Leveling of a Line of Paint Droplets on a Surface

2014 ◽  
Author(s):  
J. Esmaeelpanah ◽  
A. Dalili ◽  
S. Chandra ◽  
J. Mostaghimi
Keyword(s):  
Liquid Film ◽  
Time Scale ◽  
Water Solution ◽  
Three Dimensional ◽  
Free Surface Flow ◽  
High Viscosity ◽  
Surface Flow ◽  
Experimental Measurements ◽  
Thickness Change ◽  
Model Free

When liquid droplets are sprayed onto a solid surface during spray painting and coating, defects may be created due to non-uniformity of the liquid film. The time scale required for leveling the liquid film is of utmost importance. In this paper, the leveling of a droplet line was modeled numerically using a three-dimensional parallel code, based on a two-step projection method with a volume-of-fluid technique used to model free surface flow. Simulations and experiments were performed with a high viscosity liquid (87%wt glycerin in water solution and commercial paint) where a droplet line was deposited with varying center-to-center distance between the droplets and the time scale for leveling was measured. Predictions from the numerical model for droplet line thickness and variation in the thickness agreed well with experimental measurements. Simulation and experimental measurements clearly showed that the drastic portion of thickness change happened in the first 30 seconds. When the droplets were dispensed close to one another (initially thicker films), there was a lot of interaction between the droplets and therefore there was a huge variation in the thickness of the droplet line until the variation died down and the line was level. On the other hand, when droplets were dispensed further apart (initially thinner films), there was less interaction between the droplets and therefore less variation of the film thickness from the beginning and the leveling occurred much sooner.

scholarly journals A computational investigation of the hydrodynamics of the Badush dam in northern Iraq

2018 ◽  
Vol 240 ◽  
pp. 04009
Author(s):  
Younis Saida Saeedrashed ◽  
Ali Cemal Benim
Keyword(s):  
Three Dimensional ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Dam Failure ◽  
Northern Iraq ◽  
Digital Elevation ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Through ◽  
Elevation Model ◽  
Bottom Outlets

A computational analysis of the hydrodynamics of the Badush dam in Iraq is presented, which is planned to be reconstructed as a repulse dam, to prevent the Mosul city, in case of a failure of the Mosul dam. Computational Fluid Dynamics (CFD) is applied in combination with Geometric Information System (GIS) and Digital Elevation Model (DEM). In the first part of the study, a hydrologic study of a possible Mosul dam failure is performed, predicting the important parameters for a possible flooding of Mosul city. Here, a two-dimensional, depth-averaged shallow water equations are used to formulate the flow. Based on GIS and DEM, the required reservoir size and the water level of the Badush dam are predicted, for its acting as a repulse dam. Subsequently, a computational model of the reconstructed Badush dam is developed, combining the proposed construction with the local geographic topology to achieve a perfect fit. Finally, the water flow through the bottom outlets and stilling basin of the proposed dam is calculated by an unsteady, three-dimensional CFD analysis of the turbulent, free-surface flow. The CFD model is validated by comparing the predictions with measurements obtained on a physical model, where a quite satisfactory agreement is observed.

scholarly journals Sheared free-surface flow over three-dimensional obstructions of finite amplitude

2019 ◽  
Vol 878 ◽  
pp. 740-767
Author(s):  
Andreas H. Akselsen ◽  
Simen Å. Ellingsen
Keyword(s):  
Perturbation Technique ◽  
Three Dimensional ◽  
Free Surface Flow ◽  
Radiation Condition ◽  
Finite Amplitude ◽  
Higher Order ◽  
Surface Flow ◽  
Current Profile ◽  
Bottom Boundary Condition ◽  
Lord Kelvin

When shallow water flows over uneven bathymetry, the water surface is modulated. This type of problem has been revisited numerous times since it was first studied by Lord Kelvin in 1886. Our study analytically examines currents whose unperturbed velocity profile $U(z)$ follows a power law $z^{q}$, flowing over a three-dimensional uneven bed. This particular form of $U$, which can model a miscellany of realistic flows, allows explicit analytical solutions. Arbitrary bed shapes can readily be imposed via Fourier’s theorem provided their steepness is moderate. Three-dimensional vorticity–bathymetry interaction effects are evident when the flow makes an oblique angle with a sinusoidally corrugated bed. Streamlines are found to twist and the fluid particle drift is redirected away from the direction of the unperturbed current. Furthermore, a perturbation technique is developed which satisfies the bottom boundary condition to arbitrary order also for large-amplitude obstructions which penetrate well into the current profile. This introduces higher-order harmonics of the bathymetry amplitude. States of resonance for first- and higher-order harmonics are readily calculated. Although the method is theoretically restricted to bathymetries of moderate inclination, a wide variety of steeper obstructions are satisfactorily represented by the method, even provoking occurrences of recirculation. All expressions are analytically explicit and sequential fast Fourier transformations ensure quick and easy computation for arbitrary three-dimensional bathymetries. A method for separating near and far fields ensures computational convergence under the appropriate radiation condition.

scholarly journals CFD Code Validation against Stratified Air-Water Flow Experimental Data

2008 ◽  
Vol 2008 ◽  
pp. 1-7 ◽  
Author(s):  
F. Terzuoli ◽  
M. C. Galassi ◽  
D. Mazzini ◽  
F. D'Auria
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Water Flow ◽  
Nuclear Reactor ◽  
Cold Water ◽  
Three Dimensional ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Two Phase ◽  
Code Validation

Pressurized thermal shock (PTS) modelling has been identified as one of the most important industrial needs related to nuclear reactor safety. A severe PTS scenario limiting the reactor pressure vessel (RPV) lifetime is the cold water emergency core cooling (ECC) injection into the cold leg during a loss of coolant accident (LOCA). Since it represents a big challenge for numerical simulations, this scenario was selected within the European Platform for Nuclear Reactor Simulations (NURESIM) Integrated Project as a reference two-phase problem for computational fluid dynamics (CFDs) code validation. This paper presents a CFD analysis of a stratified air-water flow experimental investigation performed at the Institut de Mécanique des Fluides de Toulouse in 1985, which shares some common physical features with the ECC injection in PWR cold leg. Numerical simulations have been carried out with two commercial codes (Fluent and Ansys CFX), and a research code (NEPTUNE CFD). The aim of this work, carried out at the University of Pisa within the NURESIM IP, is to validate the free surface flow model implemented in the codes against experimental data, and to perform code-to-code benchmarking. Obtained results suggest the relevance of three-dimensional effects and stress the importance of a suitable interface drag modelling.

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