###### Abstract
[18], three-dimensional CFD analyses were performed on a 6-rotor UAV used for agricultural purposes using the k-\(\varepsilon\) turbulence model. The analyses examined the downwash created by the vehicle at heights of 1 to 2 m above ground level. Within these analyses, the rotational speed of the propellers was taken as 288 rad/s (2750 rpm), and according to the analysis results, the maximum velocity generated by the ground effect was determined to be 10 m/s. [PERSON] et al. performed unsteady CFD analyses of a 6-rotor UAV equipped with a spray system. The UAV was positioned at a height of 2 m and operated at a rotational speed of 3600 rpm. In these analyses, the distribution of downwash effects at different distances was determined and comparisons between experimental data and CFD results were conducted [19]. CFD analyses of an eight-rotor UAV configuration were performed by [PERSON], [PERSON] et al. The UAV model was simplified and was positioned at a height of 3 m above ground level. Additionally, rotation speed was set at 3500-4000 rpm, and crosswind and ground effects were used. As a result, it was shown that the spray systems were successful [14]. The research carried out by [PERSON], [PERSON], et al. performed CFD analyses to investigate the downwash effect at different levels using a six-rotor UAV. The analyses were based on the k-\(\varepsilon\) turbulence model, and the rotational speed of the small-sized UAV was selected as 1500 rpm. To investigate the downwash, the UAV was positioned at different heights (0.2 m; 0.5 m; 2 m, and 5 m). The results from the small-scale UAV suggest that it could potentially replace the full-scale UAV [10]. Research on aeroacoustics related to UAVs has also been conducted. In a study by [PERSON] and [PERSON], the aeroacoustics characteristics of a swarm consisting of six multi-copters were examined. The swarm was positioned horizontally in V-shaped and rectangular-shaped (U-shaped) configurations. Three-dimensional CFD analyses were performed, and the flight speed was set to 9 m/s. The aeroacoustics characteristics of the swarm were determined [20]. [PERSON], [PERSON] et al. carried out CFD analyses on a four-rotor UAV model, which is also the subject of this study, using MRF (Multiple Reference Frame) and Sliding Mesh methods. In their research, the ground effect was also examined by taking the rotation speed of propellers as 1000 rad/s and the analyses based on the initial positions of the propellers [1]. The evaluations indicated that the MRF method was a suitable option for calculating the relative positions of the propellers and the MRF method could be preferred over the Sliding Mesh method for ground effect analyses. In another study by [PERSON], [PERSON] et al. [2], the aerodynamic effects occurring from passing over an obstacle using a quad-rotor UAV model were investigated. The study successfully determined the ground effect that may occur as a UAV moves at speeds of 1.5, 7.5, and 10 m/s when passing over an obstacle. The focus of this paper is CFD analyses of four multi-rotor UAVs arranged in a rectangular formation, with two UAVs positioned above and two below at a specified proximity distance. The objective was to calculate the flight configurations of multiple UAVs in a vertical formation using CFD analyses with the k-\(\epsilon\) turbulence model and the MRF method and to investigate their flight performances. Upon examining previous research in the literature, this research represents a milestone in the aerodynamic behavior of swarm UAVs. The swarm formation that four rotary-wing unmanned aerial vehicles can create during flight was investigated in detail, their behaviors during flight were modeled and interpreted using Computational Fluid Dynamics. Additionally, the phenomenon of close UAV interaction was defined.