Airflow is recognized as an effective method for inducing the illusion of self-motion (vection) and reducing motion sickness in virtual reality. However, the quantitative relationship between virtual motion and the airflow perceived as consistent with it has not been fully explored. To address this gap, this study conducted three experiments. In Experiment 1, we carried out a series of cross-modal matching tasks to establish the relationship between the speed of virtual motion and the airflow speed perceived as consistent with it, revealing a strong linear correlation. In Experiment 2, we introduced the concept of an "Airflow Gradient" to simulate the bodily sensation of curvilinear motion and examined the relationship between the radius and angular velocity of the motion and the difference in airflow speed between the left and right sides. The results indicated a linear relationship between the radius and the left-right airflow speed difference, while the angular velocity showed a near-quadratic pattern, similar to the centripetal acceleration formula. Based on these findings, Experiment 3 developed a dynamic airflow scheme and compared it with constant airflow and no-airflow conditions during locomotion tasks in a complex urban environment. The results demonstrated that dynamic airflow, which ensures consistency between visual and bodily vection, further reduces motion sickness, enhances presence, and provides a more natural and consistent virtual motion experience.

Virtual co-embodiment in virtual reality (VR) allows two users to share an avatar, enabling skill transfer from teachers to learners and influencing their Sense of Ownership (SoO) and Sense of Agency (SoA). However, mismatches between actual movements and displayed actions in VR can impair user experience, posing challenges to learning effectiveness. Although previous studies have addressed the influence of virtual bodies' visual factors on SoO and SoA, the impact of co-embodied hands' appearances remains underexplored. We conducted two user studies to examine the effects of virtual self-hands' existence and their visual factors (transparency and congruency) on SoO, SoA, and social presence. Study One showed significant improvements in SoO and SoA with the existence of virtual self-hands. In Study Two, we kept the self-hands and further focused on hand transparency and congruency. We found that identical appearances between self-hands and co-embodied hands significantly enhanced SoO. These findings stressed the importance of visual factors for virtual hands, offering valuable insights for VR co-embodiment design.