A hybrid lattice Boltzmann model for simulating viscoelastic instabilities

Low-Reynolds-number viscoelastic fluids exhibit a chaotic behaviour linked to the growth of elastic instabilities when polymer molecules are stretched excessively. Despite offering various exciting benefits, numerical difficulties associated with simulating this complex regime have left lot still unexplored regarding transition and onset these low-Reynolds number instabilities. Recently, methods based on lattice Boltzmann method (LBM) emerged as viable tool for studying largely due simplicity, adaptability, intrinsic parallel features LBM. However, extensive memory requirements inability preserve stability restricted previous attempts from In work, hybrid model is applied simulate approach, hydrodynamic field solved using model, whereas separately high-resolution finite difference scheme logarithmic Cholesky decomposition. The first validated steady flows four-roll mill case, where results compared against analytical solution studies. then instability by initialising small perturbation isotropic stress. at different Weissenberg numbers experience flow dynamics sufficiently long time durations, which quasi-periodic periodic aperiodic states increasing effects. was found fastest into transient regime, transitioning being delayed increased. This work proves capability applying coupled exploring instabilities, allowing potential explore more challenging practical cases.