The dripping of molten thermoplastics is a widely observed phenomenon in cable and façade fire, where the large drips can often carry a blue chain flame during the free fall to ignite other flammable materials and escalate the fire hazard. This work simulated the flame evolution behind a falling thermoplastic drip with the DNS model and finite-rate flame chemistry. The accelerated free-fall of drip was modeled by fixing the position of drip, increasing the upward airflow, and setting a fuel jet on the top of the drip. Modeling reproduces the dripping flame and reveals the flame shedding to be a combination of a lifted flame and a vortex street, where the lifted flame caused by the gravity acceleration of drip is identified as the critical factor that governs the shedding formation. As the diameter of drip decreases, the falling drip becomes difficult in forming a stable shedding structure in the wake region, so that the dripping extinction occurs due to the dilution and cooling of airflow, agreeing well with the experimental observation. This work reveals the underlying mechanism of stabilizing the dripping flame and helps evaluate the fire risk and hazard of dripping phenomena.

熔融的热塑性塑料滴落是电缆和幕墙火灾中普遍观察到的现象，在自由落体中，大滴落通常会携带蓝链火焰，从而点燃其他易燃材料并加剧火灾隐患。这项工作使用DNS模型和有限速率火焰化学过程模拟了下落的热塑性塑料滴后的火焰演变。通过固定滴的位置，增加向上的气流并在滴的顶部设置一个燃料喷嘴来模拟滴的加速自由落体。建模再现了滴落的火焰，并揭示了火焰脱落是升起的火焰和涡街的结合，在这里，由滴落的重力加速度引起的升起的火焰被确定为控制脱落形成的关键因素。随着滴水直径的减小，下落的水滴难以在尾流区域形成稳定的脱落结构，从而由于气流的稀释和冷却而导致水滴的熄灭，与实验观察非常吻合。这项工作揭示了稳定滴落火焰的潜在机制，并有助于评估火灾风险和滴落现象的危害。