cylinder and transient flow around a heated cylinder. For each problem the solutions obtained using the proposed immersed boundary method are compared with solutions on body-conformal meshes having comparable mesh size distribution. The proposed approach is very accurate and effective in capturing the sharp discontinuity in the normal temperature gradient at the interface. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.

This paper presents applications of a recently proposed Immersed Boundary (IB) method to the solution of the flow around moving and complex shaped surfaces, in particular inside twin-screw extruders. Solving the flow around rotating screw elements implies significant changes in the computational topology at every time step. Using multiple meshes or adaptive methods to tackle these would require extensive meshing and interpolation work that has to be repeated each time step. Mesh generation and solution interpolation between successive grids may be costly and may introduce errors if the geometry changes significantly during the course of the computation. These drawbacks are avoided when the solution algorithm can tackle grids that do not fit the shape of immersed objects. In this work a fixed mesh is used covering both the fluid and solid regions, and the boundary of immersed objects is defined using a time dependent level-set function. The Body Conformal Enrichment (BCE) method is used to accurately impose boundary conditions on the surface of immersed bodies. The proposed algorithm enriches the finite element discretization of interface elements with additional degrees of freedom, the latter being eliminated at element level. Numerical applications are shown in which the flow inside twin-screw extruders is computed for multiple screw elements. A generalized non-Newtonian fluid is used to model molten polymer. Solutions will be shown for various rotation velocities of the screw as the viscosity depends on the shear rate.

This paper presents applications of a recently proposed immersed boundary method to the solution of fluid–solid interaction. Solid objects immersed into the fluid are considered rigid and their movement is determined from the interaction forces with the fluid. The use of body-conformal meshes to solve such problems may involve extensive mesh adaptation work that has to be repeated each time a change in the shape of the domain or in the position of immersed solids is needed. Mesh generation and solution interpolation between successive grids may be costly and introduce errors if the geometry changes significantly during the course of the computation. These drawbacks are avoided when the solution algorithm can tackle grids that do not fit the shape of immersed objects. We present here an extension of our recently developed immersed boundary (IB) finite element method to the computation of interaction forces between the fluid and immersed solid bodies. A fixed mesh is used covering both the fluid and solid regions, and the boundary of immersed objects is defined using a time dependent level-set function. Boundary conditions on the immersed solid surfaces are imposed accurately by using a Body Conformal Enrichment (BCE) method. In this approach, the finite element discretization of interface elements is enriched by including additional degrees of freedom which are latter eliminated at element level. The forces acting on the solid surfaces are computed from the enriched finite element solution and the solid movement is determined from the rigid solid momentum equations. Solutions are shown for various fluid–solid interaction problems and the accuracy of the present approach is measured with respect to solutions on body-conformal meshes.

In this work the numerical modeling of the flow inside co-rotating twin-screw extruders is performed and solutions are analyzed to determine the mixing behavior of two screw elements: conveying and mixing elements. The flow around intermeshing screws is computed using an immersed boundary finite element method capable of dealing with complex moving solid boundaries. The flow is considered isothermal and the material behaves as a generalized non-Newtonian fluid. Because the viscosity depends on the shear rate, solutions will be shown for various rotation velocities of the screw. The 3D solutions are then analyzed in order to determine various parameters characterizing the flow mixing such as the residence time and the linear stretch. Residence time distribution inside the twin-screw extruder is first computed by using a particle tracking algorithm based on a fourth order Runge-Kutta method. A large number of particles are tracked inside the extruder and the resulting particle data is used to determine the distribution of the residence time and of the linear stretch. The spatial distribution of the residence time is also computed by solving a transport equation tracking the injection time of the polymer melt. The methodology shows important differences in the mixing behavior of the screw elements considered.

SUMMARYSolving the flow around objects with complex shapes may involve extensive meshing work that has to be repeated each time a change in the geometry is needed. Time consuming meshing can be avoided when the solution algorithm can tackle grids that do not fit the shape of immersed objects. This work presents applications of a recently proposed immersed boundary—body conformal enrichment method to the solution of the flow around complex shaped surfaces such as those of a metallic foam matrix. The method produces solutions of the flow satisfying accurately Dirichlet boundary conditions imposed on the immersed fluid/solid interface. The boundary of immersed objects is defined using a level‐set function, and the finite element discretization of interface elements is enriched with additional degrees of freedom, which are eliminated at element level. The method is first validated in the case of flow problems for which reference solutions on body‐conformal grids can be obtained: flow around an array of spheres and flow around periodic arrays of cylinders. Then, solutions are shown for the more complex flow inside a metallic foam matrix. A multiscale approach combining the solution at the pore level by the immersed boundary method and the macro‐scale solution with simulated permeability is used to solve actual experimental configurations. The computed pressure drop as a function of the flow rate on the macro scale configuration replicating two experimental setups is compared with the experimental data for various foam thicknesses. Copyright © 2011 National Research Council Canada

Abstract This paper reports on the influence of the He to N2 ratio on the properties of low pressure cold sprayed titanium coatings and on the characteristics of the generated supersonic two-phase flow. Experiments were carried out varying the He to N2 concentration ranging from pure He to pure N2. Samples were characterized by their microstructural properties (i.e. microhardness and porosity). Deposition rate was evaluated and particle velocities were measured for all conditions. Deposition efficiency, coating density, and microhardness were found to be a function of particle impact velocity. Velocity data were used to validate a computational fluid dynamic model. The numerical solution of the flow inside the nozzle was obtained from the Euler equations for the various He to N2 concentrations. Particle tracking was carried out by using the computed distribution of density, Mach number, temperature, viscosity, and a second order Runge-Kutta scheme. In addition, mean particle velocities at the exit of the nozzle were determined. Computed velocities were found to be in good agreement with measured ones. The model was then used to calculate nozzle dimensions that would maximize particle velocity. Optimized dimensions are proposed.

This paper presents the extension of a recently proposed immersed boundary method to the solution of the flow around moving objects. Solving the flow around objects with complex shapes may involve extensive meshing work that has to be repeated each time a change in the geometry is needed. Mesh generation and solution interpolation between successive grids may be costly and introduce errors if the geometry changes significantly during the course of the computation. These drawbacks are avoided when the solution algorithm can tackle grids that do not fit the shape of immersed objects. This work presents an extension of our recently developed finite element Immersed Boundary (IB) method to transient applications involving the movement of immersed fluid/solid interfaces. As for the fixed solid boundary case, the method produces solutions of the flow satisfying accurately boundary conditions imposed on the surface of immersed bodies. The proposed algorithm enriches the finite element discretization of interface elements with additional degrees of freedom, the latter being eliminated at element level. The boundary of immersed objects is defined using a time dependent level-set function. Solutions are shown for various flow problems and the accuracy of the present approach is measured with respect to solutions on body-conforming meshes.

In this work the incompressible steady‐state flow through a metallic foam matrix is solved by a finite element method. A multiscale approach combining the solution at the pore level by an immersed boundary method and the macro‐scale solution with simulated permeability is used. The micro scale solution of the flow takes into account the details characterizing the geometry of the foam (μCT scans) and is used to determine the permeability coefficients in the Forchheimer’s model. In a second step, a numerical approach is used to solve the flow at the macro scale by modelling the presence of the foam via a source term corresponding to the pressure drop computed at the micro scale. Such simulation gives the opportunity to solve the flow in complex configurations in which the foam is only a part of the computational domain. The computed pressure drop as a function of the flow rate on the macro scale configuration replicating an experimental set‐up is compared with the experimental data for various foam thicknesses.

In this paper, we presents a continuous sensitivity equation method (SEM) for Unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations with an adaptative Finite Element Method. The development is performed for value parameters that do not affect the geometry of the computational domain. We use the standard k ǫ model of turbulence with wall functions and some of its usual variants such as Kato-Launder modification and RNG. The logarithmic form of transport equations for k and ǫ are used. An adaptative remeshing algorithm is developed for time integration of the URANS equations. Formulation and implementation are first verified on a problem with a closed form solution : the decay grid turbulence. This is followed by applications to transient flow reaching a steady state for a backward facing step and vortex shedding behind a cylinder. Flow and sensitivity analyses are performed. Several uses of sensitivity information are demonstrated : identification of key parameters controlling the flow, assessing the influence of closure coefficients, and nearby solutions.

This paper proposes a new stabilized finite element method to solve singular diffusion problems described by the modified Helmholtz operator. The Galerkin method is known to produce spurious oscillations for low diffusion and various alternatives were proposed to improve the accuracy of the solution. The mostly used methods are the well‐known Galerkin least squares and Galerkin gradient least squares (GGLS). The GGLS method yields the exact nodal solution in the one‐dimensional case and for a uniform mesh. However, the behavior of the method deteriorates slightly in the multi‐dimensional case and for non‐uniform meshes. In this work we propose a new stabilized finite element method that leads to improved accuracy for multi‐dimensional problems. For the one‐dimensional case, the new method leads to the same results as the GGLS method and hence provides exact nodal solutions to the problem on uniform meshes. The proposed method is a Galerkin discretization used to solve a modified equation that includes a term depending on the gradient of the original partial differential equation. Copyright © 2008 John Wiley & Sons, Ltd.

This paper presents a 3D numerical solution algorithm for the simulation of free surface flows of dense suspensions including particle migration phenomena. Segregation of the solid phase in processes such as powder injection molding and molding of semi‐solid materials affects the rheology of the mixture and therefore the filling pattern. Segregation affects also the final properties and characteristics of such molded parts as a non‐uniform particles distribution leads to non‐uniform shrinkage, warpage and non‐uniform mechanical properties. In this paper, particle migration is modeled using the diffusion flux model of Phillips et al. (Phys. Fluids A 1992; 4:30–40) and is extended to address 3D mold filling problems. The solution algorithm is validated against flow problems for which experimental and numerical data are available: circular Couette flow, piston‐driven flow and sudden contraction–expansion flow. The particle migration model is then used to simulate mold filling problems in which the piston movement in the sleeve is known to induce particle migration before the material enters the cavity. An arbitrary Lagrangian–Eulerian (ALE) formulation is developed and combined to a level‐set front capturing method to simulate the piston movement and the evolution of the free surface in molding simulations. The ALE formulation is first compared with an Eulerian solution for the case of the piston‐driven flow problem. The approach is then applied to injection molding problems to study the evolution of particle distributions during molding and in the final molded parts. Copyright © 2008 Crown in the right of Canada. Published by John Wiley & Sons, Ltd.

This paper presents the development and application of the finite node displacement (FiND) method to the incompressible Navier–Stokes equations. The method computes high‐accuracy nodal derivatives of the finite element solutions. The approach imposes a small displacement to individual mesh nodes and solves a very small problem on the patch of elements surrounding the node. The only unknown is the value of the solution (u, p) at the displaced node. A finite difference between the original and the perturbed values provides the directional derivative. Verification by grid refinement studies is shown for two‐dimensional problems possessing a closed‐form solution: a Poiseuille flow and a flow mimicking a boundary layer. For internal nodes, the method yields accuracy slightly superior to that of the superconvergent patch recovery (SPR) technique of Zienkiewicz and Zhu (ZZ). We also present a variant of the method to treat boundary nodes. The local discretization is enriched by inserting an additional mesh point very close to the boundary node of interest. Computations show that the resulting nodal derivatives are much more accurate than those obtained by the ZZ SPR technique. Copyright © 2008 John Wiley & Sons, Ltd.

The ability to predict segregation of the solid phase in processes such as powder injection molding and injection molding of semi-solid materials is of special interest since such phenomenon affects the final properties and characteristics of the molded parts. In powder injection molding, for example, defects appear very often in the debinding and sintering stages but are caused by filling problems and determined by a non-uniform distribution of the solid particles within the molded part. In this paper we propose a 3D numerical solution algorithm for the simulation of particle migration in dense suspensions. The particle migration is modeled using the diffusion flux model and integrated into the NRC's 3D injection molding software. The solution algorithm is validated by solving flow problems for which experimental and numerical data are available: circular Couette flow, piston driven flow and sudden contraction-expansion flow. Since it is observed that the piston movement in the sleeve can induce particle migration even before the material enters the cavity, an ALE (Arbitrary Lagrangian-Eulerian) formulation is also developed to include the piston movement in molding simulations. The ALE formulation is first compared with an Eulerian solution for the case of the piston driven flow problem. Then, the approach is applied to injection molding problems and the segregation inside the molded parts is studied.