###### Abstract  
The aerodynamic behavior of a square-shaped formation of four quadcopter UAVs flying in a swarm is investigated in detail through three-dimensional computer simulations utilizing Computational Fluid Dynamics (CFD) methodology. The swarm configuration comprises four UAVs positioned with two in the upper row and two in the lower row along the same propeller axes. The flow profile generated by the UAV propellers rotating at 10,000 revolutions per minute is analyzed parametrically using the Multiple Reference Frame (MRF) technique. UAVs within the swarm are positioned at 75 cm from the motion centers of adjacent propellers. This distance, the effects of horizontally and vertically positioned UAVs on each other, and the collective behavior of the swarm are thoroughly examined. Pressure, velocity, and turbulent kinetic energy values are meticulously analyzed. This research represents a milestone in understanding the aerodynamic characteristics of UAV swarms and the optimization of swarm performance. The findings highlight effective factors in swarm flights and their consequences for UAVs. Additionally, the article describes the \"near-UAV phenomenon\". Furthermore, the methodology developed for CFD simulations provides an approach to analyzing close flight scenarios and evaluating their performance in various swarm configurations. These achievements contribute to the future development of UAV technology. m _applied_  
_sciences_  
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In the research of [PERSON], [PERSON], and [PERSON], CFD analyses of body-wing UAVs were optimized using Taguchi methods and analyzed. It has been shown that performance can be improved with design variables [13]. Additionally, in another research study investigated by [PERSON], [PERSON], and [PERSON], the winglet structures with different design criteria of fixed-wing UAVs were analyzed using CFD. It was revealed that an approximate 10% increase in flight duration was achieved due to increased aerodynamic performance [5]. Fixed-wing models are preferred for their long flight range, while multi-rotor UAVs are more advantageous for short range flights. Multi-rotor vehicles are favored due to their ease of operation, flight stability, and advanced maneuverability capabilities [2]. Due to these advantageous features, multi-rotor UAVs find applications in tasks such as search and rescue, area surveillance, and smart agriculture practices including pesticide spraying, seeding, and spraying [10; 14; 15]. It is observed that there is an increasing interest in the use of multi-rotor platforms for spraying and pesticide applications. Research has also been conducted on components that affect the performance of UAVs, such as the landing gear. Experimental data obtained from wind tunnel tests of the landing gear were compared with CFD analyses by [PERSON] and [PERSON], leading to design suggestions for reducing frictional forces [16]. Moreover, different types of wings have been examined to determine the performance of the airfoil [17]. Fluid analyses were carried out using the k-\(\varepsilon\) turbulence model in a study by [PERSON] et al., which investigated a tilt-rotor UAV model with three rotors. The study examined the performance of vehicles operating at 2100 rpm with various rotor angles, thus verifying the applicability of wing movements [7]. Additionally, aerodynamic characteristics were compared by [PERSON], [PERSON] et al. through wind tunnel experiments and CFD simulations, and the results were shown to be compatible [8]. In addition to these studies, analyses have also been performed on three-rotor VTOL (Vertical Take-Off and Landing) systems [9]. In the literature, UAVs with configurations of four, six, and eight rotors have been an extensive subject of research. In a study conducted by [PERSON] et al.