Simulation of Paint Transfer in an Air Spray Process

1995 ◽  
Vol 117 (4) ◽  
pp. 713-719 ◽  
Author(s):  
P. G. Hicks ◽  
D. W. Senser
Keyword(s):  
Drop Size ◽  
Separated Flow ◽  
Transfer Efficiency ◽  
Significant Advance ◽  
Direct Effects ◽  
Air Velocity ◽  
Velocity Fluctuations ◽  
Spray Process ◽  
The Mean ◽  
Physical Phenomena

A methodology for simulating drop transport and deposition in air-spray, paint-application processes is presented. Simulation of the complex physical phenomena involved is made possible through a number of key assumptions based on measurements of typical air paint sprays. The significant advance is the inclusion of the direct effects of turbulent air velocity fluctuations on the trajectories of paint drops via a stochastic separated flow approach. The model accurately predicts the mean air velocity field, paint transfer efficiency, and drop transfer efficiency. Owing to increased inertia, the mechanisms controlling drop transport shift with increasing drop size.

scholarly journals Natural logarithms

2013 ◽  
Vol 718 ◽  
pp. 1-4 ◽  
Author(s):  
B. J. McKeon
Keyword(s):  
Turbulent Flows ◽  
Reynolds Numbers ◽  
Streamwise Velocity ◽  
Wall Turbulence ◽  
Significant Advance ◽  
Mean Velocity ◽  
Velocity Fluctuations ◽  
Logarithmic Scaling ◽  
The Mean ◽  
High Reynolds

AbstractMarusic et al. (J. Fluid Mech., vol. 716, 2013, R3) show the first clear evidence of universal logarithmic scaling emerging naturally (and simultaneously) in the mean velocity and the intensity of the streamwise velocity fluctuations about that mean in canonical turbulent flows near walls. These observations represent a significant advance in understanding of the behaviour of wall turbulence at high Reynolds number, but perhaps the most exciting implication of the experimental results lies in the agreement with the predictions of such scaling from a model introduced by Townsend (J. Fluid Mech., vol. 11, 1961, pp. 97–120), commonly termed the attached eddy hypothesis. The elegantly simple, yet powerful, study by Marusic et al. should spark further investigation of the behaviour of all fluctuating velocity components at high Reynolds numbers and the outstanding predictions of the attached eddy hypothesis.

scholarly journals Raindrop fall velocity in turbulent flow: an observational study

2021 ◽  
Vol 18 ◽  
pp. 33-39
Author(s):  
Merhala Thurai ◽  
Viswanathan Bringi ◽  
Patrick Gatlin ◽  
Mathew Wingo
Keyword(s):  
Turbulent Flow ◽  
Gold Standard ◽  
Sonic Anemometer ◽  
Terminal Velocity ◽  
Laboratory Measurements ◽  
Air Velocity ◽  
Fall Velocity ◽  
Velocity Fluctuations ◽  
The Mean ◽  
Rain Events

Abstract. Laboratory measurements of drop fall speeds by Gunn–Kinzer under still air conditions with pressure corrections of Beard are accepted as the “gold standard”. We present measured fall speeds of 2 and 3 mm raindrops falling in turbulent flow with 2D-video disdrometer (2DVD) and simultaneous measurements of wind velocity fluctuations using a 3D-sonic anemometer. The findings based on six rain events are, (i) the mean fall speed decreases (from the Gunn–Kinzer terminal velocity) with increasing turbulent intensity, and (ii) the standard deviation increases with increase in the rms of the air velocity fluctuations. These findings are compared with other observations reported in the literature.

Spray Characteristics of Plain-Jet Airblast Atomizers

1984 ◽  
Vol 106 (3) ◽  
pp. 634-638 ◽  
Author(s):  
N. K. Rizk ◽  
A. H. Lefebvre
Keyword(s):  
Drop Size ◽  
Air Pressure ◽  
Liquid Viscosity ◽  
Liquid Ratio ◽  
Air Velocity ◽  
Spray Characteristics ◽  
Test Range ◽  
Scattering Technique ◽  
The Mean ◽  
Light Scattering Technique

The effects of air and liquid properties and atomizer dimensions on the spray characteristics of plain-jet airblast atomizers are examined. Mean drop size and drop-size distribution are measured using an improved form of light scattering technique. The test range includes wide variations in air velocity, air pressure, air/liquid ratio, and liquid viscosity. The experimental data generally confirm the results of previous studies on prefilming types of airblast atomizers. They show that increases in air velocity, air pressure, and air/liquid ratio all tend to produce a more uniform spray and a lower mean drop size. It is also observed that any change in air properties, liquid properties, and atomizer geometry that lowers the mean drop size also produces a more uniform distribution of drop sizes in the spray.

scholarly journals Spray Characteristics of Plain-Jet Airblast Atomizers

1983 ◽  
Author(s):  
N. K. Rizk ◽  
A. H. Lefebvre
Keyword(s):  
Drop Size ◽  
Air Pressure ◽  
Liquid Viscosity ◽  
Liquid Ratio ◽  
Air Velocity ◽  
Spray Characteristics ◽  
Test Range ◽  
Scattering Technique ◽  
The Mean ◽  
Light Scattering Technique

The effects of air and liquid properties, and atomizer dimensions, on the spray characteristics of plain-jet airblast atomizers are examined. Mean drop size and drop-size distribution are measured using an improved form of light scattering technique. The test range includes wide variations in air velocity, air pressure, air/liquid ratio, and liquid viscosity. The experimental data generally confirm the results of previous studies on prefilming types of airblast atomizers. They show that increases in air velocity, air pressure and air/liquid ratio all tend to produce a more uniform spray and a lower mean drop size. It is also observed that any change in air properties, liquid properties and atomizer geometry that lowers the mean drop size also produces a more uniform distribution of drop sizes in the spray.

Performance of Prefilming Airblast Atomizers in Unsteady Flow Conditions

2006 ◽  
Author(s):  
A. Mu¨ller ◽  
R. Koch ◽  
H.-J. Bauer ◽  
M. Hehle ◽  
O. Scha¨fer
Keyword(s):  
Droplet Size ◽  
Droplet Diameter ◽  
Particle Diameter ◽  
Pollutant Emissions ◽  
Pulsation Frequency ◽  
Combustion Instabilities ◽  
Air Velocity ◽  
Low Frequencies ◽  
Velocity Fluctuations ◽  
The Mean

Within the context of lean premixed prevaporized combustion (LPP) which is considered as most promising technology for the next generation of low emission combustors for aero engines, combustion instabilities are a major issue. These combustion instabilities may compromise the pollutant emissions and even cause damage to the combustion chamber structure. In the literature, numerous phenomenological studies on combustion oscillation are available, but a comprehensive theory is still missing. One potential excitation mechanism is the interaction of strong air velocity fluctuations and pressure oscillations with the airblast atomizer leading to temporal fluctuations of the spray characteristics. This phenomenon was investigated experimentally at the Institute of Thermal Turbomachinery (ITS) within a parametric study. A duct with a prefilming surface was set up as an abstraction of a prefilming airblast atomizer. A mean air velocity up to 65 m/s can be reached, and periodic oscillations can be superimposed by means of a siren with a frequency up to 570 Hz. The disintegration process of the liquid fuel was studied downstream the atomizing edge of a plain airblast nozzle. Several optical diagnostics like phase resolved LDV (Laser Doppler Velocimetry) and an improved PTV technique (Particle Tracking Velocimetry) were used. The mean air velocity, the film load, the kinematic viscosity and the surface tension of the fluid as well as the pulsation frequency and amplitude of the siren were varied, and their effect on the temporal evolution of the droplet size and droplet rate was studied. It was found that the amplitude of fluctuations of the droplet size and the droplet rate is almost proportional to the air velocity fluctuations at low frequencies. At higher frequencies, however, both are nearly unaffected. In addition, the fluctuations of droplet diameter and rate increase strongly if the mean air velocity is increased. The phase shift between particle diameter, particle rate and air velocity fluctuations was found to increase at higher excitation frequencies.

Second Paper: The Effects of Physical Factors on Ignition Delay

1966 ◽  
Vol 181 (1) ◽  
pp. 34-59 ◽  
Author(s):  
W-T. Lyn ◽  
E. Valdmanis
Keyword(s):  
Ignition Delay ◽  
Drop Size ◽  
Injection Rate ◽  
Published Data ◽  
Physical Factors ◽  
Injection Timing ◽  
Air Velocity ◽  
Spray Form ◽  
Temperature And Pressure ◽  
Compression Temperature

The effects of physical factors on ignition delay have been studied on a motored research engine using a single injection technique. The fuels used included a high cetane number reference fuel, gas oil and M.T. 80 petrol. The primary factors investigated are those pertaining to the fuel spray, such as injection timing, quantity, and pressure (affecting drop size, velocity and injection rate); hole diameter (affecting drop size and injection rate) and spray form (nozzle type); and those pertaining to the engine, such as temperature, pressure and air velocity. Engine operating variables such as speed and load affect the ignition delay because they change the primary factors such as injection pressure, compression temperature, pressure and air velocity. It has been found that under normal running conditions, compression temperature and pressure are the major factors. All other factors have only secondary effects. Under starting conditions, when ignition is marginal, mixture formation becomes as important as compression temperature and pressure. Such factors as air velocity and spray form which affect the mixing pattern can have a very pronounced effect on ignition delay. Published data on ignition delay are compared with those obtained in the present investigation and a generalization of the data is recommended for engine design and computational work.

scholarly journals Instability wave models for the near-field fluctuations of turbulent jets

2011 ◽  
Vol 689 ◽  
pp. 97-128 ◽  
Author(s):  
K. Gudmundsson ◽  
Tim Colonius
Keyword(s):  
Flow Field ◽  
Large Scale ◽  
Microphone Array ◽  
Near Field ◽  
Turbulent Jets ◽  
Instability Wave ◽  
Mean Flow ◽  
Velocity Fluctuations ◽  
The Mean ◽  
Scale Structures

AbstractPrevious work has shown that aspects of the evolution of large-scale structures, particularly in forced and transitional mixing layers and jets, can be described by linear and nonlinear stability theories. However, questions persist as to the choice of the basic (steady) flow field to perturb, and the extent to which disturbances in natural (unforced), initially turbulent jets may be modelled with the theory. For unforced jets, identification is made difficult by the lack of a phase reference that would permit a portion of the signal associated with the instability wave to be isolated from other, uncorrelated fluctuations. In this paper, we investigate the extent to which pressure and velocity fluctuations in subsonic, turbulent round jets can be described aslinearperturbations to the mean flow field. The disturbances are expanded about the experimentally measured jet mean flow field, and evolved using linear parabolized stability equations (PSE) that account, in an approximate way, for the weakly non-parallel jet mean flow field. We utilize data from an extensive microphone array that measures pressure fluctuations just outside the jet shear layer to show that, up to an unknown initial disturbance spectrum, the phase, wavelength, and amplitude envelope of convecting wavepackets agree well with PSE solutions at frequencies and azimuthal wavenumbers that can be accurately measured with the array. We next apply the proper orthogonal decomposition to near-field velocity fluctuations measured with particle image velocimetry, and show that the structure of the most energetic modes is also similar to eigenfunctions from the linear theory. Importantly, the amplitudes of the modes inferred from the velocity fluctuations are in reasonable agreement with those identified from the microphone array. The results therefore suggest that, to predict, with reasonable accuracy, the evolution of the largest-scale structures that comprise the most energetic portion of the turbulent spectrum of natural jets, nonlinear effects need only be indirectly accounted for by considering perturbations to the mean turbulent flow field, while neglecting any non-zero frequency disturbance interactions.

scholarly journals Fuzzy rules based model for solute dispersion in an open channel dead zone

2002 ◽  
Vol 4 (1) ◽  
pp. 39-51
Author(s):  
Helen Kettle ◽  
Keith Beven ◽  
Barry Hankin
Keyword(s):  
Finite Volume ◽  
Fuzzy Number ◽  
Open Channel ◽  
Transverse Velocity ◽  
Dead Zone ◽  
Fuzzy Rules ◽  
Turbulent Velocity ◽  
Velocity Fluctuations ◽  
Laboratory Flume ◽  
The Mean

A method has been developed to estimate turbulent dispersion based on fuzzy rules that use local transverse velocity shears to predict turbulent velocity fluctuations. Turbulence measurements of flow around a rectangular dead zone in an open channel laboratory flume were conducted using an acoustic Doppler velocimeter (ADV) probe. The mean velocity and turbulence characteristics in and around the shear zone were analysed for different flows and geometries. Relationships between the mean transverse velocity shear and the turbulent velocity fluctuations are encapsulated in a simple set of fuzzy rules. The rules are included in a steady-state hybrid finite-volume advection–diffusion scheme to simulate the mixing of hot water in an open-channel dead zone. The fuzzy rules produce a fuzzy number for the magnitude of the average velocity fluctuation at each cell boundary. These are then combined within the finite-volume model using the single-value simulation method to give a fuzzy number for the temperature in each cell. The results are compared with laboratory flume data and a computational fluid dynamics (CFD) simulation from PHOENICS. The fuzzy model compares favourably with the experiment data and offers an alternative to traditional CFD models.

An Investigation of Flow Fields Over Multi-Element Aerofoils

2001 ◽  
Vol 124 (1) ◽  
pp. 154-165 ◽  
Author(s):  
S. R. Maddah ◽  
H. H. Bruun
Keyword(s):  
Flow Field ◽  
Computational Study ◽  
Separated Flow ◽  
Mean Flow ◽  
Model Configuration ◽  
Attached Flow ◽  
The Mean ◽  
Flap Deflection ◽  
Comparative Results ◽  
Lift And Drag

This paper presents results obtained from a combined experimental and computational study of the flow field over a multi-element aerofoil with and without an advanced slat. Detailed measurements of the mean flow and turbulent quantities over a multi-element aerofoil model in a wind tunnel have been carried out using stationary and flying hot-wire (FHW) probes. The model configuration which spans the test section 600mm×600mm, is made of three parts: 1) an advanced (heel-less) slat, 2) a NACA 4412 main aerofoil and 3) a NACA 4415 flap. The chord lengths of the elements were 38, 250 and 83 mm, respectively. The results were obtained at a chord Reynolds number of 3×105 and a free Mach number of less than 0.1. The variations in the flow field are explained with reference to three distinct flow field regimes: attached flow, intermittent separated flow, and separated flow. Initial comparative results are presented for the single main aerofoil and the main aerofoil with a nondeflected flap at angles of attacks of 5, 10, and 15 deg. This is followed by the results for the three-element aerofoil with emphasis on the slat performance at angles of attack α=10, 15, 20, and 25 deg. Results are discussed both for a nondeflected flap δf=0deg and a deflected flap δf=25deg. The measurements presented are combined with other related aerofoil measurements to explain the main interaction of the slat/main aerofoil and main aerofoil/flap both for nondeflected and deflected flap conditions. These results are linked to numerically calculated variations in lift and drag coefficients with angle of attack and flap deflection angle.

scholarly journals MEAN SURFACE TEMPERATURE OF JAPANESE QUAIL EXPOSED TO DIFFERENT LEVELS OF AIR VELOCITY AND TEMPERATURE AT START OF LAY

2020 ◽  
Vol 4 (2) ◽  
pp. 15-18
Author(s):  
Tatiany Carvalho dos Santos ◽  
Richard Stephen Gates ◽  
Ilda De Fátima Ferreira Tinôco ◽  
Sérgio Zolnier ◽  
Letícia Cibele da Silva Ramos Freitas
Keyword(s):  
Surface Temperature ◽  
Air Temperature ◽  
Japanese Quail ◽  
Systems Engineering ◽  
Air Velocity ◽  
Agricultural Engineering ◽  
Initial Stage ◽  
Different Temperatures ◽  
The Mean ◽  
Different Levels

The objective of this study was to evaluate the effect of different air velocities and temperature at the feeder on mean surface temperature of Japanese quail during the initial stage of laying. The experiment was carried out at the Center for Research in Environment and Agroindustry Systems Engineering (AMBIAGRO), Department of Agricultural Engineering, Federal University of Viçosa, Viçosa/MG, Brazil. A total of 216 Japanese quail in the initial laying phase were placed in four environmental chambers with different temperatures and air velocity, where they were housed and distributed randomly in 2 galvanized wire cages, with 3 partitions each and 27 birds/cage, and a density of approximately 155.6 cm²/bird. The experimental design consisted of randomized blocks with replications of two treatments (air velocity at the feeder: 0, 1, 2, and 3 m/s and air temperature: 17, 23, 29 and 35°C). The mean surface temperature was analyzed by Two-Way ANOVA, with treatment means separated by the Tukey test (P < 0.05). There was a significant positive correlation between air temperature and mean surface temperature (MST). Air velocity is important in removing heat from the surface of birds.

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