A decoupled lattice Boltzmann method (LBM) is developed from the conventional multiple relaxation time (MRT) model by eliminating the second-order mutual effects of viscosity modes. The dependency between relaxation times and viscosity is decoupled to remove the O($u^3$) errors in the original model, and thus a stabilization strategy is proposed by adjusting relaxation times without changing the local viscosity under the mass and momentum conservations. This new model still stays in conventional MRT framework and keeps the advantages of simplicity and efficiency of LBM implementation. The decoupled MRT is demonstrated to be valid for high-speed flow with Galilean invariance. Moreover, the pseudopotential model is employed in this paper to present the improvement in simulating the large-density-ratio multiphase flows at high Reynolds (Re) and Weber (We) numbers. Droplet collision is achieved at density ratio 1153, Re = 34474 and We = 28212. Droplet splashing is achieved at density ratio 6637, Re = 34474 (and 71928) and We = 30538 (and 259). Droplet impacting on dry wall is achieved at density ratio 5720, Re = 11462 (and 22982) and We = 13573 (and 166). All collision regimes are simulated by the decoupled MRT from low Re (We) to high Re (We).

通过消除粘度模式的二次互作用，从传统的多重弛豫时间（MRT）模型开发了解耦格子玻尔兹曼方法（LBM）。弛豫时间和粘度之间的相关性被解耦以去除O（${ü}^3$）原始模型中的误差，因此提出了一种通过调整松弛时间而不改变质量和动量守恒条件下的局部粘度的稳定策略。这个新模型仍然保留在传统的MRT框架中，并保留了LBM实现的简单性和效率的优势。事实证明，解耦的MRT对于伽利略不变的高速流动是有效的。此外，本文采用伪势模型来表示在高雷诺数（Re）和韦伯（We）数下模拟大密度比多相流方面的改进。在密度比1153，Re = 34474和We = 28212时实现液滴碰撞。在密度比6637，Re = 34474（和71928）且We = 30538（和259）下实现液滴飞溅。在密度比为5720时，液滴对干壁的影响达到了，Re = 11462（和22982），而We = 13573（和166）。通过从低Re（We）到高Re（We）的MRT解耦来模拟所有碰撞情况。