Harte N C, Obrist D, Caversaccio M, Lajoinie G P R, Wimmer W
Department of Otorhinolaryngology, TUM School of Medicine, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany.
ARTORG Center for Biomedical Engineering Research, University of Bern, Bern, Switzerland.
Eur J Mech B Fluids. 2024 Sep-Oct;107:165-174. doi: 10.1016/j.euromechflu.2024.07.001.
The cochlea, situated within the inner ear, is a spiral-shaped, liquid-filled organ responsible for hearing. The physiological significance of its shape remains uncertain. Previous research has scarcely addressed the occurrence of transverse flow within the cochlea, particularly in relation to its unique shape. This study aims to investigate the impact of the geometric features of the cochlea on fluid dynamics by characterizing transverse flow induced by harmonically oscillating axial flow in square ducts with curvature and torsion resembling human cochlear anatomy. We examined four geometries to investigate curvature and torsion effects on axial and transverse flow components. Twelve frequencies from 0.125 Hz to 256 Hz were studied, covering infrasound and low-frequency hearing, with mean inlet velocity amplitudes representing levels expected for normal conversation or louder situations. Our simulations show that torsion contributes significantly to transverse flow in unsteady conditions, and that its contribution increases with increasing oscillation frequency. Curvature alone has a small effect on transverse flow strength, which decreases rapidly with increasing frequency. Strikingly, the combined effect of curvature and torsion on transverse flow is greater than expected from a simple superposition of the two effects, especially when the relative contribution of curvature alone becomes negligible. These findings may be relevant to understanding physiological processes in the cochlea, including metabolite transport and wall shear stress. Further studies are needed to investigate possible implications for cochlear mechanics.
耳蜗位于内耳，是一个螺旋形、充满液体的负责听觉的器官。其形状的生理意义仍不明确。以往的研究几乎没有涉及耳蜗内横向流动的发生情况，特别是与其独特形状相关的横向流动。本研究旨在通过表征在具有类似于人类耳蜗解剖结构的曲率和扭转的方形管道中，由谐波振荡轴向流引起的横向流动，来研究耳蜗几何特征对流体动力学的影响。我们研究了四种几何形状，以探究曲率和扭转对轴向和横向流动分量的影响。研究了从0.125赫兹到256赫兹的12个频率，涵盖次声和低频听力，平均入口速度幅值代表正常交谈或更响亮情况下预期的水平。我们的模拟表明，在非稳定条件下，扭转对横向流动有显著贡献，且其贡献随着振荡频率的增加而增加。单独的曲率对横向流动强度的影响较小，且随着频率增加迅速减小。令人惊讶的是，曲率和扭转对横向流动的综合影响大于两种效应简单叠加的预期，特别是当单独曲率的相对贡献变得可忽略不计时。这些发现可能与理解耳蜗中的生理过程有关，包括代谢物运输和壁面剪应力。需要进一步研究来探究其对耳蜗力学可能产生的影响。
