Abstract An experimental investigation was conducted to examine the effects of helical fillets on dynamic ice accretion process over the surfaces of bridge stay cables and evaluate its effects on the aerodynamic characteristics of the stay cables under both dry rime and wet glaze icing conditions. The experimental study was performed in the Icing Research Tunnel of Iowa State University (i.e., ISU-IRT). Four bridge stay cable models, including a standard plain cable model and three helical filleted cable models of different helical pitch lengths, were used for the experimental investigation. During the experiment, in addition to using a high-speed imaging system to record the dynamic ice accretion process over the cable surfaces, a Digital Image Projection (DIP) based 3D scanning system was also utilized to quantify the 3D shapes of the ice structures accreted on the test models. While a high-resolution digital Particle Image Velocimetry (PIV) system was used to characterize the wake flows behind the cable models during the ice accreting process, the time variations of the aerodynamic drag forces acting on the test models were also measured by using a pair of force/moment transducers mounted at two ends of the cable models. It was found that, under the rime icing condition, the helical filleted cable models accreted more ice structures than the standard plain cable model. However, the helical filleted cable models were found to have less ice accretion under the wet glaze icing condition. The pitch length of the helical fillets was also found to affect the ice accretion process substantially. Under the rime icing condition, while the aerodynamic drag forces acting on the cable models were found to decrease continuously with more rime ice accreting over the cable surfaces, the drag reduction due to the rime ice accretion was found to be less obvious for the helical filleted cable models, in comparison with that obtained for the standard plain cable model. Under the glaze icing condition, the aerodynamic drag forces acting on the cable models were found to decrease quickly at the initial stage of the glaze icing process, and then increase gradually with the increasing ice accretion time at the later stage of the ice accreting process. PIV flow field measurements were correlated with the force measurement data to elucidate the underlying physics for a better understanding of the variation characteristics of the aerodynamic forces acting on the cable models under different icing conditions.

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动态积冰及其对斜拉索斜拉索气动特性影响的试验研究

摘要 通过实验研究了螺旋圆角对桥梁斜拉索表面动态积冰过程的影响，并评估了其在干雾和湿釉结冰条件下对斜拉索空气动力学特性的影响。实验研究是在爱荷华州立大学结冰研究隧道（即 ISU-IRT）中进行的。四个桥梁斜拉索模型，包括一个标准的平索模型和三个不同螺旋节距长度的螺旋圆角索模型，用于实验研究。实验过程中，除了使用高速成像系统记录电缆表面动态积冰过程外，还利用基于数字图像投影 (DIP) 的 3D 扫描系统来量化测试模型上积聚的冰结构的 3D 形状。在使用高分辨率数字粒子图像测速 (PIV) 系统来表征结冰过程中电缆模型后面的尾流时，还使用一对测量了作用在测试模型上的空气动力阻力的时间变化安装在电缆模型两端的力/力矩传感器。结果表明，在霜冻条件下，螺旋圆角索模型比标准平索模型产生更多的冰结构。然而，发现螺旋圆角电缆模型在湿釉结冰条件下积冰较少。还发现螺旋圆角的螺距长度显着影响积冰过程。在雾冰条件下，虽然发现作用在电缆模型上的气动阻力随着更多雾冰在电缆表面上的堆积而持续减小，但发现由于雾冰堆积引起的阻力减小对于螺旋圆角电缆模型，与标准普通电缆模型的比较。在结冰条件下，作用在索模型上的气动阻力在结冰过程的初始阶段迅速减小，然后在结冰过程的后期随着结冰时间的增加而逐渐增加。