基于非平衡线化碰撞的LBM精度与稳定性分析

Accuracy and stability analysis of LBM based on non-equilibrium linearized collision

  • 摘要: 本工作针对最近发展的一种基于非平衡线化碰撞的格子 Boltzmann方法(lattice Boltzmann method with a non-equilibrium linearized collision, NLC-LBM), 开展系统的不稳定性理论分析和数值精度验证。通过严格的Chapman-Enskog展开,NLC-LBM将碰撞算子中的非线性项分解为平衡态与非平衡态分量,对非平衡项进行一致性线性化处理,在保持物理准确性的同时有效抑制高波数模态的发散,不仅提升经典计算中的粗网格稳定性,还为当前正在发展的量子-经典混合线性计算架构提供理论基础。基于Von Neumann线性化不稳定性理论,分析了该方法的局部不稳定性和水动力耗散行为,证明其在粗网格下稳定性高于标准LBM,为粗网格条件下的复杂流动模拟提供了高稳定性的碰撞模型。通过顶盖方腔驱动流、自然对流和涡对合并运动三个经典算例的模拟,数值结果表明,在相同粗网格下,标准LBM相比于NLC-LBM出现明显不收敛现象;在细网格下NLC-LBM与标准LBM的计算结果和精度基本一致,验证了其物理有效性。

     

    Abstract: This work conducts a systematic and comprehensive theoretical analysis of numerical instability and numerical accuracy verification for the recently proposed lattice Boltzmann method (LBM) with non-equilibrium linearized collision (NLC-LBM). Through the rigorous Chapman–Enskog kinetic expansion method, the NLC-LBM accurately decomposes the nonlinear terms in the collision operator into equilibrium and non-equilibrium components, and then performs consistent linearization on the non-equilibrium components. This treatment not only completely retains the physical essence of fluid flow and ensures the physical accuracy of the simulation, but also effectively suppresses the divergence of high-wave-number modes in numerical calculations, fundamentally improving the numerical instability of traditional methods. This improvement not only significantly enhances the numerical stability under coarse mesh conditions in classical computing scenarios, solving the bottleneck of easy instability in coarse mesh simulation, but also provides a solid theoretical foundation and adaptation support for the currently rapidly developing quantum-classical hybrid linear computing architecture, laying the foundation for the integrated application of LBM and quantum computing. Based on the Von Neumann linearized instability theory, this paper deeply analyzes the local instability characteristics and hydrodynamic dissipation behavior of the NLC-LBM. Through comparative analysis with the standard LBM, it is clearly demonstrated that the stability of the NLC-LBM under coarse mesh conditions is significantly superior to that of the standard LBM, thereby providing a highly stable and reliable collision model for the efficient and stable simulation of complex flows under coarse mesh conditions. To further verify the physical effectiveness and numerical accuracy of the NLC-LBM, this paper conducts systematic numerical simulation research on three classic benchmark cases, including lid-driven cavity flow, natural convection, and vortex pair merging. The results show that under the same coarse mesh conditions, the standard LBM exhibits obvious non-convergence, characterized by non-physical features such as streamline distortion and velocity profile oscillation; while the NLC-LBM can maintain stable convergence of the flow field and accurately capture the flow characteristics. Under fine mesh conditions, both the computational results and numerical accuracy of the NLC-LBM are basically consistent with those of the standard LBM, fully verifying the physical rationality and numerical reliability of the method.

     

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