Computational and experimental study of an oil jet in crossflow: coupling population balance model with multifluid large eddy simulation

2021 ◽  
Vol 932 ◽  
Author(s):  
Cosan Daskiran ◽  
Fangda Cui ◽  
Michel C. Boufadel ◽  
Ruixue Liu ◽  
Lin Zhao ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Droplet Size ◽  
Balance Model ◽  
Population Balance Model ◽  
Rise Velocity ◽  
Oil Droplets ◽  
Eddy Simulation ◽  
Jet In Crossflow ◽  
Large Eddy ◽  
Oil Jet

Understanding the size of oil droplets released from a jet in crossflow is crucial for estimating the trajectory of hydrocarbons and the rates of oil biodegradation/dissolution in the water column. We present experimental results of an oil jet with a jet-to-crossflow velocity ratio of 9.3. The oil was released from a vertical pipe 25 mm in diameter with a Reynolds number of 25 000. We measured the size of oil droplets near the top and bottom boundaries of the plume using shadowgraph cameras and we also filmed the whole plume. In parallel, we developed a multifluid large eddy simulation model to simulate the plume and coupled it with our VDROP population balance model to compute the local droplet size. We accounted for the slip velocity of oil droplets in the momentum equation and in the volume fraction equation of oil through the local, mass-weighted average droplet rise velocity. The top and bottom boundaries of the plume were captured well in the simulation. Larger droplets shaped the upper boundary of the plume, and the mean droplet size increased with elevation across the plume, most likely due to the individual rise velocity of droplets. At the same elevation across the plume, the droplet size was smaller at the centre axis as compared with the side boundaries of the plume due to the formation of the counter-rotating vortex pair, which induced upward velocity at the centre axis and downward velocity near the sides of the plume.

scholarly journals A population balance model for large eddy simulation of polydisperse droplet evolution

2019 ◽  
Vol 878 ◽  
pp. 700-739 ◽  
Author(s):  
A. K. Aiyer ◽  
D. Yang ◽  
M. Chamecki ◽  
C. Meneveau
Keyword(s):  
Large Eddy Simulation ◽  
Size Distribution ◽  
Droplet Size ◽  
Droplet Breakup ◽  
Dispersed Phase ◽  
Size Distributions ◽  
Oil Droplets ◽  
One Dimensional ◽  
Eddy Simulation ◽  
Large Eddy

In the context of many applications of turbulent multi-phase flows, knowledge of the dispersed phase size distribution and its evolution is critical to predicting important macroscopic features. We develop a large eddy simulation (LES) model that can predict the turbulent transport and evolution of size distributions, for a specific subset of applications in which the dispersed phase can be assumed to consist of spherical droplets, and occurring at low volume fraction. We use a population dynamics model for polydisperse droplet distributions specifically adapted to a LES framework including a model for droplet breakup due to turbulence, neglecting coalescence consistent with the assumed small dispersed phase volume fractions. We model the number density fields using an Eulerian approach for each bin of the discretized droplet size distribution. Following earlier methods used in the Reynolds-averaged Navier–Stokes framework, the droplet breakup due to turbulent fluctuations is modelled by treating droplet–eddy collisions as in kinetic theory of gases. Existing models assume the scale of droplet–eddy collision to be in the inertial range of turbulence. In order to also model smaller droplets comparable to or smaller than the Kolmogorov scale we extend the breakup kernels using a structure function model that smoothly transitions from the inertial to the viscous range. The model includes a dimensionless coefficient that is fitted by comparing predictions in a one-dimensional version of the model with a laboratory experiment of oil droplet breakup below breaking waves. After initial comparisons of the one-dimensional model to measurements of oil droplets in an axisymmetric jet, it is then applied in a three-dimensional LES of a jet in cross-flow with large oil droplets of a single size being released at the source of the jet. We model the concentration fields using $N_{d}=15$ bins of discrete droplet sizes and solve scalar transport equations for each bin. The resulting droplet size distributions are compared with published experimental data, and good agreement for the relative size distribution is obtained. The LES results also enable us to quantify size distribution variability. We find that the probability distribution functions of key quantities such as the total surface area and the Sauter mean diameter of oil droplets are highly variable, some displaying strong non-Gaussian intermittent behaviour.

Large Eddy Simulation of Cylindrical Jet Breakup and Correlation of Simulation Results With Experimental Data

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Shashank S. Moghe ◽  
Scott M. Janowiak
Keyword(s):  
Experimental Data ◽  
Kinetic Energy ◽  
Large Eddy Simulation ◽  
Turbulent Kinetic Energy ◽  
Experimental Results ◽  
Eddy Simulation ◽  
Jet Breakup ◽  
Large Eddy ◽  
Oil Jet ◽  
Piston Cooling

Modern engines with increasing power densities have put additional demands on pistons to perform in incrementally challenging thermal environments. Piston cooling is therefore of paramount importance for engine component manufacturers. The objective of this computational fluid dynamics (CFD) study is to identify the effect of a given piston cooling nozzle (PCN) geometry on the cooling oil jet spreading phenomenon. The scope of this study is to develop a numerical setup using the open-source CFD toolkit OpenFoam® for measuring the magnitude of oil jet spreading and comparing it to experimental results. Large eddy simulation (LES) turbulence modeling is used to capture the flow physics that affects the inherently unsteady jet breakup phenomenon. The oil jet spreading width is the primary metric used for comparing the numerical and experimental results. The results of simulation are validated for the correct applicability of LES by evaluating the fraction of resolved turbulent kinetic energy (TKE) at various probe locations and also by performing turbulent kinetic energy spectral analysis. CFD results appear promising since they correspond to the experimental data within a tolerance (of ±10%) deemed satisfactory for the purpose of this study. Further generalization of the setup is underway toward developing a tool that predicts the aforementioned metric—thereby evaluating the effect of PCN geometry on oil jet spreading and hence on the oil catching efficiency (CE) of the piston cooling gallery. This tool would act as an intermediate step in boundary condition formulation for the simulation determining the filling ratio (FR) and subsequently the heat transfer coefficients (HTCs) in the piston cooling gallery.

Large-Eddy Simulation of Atomizing Spray With Stochastic Modeling of Secondary Breakup

2003 ◽  
Author(s):  
Sourabh V. Apte ◽  
Mikhael Gorokhovski ◽  
Parviz Moin
Keyword(s):  
Large Eddy Simulation ◽  
Droplet Size ◽  
Particle Tracking ◽  
Hybrid Approach ◽  
Computational Cost ◽  
Fuel Injector ◽  
Combustion Dynamics ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Secondary Breakup

Large-eddy simulation (LES) of reacting multi-phase flows in practical combustor geometries is essential to accurately predict complex physical phenomena of turbulent mixing and combustion dynamics. This necessitates use of Lagrangian particle-tracking methodology for liquid phase in order to correctly capture the droplet evaporation rates in the sparse-liquid regime away from the fuel injector. Our goal in the present work is to develop a spray-atomization methodology which can be used in conjuction with the standard particle-tracking schemes and predict the droplet-size distribution accurately. The intricate process of primary atomization and lack of detailed experimental observations close to the injector requires us to model its global effects and focus on secondary breakup to capture the evolution of droplet sizes. Accordingly, a stochastic model for LES of atomizing spray is developed. Following Kolmogorov’s idea of viewing solid particle-breakup as a discrete random process, atomization of liquid blobs at high relative liquid-to-gas velocity is considered in the framework of uncorrelated breakup events, independent of the initial droplet size. Kolmogorov’s discrete model of breakup is represented by Fokker-Planck equation for the temporal and spatial evolution of droplet radius distribution. The parameters of the model are obtained dynamically by relating them to the local Weber number. A novel hybrid-approach involving tracking of individual droplets and a group of like-droplets known as parcels is developed to reduce the computational cost and maintain the essential features and dynamics of spray evolution. The present approach is shown to capture the complex fragmentary process of liquid atomization in idealized and realistic Diesel and gas-turbine combustors.

Large-Eddy Simulation of a Round Jet in Crossflow

AIAA Journal ◽  
2009 ◽  
Vol 47 (5) ◽  
pp. 1158-1172 ◽  
Author(s):  
Jörg Ziefle ◽  
Leonhard Kleiser
Keyword(s):  
Large Eddy Simulation ◽  
Round Jet ◽  
Eddy Simulation ◽  
Jet In Crossflow ◽  
Large Eddy

Effect of Droplet Size and Atomization on Spray Formation: A Priori Study Using Large-Eddy Simulation

2010 ◽  
Vol 86 (3-4) ◽  
pp. 533-561 ◽  
Author(s):  
Ville Anton Vuorinen ◽  
Harri Hillamo ◽  
Ossi Kaario ◽  
Mika Nuutinen ◽  
Martti Larmi ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Droplet Size ◽  
A Priori ◽  
Spray Formation ◽  
Eddy Simulation ◽  
Large Eddy

scholarly journals Large Eddy Simulation of an Ethanol Spray Flame with Secondary Droplet Breakup

2021 ◽  
Author(s):  
S. Gallot-Lavallée ◽  
W. P. Jones ◽  
A. J. Marquis
Keyword(s):  
Liquid Phase ◽  
Large Eddy Simulation ◽  
Droplet Size ◽  
Size Class ◽  
Droplet Breakup ◽  
Fuel Injector ◽  
Low Oxygen ◽  
Stochastic Field ◽  
Eddy Simulation ◽  
Large Eddy

AbstractA computational investigation of three configurations of the Delft Spray in Hot-diluted Co-flow (DSHC) is presented. The selected burner comprises a hollow cone pressure swirl atomiser, injecting an ethanol spray, located in the centre of a hot co-flow generator, with the conditions studied corresponding to Moderate or Intense Low-oxygen Dilution (MILD) combustion. The simulations are performed in the context of Large Eddy Simulation (LES) in combination with a transport equation for the joint probability density function (pdf) of the scalars, solved using the Eulerian stochastic field method. The liquid phase is simulated by the use of a Lagrangian point particle approach, where the sub-grid-scale interactions are modelled with a stochastic approach. Droplet breakup is represented by a simple primary breakup model in combination with a stochastic secondary breakup formulation. The approach requires only a minimal knowledge of the fuel injector and avoids the need to specify droplet size and velocity distributions at the injection point. The method produces satisfactory agreement with the experimental data and the velocity fields of the gas and liquid phase both averaged and ‘size-class by size-class’ are well depicted. Two widely accepted evaporation models, utilising a phase equilibrium assumption, are used to investigate the influence of evaporation on the evolution of the liquid phase and the effects on the flame. An analysis on the dynamics of stabilisation sheds light on the importance of droplet size in the three spray flames; different size droplets play different roles in the stabilisation of the flames.

Large eddy simulation of an inclined jet in crossflow with vortex generators

2021 ◽  
Vol 170 ◽  
pp. 121032
Author(s):  
Zhiyuan Zhao ◽  
Fengbo Wen ◽  
Xiaolei Tang ◽  
Yuxi Luo ◽  
Rui Hou ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Vortex Generators ◽  
Eddy Simulation ◽  
Jet In Crossflow ◽  
Large Eddy
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