Oil Droplet Size Research Articles

Numerical study of swirl core-annular flow and factors influencing pressure drop in vertical pipelines for oil-water two-phase flow

As oil field production progresses, the water content of the produced fluid increases and wax deposits form on the pipe wall as the crude oil is transported vertically through the pipeline. This causes the cross-sectional area of the pipeline to decrease, the flow resistance to increase and the pipeline pressure to decrease. As a result, production from oil wells declines and extraction costs rise. Therefore, in the current study, a vortex structure is utilized to generate a vertical core-annular flow for oil production and transportation in high-water-content oil wells. This study uses computational fluid dynamics (CFD) software to investigate the influence of various oil properties on the oil phase distribution and pressure drop in core-annular flow in vertical pipes. The findings demonstrate that the ring-forming effect of the core-annular flow increases with larger oil droplet sizes and lower oil phase densities, while it becomes weaker with higher inlet oil phase volume fraction and lower inlet velocities. As the size and density of the oil droplets grow and decrease, respectively, the pressure drop reduces. On the other hand, the pressure drop increases with higher inlet oil phase volume fraction and viscosity. When the oil droplet size is greater than 0.2 mm, the density is less than 850 kg/m3, the oil phase volume fraction is less than 30% and the inlet velocity is greater than 1 m/s, the annular flow works better. When the inlet oil phase volume fraction is above 30%, and the ring formation effect decreases significantly. The utilization of swirl core-annular fluid significantly mitigates the pressure drop in pipelines compared to pure oil transport downhole, rendering it highly suitable for conveying crude oil in high-water-content oil wells.

Enhancement of the formation and stability of low-fat Pickering emulsion gels stabilized with egg yolk granules-chitosan complex: Insights into the development of mayonnaise substitutes

This study employed egg yolk granules (EYG) in combination with chitosan (CS) to evaluate the feasibility of constructing low-fat Pickering emulsion gels and investigated the properties of emulsion gels with different oil volume fractions (0–50 %) to address the stability issue. The results showed that the self-supporting structure of the emulsion gels gradually increased at 0–40 % oil phase, and the oil droplet sizes were all smaller than 10 μm. However, when the oil phase reached 50 %, the emulsion showed water-oil phase separation. The addition of oil modified the state and movement of water molecules in the emulsion system, which in turn affected the water and oil loss rates. Notably, the emulsion gels exhibited similar rheological and textural characteristics to mayonnaise at 30 % oil phase. Furthermore, the emulsion gels demonstrated promising centrifugation and freeze-thaw stability. This study suggests an innovative and efficient approach to low-fat mayonnaise substitution with consistent quality.

Optimization screening, performance and mechanism analysis of green and low-carbon surfactants for oil-based drilling cuttings treatment

Oil-Based Drilling Cuttings (OBDC) have attracted extensive attention from scholars due to their high annual generation and high toxicity. At present, the thermal cleaning technology of surfactant is one of the research hotspots for treating OBDC, but it still faces the problems of high toxicity of surfactant, high carbon emission and unknown treatment mechanism. Therefore, we sequentially optimized screening the surfactants through the perspectives of greenness, treatment performance and costs, and low-carbon. A single-variable experiment was used to optimize the process parameters for treating OBDC, and the oil removal mechanism was explored by oil droplet size, TSI, Zeta potential and SARA fractions. The SLM was the most green and low carbon surfactant in this study, and had a better treatment performance for OBDC (51.56% oil removal rate). The optimal treatment parameters for SLM treatment of OBDC were 70 °C, 45 min, 300 r/min, 1:4 (solid/liquid) and pH 8.2. The lipophilic groups of SLM "striped" the asphaltenes and saturates in oil phase from the solid phase surface and "integrated" them into the water phase by its hydrophilic group. The mean value of the oil droplet sizes (Dmean) and Turbiscan stability index (TSI) value of the OBDC-water mixtures increased and the |Zeta potential| decreased after treatment, and the mixture system became more unstable, which promotes the subsequent separation of the oil phase from the solid phase.

Preformulation studies of an emulsion containing commercially available argan oil

Background: Argan oil has gained popularity in recent years due to its potential anti-inflammatory and antioxidant properties. The present pre-formulation study sought to investigate the suitability of using commercially available argan oil as a unique pharmaceutical emulsion formulation for oral consumption. This research aimed to develop an efficient pre-formulation strategy for oil-in-water emulsion containing argan oil and optimize the formulation's optimum stability as a pharmaceutical dosage form. Methods: Various analytical and physical characterization techniques were employed in making an emulsion, such as organoleptic analysis, pH level, viscosity, particle size distribution, gravimetric test, and dye method test. The three formulations (A, B, and C) gave different results for the sizes of oil droplets, appearance, taste, and compatibilities. Results: Among the tested formulations, formulation A, containing 5 ml argan oil, exhibited a cloudy white appearance, hazelnut-like taste and texture, higher oil retention, and improved droplet size dispersion (0.58 μm - 116.21 μm). The results indicated that all three formulations have acidic pH values 4.82-5.84. Conclusion: Formulation A demonstrated notable attributes, making it the optimal choice for the oil-in-water emulsion containing argan oil. Addressing compatibility concerns and assessing sensory attributes, pH levels, and particle size distribution successfully achieved the desired pharmaceutical elegance, laying a promising foundation for developing stable and effective oral emulsions.

Oil/water interface behavior of hesperidin methylchalcone and its application in nano-emulsions

The behavior of hesperidin methylchalcone (HMC) at the oil/water interface was examined through experimental and molecular simulation methods, and a nano-emulsions based on HMC was subsequently fabricated. The findings indicated that HMC spontaneously aggregated at the oil-water interface, leading to a reduction in interfacial tension and an increase in interfacial thickness. Furthermore, its glycoside and benzene ring showed tendencies to interact with water and medium-chain triglyceride, respectively. The HMC addition amount (w), homogenization times (n) and homogenization pressure (p) significantly influenced the formation of the nano-emulsions. The nano-emulsion with an oil-droplet size of 277.26 ± 13.62 nm was obtained at w = 1.0 %, p = 200 bar, and n = 6. When compared to the Tween 20 nano-emulsion, the HMC nano-emulsion demonstrated superior storage stability, antioxidant activity, and lutein bioaccessibility. It could achieve the slow release of HMC. These findings not only broaden the application range of HMC but also contribute to the advancement of functional nano-emulsions.

Impact of Particle Size on the Physicochemical, Functional, and In Vitro Digestibility Properties of Fava Bean Flour and Bread.

Fava beans, renowned for their nutritional value and sustainable cultivation, are pivotal in various food applications. This study examined the implications of varying the particle size on the functional, physicochemical, and in vitro digestibility properties of fava bean flour. Fava bean was milled into 0.14, 0.50, and 1.0 mm particle sizes using a Ferkar multipurpose knife mill. Physicochemical analyses showed that the 0.14 mm flour had more starch damage, but higher protein and fat contents. Functionality assessments revealed that the finer particle sizes had better foaming properties, swelling power, and gelation behavior than the coarse particle size. Emulsion capacity showed that for all the pH conditions, 1.00 mm particle size flour had a significantly higher (p < 0.05) oil droplet size, while the 0.5 and 0.14 mm flours had smaller and similar oil droplet sizes. Moreover, in vitro digestibility assays resulted in improved starch digestion (p ˂ 0.05) with the increase in flour particle size. Varying the particle size of fava bean flour had less impact on the in vitro digestibility of the bread produced from wheat-fava bean composite flour, with an average of 84%. The findings underscore the critical role of particle size in tailoring fava bean flour for specific culinary purposes and nutritional considerations.

The Influencing Factors and Mechanism of Anionic and Zwitterionic Surfactant on Viscosity Reduction in Heavy O/W Emulsions.

The high viscosity of heavy crude oil has been an obstacle to its safe production and economic transportation. In this work, a screened emulsified viscosity reducer system is conducted. Experimental results demonstrate that the most effective viscosity reducing agent comprises sodium oleate (NaOl) and cocamidopropyl betaine (CAB-35) in a ratio of 1:2, achieving a viscosity reduction rate of 94.65%. Additionally, the interfacial tension between oil and water decreases from 27 to 4 mN/m with 0.1 mass % TEOA and NaOH in a 1:1 ratio. The oil droplet size is uniformly distributed with D mean is 14 μm and D 50 is 11 μm. Droplets flocculate as the salinity increases to 0.2 mol/L, which corresponds to the apparent increase of viscosity. The adsorption of long alkyl chain lipophilic groups on surfactant molecules at the oil-water interface and the water film alters the wettability of pipe steel to water-wet, further enhancing the application of emulsification and viscosity reduction effects. The primary mechanism behind the viscosity reduction in emulsification is attributed to strong electrostatic interactions stemming from molecular electrostatic potential distributions.

Potential of Raman-Reflectance Combination in Quantifying Liver Steatosis and Fat Droplet Size: Evidence From Monte Carlo Simulations and Phantom Studies.

This study explores a combined strategy of Raman and reflectance spectroscopy for quantifying liver fat content and fat droplet size, crucial in assessing donor livers. By using Monte Carlo simulations and experimental setups with oil-in-water phantoms, our findings indicate that Raman scattering can solely differentiate between varying fat contents. At the same time, reflectance intensity is influenced by both fat content and oil droplet size, with a more pronounced sensitivity to fat droplet size. This study demonstrates the efficacy of combined Raman and reflectance spectroscopy in assessing liver steatosis and fat droplet size, potentially aiding in assessing donor livers for transplantation.

Mixed superoleophilic/superoleophobic hard granular media for coalescence of oil-in-water-emulsion

To enhance the coalescence separation efficiency of oil/water emulsions, the coalescence mechanism of oil droplets between two media of opposite wettability was investigated. A coalescent-bed comprising a mix of superhydrophobic and superoleophilic quartz sand, along with superhydrophilic and underwater superoleophobic quartz sand, was constructed in a coalescer. Single-factor and response surface experiments were used to study the effects of oleophilic/oleophobic sand mixing ratio, apparent velocity, initial oil concentration, bed thickness, sand particle size on coalescence-separation performance, and to determine the optimal experimental conditions. Employing the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, the agglomeration mechanism of oil droplets within the mixed particle bed was analyzed based on interfacial energy dynamics. Results indicate that the mixing ratio of the two sands significantly influences coalescence separation performance. An optimal oleophilic/oleophobic sand mixing ratio of 1:1 yielded a mass factor of 0.69 kPa−1, showcasing superior coalescence separation efficiency and an optimal balance of separation efficiency and pressure drop. Under the optimal conditions of apparent velocity of 2.7 m/h, initial oil concentration of 471.9 mg/L, bed thickness of 12.6 cm and mixed sand particle size of 0.5 mm, the oil/water separation efficiency reached 98.08 % ± 0.87 %, with effluent oil droplet size being 2.5 to 3 times larger than at the inlet. Analysis of the oil droplet coalescence mechanism revealed a synergistic effect between the two quartz sands, enhancing oil removal performance. The strong affinity of oil to the superhydrophobic and superoleophilic sand surface increases oil droplet wetting and coalescence efficiency, while the water attraction on the superhydrophilic and underwater superoleophobic sand surface forms a stable water film, improving the flux of the continuous water phase and reducing pressure drop across the bed. This study demonstrates that combining quartz sands of opposite wettability not only overcomes the limitations of single-wettability surfaces in coalescing oil removal but also achieves high efficiency and low energy consumption in oil removal.

Maillard conjugates of whey protein and prebiotic dietary fibers: Emulsion properties, encapsulation efficiency and chemical stability after in vitro gastrointestinal digestion

The incorporation of dietary fibers into food formulations is a promising approach to developing new functional ingredients. In this study, we investigated the formation of Maillard conjugates using whey protein concentrate (WPC) combined with fructooligosaccharides (FOS) and xylooligosaccharides (XOS). These conjugates, innovatively utilized as emulsifiers for annatto seed oil, were subjected to in vitro gastrointestinal digestion to assess their chemical stability and effectiveness as encapsulating systems. Our study confirmed the occurrence of the Maillard reaction through different methods, including grafting degree (GD) assessment and sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) to evaluate molecular weight variations in the proteins. The key innovation of our research lies in demonstrating the conjugation process through carbohydrate mass balance analysis using High-Performance Anion Exchange Chromatography coupled with Pulsed Amperometric Detection (HPAEC-PAD). The GD for the WPC-XOS and WPC-FOS was 46 ± 3 % and 56 ± 3 %, respectively. Our findings suggest that sugar quantification could serve as a novel approach to confirming the formation of Maillard conjugates. The emulsions stabilized by these conjugates exhibited larger oil droplet sizes compared to those stabilized by WPC alone yet maintained high encapsulation efficiency (≥ 90 %). Notably, the WPC-XOS emulsion demonstrated kinetic stability after 30 days of storage at 4°C, while the WPC-FOS emulsion showed signs of creaming after just 16 days. In vitro gastrointestinal digestion revealed that while the conjugates were susceptible to enzymatic degradation, the FOS and XOS sugars displayed gastrointestinal resistance of up to 82 % and 83 %, respectively. This study highlights the potential of WPC-XOS conjugates not only as effective emulsifiers but also as functional ingredients that enhance the nutritional and antioxidant properties of food products, presenting a novel approach to functional food development.

Experimental study on in-situ emulsification of heavy oil in porous media

Under the strategic goal of “dual-carbon”, reducing oil viscosity by in-situ emulsification using chemical method has become a new direction for high-efficiency and low-carbon development of heavy oil reservoirs. This technology can transform the originally immovable heavy oil into movable dispersed oil droplets through in-situ emulsification, and thus enhances heavy oil recovery. However, there is still a lack of sufficient understanding about the characteristics and influencing laws of in-situ emulsification of heavy oil in porous media. So, this paper carried out experimental studies on in-situ emulsification and influencing factors for heavy oil in porous media. The results show that, due to the transport and adsorption loss of viscosity reducer in porous media, the emulsification area expands gradually from the inlet to the outlet. At the same sampling position, with the increase of injection volume, the dispersed oil droplet size decreases, the distribution density increases, and the color of produced liquid changes from light yellow to dark brown. Under the same injection volume, the closer to the outlet, the smaller the particle size of the dispersed oil droplets and the higher the distribution density, which is resulted from the shearing effect of the porous media. With the increase of injection rate, the hydrodynamic shear effect is enhanced, so the in-situ emulsification of heavy oil starts earlier and the emulsification oil ratio curves have a higher slope and distribute more densely. With the increase of agent concentration, the adsorbed number of viscosity reducer molecules on the oil–water interface is increased, making it easier to emulsify the remaining oil. With the increase of pre-conversion oil recovery, the remaining oil in the porous media is more dispersed and the oil–water contact surface increases, so the emulsification is easier and the percentage of dispersed oil droplets in the produced oil phase increases. The research results based on sampling analysis deepen our understanding on in-situ emulsification of heavy oil in porous media, which provides valuable reference for designing suitable viscosity reducer agent and effectively enhancing heavy oil recovery in the future.

Rice protein hydrolysates as natural emulsifiers for an effective microencapsulation of orange essential oil by spray drying

This study aimed to identify the influence of rice protein hydrolysates (RPH) (degree of hydrolysis DH of 2, 6, and 10%) and rice protein isolate (RPI) on the formation and stabilization of the volatile oil droplets and to verify how protein hydrolysate affects the distribution of components on the surface and physicochemical properties of the spray-dried microparticles. In general, RPHs could reduce the interfacial tension (3.78–4.04 mN/m) compared to non-hydrolyzed protein (4.74 mN/m). However, no significant difference was observed between RPH samples. A positive correlation was observed between the interfacial tension and the oil droplet size, in which RPH emulsions showed 8.29–8.66 µm while RPI was 9.06 µm. DH influenced the surface composition of the spray-dried RPH emulsions. RPH10 powder showed a greater presence of protein (3.3%) on the particle surface and consequently exhibited high oil retention (50.0%). In contrast, this sample presented high hygroscopicity attributed to the protein surface. This study provides insights into differences between RPH powders, which can potentially impact the powder functionality and protection of the active compound.

Pore-scale investigation of injectivity impairment caused by oil droplets during produced water reinjection using volume of fluid method

Produced water from subsurface may often contain oil droplets, even when not directly extracted from oil wells. Oil droplets can migrate into water-bearing stratigraphic layers, leading to the generation of oily water. This study evaluates the dynamic clogging behavior of oil droplets concerning various injection fluid properties, including injection velocity, interfacial tension, oil droplet size, concentration, viscosity, and medium wettability. The primary objective is to validate common clogging mechanisms associated with oil droplets and quantitatively assess the impact of these parameters on injectivity impairment within porous media. To achieve this, a volume of fluid approach is employed, integrating fluid interfacial properties to account for coalescence and surface adherence. The results are then compared to similar findings in existing literature. Our study reveals that increasing the capillary number enhances injectivity, up to a critical point where the flow regime attains optimal stability, contingent upon relative permeability and phase mobility. Investigation into system wettability demonstrates that while contact angle significantly affects the injectivity index, the impact on injectivity diminishes when altering it beyond 90°. Aligning droplet viscosity with that of the displacing fluid proves to be an effective solution for minimizing injectivity impairment, nearly eliminating damage. This research provides valuable insights into commonly studied emulsion parameters, like Jamin Ratio and oil concentration, and underlines the importance of investigating less-explored factors, such as wettability and oil viscosity, particularly in scenarios involving unstabilized droplets and coalescence dynamics.

Emulsions stability in weightlessness: Droplets size, droplets coalescence and phases spatial distribution

This work presents experiments for the stability study of oil-in-water emulsions at varying gravity conditions. A key factor influencing emulsions stability is droplet size which can be assessed by several techniques employing different physical principles. Experiments are performed during the 79th Parabolic Flight Campaign of European Space Agency (October 2022). A pulsatile miniature emulsification device is used to produce emulsions in ∼0 g conditions while using varying experimental parameters (oil volumetric fraction, surfactant concentration, pulsation frequency, number of strokes). The device resembles the Soft Matter Dynamics facility onboard the International Space Station whereas the examined parameters are also alike to Soft Matter Dynamics experiment. Optical measurements are employed to determine the droplet size distribution as well as, to observe coalescence events in the aqueous phase. Electrical measurements with a non-intrusive, on-line, impedance spectroscopy technique are carried out to track the evolution of oil volumetric fraction at the central region of the emulsification cell. As expected, in the absence of gravity, the buoyancy related phenomena are eliminated and, thus, phase gravitational separation between the two phases (creamy and aqueous) does not take place. Yet, the residual motion at the end of emulsification affects (a) the spatial homogeneity (distribution) of the two phases in the cell and (b) the capacity for coalescence of colliding droplets. In the absence of gravity, these two emulsion parameters are controlled solely by hydrodynamics and interfacial phenomena whereas on earth they are masked by buoyant phenomena. It is found that the oil fraction evolution curves resulting from electrical measurements are compatible with a bidisperse oil droplet size distribution. The characteristic sizes of the two droplet modes are estimated using theoretical arguments. Both the electrically volume-based determined droplet sizes and the number-based ones from high resolution image analysis are discussed in detail.

Fabrication of pea protein isolate-stabilized oil-in-water emulsions with high freeze-thaw stability: Effect of high intensity ultrasonic on emulsions and interfacial protein structure

The poor freeze-thaw stability of plant protein-based emulsions posed a major challenge for their application in the cold chain foods. The present study successfully prepared oil-in-water emulsions stabilized solely with pea protein isolate (PPI) with excellent freeze-thaw stability using a facile high intensity ultrasonic (HIU)-assisted method. The optimized emulsion can endure three freeze-thaw cycles without stratification or oil leakage, maintaining oil droplet sizes at the nanometer scale. Furthermore, changes of interfacial protein structure induced by HIU were systematically investigated to reveal the stabilizing mechanism. The freeze-thaw stability of emulsions treated under varying intensities was evaluated based on changes in the appearance and oil drop size distribution. The results showed that the oil drop size of emulsions decreased from micron to nanometer and the freeze-thaw stability was significantly enhanced with the increase of HIU intensity. The emulsion exhibited optimized freeze-thaw stability under 800W. Subsequently, the effect of HIU on the structure of interfacial protein was analyzed through SDS-PAGE, –SH/S–S contents, UV spectrum, surface hydrophobicity, protein adsorption percentage, emulsifying activity and interfacial dilatational rheology. It was found that HIU triggered crosslinking of disulfide bonds among interfacial PPI molecules and enhanced the strength of the interface layer. Additionally, HIU promoted the unfolding of interfacial PPI structure, resulting in the improvement of surface hydrophobicity, emulsifying activity, and interfacial adsorption percentage of PPI. The study demonstrated the feasibility of using HIU to improve the freeze-thaw stability of oil-in-water emulsions stabilized with PPI and provided references for the fabricating of plant protein-based frozen emulsion foods.

Integration of oleaginous yeast-produced lipids into plant-based milk alternatives

In this study, the production of a novel oleaginous yeast-based milk powder alternative is presented. Three formulations, comprising yeast oil, oleaginous yeast cell lysate, and whole cells, were analyzed and compared to a reference formulation, covering the entire process from fermentation to powder analysis. The whole cell formulation exhibited highest encapsulating efficiency and low surface lipid content, indicating improved stability. Moreover, the formulation with cell lysate and whole cells showed larger oil droplet sizes in emulsions and spray-dried particles, and higher viscosity in rheological studies compared to the reference formulation. Electron microscopic images revealed morphological differences in spray-dried particles, emphasizing the impact of yeast oil integration. Concluding, formulations using oleaginous yeast present a complex system with diverse components. While this research pioneers oleaginous yeast integration into milk alternatives, further experiments are essential for a comprehensive understanding of observed effects and unlocking the full potential of these innovative and novel formulations.

Comparative study of the emulsifying properties of blue lupin, white lupin, and soybean protein isolates

This study investigated the emulsifying properties of isoelectric pH-precipitated blue lupin (BLPI), white lupin (WLPI), and soybean (SPI) protein isolates at various protein concentrations and pH values (3, 5, 7, and 9). The solubility, secondary, and tertiary structure of the protein isolates at different pH were determined. The emulsion characteristics evaluated included the droplet size, microstructure characterization, coalescence index (CI), and flocculation index (FI). The solubility of the protein isolates was influenced by pH, with the lowest solubility recorded at pH 4–5. At pH 5, all the protein isolates had more β-sheet structure than α-helix, while at pH 9, the isolates contained the helical conformation more than β-sheet. In general, mean oil droplet size (d3,2) was bigger at pH 3 and 5 (∼5–16 μm) when compared to pH 7 and 9 (<6 μm). The presence of small spherical and uniform oil droplet emulsions (<9 μm) stabilized by WLPI, BLPI, and SPI at pH 7 and 9 was confirmed using confocal laser scanning microscopy. Oil droplet coalescence was not the most prominent mechanism of emulsion instability for both lupin isolates and SPI, but rather bridging flocculation, with the FI highest at pH 5 (50–100%).

Simultaneous vehiculation of curcumin and riboflavin in bigels produced through WPI cold-set gelation

The influence of curcumin (model hydrophobic compound) and riboflavin (model hydrophilic compound) on the structure and physicochemical properties of bigels produced with cold-set whey protein isolates (WPI) was assessed. The hydrogel phase was produced with WPI (11% w/v) while for the oleogel phase, sunflower oil and glycerol monostearate (GM) (10% w/v) were used. Curcumin (0.03 mg/mL) was added to the oil phase and riboflavin (0.5 mg/mL) to the water phase. Bigels were produced by hot emulsification (18.000 min−1, 2 min, 55 °C) of different hydrogel:oleogel ratios (90:10, 50:50 and 10:90). NaCl (200 mM) was added to the aqueous phase prior the emulsification. Bigels were evaluated through microscopy, XRD, FTIR, viscoelastic, texture, release kinetics and in vitro digestion analyses. XRD and FTIR showed that the addition of compounds led to some possible structural differences. Microscopy images showed an increase of the oil droplets size proportionally to the amount of oil present, and a conversion of the structure from oil in water (O/W) to water in oil (W/O). The structural differences led to different mechanical behavior. For the bigels with the isolated compounds an improvement in the gel network was observed, making it more structured, according to the phase that is being added. Regarding controlled release, higher values for the 90:10 formulation were observed for both compounds due to the matrix erosion. For bioaccessibility, curcumin presented similar values for 90:10 and 10:90 bigels, and riboflavin showed a growing bioaccessibility, with lower values for bigel 90:10.

Evaluating the potential importance of individual identity, maternal traits, and environment as predictors of egg characteristics in walleye Sander vitreus

Individual and environmental factors may influence gamete characteristics and contributions to recruitment in fishes. We tested for the influence of maternal, abiotic, and biotic factors on egg diameter and quality (i.e., oil droplet diameter) for walleye Sander vitreus in Escanaba Lake, Wisconsin, during 2018–2023 (omitting 2020). Analyses were conducted on fish captured once and for the same individuals captured multiple times during our study period. In the single-capture analysis, increasing maternal length was weakly related to larger egg diameter and oil droplet size. Increased yellow perch abundance was somewhat related to increased intra-clutch variation, whereas a later ice-off date was related to reduced intra-clutch variation. Fish that spawned later had more variable egg and oil droplet diameters. Among fish that were sampled over multiple years, individual identity was a strong predictor of egg and oil diameter. Our results suggest that regulations that preserve among individual variation in egg traits could increase the chances that environmental conditions will be favorable for spawning and recruitment for at least some fish.

Flow field analysis and performance evaluation of a mini-hydrocyclone for ultra-low inlet flow rate

It is difficult for hydrocyclone to separate oil-water under the condition of ultra-low inlet flow rate, which commonly exist in the field of energy engineering. Mini-hydrocyclone is an effective technology to solve this problem. The flow field characteristics and oil droplet migration trajectory in the mini-hydrocyclone are the key to guide its efficient work. An innovative mini-hydrocyclone are studied via computational fluid dynamics (CFD) and experiment method. The good separation performance of mini-hydrocyclone for ultra-low inlet flow rate and tiny particle size of oil droplets is verified and analyzed. Furthermore, The distribution of velocity, oil volume fraction and oil migration trajectories in the mini-hydrocyclone are analyzed systematically. The effects of oil droplet size, inlet flow rate and split ratio on the separation performance of mini-hydrocyclone are investigated. The results show that the maximum separation efficiency of the mini-hydrocyclone for 1.0 L/min ultra-low inlet flow rate is 99.98 %, when the split ratio is 30 %, the oil phase volume fraction is 2 %. Moreover, the morphological and distribution of oil core in mini-hydrocyclone are basically consistent between simulation and experiment results, under the conditions of different operating parameters. The minimum error of numerical simulation and experiment results is less than 2.23 %, the accuracy of the numerical simulation method is verified.