Finite-element analyses of blade and slot coating flows using an implicit pseudo-solid domain mapping technique coupled with unstructured grids

In coating processes (e.g. in blade coating) the flow domain inherently contains free surfaces and three-phase contact lines, and characteristic length scales of flow features in the dimension transverse to the web-movement vary by an order of magnitude or more from a fraction of a millimeter or more to tens of microns or less). The presence of free surfaces and three-phase contact lines, and the sudden changes of flow geometry and directions create difficulties in theoretical analyses of such flows. Though simulations of coating flows via finite-element methods using structured grids have been reportedly demonstrated in the literature, achieving high efficiency of such numerical experiments remains a grand challenge -- mainly due to difficulties in local mesh-refinement and in avoiding unacceptably distorted grids. High efficiency of computing steady flow fields under various process conditions is crucial in shortening turn-around time in design and optimization of coating-flow processes. In this paper we employ a fully-implicit, pseudo-solid, domain mapping technique coupled with unstructured meshes to analyze blade and slot coating flows using Galerkin`s method with finite element basis functions. We demonstrate the robustness and efficiency of our unique technique in circumventing shortcomings of mesh-motion schemes currently being used in the coating-flow research community. Our goal is to develop an efficient numerical tool, together with a suitable optimization toolkit, that can be used routinely in design and optimization of coating-flow processes

GOMA - A full-Newton finite element program for free and moving boundary problems with coupled fluid/solid momentum, energy, mass, and chemical species transport: User`s guide

GOMA is a two- and three-dimensional finite element program which excels in analyses of manufacturing processes, particularly those involving free or moving interfaces. Specifically, the full-Newton-coupled heat, mass, momentum, and pseudo-solid mesh motion algorithm makes GOMA ideally suited for simulating processes in which the bulk fluid transport is closely coupled to the interfacial physics. Examples include, but are not limited to, coating and polymer processing flows, soldering, crystal growth, and solid-network or solution film drying. The code is based on the premise that any boundary can be (1) moving or free, with an apriori unknown position dictated by the distinguishing physics, (2) fixed, according to a global analytical representation, or (3) moving in time and space under user-prescribed kinematics. The goal is to enable the user to predict boundary position or motion simultaneously with the physics of the problem being analyzed and to pursue geometrical design studies and fluid-structure interaction problems. The moving mesh algorithm treats the entire domain as a computational Lagrangian solid that deforms subject to the physical principles which dictate boundary position. As an added benefit, the same Lagrangian solid mechanics can be exploited to solve multi-field problems for which the solid motion and stresses interact with other transport phenomena, either within the same material phase (e.g. shrinking coating) or in neighboring material phases (e.g. flexible blade coating). Thus, analyses of many fluid-structure interaction problems and deformable porous media problems are accessible. This document serves as a user`s guide and reference for GOMA and provides a brief overview of GOMA`s capabilities, theoretical background, and classes of problems for which it is targeted

A Finite Element Method for Free-Surface Flows of Incompressible Fluids in Three Dimensions, Part II: Dynamic Wetting Lines

To date, few researchers have solved three-dimensional free-surface problems with dynamic wetting lines. This paper extends the free-surface finite element method described in a companion paper [Cairncross, R.A., P.R. Schunk, T.A. Baer, P.A. Sackinger, R.R. Rao, "A finite element method for free surface flows of incompressible fluid in three dimensions, Part I: Boundary-Fitted mesh motion.", to be published (1998)] to handle dynamic wetting. A generalization of the technique used in two dimensional modeling to circumvent double-valued velocities at the wetting line, the so-called kinematic paradox, is presented for a wetting line in three dimensions. This approach requires the fluid velocity normal to the contact line to be zero, the fluid velocity tangent to the contact line to be equal to the tangential component of web velocity, and the fluid velocity into the web to be zero. In addition, slip is allowed in a narrow strip along the substrate surface near the dynamic contact line. For realistic wetting-line motion, a contact angle which varies with wetting speed is required because contact lines in three dimensions typically advance or recede a different rates depending upon location and/or have both advancing and receding portions. The theory is applied to capillary rise of static fluid in a corner, the initial motion of a Newtonian droplet down an inclined plane, and extrusion of a Newtonian fluid from a nozzle onto a moving substrate. The extrusion results are compared to experimental visualization. Subject Categorie

Moving/deforming mesh techniques for computational fluid dynamics and heat transfer

This report represents a summary of a Laboratory Directed Research and Development (LDRD) project to develop general purpose unstructured grid techniques for solving free and moving boundary problems in computational fluid dynamics and heat transfer. Both control volume finite element and Galerkin finite element techniques were utilized. A very robust technique for keeping the deforming mesh from tangling was implemented; the mesh was treated as a fictitious elastic body. Sample results for an ablating nose tip and buoyancy driven flow in a box are presented. References to additional publications resulting from this work are included

Verification and Validation of Encapsulation Flow Models in GOMA, Version 1.1

Encapsulation is a common process used in manufacturing most non-nuclear components including: firing sets, neutron generators, trajectory sensing signal generators (TSSGs), arming, fusing and firing devices (AF and Fs), radars, programmers, connectors, and batteries. Encapsulation is used to contain high voltage, to mitigate stress and vibration and to protect against moisture. The purpose of the ASCI Encapsulation project is to develop a simulation capability that will allow us to aid in the encapsulation design process, especially for neutron generators. The introduction of an encapsulant poses many problems because of the need to balance ease of processing and properties necessary to achieve the design benefits such as tailored encapsulant properties, optimized cure schedule and reduced failure rates. Encapsulants can fail through fracture or delamination as a result of cure shrinkage, thermally induced residual stresses, voids or incomplete component embedding and particle gradients. Manufacturing design requirements include (1) maintaining uniform composition of particles in order to maintain the desired thermal coefficient of expansion (CTE) and density, (2) mitigating void formation during mold fill, (3) mitigating cure and thermally induced stresses during cure and cool down, and (4) eliminating delamination and fracture due to cure shrinkage/thermal strains. The first two require modeling of the fluid phase, and it is proposed to use the finite element code GOMA to accomplish this. The latter two require modeling of the solid state; however, ideally the effects of particle distribution would be included in the calculations, and thus initial conditions would be set from GOMA predictions. These models, once they are verified and validated, will be transitioned into the SIERRA framework and the ARIA code. This will facilitate exchange of data with the solid mechanics calculations in SIERRA/ADAGIO

Preliminary monolithic fluid structure interaction model for ventricle contraction

In this work we test the performance of different algorithms for the solution of a monolithic Fluid Structure Interaction (FSI) problem with a simplified ventricle model with the purpose to reduce the computational time. We study this challenging FSI problem by solving the fully coupled and the projection algorithm with a different number of penalty correction steps. The proposed FSI penalty projection algorithm is a modification of the Chorin method for fluids based on a predictor and a corrector step. The performance of the modified algorithm is tested by comparing the results obtained with the standard coupled algorithm with the ones obtained with the modified penalty projection scheme