Analysis of arm sweep in artistic swimming using COMSOL

Abstract

In this project, we created a one arm sweeping motion submerged in fluid which simulates an artistic swimming scull technique using COMSOL Multiphysics. We will be analyzing the arm sweeping motion in various simulations. The model is built with the shoulder joint fixed to the origin coordinate while the arm executes a 90° sweeping rotation motion from horizontal to vertical. The total force on the shoulder joint generated is recorded with different angular velocities on 3 different models of the arm generated in COMSOL. The first model is a 2D straight arm sweeping motion, the second one is a 2D bent arm sweeping motion, and the third one is a 3D straight arm sweeping motion. Fluid flow caused by the arm sweeping motion is studied in this project. Through all the simulations generated, we noticed that the total force on the shoulder joint along the y-axis (vertical direction) during the initial motion changes from positive to negative to positive again during the initial sweeping motion. This is due to the fluid motion around the arm, and when the arm moves downward during the initial motion, it also creates a downward force on the shoulder joint. The peak total force is also generated at the initial motion of the arm regardless of the different angular velocities. This is because when the arm is horizontal, it exerts the largest downward force on the fluid. Hence, the total force acting on the arm is the greatest during this initial motion. The magnitude of the total force acting on the shoulder joint is also much larger in the 2D model than in the 3D model. This is due to the limitations of the fluid flow in 2D where fluid is only able to flow in a singular plane direction. Whereas fluid is able to flow over and around the arm in a 3D model. Therefore, the magnitude of the total force attained in 3D model is more realistic than in 2D model. Studies of the fluid flow were also made between the 2D straight arm and bent arm model. While comparing the total force generated across different angular velocities, we can conclude that the faster the angular velocity, the greater the total force generated.