# Advancements and Applications of Rim-Driven Fans in Aerial Vehicles: A Comprehensive Review
## 9 FEA and CFD  
Rim-driven thrusters (RDTs) have been studied extensively using various numerical methodologies, including finite element analysis (FEA) and computational fluid dynamics (CFD). A number of factors have been explored to optimize RDT performance, including length diameter ratio, diffusion ratio, contraction ratio, tip diameter ratio, and blade size and shape. Additionally, researchers have investigated the impact of different RDT configurations, including hubless and hub-type designs. Finite element analysis (FEA) and computational fluid dynamics (CFD) methods have been used in previous studies to analyze the performance of rim-driven thrusters (RDTs) [57, 87]. A study by [PERSON] et al. employs a numerical methodology to investigate the influence factors of the rim-driven propeller. The hydrodynamic performance is scrutinized in a stepwise manner by analyzing the impact of the length diameter ratio, diffusion ratio, contraction ratio, and tip diameter ratio, utilizing the concept of sensitivity analysis [88]. A rotor parametric model comprising of blades and a rim has been formulated. The model incorporates a range of variables that have been subjected to multi-objective optimization using ModeFrontier (ESTECO). The optimization process involved measurement of selected parameters through CFD simulations conducted with the Star-CCM+ solver (SIEMENS) [89]. In a similar study, based on the findings, it can be inferred that with a marginal enhancement in the propulsion efficiency as compared to the initial blade, the optimized blade has the potential to augment the RDT thrust coefficient by approximately 15% [90]. [PERSON] and [PERSON] analyzed a 280 mm diameter RDT using FEA and CFD to study the natural frequency and mode shape, flow paths, blade surface pressure, and thrust [91]. [PERSON] developed a rim-driven water-jet pump and used a simplified steady-state computational fluid dynamics model to investigate the impact of hub-type and hubless guiding vanes on the overall efficiency of the impeller [92]. The impeller efficiency of pumps with hubless guiding vanes was reduced by roughly 10 percentage points as a result of energy losses that occurred in the center line. The CFD simulation method was applied to design a rim-driven thruster and a comparison between the calculated and experimental results of NO. 19A + Ka4\(-\)70 ducted propeller was conducted [93]. As a result, the numerical method was verified and the improved Ka-series propeller was introduced and implemented. Finally, the study analyzed the effects of the propeller's hydrodynamic performance as regards the number of blades, rake angle, and pitch. The hydrodynamic performance of the propeller is similar to that of the traditional ducted propeller and the absence of a hub improves cavitation and reduces noise. The rake angle does not have much impact on performance, but it should be determined based on the vibration of the tail. The propeller's thrust, torque, and efficiency increase with the pitch, while the number of blades increases torque and thrust but decreases efficiency and cavitation performance. A lesser number of blades helps avoid cavitation, but it increases vibration. The aerodynamic characteristics of the RDF were studied by investigating the effects of four key parameters, including the rotor disk height, number of blades, central hole radius, and blade root mounting angle [94]. The research found that rotational speed greatly affects thrust performance, with performance improving as speed increases. Placing the rotor away from the duct entrance results in better aerodynamic performance. A larger number of blades increases peak thrust and ducted thrust performance but reduces the power load. Reducing the central hole radius decreases overall aerodynamic performance due to enhancing airflow blocking. Increasing the blade root mounting angle generates more thrust but reduces power load.