## 2 Literature Survey
In [7], computational and experimental investigations were carried out on an octorotor-based small multirotor UAV. Comprehensive performance analyses were computed and tested based on the predominant consideration of the rotor spacing and its variations. The fundamental object of this study was a medium-sized propeller, with dimensions of 15.75 in diameter and six-inch pitch. The rotodynamic effect of the propeller can create a cascade effect, thereby affecting the entire performance of the octocopter; therefore, this study provides significant information about perfectly positioning the eight rotors in the octorotor system. The computational investigations were computed using an octorotor with the discretization category of an unstructured grid formation. Through the inclusion of the study [7], the design ratio between the diameter of the propeller and the length of the connecting arm was fixed at two for the current design. Through this high design ratio, the possible cascade-based effect on performance should never occur in the proposed design. In [8], the CFD and FSI computational approaches were imposed on an unmanned amphibious vehicle [UAmV], in which the aerodynamic-dependent initial and boundary conditions were useful data for this study. In particular, two important observations noted from the study [8] are that the k-epsilon turbulence model was imposed for the prediction of wake in and around the UAmV, and that the [semi-implicit method for pressure-linked equations] SIMPLE-based pressure- and velocity-coupling approach was implemented for the internal computations. In addition to these conditions, the design procedure involved in the study for four-bladed amphibian rotors has been adopted for the design of the current propulsive system. In [9], the authors computationally investigated the performance of various ducts and ducted propellers using a CFD approach. The ducts involved in this comparative investigation were convergent, divergent, and convergent-divergent. Based on the high induced-velocity factor, the convergent-divergent duct was selected as the best performer over the other two ducts. An unstructured discretized control volume was constructed, in which the k-epsilon turbulence model was imposed to predict the flow inside the ducts. In this study, the implementation of a CD duct-based storage tank in an octocopter emerged because of the need for a high fluid velocity at the exit of the tank. In [10], the authors computed fluid dynamic behavioral analysis for a hexacopter using ANSYS Fluent. The major focus was on the variations in the angle arrangement of the connecting arms in the frame of the UAV. Owing to the angle variations of the connecting arms in the UAV, the aerodynamic forces were moderated and twisted. Because of this segregation of aerodynamic forces, additional sideward forces were induced, which provided static stability to the multirotor UAV. The assembly of connecting arms for the current study was constructed using a literature survey [10]. The main observation of the study [11] was the computational procedure for the execution of the moving reference frame (MRF) approach on the propeller. In the current work, the MRF analyses are planned to be imposed on eight different rotors, so the implementation of MRF is unavoidable. From the study [11], it was also found that suitable initial and boundary conditions are also suitable for transient-flow computations. Through these inputs, the convergence of the current computation occurs without any computational oscillations. The objective of the current study is to develop an octorotor-configured multirotor UAV for clear visibility-based environmental applications in terminals such as airports, railway stations, and bus stands.