Improved models of surface tension and air resistance for multiphysics particle method

2017 ◽  
Vol 55 (2) ◽  
pp. 169-180 ◽  
Author(s):  
Kenta Inagaki
Keyword(s):  
Surface Tension ◽  
Particle Method ◽  
Air Resistance

Spreading-Droplet Simulation With Surface Tension Model Using Inter-Particle Force in Particle Method

2013 ◽  
Author(s):  
Eiji Ishii ◽  
Taisuke Sugii
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Dynamic Contact Angle ◽  
Particle Method ◽  
Dynamic Contact ◽  
Contact Angles ◽  
Particle Methods ◽  
Static Contact ◽  
Particle Force ◽  
Surface Tension Model

Predicting the spreading behavior of droplets on a wall is important for designing micro/nano devices used for reagent dispensation in micro-electro-mechanical systems, printing processes of ink-jet printers, and condensation of droplets on a wall during spray forming in atomizers. Particle methods are useful for simulating the behavior of many droplets generated by micro/nano devices in practical computational time; the motion of each droplet is simulated using a group of particles, and no particles are assigned in the gas region if interactions between the droplets and gas are weak. Furthermore, liquid-gas interfaces obtained from the particle method remain sharp by using the Lagrangian description. However, conventional surface tension models used in the particle methods are used for predicting the static contact angle at a three-phase interface, not for predicting the dynamic contact angle. The dynamic contact angle defines the shape of a spreading droplet on a wall. We previously developed a surface tension model using inter-particle force in the particle method; the static contact angle of droplets on the wall was verified at various contact angles, and the heights of droplets agreed well with those obtained theoretically. In this study, we applied our surface tension model to the simulation of a spreading droplet on a wall. The simulated dynamic contact angles for some Weber numbers were compared with those measured by Šikalo et al, and they agreed well. Our surface tension model was useful for simulating droplet motion under static and dynamic conditions.

3D Simulation of Drop Impact on Dry Surface Using SPH Method

2018 ◽  
Vol 15 (03) ◽  
pp. 1850011 ◽  
Author(s):  
Xiufeng Yang ◽  
Song-Charng Kong
Keyword(s):  
Surface Tension ◽  
Impact Velocity ◽  
Free Particle ◽  
Particle Method ◽  
Drop Impact ◽  
Sph Method ◽  
Spherical Drop ◽  
Mesh Free ◽  
Particle Hydrodynamics ◽  
The Impact

The purpose of this paper is to present and illustrate a smoothed particle hydrodynamics (SPH) method to study the process of a drop impacting on a dry solid surface. SPH is a Lagrangian mesh-free particle method that offers advantages in modeling the evolution of the liquid surface during drop impact. A new surface tension model is used. The artificial viscosity is also used, which is demonstrated to be, approximately, a linear function of the dynamic viscosity of the liquid. The SPH method is used to simulate different liquid drops impacting on dry surfaces. The numerical results agree with experimental data obtained from the literature. The influence of various parameters on the drop impact, including impact velocity, diameter, viscosity, surface tension, and density of the drop, is also studied. The results show that the dimensionless spreading diameter of the drop increases if the impact velocity, diameter, or density increases, while the increase in viscosity and surface tension decreases the spreading diameter. The results indicate that the drop impact depends more strongly on the viscosity and impact velocity than on the diameter, surface tension, and density of the drop. In addition to the impact of a spherical drop, the impact of an ellipsoidal drop on a dry surface is also studied. The results show that the aspect ratio of the drop has a significant influence on the outcome of drop impact.

Surface Tension Model for Particle Method Using Inter-Particle Force Derived From Potential Energy

2012 ◽  
Author(s):  
Eiji Ishii ◽  
Taisuke Sugii
Keyword(s):  
Surface Tension ◽  
Fluid Flow ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Particle Method ◽  
Surface Force ◽  
Continuous Surface ◽  
Particle Force ◽  
Surface Tension Model

Fluid-flow simulation within micro/nano spaces is essential for designing micro/nano devices, such as those in micro-electro-mechanical systems and nanoimprint processes. Surface tension is a dominant force in the fluid flow within micro/nano spaces. Surface-tension models can be classified into two groups: models based on continuous surface force in immiscible phases, and models based on inter-particle force in miscible phases. The surface-tension model based on inter-particle force for modeling interactions between materials would fit fluid-flow simulation within micro/nano spaces better than the surface-tension model based on continuous surface force. We developed a surface tension model using inter-particle force for use with a particle method in a past study. However, workings of inter-particle forces in miscible phases were not verified. Furthermore, accuracy in three-dimensional simulation needed to be verified. These subjects were verified in this study using simple benchmark tests. First, cohesion based on potential energy was validated to qualitatively check the workings of inter-particle force. The phase separation from the mixed two-phase flow due to inter-particle force was simulated. Next, the inter-particle force at the gas-liquid interface was quantitatively verified using the theory of the Young-Laplace equation; the pressure in a droplet was compared in two- and three-dimensional simulations, and the predicted pressures in a droplet agreed well with this theory. The inter-particle force at the gas-liquid-solid interface for the wall adhesion of a droplet was also verified; the results for wall adhesion in three-dimensional space agreed much better than that in two-dimensional space. We found that our surface tension model was useful for simulating the fluid flow within micro/nano spaces.

Late-Fuel Simulation Near Nozzle Outlet of Fuel Injector During Closing Valve

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Eiji Ishii ◽  
Kazuki Yoshimura ◽  
Yoshihito Yasukawa ◽  
Hideharu Ehara
Keyword(s):  
Surface Tension ◽  
Hybrid Method ◽  
Particle Method ◽  
Particulate Matters ◽  
Fuel Injector ◽  
Nozzle Outlet ◽  
Flow Paths ◽  
Fuel Injectors ◽  
Low Speed ◽  
Fuel Behavior

Late fuel during closing of the valve of a fuel injector and fuel films stuck on the wall around the nozzle outlets are sources of particulate matters (PM). In this study, we focused on the effects of the valve motions on the late fuel and the fuel films stuck on the walls around the nozzle outlets. We previously developed a particle/grid hybrid method: fuel flows within the flow paths of fuel injectors were simulated by a front capturing method, and liquid-column breakup at the nozzle outlets was mainly simulated by a particle method. The velocity at the inlet boundary of a fuel injector was controlled in order to affect the valve motions on the late-fuel behavior. The simulated late fuel broke up with surface tension around the time of zero-stroke position of the valve, then liquid columns and coarse droplets formed after the bounds of the valve, and finally only coarse droplets were left. We found that the late fuel was generated by low-speed fuel-flows through the nozzles during the bounds of the valve. The effect of the bounds of the valve on the fuel films stuck on the wall around the nozzle outlets was also studied with a simulation that removed the bounds of the valve. The volume of the fuel films stuck on the wall of the nozzle outlets decreased without the bounds of the valve.

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