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Rotor unmanned aerial vehicles (UAVs) for pesticide spraying have been widely used in China during the past three years. In order to improve the effectiveness of pesticide application and reduce environmental risk caused by spray drift, it is important to clarify the spatiotemporal distribution characteristics of airflow field of the drone. The airflow field produced by the UAV plays a key role in droplets delivery during the spraying. In this study, the lattice Boltzmann method (LBM) based on a mesoscopic kinetic model was used to simulate the airflow field of a six–rotor plant protection drone. The airflow field of drone in hover and at varied flight speeds (1.0–5.0 m s−1) and various altitudes (1.5–3.5 m) was investigated. The characteristics of airflow separation, airflow coverage equivalent area and "steep" effect were investigated numerically. The peak value of vertical downward velocity (V– Y) on the detection surface was analysed. Results indicate that the flight speed and altitude had a significant effect on the distribution of the airflow field. The predicted values in the vertical direction using the average velocity attenuation model (Y–DAVA) corresponded well with experimental measurements. The wake of airflow field had a significant backward tilt when the drone was flying forwards, thus when the flight speed was 4.0 m s−1 and 5.0 m s−1, the wake of the airflow field lifted off the ground, whereas the transverse separation appeared as horseshoe vortices. For flight speeds of 3.0 m s−1 and an altitude of 3.0 m the distribution of V– Y was the most uniform. • Airflow field of drone plays a key role in droplets delivery during the spraying. • The airflow field was simulated successfully by LBM. • Flight speed and altitude had a significant effect on the distribution of airflow field. [ABSTRACT FROM AUTHOR]

In rice–wheat rotation areas of China, traditional wheat seeders have severe blockage, low working efficiency and poor seeding quality. In this study, a pneumatic shooting technology was designed, consisting mainly of a nozzle, shell and acceleration tube. To improve the sowing depth of the pneumatic shooting device, the response-surface methodology of structure parameters and CFD simulation technology was adopted in this work. The effects of working pressure, acceleration-tube diameter and throat distance on the steady airflow length (SAL) and steady airflow velocity (SAV) were studied by airflow field analysis, and the response-surface method was introduced to obtain the optimal parameter combination of the pneumatic shooting device for wheat. The optimal parameter combination was working pressure 686 kPa, acceleration tube diameter 8 mm and throat distance 20 mm. The simulation result showed that the optimized device of pneumatic shooting performs faster and has more stable airflow field characteristics in comparison to the initial device. The field test demonstrated that the optimized device has about 68% higher seeding depth than the initial device. The average field-seeding depth of the optimized device was 19.95 mm, which is about 68% higher than the initial device. The emergence rate for the optimized device was about 88.7% without obvious reduction. CFD and response-surface methods positively affect the optimization of pneumatic wheat-shooting devices, and the significance was also confirmed. [ABSTRACT FROM AUTHOR]

In the evening of 11 April 2011, vortex/wave shedding from a mountain to the south of the Hong Kong International Airport (HKIA) appeared to occur following the establishment of fresh to strong easterly airflow in Hong Kong. This paper documents the observations by the various meteorological instruments of the event and discusses the possibility of forecasting the vortex/wave shedding using a high resolution numerical weather prediction (NWP) model. The vortex/wave shedding was well observed by the Light Detection and Ranging (LIDAR) system at HKIA. The vortex/wave appeared as an area of reversed flow against the background east to southeasterly airflow in the airport area. It was detached from the mountain and moved to the northwest with the background southeasterly flow, with a gradual decrease of the spatial extent in the area of reversed flow. The vortex/wave brought about significant wind shear to both arrival flight paths to the west of HKIA, as evidenced from the headwind profile data measured by the LIDARs and the aircraft data. It had rather large vertical extent, reaching the top of the boundary layer, but did not extend downward to the surface, as shown from the vertical scans of the LIDAR and the surface wind observations. The shedding event is successfully captured by high-resolution NWP model with a spatial resolution of 50 m. The model output has a lead time of 6-7 h ahead of the event, indicating the possible occurrence of terrain-induced wind shear in the form of vortex/wave shedding from a mountain. As a result, the numerical simulation could be useful in giving an early alert to the aviation weather forecaster about the significant wind shear event, which could be hazardous to the landing aircraft. Copyright © 2011 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

Abstract: Numerical simulation method is adopted to optimize the design of air flow distribution in China Pavilion. Four cases of different supply air velocity and temperature based on the same cooling capacity are simulated. Through comparing draught sensation (DR), ADPI index, energy consuming and so on, indoor thermal comfort and energy-saving are analyzed. The results show that, under the case which the supply air velocity is 2m/s, the indoor air velocity in occupied zone is mainly 0.2m/s, draft sensation is about 8%, the temperature, velocity field and energy consuming are basically meet the requirement of thermal comfort and energy saving. [Copyright &y& Elsevier]

Abstract: Experiments in a comparable hot-box have been carried out for the study of the thermal performance and power generation of a double-glazing window system integrated with amorphous silicon (a-Si) photovoltaic (PV) cells in Hefei, east region of China. Compared to PV single-glazing window, the indoor heat gain of PV double-glazing window is reduced to 46.5% based on experiment data. The electric efficiencies are both about 3.65% with packing factor 0.8 of PV single-glazing window and PV double-glazing window. The numerical simulation with computational fluid dynamics (CFD) method has been performed for the prediction of air flow and thermal performance of PV double-glass window. The temperature distribution and thermal performance predicted by the CFD model are in good agreement with the experimental data. Compared between the experimental and numerical results, temperature differences of PV modules are only 1.7% and 1.1% for PV double-glazing and PV single-glazing window, respectively. Because of the much lower inner surface temperature of PV double-glazing window compared with that of PV single-glazing window, the predicted mean vote (PMV) of the office work stage area with PV double-glazing window is well improved. [ABSTRACT FROM AUTHOR]