Numerical Analysis of Droplet Impact, Deformation of a Droplet Train in Direct Print Technology

2013 ◽  
Author(s):  
Muhammad Noman Hasan ◽  
Morteza Vatani ◽  
Yanfeng Lu ◽  
Ho-Chan Kim ◽  
Jae-Won Choi
Keyword(s):  
Numerical Analysis ◽  
Liquid Film ◽  
Adaptive Mesh Refinement ◽  
Liquid Droplet ◽  
Adaptive Mesh ◽  
Droplet Impact ◽  
Experimental Result ◽  
Interface Tracking ◽  
Two Phase ◽  
Impact Deformation

Numerical analysis for a two dimensional case of two–phase fluid flow has been performed to investigate droplet impact, deformation for a droplet train. The purpose of this investigation is to study the phenomenon of liquid droplet impact on a liquid film created by a flattened droplet and the consequent deformation of the film while merging and advancing of the moving front of the film, during the manufacturing processes with jetting technology such as a direct printing process and inkjet printing. This investigation focuses on the analysis of interface tracking and the change of shape for an impacted droplet of a dispensed material. Investigations have been made on the performance of an adaptive quadtree spatial discretization with geometrical Volume–Of–Fluid (VOF) interface representation, continuum–surface–force surface tension formulation and height-function curvature estimation for interface tracking during droplet impact deformation and coalescence of droplet and liquid film produced by flattened droplets to form a printed line. Gerris flow solver, an open source finite volume code, has been used for the numerical analysis which uses a quadtree based adaptive mesh refinement for 2D. The results have been compared with an experimental result from the literature. The investigation has been performed for Reynolds number, Re of 21.1; Weber number, We of 93.8, and contact angle, θ of 30°. For the experimental result considered, the frequency of jetting is 12 kHz.

High Fidelity Simulation of the Spray Generated by a Realistic Swirling Flow Injector

2013 ◽  
Author(s):  
X. Li ◽  
M. C. Soteriou ◽  
W. Kim ◽  
J. M. Cohen ◽  
M. Herrmann ◽  
...  
Keyword(s):  
Adaptive Mesh Refinement ◽  
Fuel Injection ◽  
Swirling Flow ◽  
Density Ratio ◽  
Adaptive Mesh ◽  
Uniform Grid ◽  
High Fidelity ◽  
Engine Fuel ◽  
Time Step ◽  
Two Phase

Practical aero-engine fuel injection systems are highly complicated, combining complex fuel atomizer and air swirling elements to achieve good fuel-air mixing as well as long residence time in order to enhance both combustion efficiency and stability. While detailed understanding of the multiphase flow processes occurring in a realistic injector has been limited due to the complex geometries and the challenges in near-field measurements, high fidelity, first principles simulation offers, for the first time, the potential for a comprehensive physics-based understanding. In this work, such simulations have been performed to investigate the spray atomization and subsequent droplet transport in a swirling air stream generated by a complex multi-nozzle/swirler combination. A Coupled Level Set and Volume Of Fluid (CLSVOF) approach is used to directly capture the liquid-gas interface and an embedded boundary (EB) method is applied to flexibly handle the complex injector geometry. The ghost fluid (GF) method is also used to facilitate simulations at realistic fuel-air density ratio. Adaptive mesh refinement (AMR) and Lagrangian droplet models are used to efficiently resolve the multi-scale processes. To alleviate the global constraint on the time-step imposed by locally activated AMR near liquid jets, a separate AMR simulation focusing on jet atomization was performed for relatively short physical time and the resulting Lagrangian droplets are coupled into another simulation on a uniform grid at larger time-steps. The high cost simulations were performed at the U.S. Department of Defense high performance computing facilities using over 5000 processors. Experiments at the same flow conditions were conducted at UTRC. The simulation details of flow velocity and vorticity due to the interaction of the fuel jet and swirling air are presented. The velocity magnitude is compared with experimental measurement at two downstream planes. The two-phase spray spreading is compared with experimental images and the flow details are further analyzed to enhance understanding of the complex physics.

Experimental Investigation of Falling Liquid Film in Vertical Downward Two-Phase Pipe Flow

2012 ◽  
Author(s):  
Jose M. Lopez ◽  
Ram Mohan ◽  
Ovadia Shoham ◽  
Shoubo Wang ◽  
Gene Kouba
Keyword(s):  
Film Thickness ◽  
Liquid Film ◽  
Two Phase Flow ◽  
Liquid Velocity ◽  
Liquid Droplet ◽  
Mineral Oil ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Measurements ◽  
Falling Liquid Film

In this research the hydrodynamics of falling liquid film in a vertical downward two-phase flow (liquid-gas) is experimentally studied. The 4 inch clear PVC test section is 6.1 meters long, with a length to diameter ratio (L/D) of 64. The fluids utilized are compressed air, water, Conosol mineral oil (light oil) and Drake mineral oil (heavy oil). The superficial liquid velocities tested range from 12 to 72 cm/s while the superficial gas velocities range from 0.2 to 29 cm/s. The vertical facility is equipped with the state-of-the-art instrumentation for two-phase flow measurements, the capacitance Wire-Mesh Sensor (WMS), allowing two-phase flow measurements with conducting and non conducting fluids. Experimental results show that the liquid film thickness has a quasi-linear relationship with the superficial liquid velocity for the air-water case. For the air-oil cases, at superficial liquid velocities higher than 50 cm/s, the liquid film thickness trend is affected by the liquid droplet entrainment. Furthermore, it was found that the liquid droplet entrainment increases as the superficial liquid velocity increases or the surface tension decreases. Details of the liquid droplets traveling in the gas core, wave formation, wave breakup and film thickness evolution are observed in the WMS phase reconstruction.

High Fidelity Simulation of the Spray Generated by a Realistic Swirling Flow Injector

2014 ◽  
Vol 136 (7) ◽  
Author(s):  
Xiaoyi Li ◽  
Marios C. Soteriou ◽  
Wookyung Kim ◽  
Jeffrey M. Cohen
Keyword(s):  
Adaptive Mesh Refinement ◽  
Fuel Injection ◽  
Swirling Flow ◽  
Density Ratio ◽  
Adaptive Mesh ◽  
Uniform Grid ◽  
High Fidelity ◽  
Engine Fuel ◽  
Time Step ◽  
Two Phase

Practical aero-engine fuel injection systems are highly complicated, combining complex fuel atomizer and air swirling elements to achieve good fuel-air mixing and long residence time in order to enhance both the combustion efficiency and stability. While a detailed understanding of the multiphase flow processes occurring in a realistic injector has been limited due to the complex geometries and the challenges in near-field measurements, high fidelity, first principles simulation offers, for the first time, the potential for a comprehensive physics-based understanding. In this work, such simulations have been performed to investigate the spray atomization and subsequent droplet transport in a swirling air stream generated by a complex multinozzle/swirler combination. A coupled level set and volume of fluid (CLSVOF) approach is used to directly capture the liquid-gas interface and an embedded boundary (EB) method is applied to flexibly handle the complex injector geometry. The ghost fluid (GF) method is also used to facilitate simulations at a realistic fuel-air density ratio. Adaptive mesh refinement (AMR) and Lagrangian droplet models are used to efficiently resolve the multiscale processes. To alleviate the global constraint on the time step imposed by the locally activated AMR near liquid jets, a separate AMR simulation focusing on jet atomization was performed for a relatively short physical time and the resulting Lagrangian droplets are coupled into another simulation on a uniform grid at larger time-steps. The high cost simulations were performed at the U.S. Department of Defense high performance computing facilities using over 5000 processors. Experiments at the same flow conditions were conducted at the United Technologies Research Center (UTRC). The simulation details of flow velocity and vorticity due to the interaction of the fuel jet and swirling air are presented. The velocity magnitude is compared with the experimental measurement at two downstream planes. The two-phase spray spreading is compared with experimental images and the flow details are further analyzed to enhance the understanding of the complex physics.

An adaptive mesh refinement algorithm for compressible two-phase flow in porous media

2011 ◽  
Vol 16 (3) ◽  
pp. 577-592 ◽  
Author(s):  
George Shu Heng Pau ◽  
John B. Bell ◽  
Ann S. Almgren ◽  
Kirsten M. Fagnan ◽  
Michael J. Lijewski
Keyword(s):  
Porous Media ◽  
Adaptive Mesh Refinement ◽  
Two Phase Flow ◽  
Mesh Refinement ◽  
Adaptive Mesh ◽  
Flow In Porous Media ◽  
Phase Flow ◽  
Two Phase ◽  
Refinement Algorithm

A numerical analysis of air entrapment during droplet impact on an immiscible liquid film

2020 ◽  
Vol 124 ◽  
pp. 103175 ◽  
Author(s):  
Firoozeh Yeganehdoust ◽  
Reza Attarzadeh ◽  
Ida Karimfazli ◽  
Ali Dolatabadi
Keyword(s):  
Numerical Analysis ◽  
Liquid Film ◽  
Immiscible Liquid ◽  
Droplet Impact ◽  
Air Entrapment
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