A Procedure for Encapsulation in Microchannel

2007 ◽  
Author(s):  
Y. F. Yap ◽  
J. C. Chai ◽  
N. T. Nguyen ◽  
T. N. Wong ◽  
L. Yobas
Keyword(s):  
Surface Force ◽  
High Viscosity ◽  
Moving Boundaries ◽  
Body Motion ◽  
Force Model ◽  
Governing Equations ◽  
Strongly Coupled ◽  
Carrier Fluid ◽  
Grid Approach ◽  
Three Phases

A fixed-grid approach for modeling the motion of a particle-encapsulated droplet carried by a pressure driven immiscible carrier fluid in a microchannel is presented. Three phases (the carrier fluid, the droplet and the particle), and two different moving boundaries (the droplet-carrier fluid and droplet-particle interfaces), are involved. This is a moving boundaries problem with the motion of the three phases strongly coupled. In the present article, the particle is assumed to be a fluid of high viscosity and constrained to move with rigid body motion. A combined formulation using one set of governing equations to treat the three phases is employed. The droplet-carrier fluid interface is represented and evolved using a level-set method with a mass correction scheme. Surface tension is modeled using the Continuum Surface Force model. An additional signed distance function is employed to define the droplet-particle interface. Its evolution is determined from the particle motion governed by the Newton-Euler equations. The governing equations are solved numerically using a Finite Volume method on a fixed Cartesian grid. For demonstration purpose, the flows of particle-encapsulated droplets through a constricted microchannel and through a microchannel system are presented.

scholarly journals An Improved Procedure for Strongly Coupled Prediction of Sailing Yacht Performance

2021 ◽  
Vol 6 (01) ◽  
pp. 133-150
Author(s):  
A. Persson ◽  
L. Larsson ◽  
C. Finnsgård
Keyword(s):  
Free Surface ◽  
Wind Speed ◽  
Control Algorithm ◽  
Body Motion ◽  
Force Model ◽  
Strongly Coupled ◽  
Performance Predictions ◽  
Correct Alignment ◽  
Sailing Yacht ◽  
Background Grid

Abstract In this paper, an improved procedure for strongly coupled prediction of sailing yacht performance is developed. The procedure uses 3D RANS CFD to compute the hydrodynamic forces. When coupled to a rigid body motion solver and a sail force model, along with a rudder control algorithm, this allows sailing yacht performance to be predicted within CFD software. The procedure provides improved convergence when compared to a previously published method. The grid motion scheme, partially using overset grid techniques, means that correct alignment between the free surface and the background grid is ensured even at large heel angles. The capabilities are demonstrated with performance predictions for the SYRF 14 m yacht, at one true wind speed, over a range of true wind angles, with up- and downwind sailsets. The results are compared to predictions from the ORC-VPP for a yacht with similar main particulars.

Nonboundary Conforming Methods for Large-Eddy Simulations of Biological Flows

2005 ◽  
Vol 127 (5) ◽  
pp. 851-857 ◽  
Author(s):  
Elias Balaras ◽  
Jianming Yang
Keyword(s):  
Body Surface ◽  
Computational Algorithm ◽  
The Body ◽  
Large Eddy Simulations ◽  
Moving Boundaries ◽  
Lagrangian Formulation ◽  
Governing Equations ◽  
Solid Interface ◽  
Large Eddy ◽  
Biological Flows

In the present paper a computational algorithm suitable for large-eddy simulations of fluid/structure problems that are commonly encountered in biological flows is presented. It is based on a mixed Eurelian-Lagrangian formulation, where the governing equations are solved on a fixed grid, which is not aligned with the body surface, and the nonslip conditions are enforced via local reconstructions of the solution near the solid interface. With this strategy we can compute the flow around complex stationary/moving boundaries and at the same time maintain the efficiency and optimal conservation properties of the underlying Cartesian solver. A variety of examples, that establish the accuracy and range of applicability of the method are included.

Numerical Simulation of Interior Flow in Evaporation Droplet

2014 ◽  
Author(s):  
Qingming Dong ◽  
Zhentao Wang ◽  
Yonghui Zhang ◽  
Junfeng Wang
Keyword(s):  
Numerical Simulation ◽  
High Temperature ◽  
Internal Flow ◽  
Surface Force ◽  
Droplet Surface ◽  
Force Model ◽  
Marangoni Flow ◽  
High Temperature Area ◽  
Interior Flow ◽  
Temperature Area

In this present study, the VOF (Volume of Fluid) approach is adopted to capture the interface, and CSF (Continuum Surface Force) model to calculate the surface tension, and the governing equations are founded in numerical simulation of evaporating droplets. In this work, a water droplet is assumed to be suspending in high temperature air, and the gravity of a droplet is ignored. During evaporating process of the droplet, the internal circulation flow will be induced due to the gradient of temperature at the droplet surface. The interface flows from high temperature area to low temperature area, which pulls the liquid to produce convective flow inside the droplet called as Marangoni flow. Marangoni flow makes the temperature distribution tend to uniformity, which enhances heat transfer but weakens Marangoni flow in turn. So, during droplet evaporation, the internal flow is not steady.

Interactions Between High-Viscosity Droplets Deposited on a Surface: Experiments and Simulations

2012 ◽  
Author(s):  
J. Esmaeelpanah ◽  
A. Dalili ◽  
S. Chandra ◽  
J. Mostaghimi ◽  
H. C. Fan ◽  
...  
Keyword(s):  
Surface Tension ◽  
Free Surface ◽  
Piecewise Linear ◽  
Three Dimensional ◽  
Surface Force ◽  
Line Length ◽  
High Viscosity ◽  
Droplet Shape ◽  
Viscous Liquids ◽  
Straight Lines

A combined numerical and experimental investigation of coalescence of droplets of highly viscous liquids dropped on a surface has been carried out. Droplets of 87 wt% glycerin-in-water solutions with viscosity 110 centistokes were deposited sequentially in straight lines onto a flat, solid steel plate and droplet impact photographed. Impacting droplets spread on the surface until liquid surface tension and viscosity overcame inertial forces and the droplets recoiled, eventually reaching equilibrium. Droplet center-to-center distance was varied and droplet line length was measured from photographs. As droplet spacing was increased there was less interaction between the droplets. A three dimensional parallel code has been developed to simulate fluid flow and free surface interaction by solving the continuity, momentum and volume-of-fluid (VOF) equations. The two-step projection method was employed to solve the governing equations for the whole domain including both liquid and air phases. The continuum-surface-force (CSF) scheme was applied to model surface tension and the piecewise-linear-interface-construction (PLIC) technique used to reconstruct the free surface. Computer generated images of impacting droplets modeled droplet shape evolution correctly and compared well with photographs taken during experiments. Accurate predictions were obtained for droplet line length during spreading and at equilibrium.

Numerical Methods for Tracking Interfaces With Surface Tension in 3-D Mold Filling Processes

2002 ◽  
Author(s):  
Matthew W. Williams ◽  
Doug Kothe ◽  
Deniece Korzekwa ◽  
Phil Tubesing
Keyword(s):  
Surface Tension ◽  
Weber Number ◽  
Three Dimensional ◽  
Surface Force ◽  
Qualitative Behavior ◽  
Force Model ◽  
Simulation Tool ◽  
Software Simulation ◽  
Number Problem ◽  
Asymmetric Top

Gravity-pour casting processes are simulated for both low and high Weber number flows. The validation problems examined are a symmetric side-fill problem and a more complex asymmetric top-fill problem with flow over and obstacle. A recently developed continuum surface force model was implemented within a transient three-dimensional software simulation tool and applied to the low Weber number problem. The resulting simulations are compared with experiments that were conducted in order to validate current and future gravity-pour casting simulations. The simulations are found to capture much of the qualitative behavior of the complex three-dimensional flows.

Surface Tension Capability Within an Adaptively Refined Compressible Flow Code

2017 ◽  
Author(s):  
Z. Jibben ◽  
J. Velechovsky ◽  
T. Masser ◽  
M. Francois
Keyword(s):  
Surface Tension ◽  
Compressible Flow ◽  
Piecewise Linear ◽  
Surface Force ◽  
Force Model ◽  
Material Interface ◽  
Flow Solver ◽  
Interface Reconstruction ◽  
Volume Method ◽  
Inviscid Compressible Flow

We present a method to simulate surface tension between immiscible materials within an inviscid compressible flow solver. The material interface is represented using the volume of fluid technique with piecewise-linear interface reconstruction. We employ the continuum surface force model for surface tension, implemented in the context of the MUSCL-Hancock finite volume method for the Euler equations on an adaptively refined Eulerian mesh. We show results for droplet verification test cases.

scholarly journals A Computational Study on the Aerodynamic Influence of a Propeller on an MAV by Unstructured Overset Grid Technique and Low Mach Number Preconditioning

2012 ◽  
Vol 5 (1) ◽  
pp. 11-21 ◽  
Author(s):  
S. Deng ◽  
B. W. van Oudheusden ◽  
T. Xiao ◽  
H. Bijl
Keyword(s):  
Computational Study ◽  
Aerodynamic Performance ◽  
Moving Boundaries ◽  
Simulation Tool ◽  
Overset Grid ◽  
Low Mach Number ◽  
Speed Flow ◽  
Grid Approach ◽  
Preconditioning Method ◽  
Grid Technique

The influence of a propeller on the aerodynamic performance of an MAV is investigated using an unstructured overset grid technique. The flow regime of a fixed-wing MAV powered by a propeller contains both incompressible regions due to the low flight speed, as well as compressible flow areas near the propeller-tip region. In order to simulate all speed flow efficiently, a dual-time preconditioning method is employed in the present study. The methodology in this paper is verified as providing a reliable numerical simulation tool for all flow regimes, in the additional presence of moving boundaries, which is treated with an overset grid approach.

Mitigation of Biodynamic Response to Shock Loads Using Semi-Active Vertically Stroking Crew Seats

2010 ◽  
Author(s):  
Harinder J. Singh ◽  
Norman M. Wereley
Keyword(s):  
Human Body ◽  
Control Algorithm ◽  
Equations Of Motion ◽  
Comprehensive Analysis ◽  
Lumped Parameter Model ◽  
Force Model ◽  
Body Parts ◽  
Governing Equations ◽  
Lumped Parameter ◽  
Yield Force

This study addresses mitigation of biodynamic response due to an initial velocity impact of a vertically stroking crew seat using an adaptive magnetorheological energy absorber. Under consideration is a multiple degree-of-freedom detailed lumped parameter model of a human body falling with prescribed initial crash velocity (sink rate). The lumped parameter model of the human body consisted of four main parts: pelvis, upper torso, viscera and head. The governing equations of motion of a vertically stroking crew seat incorporating a human body were derived using parameters such as available damper stroke as well as MR yield force. The control algorithm for smooth landing of a rigid occupant was examined for compliant occupant and was modified accordingly. Four MR yield force models were analyzed to shape decelerations experienced by human body and an appropriate model was selected for comprehensive analysis. The simulated responses were analyzed with selected MR yield force model for a crew seat with an occupant corresponding to 90th percentile male at sink rates varying from 8 to 12 m/s. In addition, the mitigation of injuries to the human body parts due to load transmissions corresponding to crash velocities was also evaluated for the selected MR yield force model along with terminal conditions necessary for smooth landing.

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