Drop Size Measurements Research Articles

Cloud and precipitation microphysical retrievals from the EarthCARE Cloud Profiling Radar: the C-CLD product

Abstract. The Earth Clouds, Aerosols and Radiation Explorer (EarthCARE) satellite mission is a joint endeavour developed by the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) and features a 94 GHz Doppler Cloud Profiling Radar. This paper presents the theoretical basis of the cloud and precipitation microphysics (C-CLD) EarthCARE Level 2 (L2) algorithm. The C-CLD algorithm provides the best estimates of the vertical profiles of water mass content and hydrometeor characteristic size, obtained from radar reflectivity, path-integrated signal attenuation and hydrometeor sedimentation Doppler velocity estimates using optimal estimation (OE) theory. To obtain the forward model relations and the associated uncertainty, an ensemble-based method is used. This ensemble consists of a collection of in situ measured drop size distributions that cover natural microphysical variability. The ensemble mean and standard deviation represent the forward model relations and their microphysics-based uncertainty. The output variables are provided on the joint standard grid horizontal and EarthCARE Level 1b (L1b) vertical grid (1 km along track and 100 m vertically). The OE framework is not applied to liquid-only clouds in drizzle-free and lightly drizzling conditions, where a more statistical approach is preferred.

Depth from defocus technique applied to unsteady shock-drop secondary atomization

The two-sensor depth from defocus technique for the measurement of drop sizes in a spray is further developed to achieve higher spatial and temporal resolution, to improve estimates of spatial size distribution and number concentration, and to provide additional guidelines for the calibration and design of the optical system for a specific application. The technique and these improvements are demonstrated using the case of secondary atomization when a shock wave interacts with a single drop. This is an application in which both high spatially and temporally resolved number density and size distributions of secondary droplets generated in the wake of the original drop are necessary.

Drop Size Measurement Techniques for Agricultural Sprays:A State-of-The-Art Review

Plant protection control based on the spray application of plant protection products is a very complex task depending on a series of factors, among which droplet size is the most influential for deposition and pesticide effectiveness. In fact, the adoption of the correct droplet size can ensure that the required dose reaches the target area and is not wasted, minimizes the off-target losses due to evaporation, drift and run-off and, at the same time, enhances the operator’s safety in terms of inhalation, ingestion and dermal exposure. In this paper, after defining some mean characteristic diameters helpful for a description of a drop population and focusing on the main drop size distribution functions for the statistical characterization of sprays, a critical analysis of known methods, both intrusive and non-intrusive, for drop size measurement is carried out by reviewing the literature. Among intrusive methods, the liquid immersion method and the use of water-sensitive papers are discussed, whereas, among non-intrusive methods, laser-based systems (laser diffraction, phase Doppler particle analysis) and high-speed imaging (shadowgrapy) are presented. Both types of method, intrusive and non-intrusive, can be used in machine-learning-based approaches exploiting regression techniques and neural network analysis.

DOPPLER OPTICAL PROBE FOR DROP SIZE, VELOCITY, AND FLUX MEASUREMENTS IN ASSISTED ATOMIZATION

For research as well as for process control, reliable drop size, velocity, and flux measurements are desirable in particular in dense, high-speed flows. A new optical probe has been recently manufactured by A2 Photonic Sensors company that combines an accurate phase detection capability (its latency length is small, about 6 µm) with the collection of a Doppler signal that provides the absolute velocity of an incoming gas-liquid interface. In this article, raw signals acquired over diverse flow conditions in terms of gas velocity and liquid concentration are analyzed. A dedicated signal processing routine is then proposed and optimized. The latter provides statistics on drop velocity and size. It also gives access to local liquid concentration and liquid flux. This Doppler probe combined with its processing has been tested in sprays produced from assisted atomization over a wide range of flow conditions. Transverse profiles of spray characteristics are presented for gas injection velocities ranging from 32 m/s to 283 m/s, for drops Sauter mean diameters D<sub>32</sub> varying from 37 µm to 275 µm, and for number densities-as estimated from liquid concentration and D<sub>32</sub>-comprised between 1 #/mm<sup>3</sup> and 218 #/mm<sup>3</sup>. The Doppler probe happens to be able to consistently detect chords as small as 4 µm, and to ensure a significant (up to 70%) fraction of direct velocity measurements. Besides, the injected liquid flow rate is recovered from the spatial integration of local liquid fluxes within 8% for gas velocities up to 50 m/s and within 17% for gas velocities above 90 m/s. Hence, the new Doppler probe combined with the proposed processing provides reliable statistics on drop velocity, size, and flux, and is a valuable tool for investigating dense, high-velocity, and fine sprays.

Pipe flow experiments of unstable oil-water dispersions with three different oil viscosities: Flow pattern, pressure drop and droplet size measurements

The transport of oil-water dispersions in petroleum production pipelines is difficult to predict and requires special attention since it affects the performance of the entire system. For future field developments it is required to generate accurate predictive models to guarantee an optimal field design. The purpose of this work is to present novel experimental data suitable for improving mechanistic flow models in future works. Oil-water pipe flow experiments were conducted in a stainless-steel flow loop with a L/D ratio of 3766, larger than any comparable setups reported in the literature and sufficient to obtain fully developed flow. A novel level of detail measurements included pressure gradients, density profiles and droplet size distributions.Three oils with different viscosities (oil A: 1.3 cP; oil B: 7 cP; oil C: 22 cP) and brine (3.5 wt% NaCl) as the water phase constituted the three fluid systems used. For each fluid system, several flow rates, and a wide range of water fractions were studied. The fluids were not stabilized by any type of chemical additives.The oil viscosity influences the dispersion behavior, especially for oil continuous flow. For higher oil viscosities the dispersion tends to be more homogeneous, and the pressure drop increases due to increasing wall friction. The droplet size decreases as the oil viscosity increases, presumably due to higher shear stress. Water continuous flows, on the other hand, are less affected by the oil viscosity. A strong drag reduction was found for dispersed flow of all three oils and both oil and water continuous flow. A simple model for the dispersion viscosity and drag reduction was developed based on additional bench scale characterization experiments. With this model the pressure drop could be predicted with good agreement.The data reported in this paper will facilitate the development and validation of mechanistic models for predicting oil-water flows. Previous modelling efforts have been hampered by a lack of detailed measurements, in particular droplet size measurements, hence we believe that this data will allow for significant advancements on the modelling side.

Nano Filling Effect of Nonmeat Protein Emulsion on the Rheological Property of Myofibrillar Protein Gel.

Incorporation of vegetable oils through pre-emulsification has received notable attention for delivering polyunsaturated fatty acids to emulsified-type meat products. The two important influencing factors of the rheological property of composite myofibrillar protein (MP) gel are emulsion droplet size and active or inactive interaction between interface and meat proteins. Incorporation of nonmeat protein emulsion (2% protein (w/w), egg-white protein isolate (EPI), porcine plasma protein (PPP), or sodium caseinate (SC)) with different droplet sizes (nano or macro) to a model of 2% MP gel was investigated in this research. The results of drop size measurement showed that 15,000 psi homogenizing could decrease the diameter of emulsion drop from macro- to nanoscale in the range of 324.4–734.5 nm. Active fillers (PPP and EPI emulsions) with nanodroplet size did not influence the viscosity of emulsion-filled composite cold sols but caused positive filling effects on the MP gel matrix after heating, as evidenced by the density microstructure. PPP and EPI nano-emulsion-filled composite MP had a significant high storage modulus enforcement effect, which reached nearly eight times those of other treatments (p < 0.05). Similarly, the results of thermal scanning rheology and a large-deformation mechanical test showed that PPP and EPI emulsions with nanoscale droplets, other than macroscale, had the highest gel strength of heat-induced emulsion-filled composite MP gel (p < 0.05). Overall, these findings will be helpful for selecting the correct pre-emulsified protein and designing the textural properties of foods.

Ultrasonic Atomization: New Spray Characterization Approaches

In particle engineering, spray drying is an essential technique that depends on producing sprays, ideally made of equal-sized droplets. Ultrasonic sprays appear to be the best option to achieve it, and Faraday waves are the background mechanism of ultrasonic atomization. The characterization of sprays in this atomization strategy is commonly related to the relation between characteristic drop sizes and the capillary length produced by the forcing frequency of wavy patterns on thin liquid films. However, although this atomization approach is practical when the intended outcome is to produce sprays with droplets of the same size, drop sizes are diverse in real applications. Therefore, adequate characterization of drop size is paramount to establishing the relations between empirical approaches proposed in the literature and the outcome of ultrasonic atomization in actual operating conditions. In this sense, this work explores new approaches to spray characterization applied to ultrasonic sprays produced with different solvents. The first two introduced are the role of redundancy in drop size measurements to avoid resolution limitation in the measurement technique and compare using regular versus variable bin widths when building the histograms of drop size. Another spray characterization tool is the Drop Size Diversity to understand the limitations of characterizing ultrasonic sprays solely based on representative diameters or moments of drop size distributions. The results of ultrasonic spray characterization obtained emphasize: the lack of universality in the relation between a characteristic diameter and the capillary length associated with Faraday waves; the variability on drop size induced by both liquid properties and flow rate on the atomization outcome, namely, lower capillary lengths produce smaller droplets but less efficiently; the higher sensibility of the polydispersion and heterogeneity degrees in Drop Size Diversity when using variable bin widths to build the histograms of drop size; the higher drop size diversity for lower flow rates expressed by the presence of multiple clusters of droplets with similar characteristics leading to multimodal drop size distributions; and the gamma and log-normal mathematical probability functions are the ones that best describe the organization of drop size data in ultrasonic sprays.

Modelling Spray Pressure Effects on Droplet Size Distribution from Agricultural Nozzles

For spray applications, drop size is the most important feature as it affects all aspects of a phytosanitary treatment: biological efficacy, environmental pollution, and operator safety. In turn, drop size distribution depends on nozzle type, liquid properties, and working pressure. In this research, three nozzles were studied under ordinary working conditions and the effect of pressure on drop size distribution was assessed. The nozzles under test, all from Albuz (France), were an orange hollow cone nozzle ATR 80 (European color code), an air induction flat spray nozzle AVI 11003, and an air induction hollow cone nozzle TVI 8002. The ATR 80 and the TVI 8002 nozzles were tested at four pressure values: 0.3, 0.5, 1.0, and 1.5 MPa; the AVI 11003 nozzle was tested at 0.3 and 0.5 MPa. The drop size measurement technique was based on the liquid immersion method by using a custom-made test bench; spray quality parameters were computed by means of suitable functions written in R language. Results showed that an increase in working pressure caused an increase in drop pulverization regardless of the type of nozzle, and drop pulverization was higher for the turbulence nozzle than for the two air induction nozzles. Based on skewness and kurtosis values, the theoretical gamma distribution was the most adapt to fit the experimental data. The scale parameter showed a decreasing trend with the increase in the pressure, a clear index of higher drop pulverization.

Monofiber optical probe using Doppler signals detection for Drop Size and Velocity measurement in air assisted atomization

Reliable measurement of droplet/bubble size and velocity distributions in dense flows is desired in a variety of research fields, both for laboratory and industrial use. A new type of single-mode monofiber optical probe manufactured by A2 Photonic Sensors is introduced in this paper: it combines traditional phase detection with the collection of a Doppler signal returned by an incoming gas-liquid interface to provide information on residence times, drop concentration and velocity, which afford then drop chords and liquid flux measurements. Compared with classical optical probes, that new sensor does not require any calibration. The purpose of the present work is to test this technique in assisted atomization in order to provide a mean for spray characterization and ultimately to improve our understanding of atomization mechanisms. The probe has been tested downstream of a coaxial air-assisted atomizer operated at liquid velocity =. to. / , and gas velocity from = to about /. We first analyzed raw signals in various flow conditions. It happens that, when increasing the gas velocity and the number density of drops, the signal experiences very strong fluctuations of the gas level, making the identification of individual droplets more difficult. That leads us to develop a new signal processing routine specifically adapted to such complex working conditions. At = / and for three liquid flow rates, the spatial integration of local liquid fluxes represents 92 to 99% of the injected liquid flow rate. These good results demonstrate that the Doppler probe provides reliable statistics on drops velocity and size.

Spray characteristics of standard and alternative aviation fuels at high ambient pressure conditions

The spray characteristics of standard and alternative aviation fuels generated by a hybrid pressure-swirl airblast (HPSA) atomizer were investigated at high ambient pressure conditions. The measurements were performed in an optically accessible pressure vessel at pressures of 1, 2, 3, 4, 5, and 9.5 bar with heated gas and fuel temperatures of 394 K and 332 K, respectively. The drop size and drop velocity of sprays from a standard (Jet-A) and an alternative (C-5) aviation fuels were measured using phase Doppler anemometry (PDA), and 2-D visualization of spray was imaged using simultaneous fuel-Planar Laser Induced Fluorescence (PLIF) and Mie scattering. The spatially resolved PDA drop size measurements were obtained at 25.4 mm downstream of the swirler exit plane and up to 30 mm in the radial direction from the spray centerline. The Sauter Mean Diameter (D32) was observed to decrease significantly with increasing ambient pressure, up to 5 bar. However, the change in D32 was observed to be limited with a further increase in the ambient pressure. A higher swirler pressure drop resulted in a significant reduction in the D32 at an ambient pressure of 5 bar. Using simultaneous fuel-PLIF and Mie scattering imaging, the feasibility of the laser sheet drop-sizing (LSD) technique was examined for the spray at high ambient pressure application. In addition, the effect of ambient pressure on the spray cone angle was investigated using both instantaneous and averaged Mie images. The distribution of fuel vapor and droplets in the spray was also imaged and identified by comparing instantaneous fuel-PLIF and Mie images. A phenomenological three-step atomization model was used to predict the drop size and demonstrate the drop size trend with increasing ambient pressure.

Ultrasonic Propagation in Liquid and Ice Water Drops. Effect of Porosity.

This work studies ultrasonic propagation in liquid and ice water drops. The effect of porosity on attenuation of ultrasonic waves in the drops is also explored. The motivation of this research was the possible application of ultrasonic techniques to the study of interstellar and cometary ice analogs. These ice analogs, made by vapor deposition onto a cold substrate at 10 K, can display high porosity values up to 40%. We found that the ultrasonic pulse was fully attenuated in such ice, and decided to grow ice samples by freezing a liquid drop. Several experiments were performed using liquid or frozen water drops with and without pores. An ultrasonic pulse was transmitted through each drop and measured. This method served to estimate the ultrasonic velocity of each drop by measuring drop size and time-of-flight of ultrasonic transmission. Propagation of ultrasonic waves in these drops was also simulated numerically using the SimNDT program developed by the authors. After that, the ultrasonic velocity was related with the porosity using a micromechanical model. It was found that a low value of porosity in the ice is sufficient to attenuate the ultrasonic propagation. This explains the observed lack of transmission in porous astrophysical ice analogs.

Understanding the mechanism of froth flotation of molybdenite using oily collectors from a perspective of thinning and rupture of thin liquid film

Froth flotation of molybdenite is commonly achieved using hydrocarbon oils as the collector. The insoluble hydrocarbon oils adsorb on molybdenite surfaces, resulting in an increase in its surface hydrophobicity and thereby its flotation recovery. However, the underlying mechanism on a microscopic scale was poorly understood. In this study, the effect of insoluble oily collectors on thinning and rupture of thin liquid films (TLFs) between air bubbles and molybdenite face surfaces has been investigated by monitoring the spatial and temporal evolution of the TLFs using a synchronized tri-wavelength reflection interferometry microscope (STRIM) as well as by drop size and contact angle measurements. Two hydrocarbon oils, namely kerosene and dodecane, have been studied. The result from the STRIM measurements shows that the TLF is stable in a 1 mM NaCl solution between an air bubble and a molybdenite face surface despite the molybdenite face being hydrophobic. The TLF becomes unstable when the surface is treated in both dodecane and kerosene emulsion solutions and ruptures at a critical rupture thickness of 60–340 nm. The film rupture is predominantly attributed to the instability of the TLFs between air bubbles and oil droplets adsorbed on the molybdenite surfaces. It is found that both the thinning kinetics and the rupture thicknesses of the TLFs correlate with both the coverage and sizes of the oil droplets on molybdenite surfaces. Kerosene exhibits a better dispersibility in DI water than dodecane, and therefore performs better as the collector than dodecane from a perspective of film stability. The present work provides new insight into the underlying mechanism of oily collectors in the froth flotation of molybdenite and other naturally hydrophobic minerals. The result obtained from this study enables the development of new oil collectors in the future.

Drop size measurement techniques for sprays: Comparison of image analysis, phase Doppler particle analysis, and laser diffraction

Four different methods for measuring droplet size distributions are evaluated: the Image Analysis VisiSizer technique, a stroboscopic imaging method developed in-house, phase Doppler particle analysis (PDPA), and laser diffraction (Malvern Spraytec). We find that the larger the droplets, the bigger the differences between the results obtained by the different methods. The Image Analysis VisiSizer technique yields results that are comparable with those of the stroboscopic imaging method, provided that the raw Visisizer data are used, as the VisiSizer software makes corrections that can skew the results. Our measurements confirm how the limitations of PDPA can influence its outcomes; the presence of air bubbles inside droplets will cause PDPA to mistake them for smaller droplets. The fact that PDPA reports no droplets larger than 1200 μm might be caused by large drops often not being spherical. The results of the laser diffraction technique are influenced by its fitting method to obtain the droplet size distribution and by overestimation of the number of small droplets due to their low velocity and thus higher concentration in the sample volume. Our results emphasize the need for selecting the size measurement technique to fit the physical nature and expected range of droplet parameters.

Prediction of the Initial Drop Size and Velocity Distribution in the Cold Cryogenic Spray

The polydispersed nature of the spray is captured through the use of probability density functions based on the maximum entropy method to stand for the complete atomization characteristics of spray dynamics. The droplet and velocity size distributions are practical tools for the analysis of sprays cooling. The special benefit of the model is a Eulerian based which is less computationally intensive when compared to models that are based on the Lagrangian approach that tracks droplet parcel. The accuracy of using Lagrangian approach in polydispersed phase is always accurately less than Eulerian approach because it depends on the number of parcels while in Eulerian approach it depends on the proposed continuous distribution function. The main intent of the current work is to evaluate the capability of using the model for the initial predictions of the droplet size and velocity distribution for liquid nitrogen spray of solid-cone pressure swirl nozzle. The use of liquid injection pressure cases of up to 0.6MPa and spray cone angles of just 30◦ from three different sets of experimental data. The results being characterized are spray drop size distribution, liquid volume fraction and spray cone angle values. The unsteady analyses of the effect of injection pressure are studied on the cryogenic liquid nitrogen. The numerical results show that the maximum entropy method applies to liquid cryogenic spray and indicates that the model reacts correctly to changes in different injection pressures. Comparisons are also made with measured drop size distribution data that are reasonably captured and the spray cone angle is found to be in good agreement during initial and far-field spray angles.

Estimation of measurement error and depth of field in PDIA experiments: a comparative study using water droplets and a calibration target

The particle/droplet image analysis (PDIA) technique is often used for droplet sizing in sprays. Successful use of PDIA for drop size measurement in sprays mandates careful calibration, and determination of the depth of field (DOF) for particles of different size classes. This is typically done with a calibration target that has circles etched on it. In the present study, a calibration experiment was performed with a calibration target as well as droplets, to evaluate the uncertainties in the measured sizes and also to compare the measured DOF values. A continuous-jet droplet generator was used to produce mono-disperse droplets of sizes ranging from 54–393 µm, and the calibration glass plate used contained circles of sizes ranging from 20–400 µm. Images of these were captured using a CCD camera equipped with a long-distance microscope, and were processed using a code written in MATLAB®. Differences in the measured sizes of droplets and circles, and their DOF values are reported. It was observed that the use of the calibration target led to an underestimation of the error in droplet size measurements, and an overestimation of the DOF. For the droplets, the measurement error was observed to be less than 5%, with the parameters chosen.

Characterization of spray formed by diesel-water mixture jet injection into an air crossflow

This paper presents experimental results on spray characteristics of the water-diesel fuel mixture in air crossflow. Penetration of jet, droplet size distribution and mean droplet size are determined to characterize the near field jet and far field spray field for various mixtures of water and diesel which are mixed by using a static mixer before it is fed into to an injector. Both near filed visualization of jet and far field spray field indicate that the spray field formed by immiscible water/diesel mixture injection in a crossflow can be determined by assuming the nature of mixture jet at the exit of injector as quasi-steady injection of alternating water and diesel without significant mixing between them. Based on this observation, number-density/volume distributions are predicted from the measured drop size distribution of pure fluids at the same flow conditions by weighting those quantities by mass fraction of each fluid. The predicted distributions agree very well with the measured ones, confirming that the assumption is valid. The calculated droplet size from predicted droplet size distribution linearly increases as the content of water in mixture increases.

Comparison of three types of laser optical disdrometers under natural rainfall conditions

ABSTRACTOptical disdrometers can be used to estimate rainfall erosivity; however, the relative accuracy of different disdrometers is unclear. This study compared three types of optical laser-based disdrometers to quantify differences in measured rainfall characteristics and to develop correction factors for kinetic energy (KE). Two identical PWS100 (Campbell Scientific), one Laser Precipitation Monitor (Thies Clima) and a first-generation Parsivel (OTT) were collocated with a weighing rain gauge (OTT Pluvio2) at a site in Austria. All disdrometers underestimated total rainfall compared to the rain gauge with relative biases from 2% to 29%. Differences in drop size distribution and velocity resulted in different KE estimates. By applying a linear regression to the KE–intensity relationship of each disdrometer, a correction factor for KE between the disdrometers was developed. This factor ranged from 1.15 to 1.36 and allowed comparison of KE between different disdrometer types despite differences in measured drop size and velocity.

Integrated Monitoring of Volcanic Ash and Forecasting at Sakurajima Volcano, Japan

The Sakurajima volcano is characterized by frequent vulcanian eruptions at the Minamidake or Showa crater in the summit area. We installed an integrated monitoring system for the detection of volcanic ash (composed of remote sensing sensors XMP radars, lidar, and GNSS with different wave lengths) and 13 optical disdrometers on the ground covering all directions from the crater to measure drop size distribution and falling velocity. Campaign sampling of volcanic ash supports the conversion of particle counts measured by the disdrometer to the weight of volcanic ash. Seismometers and tilt/strain sensors were used to estimate the discharge rate of volcanic ash from the vents. XMP radar can detect volcanic ash clouds even under visual difficulty because of weather such as fog or clouds. A vulcanian eruption on November 13 was the largest event at the Sakurajima volcano in 2017; however, the volcanic plume was not visible due to clouds covering the summit. Radar revealed that the volcanic plume reached an elevation of 4.2–6.2 km. Post-fit phase residuals (PPR) from the GNSS analysis increased suddenly after the eruption, and large-PPR paths from the satellites to the ground-based receivers intersected each other at an elevation of 4.2 km. The height of the volcanic plume was also estimated from the discharge rate of volcanic ash to be 4.5 km, which is empirically related to seismic energy and the deflation volume obtained via ground deformation monitoring. Using the PUFF model, the weight of the ash-fall deposit was accurately forecast in the main direction of transport of the volcanic ash, which was verified by disdrometers. For further advances in forecasting of the ash-fall deposit, we must consider high-resolution wind field, shape of volcanic plume as the initial value, and the particle number distribution along the volcanic plume.

Numerical and experimental evaluation of droplet breakage of O/W emulsions in rotor-stator mixers

Emulsification of a high viscosity oil in water mixture was studied in a rotor-stator mixer. Experimental characterization of drop sizes and high-speed visualizations of drop breakup phenomena were performed, combined with computational fluid dynamics analysis of the flow field and population balance modeling. Single-phase flow simulations were carried out with a sliding mesh CFD model and combined with analysis of streamlines, turbulent eddy dissipation fields and high-speed visualizations of drop breakage. From frames taken over few seconds, with the oil-water system initially fully segregated, three drop breakage mechanisms were identified, supported by the CFD analysis: (i) a combination of the large scale circular motion in the tank and the fluid jet emanating from the stator holes; (ii) droplets that are pulled into the rotor – stator system from the bottom and flow through the gap between the stator and rotor, undergoing extremely high shear stresses, being expelled through the stator slots in several fragments, and iii) droplets that remain caught at the recirculation zones in the stator holes, increasing exposure time to high shear during the rotor blade passage. Finally, an optimization algorithm was coupled to a population balance model and the measured drop size distributions were reproduced in good agreement with experimental data, including the bimodal behavior attributed to the generation of satellite droplets.

Characterizing primary atomization of cryogenic LOX/Nitrogen and LOX/Helium sprays by visualizations coupled to Phase Doppler Interferometry

There is a need for experimental data in conditions representative injection in rocket engines to validate or initiate droplet formation models used in numerical simulations. A new cryogenic vessel was built upon the MASCOTTE test bench to study the atomization of a single oxygen liquid jet, under non-reactive conditions, with simultaneous optical diagnostics. A test plan was built to explore the fiber-type regime occurring in liquid rocket injection systems, with a fixed Reynolds number and a large range of Weber number and momentum flux ratio, compared to existing studies. High-speed images are used to describe qualitatively the fiber-type regime and to visualize were droplets are present, in order to prepare the drop-size measurements. Phase Doppler Interferometry is used to measure the size and velocity of droplets produced by atomization of a liquid oxygen jet by a co-flowing gas. Droplet size and velocity measurements were performed with a PDI close to the nozzle exit in order to provide data on droplets produced by the primary atomization process, which can be useful for numerical simulations initialisation. The radial evolutions of the axial velocity and of the drop size distribution show similar trends as observed in the literature. The axial velocity is investigated for different operating conditions with helium or nitrogen as atomizing gas, showing an increase on the side of the spray. The radial evolution of the droplet size shows a translation of the drop size distribution on the edge of the spray towards the smaller sizes, indicating that the biggest liquid elements stay close to the LOX jet.