发表机构
SR University; PDPM Indian Institute of Information Technology Design and Manufacturing（SR大学; 印度信息与制造技术设计研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过多重尺度展开和Stuart-Landau方程，分析了斜向辐照下藻类悬浮液中趋光性生物对流的弱非线性演化，揭示了不同边界条件下失稳阈值和分岔特性的差异。
AI 中文摘要
我们研究了在斜向和正常准直辐照下，吸收性和各向同性散射藻类悬浮液中由趋光性诱导的生物对流的弱非线性演化。考虑了两种流体动力学构型：刚性下边界分别与无应力或刚性上表面组合。我们进行了三阶多重尺度展开，Fredholm可解性条件给出了临界模式振幅的Stuart-Landau方程。斜向辐照在两种构型中对失稳阈值的影响方向相反：在无应力表面下方，它逐渐降低临界瑞利数；而在刚性表面下方，它逐渐提高临界瑞利数。在无应力表面下方，失稳保持静止，但叉形分岔从超临界变为亚临界，并在大入射角下变得强烈亚临界，此时优选图案波长也显著增加。在刚性表面下方，临界模式在中等倾斜度下从静止变为振荡，产生超临界Hopf分岔，并在大倾斜度下恢复为静止，此时叉形分岔变为亚临界。
英文摘要
We investigate the weakly nonlinear evolution of phototaxis-induced bioconvection in an absorbing and isotropically scattering algal suspension subjected to oblique and normal collimated irradiation. Two hydrodynamic configurations are considered, a rigid lower boundary with either a stress-free or a rigid upper surface. A multiple-scales expansion is carried to third order, and the Fredholm solvability condition yields a Stuart--Landau equation for the amplitude of the critical mode. Oblique irradiation affects the onset threshold in opposite ways in the two configurations. It progressively lowers the critical Rayleigh number beneath a stress-free surface and progressively raises it beneath a rigid surface. Beneath a stress-free surface the onset remains stationary, but the pitchfork bifurcation changes from supercritical to subcritical and becomes strongly subcritical at large incidence angles, where the preferred pattern wavelength also increases markedly. Beneath a rigid surface the critical mode changes from stationary to oscillatory at moderate obliquity, giving a supercritical Hopf bifurcation, and returns to stationary at large obliquity, where the pitchfork bifurcation becomes subcritical.
