Effect of inclined configuration of superficial neuromast on hydrodynamic signal perception of the fish lateral line

The fish lateral line plays a crucial role in sensing surrounding hydrodynamic signals, which assist fish in foraging and evading predators. Superficial neuromasts (SNs) in the lateral line are important sensory units, most of which are inclined and exhibit a broad range of structural sizes. However, the SNs studied previously are vertical, and the effects of inclined SN configurations on their perception of hydrodynamic signals remain unclear. This paper establishes a fluid-structure interaction model considering oscillation fluid (perturbation or hydrodynamic signal) and inclined SN configuration, and the effects of inclined morphology and structural size on the SN’s flow perception ability are investigated. For the inclined morphology, a larger inclined angle (IA) leads to a smaller hydrodynamic response, thus reducing SN sensitivity but enhancing the ability to suppress flow-induced noise. When the perturbation oscillation frequency is 0.01 Hz, and the IA is 30°, the sensing ability (Γ) is approximately 300 times higher than that of the vertical configuration. Thus, although the inclined morphology of the SN reduces its perception sensitivity, in certain cases, it can improve the Γ by suppressing the interference of flow-induced noise. For the structural size, the effects of SN diameter (D), kinocilium height (h_k), and cupula height (h_c) on perception sensitivity are analyzed. As D increases, the SN perception sensitivity undergoes two distinct stages. When D is less than 45 µm, the cut-off frequency of perception sensitivity increases as D increases. When D exceeds 45 µm, the sensitivity reaches a peak due to structural resonance induced by fluid forces. As D increases further, the peak sensitivity becomes larger, and the resonance peak shifts to the left. Additionally, increasing the h_k and h_c reduces the cut-off frequency while enhancing the perception of low-frequency hydrodynamic signals. These findings contribute to a deeper understanding of the flow perception mechanism in SNs.