纵荡较明显地改变了漂浮式风力机的气动性能，也使局部翼型的绕流场发生剧烈变化，翼型产生动态失速的机理复杂化。本文以S809翼型为研究对象，从向后纵荡与下俯、向前与下俯、向后与上仰和向前与上仰四种复合运动、fy=0.083Hz和fy=0.121Hz两种纵荡频率，来分析纵荡对动态失速过程中的迟滞响应特性、翼型表面分离涡和载荷变化的影响规律。结果表明：纵荡方向影响翼型动态失速变化趋势，向后纵荡时翼型附近流体对边界层施加向下作用力，抑制分离涡产生；向前纵荡导致失速提前，形成大规模分离涡，流场迟滞响应明显。纵荡频率影响升阻力幅值大小，升阻力系数随纵荡频率增加而非定常程度加大。

The surge motion significantly affects the FOWT’s aerodynamic performance and the flow field around the blade. The mechanism underlying the dynamic stall of the airfoil is complex. This paper analyzes the S809 airfoil. Four coupled pitch and surge motions are produced: backward surge and downward pitch, forward surge and downward pitch, backward surge and upward pitch, and forward surge and upward pitch. Two surge frequencies are considered: fy=0.083Hz and fy = 0.121Hz. The analysis focuses on the effects of different coupled motions on the hysteresis response characteristics, the separation vortex on the airfoil surface, and load changes during the dynamic stall of the airfoil. The results indicate that the surge direction affects the dynamic stall trend of the airfoil. When the surge motion is backward, the airflow near the airfoil exerts a downward force on the boundary layer, preventing the generation of the separation vortex. A forward surge motion advances the stall, creates a large separation vortex, and results in a large hysteretic response of the flow field. The surge frequency affects the lift and drag amplitude, and the unsteady lift and drag coefficients increase with the surge frequency.