Models of the four spiral-like structures in Oph IRS 63 (Figs. 1 and 2) generated by free-fall streamers, with colors representing the line-of-sight velocity. Model parameters are provided in Table 2 (Sect. 3.1). The dotted gray lines indicate the observed spiral-like structures (Fig. 1), and the blue ellipse marks the SO ring with a major-axis diameter of 1″ (130 au). The color map corresponds to that in panel a of Fig. 2. Velocities are scaled down by a factor of 2 (from the free-fall values) to approximate the observed velocity range (Fig. 2), with justification provided in Sect. 3.1.2.