Air-Assisted Atomization at Constant Mass and Momentum Flow Rate: Investigation into the Ambient Pressure Influence With the Smoothed Particle Hydrodynamics Method

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Geoffroy Chaussonnet ◽  
Shreyas Joshi ◽  
Simon Wachter ◽  
Rainer Koch ◽  
Tobias Jakobs ◽  
...  
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
High Speed ◽  
Ambient Pressure ◽  
Velocity Ratio ◽  
Flux Ratio ◽  
Mean Velocity ◽  
Air Stream ◽  
Fragmentation Spectrum ◽  
Particle Hydrodynamics ◽  
Smoothed Particle

Abstract A twin-fluid atomizer configuration is simulated by means of the two-dimensional (2D) weakly compressible smoothed particle hydrodynamics (SPH) method and compared to experiments. The gas-to-liquid ratio (GLR), the momentum flux ratio, and the velocity ratio are set constant for different ambient pressures, which lead to different gaseous flow sections. The objectives of this study are (i) to investigate the effect of ambient pressure at constant global parameters and (ii) to verify the capability of 2D SPH to qualitatively predict the proper disintegration mechanism and to recover the correct evolution of the spray characteristics. The setup consists of an axial liquid jet of water fragmented by a coflowing high-speed air stream (Ug = 80 m/s) in a pressurized atmosphere up to 16 bar. The results are compared to the experiment and presented in terms of (i) mean velocity profiles, (ii) drop size distributions, and (iii) Sauter mean diameter (SMD) of the spray. It is found that there exists an optimal pressure to minimize the mean size of the spray droplets. Finally, two new quantities related to atomization are presented: (i) the breakup activity that quantifies the number of breakup events per time and volume unit and (ii) the fragmentation spectrum of the whole breakup chain, which characterize the cascade phenomenon in terms of probability. The breakup activity confirms the presence of the optimal pressure, and the fragmentation spectrum gives information on the type of breakup, depending on the ambient pressure.

scholarly journals Air-Assisted Atomization at Constant Mass and Momentum Flow Rate: Investigation of the Ambient Pressure Influence With the SPH Method

2019 ◽  
Author(s):  
G. Chaussonnet ◽  
S. Joshi ◽  
S. Wachter ◽  
R. Koch ◽  
T. Jakobs ◽  
...  
Keyword(s):  
High Speed ◽  
Ambient Pressure ◽  
Velocity Ratio ◽  
Flux Ratio ◽  
Mean Velocity ◽  
Air Stream ◽  
Fragmentation Spectrum ◽  
Particle Hydrodynamics ◽  
Volume Unit ◽  
Drop Size Distributions

Abstract A twin-fluid atomizer configuration is simulated by means of the 2D weakly-compressible Smooth Particle Hydrodynamics method, and compared to experiments. The Gas-to-Liquid-Ratio, the momentum flux ratio and the velocity ratio are set constant for different ambient pressures, which leads to different gaseous flow sections. The objectives of this study are to (i) investigate the effect of ambient pressure at constant global parameters, and (ii) to verify the capability of 2D SPH to qualitatively predict the proper disintegration mechanism and to recover the correct evolution of the spray characteristics. The setup consists of an axial liquid jet of water fragmented by a co-flowing high-speed air stream (Ug = 80 m/s) in a pressurized atmosphere up to 16 bar. The results are compared to the experiment, and presented in terms of (i) mean velocity profiles, (ii) drop size distributions and (iii) Sauter Mean Diameter of the spray. It is found that there exists an optimal pressure to minimize the mean size of the spray droplets. Finally, two new quantities related to atomization are presented: (i) the breakup activity that quantifies the number of breakup events per time and volume unit and (ii) the fragmentation spectrum of the whole breakup chain, which characterizes the cascade phenomenon in terms of probability. The breakup activity confirms the presence of the optimal pressure and the fragmentation spectrum gives information on the type of breakup, depending on the ambient pressure.

scholarly journals Progress in the Smoothed Particle Hydrodynamics Method to Simulate and Post-process Numerical Simulations of Annular Airblast Atomizers

2020 ◽  
Vol 105 (4) ◽  
pp. 1119-1147
Author(s):  
G. Chaussonnet ◽  
T. Dauch ◽  
M. Keller ◽  
M. Okraschevski ◽  
C. Ates ◽  
...  
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Flux Ratio ◽  
Liquid Sheet ◽  
Sph Method ◽  
Post Process ◽  
Finite Time Lyapunov Exponent ◽  
Fragmentation Spectrum ◽  
Particle Hydrodynamics ◽  
Primary Breakup ◽  
Smoothed Particle

AbstractThis paper illustrates recent progresses in the development of the smoothed particle hydrodynamics (SPH) method to simulate and post-process liquid spray generation. The simulation of a generic annular airblast atomizer is presented, in which a liquid sheet is fragmented by two concentric counter swirling air streams. The accent is put on how the SPH method can bridge the gap between the CAD geometry of a nozzle and its characterization, in terms of spray characteristics and dynamics. In addition, the Lagrangian nature of the SPH method allows to extract additional data to give further insight in the spraying process. First, the sequential breakup events can be tracked from one large liquid blob to very fine stable droplets. This is herein called the tree of fragmentation. From this tree of fragmentation, abstract quantities can be drawn such as the breakup activity and the fragmentation spectrum. Second, the Lagrangian coherent structures in the turbulent flow can be determined easily with the finite-time Lyapunov exponent (FTLE). The extraction of the FTLE is particularly feasible in the SPH framework. Finally, it is pointed out that there is no universal and ultimate non-dimensional number that can characterize airblast primary breakup. Depending on the field of interest, a non-dimensional number (e.g. Weber number) might be more appropriate than another one (e.g. momentum flux ratio) to characterize the regime, and vice versa.

Numerical modelling of oil distribution and churning gear power losses of gearboxes by smoothed particle hydrodynamics

2018 ◽  
Vol 233 (1) ◽  
pp. 74-86 ◽  
Author(s):  
Hua Liu ◽  
Ghaith Arfaoui ◽  
Milos Stanic ◽  
Laurent Montigny ◽  
Thomas Jurkschat ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Smoothed Particle Hydrodynamics ◽  
High Speed ◽  
Operational Reliability ◽  
Power Losses ◽  
Oil Distribution ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Smoothed Particle Hydrodynamics Method

Sufficient oil supply of all machine elements in gearboxes is usually required to avoid damage during operation. Quite frequently, transmissions are conservatively designed with an oversupply of oil to guarantee operational reliability. An oversupply of oil results in an unnecessarily high amount of oil being kept in motion, which in turn leads to excessive hydraulic gear power losses. In high-speed gearboxes in particular, churning losses can contribute greatly to the total power losses. Further detailed information on the oil distribution in gearboxes is needed in order to increase the efficiency and operational reliability of gearboxes. Computational Fluid Dynamics methods provide a flexible way of investigating oil behaviour in transmissions with almost no restrictions regarding geometry and operating conditions. Generally, there are two main methods of computational fluid dynamics simulation in gearboxes: the traditional finite-volume based method (Eulerian approach) and the mesh-free particle-based method (Lagrangian approach). In this work, a computational fluid dynamics model based on the particle-based smoothed particle hydrodynamics method is built to investigate the oil distribution and churning losses of a dip-lubricated single stage gearbox on an efficiency gear test rig. Results are shown and discussed for different rotational speeds and oil temperatures. The smoothed particle hydrodynamics method provides a high potential of predicting the oil distribution of modern dip-lubricated transmission systems. Comparisons with high-speed camera recordings show good agreement. However, the method shows a need for improvement in churning loss prediction.

Smoothed Particle Hydrodynamics Simulation of Oil-Jet Gear Interaction

2017 ◽  
Author(s):  
Marc C. Keller ◽  
Samuel Braun ◽  
Lars Wieth ◽  
Geoffroy Chaussonnet ◽  
Thilo F. Dauch ◽  
...  
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
High Speed ◽  
Single Phase ◽  
Jet Impingement ◽  
Spur Gear ◽  
Computational Time ◽  
Qualitative Comparison ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Oil Jet

In this paper the complex two-phase flow during oil-jet impingement on a rotating spur gear is investigated using the meshless Smoothed Particle Hydrodynamics (SPH) method. A comparison of single-phase SPH to multi-phase SPH simulation and the application of the Volume of Fluid method on the basis of a two-dimensional setup is drawn. The results of the different approaches are compared regarding the predicted flow phenomenology and computational effort. It is shown that the application of single-phase SPH is justified and that this approach is superior in computational time, enabling faster simulations. In a next step, a three-dimensional single-phase SPH setup is exploited to predict the flow phenomena during the impingement of an oil-jet on a spur gear for various jet inclination angles. Thereby, a significant effect of the inclination angle on the oil spreading and splashing process is revealed. Finally, a qualitative comparison to an experimental high-speed image shows good accordance.

Numerical Simulation of Severe Plastic Deformation of Titanium Specimens under Dynamic Channel Pressing

2014 ◽  
Vol 1040 ◽  
pp. 107-112 ◽  
Author(s):  
Vladimir A. Krasnoveikin ◽  
Vladimir Skripnyak ◽  
Alexander A. Kozulin ◽  
Olga Senatova
Keyword(s):  
Numerical Simulation ◽  
Smoothed Particle Hydrodynamics ◽  
High Speed ◽  
Angular Pressing ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Smoothed Particle Hydrodynamics Method ◽  
Deformation Processes ◽  
Dynamic Channel ◽  
Dynamic Pressing

Deformation processes of the α-titanium specimens moving through the channels of the die for two loading schemes: equal channel angular pressing (ECAP) and channel pressing through the channel of variable form (CVF) are investigated. Schemes of dynamic pressing in case the block is extruded at high speed through the channel of the die due to the pressure of the punch or the pressure of powder gases were analyzed. The problem is solved by the smoothed particle hydrodynamics method (SPH) within the framework of elastoplastic continuum.

A novel non-reflecting boundary condition for fluid dynamics solved by smoothed particle hydrodynamics

2018 ◽  
Vol 860 ◽  
pp. 81-114 ◽  
Author(s):  
Pingping Wang ◽  
A-Man Zhang ◽  
Furen Ming ◽  
Pengnan Sun ◽  
Han Cheng
Keyword(s):  
Fluid Dynamics ◽  
Smoothed Particle Hydrodynamics ◽  
High Speed ◽  
Computational Domain ◽  
Infinite Domain ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Broad Variety ◽  
Pass Through ◽  
The Time Domain

Non-reflecting boundary conditions (NRBCs) play an important role in computational fluid dynamics (CFD). A novel NRBC based on the method of characteristics using timeline interpolations is proposed for fluid dynamics solved by smoothed particle hydrodynamics (SPH). It is performed by four layers of particles whose pressures and velocities are obtained through the Lagrange interpolation in the time domain which is derived from the propagation of characteristic waves between particles. The proposed NRBC can allow outward travelling pressure and velocity messages to pass through the boundary without obvious reflection. That is, with the implementation of the NRBC, the solution in a finite computational domain of interest is close to that in an infinite domain. Several numerical tests show that this NRBC is robust and applicable for a broad variety of hydrodynamics ranging from low to high speed.

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