Numerical research on melt pool dynamics of oscillating laser-arc hybrid welding

•Melt pool morphology of oscillating laser-arc hybrid welding is accurately simulated.•Beam oscillation contributes to the heat transfer and temperature equalization of the melt pool.•Vortex is the common flow pattern in the melt pool under the effect of beam stirring.•The mathematical model of oscillating shear force is proposed to quantify the beam stirring effect.•the oscillating shear force increases with oscillation frequency and stabilizes the melt flow by the vortex.