scholarly journals Directional Water Wicking on a Metal Surface Patterned by Microchannels

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 490
Author(s):  
Nima Abbaspour ◽  
Philippe Beltrame ◽  
Marie-Christine Néel ◽  
Volker P. Schulz
Keyword(s):  
Contact Angle ◽  
Stokes Equations ◽  
Industrial Applications ◽  
Type Structure ◽  
Navier Stokes ◽  
Small Space ◽  
Dimensionless Numbers ◽  
Navier Stokes Equations ◽  
Static Contact ◽  
Insight Into

This work focuses on the simulation and experimental study of directional wicking of water on a surface structured by open microchannels. Stainless steel was chosen as the material for the structure motivated by industrial applications as fuel cells. Inspired by nature and literature, we designed a fin type structure. Using Selective Laser Melting (SLM) the fin type structure was manufactured additively with a resolution down to about 30 μm. The geometry was manufactured with three different scalings and both the experiments and the simulation show that the efficiency of the water transport depends on dimensionless numbers such as Reynolds and Capillary numbers. Full 3D numerical simulations of the multiphase Navier-Stokes equations using Volume of Fluid (VOF) and Lattice-Boltzmann (LBM) methods reproduce qualitatively the experimental results and provide new insight into the details of dynamics at small space and time scales. The influence of the static contact angle on the directional wicking was also studied. The simulation enabled estimation of the contact angle threshold beyond which transport vanishes in addition to the optimal contact angle for transport.

The Role of Coulombic Forces in Quasi-Two Dimensional Electrochemical Deposition

1996 ◽  
Vol 451 ◽  
Author(s):  
G. Marshall ◽  
P. Mocskos ◽  
F. Molina ◽  
S. Dengra
Keyword(s):  
Numerical Modeling ◽  
Pattern Formation ◽  
Electrochemical Deposition ◽  
Growth Pattern ◽  
Stokes Equations ◽  
Fluid Motion ◽  
Navier Stokes ◽  
Experimental Measurements ◽  
Dimensionless Numbers ◽  
Navier Stokes Equations

ABSTRACTRecent work demonstrates the relevant influence of convection during growth pattern formation in thin-layer electrochemical deposition. Convection is driven mainly by coulombic forces due to local charges at the tip of the aggregation and by buoyancy forces due to concentration gradients. Here we study through physical experiments and numerical modeling the regime under which coulombic forces are important. In the experimental measurements fluid motion near the growing tips of the deposit is visualized with neutrally buoyant latex spheres and its speed measured with videomicroscope tracking techniques and image processing software. The numerical modeling consists in the solution of the 2D dimensionless Nernst-Planck equations for ion concentrations, the Poisson equation for the electric field and the Navier-Stokes equations for the fluid flow, and a stochastic growth rule for ion deposition. A new set of dimensionless numbers governing electroconvection dominated flows is introduced. Preliminary experimental measurements and numerical results indicate that in the electroconvection dominated regime coulombic forces increase with the applied voltage, and their influence over growth pattern formation can be assessed with the magnitude of the dimensionless electric Froude number. It is suggested that when this number decreases the deposit morphology changes from fractal to dense branching.

Aerodynamic Origin of Rotor-Rotor Interaction Noise From Unducted Propulsors

2013 ◽  
Author(s):  
Florian Danner ◽  
Christofer Kendall-Torry ◽  
Hans-Peter Kau
Keyword(s):  
Stokes Equations ◽  
Navier Stokes ◽  
Propagation Characteristics ◽  
Propulsion Systems ◽  
Navier Stokes Equations ◽  
Pressure Distributions ◽  
Blade Row ◽  
Open Rotor ◽  
Blade Row Interaction ◽  
Insight Into

The sound arising from blade row interaction in open rotor propulsion systems is known to significantly contribute to overall noise emissions. The present paper therefore addresses the origination of rotor-rotor interaction noise from a pair of unducted counter-rotating fans. The focus is on the aerodynamic mechanisms that involve sound generation, in order to provide the physical understanding required to find noise-reducing means. Detailed insight into the underlying phenomena is provided on the basis of numerical simulations applying the unsteady Reynolds-averaged Navier-Stokes equations. The interaction mechanisms are identified by extracting the time-dependent disturbances of the flow field in the respective rotor relative frame of reference. Conclusions on the sources of interaction noise and potential noise-reducing means are drawn by evaluating polar directivities, blade surface pressure distributions and propagation characteristics.

Level Set Based Modeling of Electrowetting on Dielectrics Droplet

2012 ◽  
Vol 461 ◽  
pp. 138-141
Author(s):  
Yin Xia Chang ◽  
Si Xiang Zhang ◽  
Wei Zhou ◽  
Bao Liu
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Level Set ◽  
Stokes Equations ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Navier Stokes ◽  
Electric Force ◽  
Electrowetting On Dielectric ◽  
Static Contact

This paper discusses the modeling of Electrowetting On Dielectric (EWOD) device that moves fluid droplets through surface tension effects and electric force. Instead of using a static contact angle as most papers did, we take the dynamic contact angle into count by using expression proposed by Voinov and Tanner. Firstly, the level set model and its initial values is present. Then the governing equations are discussed, and the diffused format is adopted for density and viscosity varies to smooth over the interface. The detailed expression for surface tension and electric force are also described for Navier–Stokes equations. After presenting the boundary conditions, the steps of numerical implementation are detailed.

A CFD Model for Real Gas Flows

2000 ◽  
Author(s):  
Carlo Cravero ◽  
Antonio Satta
Keyword(s):  
Numerical Solutions ◽  
Turbulence Modeling ◽  
Stokes Equations ◽  
Fluid Model ◽  
Industrial Applications ◽  
Navier Stokes ◽  
Gas Flows ◽  
Navier Stokes Equations ◽  
Real Fluid ◽  
Solution Methods

Numerical solutions of Navier-Stokes equations are nowadays widely used for several industrial applications in different fields (aerodynamic, propulsion, naval, combustion, etc..), but the solution methods still require significant improvements especially in two aspects: turbulence modeling and fluid modeling. The paper describes in some detail a real fluid model based on Redlich-Kwong-Aungier equation of state and its implementation into a Navier-Stokes solver developed by the authors for turbomachinery flows analysis.

scholarly journals 3D Flow Structures and Operating Characteristic of an Industrial Fluid Coupling

1995 ◽  
Author(s):  
H. Huitenga ◽  
T. Formanski ◽  
N. K. Mitra ◽  
M. Fiebig
Keyword(s):  
Turbulence Modeling ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Complex Flow ◽  
Navier Stokes Equations ◽  
Laminar And Turbulent Flow ◽  
Fluid Coupling ◽  
Complex Flow Structure ◽  
Insight Into

A liquid circulating between an input rotor and an output rotor transmits power in a fluid coupling. Insight into the flow field is required to influence the transmission behaviour. Parameter studies of model geometries of fluid couplings were presented previously. Laminar and turbulent flow fields and characteristic curves of an actual industrial fluid coupling have been computed from the numerical solution of the three-dimensional, nonsteady Navier-Stokes equations on a body fitted rotating coordinate system. Results show the complex flow structure and vortices that determine the transported angular momentum. Comparison with measured torque suggests that the turbulence modeling by standard k-ϵ model may be inadequate at large slip.

A Numerical Simulation of a Brush Seal Section and Some Experimental Results

1995 ◽  
Vol 117 (1) ◽  
pp. 190-202 ◽  
Author(s):  
M. J. Braun ◽  
V. V. Kudriavtsev
Keyword(s):  
Stokes Equations ◽  
Numerical Models ◽  
Navier Stokes ◽  
Local Pressure ◽  
Local Flow ◽  
Navier Stokes Equations ◽  
Pressure Fields ◽  
Brush Seal ◽  
Flow Phenomena ◽  
Insight Into

The brush seal technology represents quite a promising advance in the effort of construction of more efficient, and possibly smaller size engines. Conclusions of recent workshops determined that while the brush seal works well, there is a need to improve its performance characteristics. The considerable amount of experimental work performed to date has indicated the importance of the local flow phenomena in the global sealing process performance of the brush (Braun et al., 1990a, 1991b, 1992; Hendricks et al., 1991a). The distributed flow and pressure fields are thus of vital importance for the prediction of the possible sudden failure of the brush seal under unexpected local “pressure hikes.” It is in this context that the authors developed a numerical, two-dimensional time accurate dependent formulation of the Navier–Stokes equations with constant properties, and included the effects of inertia, viscous, and pressure terms. The algorithm is applied to a set of noncompliant multirow, multicolumn pin configurations that are similar to the ones found in an idealized brush seal configuration. While the numerical parametric investigation aims at establishing the occurrence of major flow patterns and associated pressure maps, the experimental portion of the paper is aimed at gaining further insight into the relevant flow structures, and thus guiding the development of the mathematical and numerical models.

NUMERICAL STUDY OF ASYMMETRIC EFFECT ON A PITCHING FOIL

2009 ◽  
Vol 20 (10) ◽  
pp. 1663-1680 ◽  
Author(s):  
QING XIAO ◽  
WEI LIAO
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Navier Stokes ◽  
Asymmetric Effect ◽  
Low Thrust ◽  
Navier Stokes Equations ◽  
Propulsion Performance ◽  
Karman Vortex ◽  
Oscillating Motion ◽  
Insight Into

This study investigates numerically the effect of asymmetric sinusoidal oscillating motion on the propulsion performance of a pitching foil and attempts to gain insight in whether the low thrust generated by pure pitching could be improved by asymmetric motion. The propulsion performance and flow structure are explored by solving the unsteady Navier–Stokes equations. Computations are conducted for a range of oscillation frequency, pitching amplitude, and asymmetry. The results show that the higher asymmetry can induce the stronger reverse Von Karman vortex in the wake, which in turn leads to the increased thrust. However, the propulsion efficiency reduces as increasing asymmetry. Computed results are further adopted to shed insight into the mechanism of thrust enhancement.

Numerical Study of Liquid Slug Stability During Adiabatic Two Phase Flow Inside a Minichannel

2007 ◽  
Author(s):  
A. Mukherjee ◽  
J. S. Allen
Keyword(s):  
Contact Angle ◽  
Continuity Equation ◽  
Stokes Equations ◽  
Numerical Study ◽  
Navier Stokes ◽  
Phase Flow ◽  
Liquid Slug ◽  
Two Phase ◽  
Navier Stokes Equations ◽  
Liquid Plug

The present study is performed to analyze stability of a liquid meniscus inside a microchannel. A liquid plug is placed inside a microchannel and the shape and stability of upstream and downstream interfaces have been studied for different airflow rates. The thickness of the liquid plug and the contact angle has been varied systematically. In the numerical model the complete Navier-Stokes equations along with continuity equation are solved using the SIMPLER method. The liquid vapor interface is captured using the level set technique. The liquid plug is seen to move downstream along with the air and surface instabilities are noted at the upstream and downstream interfaces. At low contact angle, water is found to accumulate at the channel corners due to capillary forces causing the slug to disintegrate. The numerical results are found to be qualitatively similar to experimental data.

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