Bottom-up computational design of a hybrid tricopter agricultural spray UAV: propeller, nozzle, tank and airframe CFD optimization

Purpose This paper aims to develop and validate a hybrid tri-agri-copter (TAC) unmanned aerial vehicle (UAV) for precision agricultural spraying using a bottom-up computational fluid dynamics (CFD)-first design methodology that sequentially evaluates each sub-system before full-vehicle integration. Design/methodology/approach A 2.5 kg payload is adopted as the primary design driver. Critical components, including a coaxial propeller unit, Y-shaped airframe, three nozzle configurations and two tank geometries, are modeled in 3DEXPERIENCE and evaluated using ANSYS Fluent under vertical take-off and landing, hover and forward-flight conditions. Validation is conducted via wind tunnel drag measurements and laboratory nozzle flow tests. Findings Nozzle-2 produces a uniform, well-collimated jet free of recirculation, with an exit velocity of 16.46 m/s at 2 bar; the proposed rectangular-convergent tank provides superior flow uniformity and a 29.4% higher exit velocity than the conventional conical tank. Wind tunnel validation yields a root-mean-square error of 0.00013 on the drag coefficient; the nozzle flow rate matches CFD within 3.3%. The thrust margin of the design payload is 3.6%. Research limitations/implications Only three nozzle and tank geometries are compared; field trials remain as future work. Practical implications The validated CFD-first framework enables agricultural UAV developers to select components before hardware commitment, reducing development cost and iteration time. Originality/value To the best of the authors’ knowledge, this is the first study to apply sequential, component-level CFD to the propeller, nozzle, tank and full airframe in a single bottom-up design chain for an agricultural TAC.