Flexible filamentous particles are a special kind of particles and play a significant role in many industrial processes.The mixing dynamics of flexible filamentous particles in the transverse section of a rotary drum were analyzed numerically in two dimensions.First,a chain model of slender bodies was introduced for particle dynamic studies,and each individual particle as well as each segment of the particle was tracked during the process.Then,the bulk movement of particles in the transverse section of a rotary drum was explored numerically and mixing dynamics of the particles were further investigated with visual representation.To quantify the quality of mixing,the mixing rates were investigated to determine the mixing extent of particles in the rotary drum.Furthermore,the effects of rotational velocity,flight height and filling degree on mixing dynamics were examined in detail.Moreover,the numerical results were compared with experimental data,and reasonable agreements were obtained.The numerical analyses provide valuable insights into the mixing dynamics of flexible filamentous particles. The following is a list of articles in slender bodies was introduced for particle dynamic studies, and each individual particle as well as each segment of the particle was tracked during the process. Chen, the bulk movement of particles in the transverse section of a rotary drum was explored numerically and mixing dynamics of the particles were further investigated with visual representation.To quantify the quality of mixing, the mixing rates were investigated to determine the mixing extent of particles in the rotary drum.Furthermore, the effects of rotational velocity, flight height and filling degree on mixing dynamics were examined in detail. Moreover, the numerical results were compared with experimental data, and reasonable agreements were obtained. The numerical analyzes;