# Parameter Design and Optimization of Grass Aerial Seeding Tower Based Computational Fluid Dynamics
## 1 Introduction  
Desertification, a concerning environmental phenomenon, represents the gradual transformation of fertile land into arid desert landscapes due to various factors such as climate change, unsustainable land management practices, and human activities. With over 100 countries and regions grappling with the effects of desertification, urgent action and sustainable solutions are imperative to mitigate its devastating impact and safeguard the health and resilience of ecosystems worldwide [1; 2; 3]. The alarming rate of expansion of land desertification each year has significant impacts on both natural and social environments [4; 5; 6; 7; 8]. China faces various forms of desertification, mainly wind erosion, comprising nearly 70% of cases [4; 9]. Successful management efforts in places like the Mu Us and Kubuqi Deserts highlight the importance of proactive measures [10; 11]. [PERSON] et al. have found that the restoration of degraded grasslands after light harvesting takes about 30 years to return to native vegetation [12]. Therefore, adopting effective prevention and control measures to address land desertification is imperative.  
No-tillage reseeding technology has emerged as a promising solution, especially in the northern regions of China, notably in arid and semi-arid areas. This technology not only finds applicability in agricultural production but also plays a significant role in grassland improvement and prairie ecosystem construction. However, due to environmental factors, issues such as the stability of total seeding volume, consistency in row spacing, and uniformity in seeding density have emerged. Aerial seeding technology used for unmanned aerial vehicles (UAVs) offers a rapid but costly solution, with successful applications seen in areas like the Bayan-Ondor Desert [13]. Innovations like [PERSON]'s small UAVs design enhance precision and efficiency in aerial seeding efforts [14]. Overall, addressing desertification demands effective measures and innovative technologies to safeguard ecosystems and livelihoods.  
Therefore, the construction of a grass aerial seeding tower relying on natural wind power is feasible and has high practical value. Compared to manual methods, it reducescosts, is suitable for open land, and allows for repeated seeding, enabling sustainable development of an area. In comparison to UAVs, it conserves energy as it relies on natural wind power and can be reused in a repetitive cycle, reducing the overall environmental impact. Additionally, periodic seeding can be performed based on seasonal changes, as well as the migration of livestock. In this context, the research team, based on the principles of the Laval nozzle and the design of the one-way filter, designed a grass aerial seeding tower structure that relies on natural wind power. The design was applied in the 2023 eVolo Skyscraper Competition, standing out for its scientific and practical significance. Our team received 1 of only 15 honorable mentions in this international architectural competition. However, the effectiveness of aerial seeding was compromised by internal airflow instability within the structure. Therefore, this paper further utilizes FLUENT 2020 R2 to simulate the fundamental components of the grass aerial seeding tower structure, and the interior flow characteristics of the tower were analyzed. Taking the cross-sectional inclination angle as the design parameter, and considering the coefficient of variation, uniformity index, and velocity direction index as constraints, an optimization was undertaken to enhance the internal airflow's uniform stability within the structure of the grass aerial seeding tower.