Aug 2026· Agriculture· Vol 16, pp. 1827· 0 citations· 41 references
Abstract
Flow distortion generated by L-shaped elbows in plant-protection spraying equipment disturbs the inlet flow of flat-fan nozzles, causing non-uniform outlet velocity distributions and reduced foliar deposition uniformity. This study developed a flat-fan nozzle with built-in flow-straightening vanes to improve spray stability under complex pipeline conditions. A three-dimensional CFD model integrating an L-shaped elbow, nozzle, and external spray region was established, and the Volume of Fluid (VOF) model was used to examine the effects of flow-dividing channel number, vane geometry, and vane insertion depth on velocity distribution on the spray fan plane. Structural parameters were optimized using a Box–Behnken response surface design. Field experiments on soybean seedlings evaluated droplet deposition using a carmine tracer assay with microplate reader measurement. The built-in vanes reduced elbow-induced flow deflection, swirl, and localized high-velocity zones, thereby improving spray fan velocity uniformity. The influence on the coefficient of variation of normal velocity followed the order: vane geometry > insertion depth > channel number. The optimal configuration comprised four channels, a star-shaped vane, and a 10 mm insertion depth, yielding a normal-velocity coefficient of variation of 16.12% at 400 mm downstream of the nozzle. Field trials showed that the developed nozzle reduced droplet deposition CV from 4.46% to 2.03% compared with the conventional flat-fan nozzle, a 54.5% decrease, with a significant difference between nozzles (p = 0.006). These results indicate that built-in flow-straightening vanes can improve spray stability and foliar deposition uniformity under elbow-induced flow distortion.
Spray pretreatment is a key step in short-process textile cleaning, and spray deposition uniformity on the target plane directly determines the quality consistency of subsequent dyeing and finishing, with nozzle layout exerting a direct influence on this uniformity. However, the existing non-submerged free jet model suffers from physical distortions in planar flow projection, namely multi-valued flow at the origin and non-convergent far-field flow. To address this, the proportionality coefficient of the Gaussian distribution is redefined to establish a corrected planar flow distribution function with a unique origin flow and natural far-field convergence. Treating continuous fabric motion as equivalent nozzle translation, a cumulative flow superposition model for moving planes is constructed, and a collaborative optimization model for nozzle spacing, mounting height, and attitude angle is established using the Particle Swarm Optimization (PSO) algorithm, with adjacent nozzle pairs as the periodic unit. Experimental calibration shows that relative errors between theoretical and measured flow rates remain within 10%. Nozzle rotation about the local z-axis is identified as the most effective attitude variable for uniformity tuning; a 0.1 m increase in nozzle spacing reduces peak overlap flow by about 30% and overlap width by about 40%. For a dual-nozzle system on a 0.66 m-wide target plane, numerical simulation results show that the calculated cumulative flow variance decreases from 5.9193 to 1.1588, corresponding to an 80.4% reduction in the numerical uniformity index. This numerical optimization framework provides a quantitative reference for nozzle layout design in textile spraying processes.
In air-assisted orchard spraying, airflow characteristics strongly determine spray performance. This study designed a tower-shaped fan for grape canopies and investigated its aerodynamic behaviour. A three-dimensional computational fluid dynamics (CFD) model of the internal flow field was established to quantify the effects of shroud taper, upper and lower guide-vane angles, inlet diameter, and inlet position on outlet air-velocity uniformity. Single-factor simulations confirmed that all selected structural parameters significantly affect the outlet air velocity’s coefficient of variation (CV). Based on these results, central composite design was applied for multi-parameter optimisation. A second-order regression model was developed to describe the relationship between guide-vane angles, shroud taper, inlet position, inlet diameter, and air-velocity CV response. Analysis of variance showed that the influence of the factors decreased in the following order: guide-vane angle > inlet position > inlet diameter > shroud taper. Numerical optimisation identified the optimal configuration as a guide-vane angle of 118.37°, shroud taper of 23.84°, inlet position of 29.35 mm, and inlet diameter of 493.92 mm. Under these conditions, the predicted air-velocity CV decreased to 12.07%. A field validation experiment was conducted using representative measurement points selected from the simulated velocity distribution. The maximum relative error between measured and simulated values was below 6%, indicating strong agreement. These results confirm the reliability of the CFD model and demonstrate its effectiveness for structural optimisation of orchard air-assisted spraying equipment.
P. Zhan, Z. Y. Sun, Q. Meng et al.· Journal of Applied Fluid Mec...· 0 citations
The clearance of the nozzle vane significantly influences the aerodynamic performance of variable nozzle turbines (VNTs), often leading to increased flow losses and performance degradation. Although nozzle vane clearance often exhibits a non-uniform distribution due to corrosion, wear, machining tolerances, or assembly errors, the aerodynamic effects of such non-uniform clearance have rarely been investigated. This study aims to fill the research gap regarding the influence of non-uniform nozzle guide vane clearance on tip leakage flow and aerodynamic performance in a supersonic VNT. By systematically examining the flow field features under different clearance profiles via three-dimensional numerical simulations, this work seeks to identify a potential clearance configuration that can reduce flow loss and improve turbine efficiency. The flow losses, tip leakage vortex patterns, and the interaction between the leakage vortex and shock waves are analyzed in detail for different clearance profiles. The results indicate that for a rear-loaded vane profile, the shrinking clearance (SC) configuration yields a lower mass flow rate and higher aerodynamic efficiency compared to the expanding clearance (EC) and uniform clearance (UC) configurations. Specifically, the SC configuration effectively reduces leakage mass flow and vortex intensity. Consequently, the interaction between the leakage vortex and the shock wave is suppressed. This suppression significantly mitigates flow losses, which are primarily driven by the shock–vortex interaction rather than the interaction between the leakage flow and the main flow, thereby enhancing aerodynamic performance. These findings suggest that a rational design of non-uniform clearance profiles can substantially improve the aerodynamic performance of supersonic turbines.
Qin Luo, Cong Xiang, X. Lei et al.· International Journal of The...· 0 citations
Continuous coaxial nozzles are widely used in directed energy deposition (DED) processes; however, many numerical studies rely on substrate-free free-jet models that fail to capture critical gas–surface interactions. This study presents a design-oriented investigation of continuous coaxial DED nozzles by examining the influence of nozzle geometry and gas flow interactions under realistic deposition conditions. A three-dimensional CFD framework incorporating particle tracing was applied, in which a physical substrate was explicitly included at the intended standoff distance to account for stagnation pressure formation, gas rebound, and near-wall flow effects. Two nozzle geometries, a narrow nozzle (β = 24°) and a wide nozzle (β = 35°), were evaluated under varying carrier and shaping gas velocities relative to a fixed optical shielding gas velocity. Powder convergence behavior was quantified using a layered particle counting strategy and analyzed through number density distributions in the focal region. The results show that nozzle geometry strongly governs powder focusing behavior. The narrow nozzle consistently produced a compact and axisymmetric powder stream with higher catchment efficiency, whereas the wide nozzle exhibited diffuse flow patterns and reduced focal coherence. Excessive shaping gas velocities were found to degrade convergence by expanding the substrate-induced stagnation pressure zone. These findings provide a physics-based rationale for geometry-dependent nozzle selection in continuous coaxial DED applications.
Mehmet Ermurat, Muhammet İbrahim Aşçı, Ibrahim Hakki Ince· Strojniski Vestnik-journal o...· 0 citations
This study investigates an SAC-type injector nozzle used in a diesel high-pressure common-rail fuel-injection system. The mixture multiphase-flow model, RNG k-ε turbulence model, and Schnerr–Sauer cavitation model were employed to compare the internal flow characteristics of circular and elliptical nozzle orifices under different operating and geometric parameters. The results show that, as the inlet pressure increased from 110 to 170 MPa, the outlet velocity and mass flow rate of the elliptical orifice reached 495.80 m/s and 27.28 g/s, respectively, while the outlet vapor volume fraction increased to 0.161. As the outlet back pressure increased from 5 to 20 MPa, the outlet vapor volume fraction of the elliptical orifice was 41.32–46.49% lower than that of the circular orifice, whereas its mass flow rate was 4.84–23.54% higher. The geometric-parameter analysis indicated that superior internal flow performance was obtained at a nozzle-orifice angle of 75° and an inlet rounding radius of 0.03 mm. The converging elliptical orifice increased the outlet velocity and mass flow rate by 18.3% and 23.29%, respectively. These results demonstrate that the converging elliptical orifice can effectively mitigate flow separation and cavitation while improving outlet-flow uniformity and fuel-delivery performance.
Jikang Xu, Yuqi Chang, Zhaoyue Liu et al.· Processes· 0 citations
Radial jet drilling (RJD) enhances oil and gas production by constructing radial boreholes from the main wellbore, with the nozzle as its core component. The swirling abrasive waterjet (SAWJ) generated by a swirling impeller nozzle (SIN) offers both high erosion capacity and wide coverage, yet how the nozzle structural parameters affect this performance remains unclear. To address this gap, a computational fluid dynamics coupled with the discrete phase model with non-spherical drag correction is developed to simulate the SAWJ impingement flow field. Eight structural parameters are evaluated against the erosion rate (Rerosion) and the equivalent erosion radius (Req) by a controlled-variable method, with Pearson correlation analysis quantifying their sensitivity. The SIN converts pressure energy into a three-dimensional swirling velocity field, and the swirl number peaking at 1.172 within the impeller section and decaying to 0.551 at the nozzle exit. The nozzle outlet diameter is the dominant parameter, showing a strong negative correlation with Rerosion (correlation coefficient CC = −0.88) and a strong positive correlation with Req (CC = 0.79). The impeller length is the only parameter positively correlated with both indicators. On this basis, optimized nozzle parameter ranges are proposed for RJD applications.
Kang Cheng, M. Annoni, Chenrui Guo et al.· The Physics of Fluids· 0 citations
