Figure 8

Shapes, material properties, and performances of newly designed convective cloaks. (a) Schematics of acoustic cloaks with modified material properties as shown in equation (9). Type A shows a single-zone modification (N = 1) with optimized value of β₁, and types B and C show multiple-zone modifications (N = 4) with optimized values of β _i for i = 1, 2, 3, 4. (b) Polar plot of directivity patterns of the previous and present cloaks in moving medium for M = 0.2. (c) Rectangular plot of directivity patterns of the previous and present cloaks in moving medium for M = 0.2. The directivity patterns are calculated in dB scale by using equation (5) at r = 10R₁. (d) Maximal errors calculated by using equation (8) at r = 10R₁ for the previous and present cloaks. As shown in (d), three types of acoustic cloaks show better performance compared to the existing convective cloak⁷.