The two-phase flow atomization process of liquid fuels in the aero-engine is highly complicated, particularly in the initial atomization process, and the accurate primary atomization mode has not been proposed yet.This study adopts the linear instability analysis method to explore the break of different viscous liquids in uniform cross airflow and 2D shear crossflow.In the cylindrical coordinate, the viscous dispersion equation is established and the surface wave growth rate variation with the change in the wave number is calculated using the Muller method.When the incoming flow is uniform and the viscosity of the liquid jet is considered, the ratio of the reduction to the growth rate of the surface wave increases by 1 000 times compared with that under the inviscid condition.The viscosity weakens the instability of both Kelvin-Helmholtz (K-H) and Rayleigh-Taylor (R-T) and inhibits the jet break.The larger the surface wave is, the stronger the inhibition effect of viscosity on the break; however, viscosity has no effect on the unsteady wave number range of the jet.When the viscosity coefficient increases by 500 times, the maximum surface wave growth rate and the optimum wave number decrease by 80.37% and 40%, respectively, and the effect of the viscous force on the surface wave is clear.When the transverse flow is 2D shear flow, the transverse aerodynamic force and shear velocity promote the surface wave of the liquid jet growth and leads to breakup, while the surface tension and viscosity inhibit the generation of surface waves.The larger the ratio of the liquid to air kinetic energy, the stronger the influence of velocity shear effect on instability, and the K-H instability dominates the generation of the jet surface wave.Further investigation into the inhibition effect of liquid viscosity on jet instability shows that the inhibition of viscosity on the growth rate of K-H instability is larger than that on R-T instability.The reduction of instability growth rate of the former can reach 82.7%, while that of the latter is 49.1%.
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