# CFD Analysis and Validation of a Foreign Material Winnowing Machine for Pepper Harvester
## 1 Introduction
As a result of the test, the foreign material separation rate was 53.5% under a straight-line card arrangement, an inclination angle of 15\({}^{\circ}\), and a rotation speed of 50 RPM. Statistical analysis showed that the foreign material separation rate was significantly related to the inclination angle and the rotating speed. [PERSON] et al. [20] have established optional conditions of a card cleaner device by grasping its mechanical and physical properties using the discrete element method (EDEM) and found that conditions are similar to those of the factorial performance experiment of [PERSON] et al. [19]. In a study on the aerodynamic winnowing method, [PERSON] et al. [21] have experimentally obtained and induced terminal velocity of freely falling grains using a time-displacement technique to measure terminal velocities of seven kinds of grains and seeds such as wheat about that of a plastic sphere. In an aerodynamic study on the air stream separation of grains, [PERSON] et al. [22; 23] analyzed the effect of rice and barley sizes and moisture content on the measurement of terminal velocity. Their measurement results showed that the terminal velocity of rice was 4.6 to 4.8 m/s and that of barley was 4.9 to 5.5 m/s. [PERSON] et al. [24] have experimentally investigated aerodynamic characteristics of the separation section in a combine. As a result of making measurements at a winnower rotating speed of 1150 RPM, it was found that air separation of wheat, branch straw, and leave straw was possible at 4.1 m/s, 2.4 m/s, and 1.3 m/s, respectively. To confirm the physical, mechanical, and aerodynamic properties required for separation after the mechanical harvesting of peanuts, [PERSON] et al. [25] have compared the results of a modeling calculation and an actual test. Their test results showed that the breaking power of peanut hulls was irrelevant to their shape, size, or moisture content, with a drag coefficient range of 0.67 to 0.93. [PERSON] [26] has conducted a test after fabricating a device to separate chili pepper using a winnowing fan and a vibrating separation sieve. As a result of the separation, the chili pepper separation rate was 68.2% when the wind speed of the winnowing machine was 6.2 m/s, the frequency of the separating sieve was 6.9 Hz, the amplitude was 40 mm, and the thickness and interval of the separation sieve rods were 6 mm and 29 mm, respectively. As a result of conducting a test of removing foreign materials from chili peppers by organizing a fan absorption winnowing device, a discharge conveyor, and a foreign material collecting bin, [PERSON] et al. (2017) have found that chili pepper leaves are absorbed in a winnowing machine wind speed of 12 to 15 m/s and the foreign material removal rate is 95%. [PERSON] et al. (2018) have evaluated the separation rate and loss rate at the foreign material separation winnowing machine's rotation speed of 180 to 300 RPM to develop a sesame harvester. As a result of the test, separation rates of sesame were 99.7% and 99.8% at 220 and 240 RPM, respectively. These were reported as the optimal RPMs of the winnowing machine with the least loss. [PERSON] et al. (2019) have analyzed the fluid flow of a peanut harvester's winnowing machine by conducting a CFD analysis. They found that the fluid flow was adequate when the direction was counterclockwise and the rotating speed and the flow field velocity were 1500 RPM and 8 to 17 m/s, respectively. The separation system of the peanut harvester was investigated in a factor experiment using the analyzed result ([PERSON] et al., 2018). [PERSON] et al. (2018) have analyzed the separation performance using the CFD-DEM (Computational Fluid Dynamics--Discrete Element Method model) to improve the separation performance of a combine and save the cost. Separation and performance efficiencies were 98.9% and 87.7%, respectively, at a wind speed of 11.0 m/s. The error in the separation rate was 5% or less.