Evaluation of spray penetration on different planes in pesticide applications using an agricultural Unmanned Aerial Vehicle (UAV) sprayer

Agricultural Unmanned Aerial Vehicles (UAVs) mainly leverage the downwash airflow generated by rotors for spraying. However, due to the inherent instability of the downwash airflow, there may be droplet drift problems. Computational fluid dynamics is used to investigate the behavior of droplet deposition in the downwash flow field of an agricultural hybrid wing UAV under different operating conditions. The results indicate that as the height increases, the deposition distribution of droplets becomes more uniform, and the drift problem is also improved. Compared with the quadrotor UAV, hybrid wing UAVs have a faster downwash airflow velocity, which helps achieve a more uniform distribution of droplets. However, the phenomenon of “negative velocity channels” is more pronounced and may lead to additional droplet drift. When UAVs encounter crosswinds during spraying, it can ensure a uniform droplet distribution by increasing the rotor velocity. The findings reveal the deposition behavior of sprayed droplets under different operating conditions and provide a reference for the practical operations of UAVs.

The development of modern technologies in agriculture, particularly the use of unmanned aerial vehicles (UA Vs), has enabled significant advancements in pesticide application, resulting in greater efficiency and precision in crop protection. This study aims to analyze the effects of various UA V flight parameters, specifically flight altitude, on droplet size and distribution uniformity. Field trials were conducted on the municipality of Zemun-Belgrade, Republic of Serbia, Latitude: North 44° 49' 22.2" and Longitude: East 20° 13' 19,2", with an altitude of 73 m. Different flight heights (1.5 m and 2.5 m) were tested at a constant flight speed of 3 m/s. The results indicated that smaller droplets, generated at higher flight altitudes, contributed to more uniform droplet distribution, while larger droplets at lower flight altitudes ensured better coverage. The most favorable outcomes were observed at a flight altitude of 2,5 m, where droplet distribution was both more uniform and of higher quality.

A one-dimensional imaging probe was used to measure samples of the spray distribution produced by four different rotary atomizers operating at several different flow rates and rotary speeds using tap water and vegetable oil as carriers. The operating characteristics of the laser imaging probe affected the data collection results. The warm-up interval, effective sampling width, droplet velocity, and spray density were the most critical factors. Each rotary atomizer produced a range of droplet sizes for which uniformity depended on the operating conditions and liquid carrier. At water flow rates below 0.5 L/min, the Micron Micromax produced the most uniform droplet distributions. At rates above 0.5 L/min of water, the Spraying Systems RotoJet produced the most uniform droplet distributions. A larger selection of volume median diameters was produced using vegetable oil rather than water as the carrier. The uniformity of the droplet distributions is controlled better with oil. The RotoJet produced the most uniform droplet distribution with oil in comparison with the other atomizers. There was little difference between water and oil as carries in the drift potential at low rotational speeds. However, at higher operating speeds the drift potential was reduced by using oil as the liquid carrier.

Spraying of defoliant can promote centralized defoliation of cotton and advance maturity to facilitate harvesting. Modern pesticide application equipment includes plant protection unmanned aerial vehicles (UAVs), which are used widely for spraying defoliants. However, commonly used defoliant formulations are mainly suspension concentrates and water-dispersible granules, which need to be diluted with water when used. These are not suitable for plant protection UAVs with limited load capacity, especially in arid areas such as Xinjiang, China. Therefore, we prepared a thidiazuron·diuron ultra-low-volume (ULV) spray, which can be used directly without dilution in water. We found that ULV sprays had better wettability than the commercially available suspension concentrate, could quickly wet cotton leaves and spread fully. The volatilization rate was lower. ULV sprays also showed better atomization performance and more uniform droplet distribution than the commercially available suspension concentrate. At a dosage of 4.50–9.00 L/ha, the coverage rate on cotton leaves was 0.85–4.15% and droplet deposition densities were 15.63–42.57 pcs/cm2; defoliation rate and spitting rate were also greater than those of the reference product. This study could be contributed to the development of special pesticide formulations suitable for UAVs.

Unmanned aerial vehicles (UAVs) are widely used as the sprayers for low-volume pesticide application in recent years. Droplet distribution characteristics of UAV spraying in the cotton canopy have notable effect on the biological control efficacy of the targets and the defoliation efficiency of the harvest aids. In this work, the influences on droplet distribution in the cotton canopy with respect to the flight height, forward mode, and spraying volume were evaluated by conducting the field trials during two cotton growth stages in 2020, respectively. The first field trial was performed in the cotton flowering stage and the second one was conducted in the early boll development stage. Two typical UAVs equipped with a single-rotor and four-rotor, respectively, were adopted as the spraying platforms in this work. Droplet deposition obtained by water sensitive papers (WSPs) clipped on the cotton leaves was considered as the observing metric. All cotton leaves in the canopy were divided into three groups (i.e., upper, middle, and bottom layers) in both trials. Furthermore, the cotton canopy was divided as eight directions to assess the droplet distribution in the canopy from different directions. The results showed that the droplet deposition varied remarkable between the treatments and in the same canopy within a treatment. The upper layer obtained higher droplet deposition than those of the middle and bottom layers and plants P4 to P8 accessed more droplets than those of the remaining sampling plants in most treatments of both trials for the two UAVs. The upper layer droplet deposition of the four-rotor UAV treatments outperformed that of the single-rotor treatments under the same operating parameters. The forward modes rarely affected the droplet distribution of the four-rotor UAV treatments but significantly influenced that of the single-rotor UAV treatments. For the single-rotor UAV spraying with “head forward”, the droplet distribution of the treatment with a flight height of 2 m was more even than that of the 1 and 3 m in the first trial. Under the same flight height, droplet deposition of the treatments with a spraying volume of 22.5 L ha−1 was remarkably higher than that of the 12 L ha−1 for both forward modes in the second trial. “Tail forward” of the single-rotor UAV treatment had better penetration at a flight height of 2 m in both trials. Therefore, for the single-rotor UAV, under a flight height of 2 m and a spraying volume of 22.5 L ha−1, “tail forward” was recommended for applying pesticides to control targets at the lower canopy and “head forward” was a better choice for harvest aid application. Four-rotor UAV was a suitable adoption for the harvest aid application and controlling the targets of the upper canopy. The results also indicate that the systemic pesticides are recommended for UAV spraying due to its uneven droplet distribution uniformity in the whole cotton canopy.

Abstract.This study assesses the potential of dynamic nozzle height adjustment for overhead irrigation systems. This system would maintain the nozzle or emitter a constant distance above the crop canopy throughout the growing season and would dynamically respond to variability in canopy height across the field. Within such systems, nozzle height would no longer be fixed in space and time. Nozzle heights would instead vary across space and time. This dynamic system response may therefore have adverse impacts on water application uniformity. The impact of DESA on application uniformity was assessed in three steps. First, changes in individual sprinkler patterns for pressure, nozzle type, flow rate, and nozzle height were measured in controlled experiments. Next, parametrized equations of the individual sprinkler patterns and how they are altered by nozzle height are developed. Next, the Center Pivot Evaluation and Design software was used to simulate theoretical uniformity, and these simulations were tested against field measurements of the coefficient of uniformity. Finally, we use the parameterized equations within the Center Pivot Evaluation and Design software to simulate the coefficient of uniformity for pivots with constant nozzle heights with a random distribution of nozzle heights, which simulate a dynamic elevation system. It was found that the uniformity coefficient decreased by 4-6% as the distribution of heights throughout the pivot become more variable, due to localized dynamic height adjustment. Systems equipped with nozzles with triangular spray patterns were less impacted than systems equipped with nozzles with elliptical spray patterns. Keywords: Keyword. Center pivot, Center Pivot Elevation and Design (CPED), Nozzle height, Sensor, Sprinkler pattern, Uniformity coefficient.

Aerial spraying plays an important role in promoting agricultural production and protecting the biological environment due to its flexibility, high effectiveness, and large operational area per unit of time. In order to evaluate the performance parameters of the spraying systems on two fixed wing airplanes M-18B and Thrush 510G, the effective swath width and uniformity of droplet deposition under headwind flight were tested while the planes operated at the altitudes of 5 m and 4 m. The results showed that although wind velocities varied from 0.9 m/s to 4.6 m/s, and the directions of the atomizer switched upward and downward in eight flights, the effective swath widths were kept approximately at 27 m and 15 m for the M-18B and Thrush 510G, respectively, and the latter was more stable. In addition, through analyzing the coefficients of variation (CVs) of droplet distribution, it was found that the CVs of the M-18B were 39.57%, 33.54%, 47.95%, and 59.04% at wind velocities of 0.9, 1.1, 1.4 and 4.6 m/s, respectively, gradually enhancing with the increasing of wind speed; the CVs of Thrush 510G were 79.12%, 46.19%, 14.90%, and 48.69% at wind velocities of 1.3, 2.3, 3.0 and 3.4 m/s, respectively, which displayed the irregularity maybe due to change of instantaneous wind direction. Moreover, in terms of the CVs and features of droplet distribution uniformity for both airplanes in the spray swath, choosing smaller CV (20%-45%) as the standard of estimation, it was found that the Thrush 510G had a better uniform droplet distribution than the M-18B. The results provide a research foundation for promoting the development of aerial spraying in China. Keywords: aerial spraying, effective swath width, droplet distribution, coefficients of variation, agricultural airplane DOI: 10.3965/j.ijabe.20150802.1493

In this study, the nozzle types Agrotop TDXL 80-015, TDXL 80-02 and TDXL-D 110-02 were investigated to classify their drift reduction potential for downward spray applications (at 2, 3 and 3 bar spraying pressure, respectively). The uniformity of the spray distribution was tested on a patternator for the appropriate nozzle height (default height 0.50 m; for the 80-degree nozzles lowered to 0.30 m). For all three nozzle types the resulting coefficient of variation (CV) was less than 10%. Droplet size measurements were done using a PDPA system and the resulting droplet size spectra and droplet velocities were used in the IDEFICS spray drift model. Spray drift deposits on a standardized ditch were computed, as well as the corresponding drift reductions compared to the reference situation. According to the current classification system for drift reducing nozzles, the drift reduction capability of all nozzle types must be evaluated at nozzle height 0.50 m above the crop. At this nozzle height and a nozzle spacing of 0.50 m, nozzle type TDXL-D 110-02 could be classified as 75% drift-reducing (DRD75) at liquid pressure of 3 bar. At a nozzle spacing of 0.25 m, the nozzle types TDXL 80-015 and TDXL 80-02 could also be classified as DRD75, at a nozzle pressure of 2 and 3 bar, respectively. Therefore, these 80-degree nozzle types are eligible to be used as DRD75 nozzles at the given liquid pressures in the drift-reducing technique (DRT) of ‘lowered sprayer boom’.

Ground-based active sensors have been used in the past with success in detecting nitrogen (N) variability within maize production systems. The use of unmanned aerial vehicles (UAVs) presents an opportunity to evaluate N variability with unique advantages compared to ground-based systems. The objectives of this study were to: determine if a UAV was a suitable platform for use with an active crop canopy sensor to monitor in-season N status of maize, if UAV’s were a suitable platform, is the UAV and active sensor platform a suitable substitute for current handheld methods, and is there a height effect that may be confounding measurements of N status over crop canopies? In a 2013 study comparing aerial and ground-based sensor platforms, there was no difference in the ability of aerial and ground-based active sensors to detect N rate effects on a maize crop canopy. In a 2014 study, an active sensor mounted on a UAV was able to detect differences in crop canopy N status similarly to a handheld active sensor. The UAV/active sensor system (AerialActive) platform used in this study detected N rate differences in crop canopy N status within a range of 0.5–1.5 m above a relatively uniform turfgrass canopy. The height effect for an active sensor above a crop canopy is sensor- and crop-specific, which needs to be taken into account when implementing such a system. Unmanned aerial vehicles equipped with active crop canopy sensors provide potential for automated data collection to quantify crop stress in addition to passive sensors currently in use.

Allometric comparison of viral dynamics in the nasal cavity-nasopharyngeal mucus layer of human and rhesus monkey by CFD-HCD approach

Droplet distributions in cotton harvest aid applications vary with the interactions among the unmanned aerial vehicle spraying parameters

<b><sc>Abstract.</sc></b> <b>The manually high-volume spray techniques are widely used in China to apply plant-protection products in glasshouses, having poor efficiency due to heavy losses to the soil and high risks of worker exposure. Accordingly, a fixed-pipes twin fluid cold fogging system realized the ultra-low volume spray was designed based on the self-developed venturi nozzles. The system performance were investigated in comparison with a trolley cold fogger. Meanwhile peppers in fruiting period were chosen to explore the influence of canopy on droplet distribution of the fogging system. In the test, the air and water pressure of the fogging system were 0.3 MPa and 0.05 MPa with application rate of 2 L/min. The trolley cold fogger was placed at a distance of 2 m from the front collection area in the middle of the greenhouse, the angle between air cylinder and horizontal ground was 15°. The application rate of the trolley fogger was 1.5 L/min. The total application time was 5 min. Results show that compared with the trolley cold fogger, the droplet deposition coefficient of variation of the fogging system among different collection areas was only 13%, the fogging system can achieve unmanned pesticide application throughout the greenhouse with desired uniformity of droplet distribution; the presence of peppers was conducive to droplets gather on surrounding leaves, droplet deposition in vertical height in different regions had no significant difference. Consequently, the fogging system had better working performance and uniform droplet distribution can realize the separation work between human and the fogging system.</b>

Unmanned aerial vehicles (UAVs) have emerged as promising technologies for agricultural applications, including pesticide spraying in paddy fields. Droplet size is a critical factor influencing the effectiveness and efficiency of pesticide application. This study investigated the impact of various spray parameters of UAV sprayers on droplet size during paddy spraying. The experimental setup involved a UAV equipped with different nozzle types (flat fan nozzle, hollow cone nozzle and spinning disc nozzle), operating at varying forward speeds (2, 3, 4, 5 and 6 m s-l) and spray heights (l, 1.5, 2, 2.5 and 3 m above the crop canopy). The results demonstrated that among the three operational parameters, the type of nozzle had a significant effect on the droplet size, whereas the forward speed and height of the spray were not significantly different. A larger droplet size was obtained for the flat fan nozzle, followed by the hollow cone and spinning disc nozzles. These findings provide valuable insights for optimizing UAV sprayer settings to achieve the desired droplet size distributions and improve pesticide application efficiency in paddy fields.

This study was undertaken to analyze the influence of nozzle type on a mass spray density. The results indicated that the most uniform droplet distribution and spraying area was observed for the impact nozzle P 54. The highest mass spray density and the lowest spraying were noticed for the spiral nozzle TF 6. The high values of mass spray density for TF 6 nozzle were associated with the high K-factor value and the low spray angle. The results also showed that the construction of spiral nozzles influence the stream structure. The value of average mass spray density was twice as low for CW-50 F nozzle compared to TF 6.

Since the 2010s, unmanned aerial vehicle (UAV) sprayer was applied more and more widely for low-volume aerial pesticides spraying operations in China. However, droplets from the UAV sprayer have a higher drift risk due to more fine droplets sprayed and a higher flight height than ground sprayers. Study on UAV spray drift has been a new hot spot within the field of pesticide application technology. Most of previous studies used direct field methods for spray drift, but the meteorological conditions in field were unstable and uncontrollable, and drift research under an actual operation state in wind tunnel has not been reported. Therefore, 25 treatments of wind tunnel measurements and droplets spectrum tests of 10 models of nozzles were conducted to explore the influence factor on spray drift characteristics of UAV chemicals application in this study. A spray unit with a rotor of UAV was innovatively installed in wind tunnel, and the airstream from the wind tunnel was regarded as the relative moving natural wind to simulate the flight status. The airborne and the sediment spray drift was measured to study the effects of the nozzle type and size (flat fan, hollow cone and air-inclusion nozzles), flight speed, adjuvant (DRS-60, Y-20079, MF and G-611) and meteorological parameters (20°C & 40%, 20°C & 80%, 30°C & 40% and 30°C & 60%). The drift potential (DP) and the drift potential reduction percentage (DPRP) in vertical and horizontal directions were obtained for each test. Both nozzle type and size had an impact on the spray drift potential obviously by affecting the droplet size and the ratio of fine droplets, and the regression linear models between DPRPV/DPRPH and DV50, V75 were established (R2=0.934/0.925). Flight speed also had a significant effect on the spray drift characteristics, and reducing the flight speed could increase the DP effectively. Adding spray adjuvants could affect the DP under experimental meteorological parameters, and the anti-drift performance ranked in the order of DRS-60>MF>Y-20079>G-611. Recommendations were proposed in order to reduce the spray drift for UAV sprayer’s operation. These findings can contribute to provide guidelines and technical support for the wind tunnel spray drift tests of UAV and the field operation regulation of unmanned aerial PPP application. Keywords: unmanned aerial vehicle (UAV) sprayer, wind tunnel, spray drift potential, nozzle, adjuvant DOI: 10.25165/j.ijabe.20201303.5716 Citation: Wang C L, Zeng A J, He X K, Song J L, Herbst A, et al. Spray drift characteristics test of unmanned aerial vehicle spray unit under wind tunnel conditions. Int J Agric & Biol Eng, 2020; 13(3): 13–21.