Moving Boundary Transport Phenomena in Selective Area Laser Deposition Process

The overall selective area laser deposition process was modeled using the two-layer, three dimensional solid phase heat transfer with the moving boundary condition considered, gas phase mass transfer, and film growth coupled equations. A modified front-tracking finite difference method was used to solve the moving boundary heat conduction in thick deposits. The results correlate with the experimental observations.Mechanical Engineerin

Numerical simulation of super-square patterns in Faraday waves

We report the first simulations of the Faraday instability using the full three-dimensional Navier-Stokes equations in domains much larger than the characteristic wavelength of the pattern. We use a massively parallel code based on a hybrid Front-Tracking/Level-set algorithm for Lagrangian tracking of arbitrarily deformable phase interfaces. Simulations performed in rectangular and cylindrical domains yield complex patterns. In particular, a superlattice-like pattern similar to those of [Douady & Fauve, Europhys. Lett. 6, 221-226 (1988); Douady, J. Fluid Mech. 221, 383-409 (1990)] is observed. The pattern consists of the superposition of two square superlattices. We conjecture that such patterns are widespread if the square container is large compared to the critical wavelength. In the cylinder, pentagonal cells near the outer wall allow a square-wave pattern to be accommodated in the center

Detailed 3D modelling of mass transfer processes in two phase flows with dynamic interfaces

We developed a method that will enable us to determine mass transfer coefficients for a\ud large number of two phase flow conditions based on numerical simulation. A three-dimensional\ud direct numerical simulation based on the Front Tracking technique taking into account the mass\ud transfer process was chosen for this purpose. The dissolved species concentration in the liquid\ud phase is tracked using a scalar mass balance while the value of the concentration at the interface\ud is determined via an immersed boundary technique. In the present study, simulations are carried\ud out to investigate the effect of the bubble shape on the dissolved species concentration fiel

Hydrodynamic structures of droplets in square micro-channels

This paper reports on numerical simulations of the hydrodynamics inside droplets in rectangular micro-channels. We use a finite-volume/front-capturing method that allows us to perform two- and three-dimensional simulations with a reasonable cost. The numerical method is an interface-capturing technique without any interface reconstruction. Therefore no complex or expensive interface tracking is needed. Droplet interface deformation and velocity fields inside both droplets and continuous phase can then be followed. This study leads to important results about droplet deformation and inner streamlines for mass and heat transfer studies. More particularly, the capillary number seems to have a great influence on the liquid/liquid flow hydrodynamics whatever is the channel width

Faraday instability on a sphere: numerical simulation

We consider a spherical variant of the Faraday problem, in which a spherical drop is subjected to a time-periodic body force, as well as surface tension. We use a full three-dimensional parallel front-tracking code to calculate the interface motion of the parametrically forced oscillating viscous drop, as well as the velocity field inside and outside the drop. Forcing frequencies are chosen so as to excite spherical harmonic wavenumbers ranging from 1 to 6. We excite gravity waves for wavenumbers 1 and 2 and observe translational and oblate-prolate oscillation, respectively. For wavenumbers 3 to 6, we excite capillary waves and observe patterns analogous to the Platonic solids. For low viscosity, both subharmonic and harmonic responses are accessible. The patterns arising in each case are interpreted in the context of the theory of pattern formation with spherical symmetry

Comparison and verification of enthalpy schemes for polythermal glaciers and ice sheets with a one-dimensional model

The enthalpy method for the thermodynamics of polythermal glaciers and ice sheets is tested and verified by a one-dimensional problem (parallel-sided slab). The enthalpy method alone does not include explicitly the transition conditions at the cold-temperate transition surface (CTS) that separates the upper cold from the lower temperate layer. However, these conditions are important for correctly determining the position of the CTS. For the numerical solution of the polythermal slab problem, we consider a two-layer front-tracking scheme as well as three different one-layer schemes (conventional one-layer scheme, one-layer melting CTS scheme, one-layer freezing CTS scheme). Computed steady-state temperature and water-content profiles are verified with exact solutions, and transient solutions computed by the one-layer schemes are compared with those of the two-layer scheme, considered to be a reliable reference. While the conventional one-layer scheme (that does not include the transition conditions at the CTS) can produce correct solutions for melting conditions at the CTS, it is more reliable to enforce the transition conditions explicitly. For freezing conditions, it is imperative to enforce them because the conventional one-layer scheme cannot handle the associated discontinuities. The suggested numerical schemes are suitable for implementation in three-dimensional glacier and ice-sheet models.Comment: 16 pages, 8 figure

Three-dimensional motion of shoulder complex during front crawl swimming

The purposes of the study were to describe glenohumeral joint motion during front crawl swimming and to determine if the glenohumeral joint motion could be predicted by the humero-thoracic motion using linear regression model. Fourteen swimmers were asked to perform a resisted front crawl swimming. Three-dimensional motions of shoulder complex were measured with an electromagnetic tracking devise. The results showed that humerus and scapula did not move in a set ratio during front crawl swimming and the glenohumeral joint motion could not be predicted accurately from the humero-thoracic motion. A characteristic movement pattern was observed in the catch phase in which the humerus moved caudally behind the scapular plane while moving in front of the torso. This movement pattern may facilitate internal rotation of the shoulder to execute the catch and pull vigorously