目前的民机结冰适航规范中,大粒径过冷水滴(supercooled large droplet,SLD)环境尚未得到规定,是一个重大的飞行安全隐患。由于SLD的粒径较大(大于50μm),在研究其结冰时需要考虑水滴动力学过程。针对SLD成冰模拟中破碎模型的不足,根据...目前的民机结冰适航规范中,大粒径过冷水滴(supercooled large droplet,SLD)环境尚未得到规定,是一个重大的飞行安全隐患。由于SLD的粒径较大(大于50μm),在研究其结冰时需要考虑水滴动力学过程。针对SLD成冰模拟中破碎模型的不足,根据对破碎机理的认识提出了多因素破碎(multifactor-effected breakup,MEB)判定模型,并结合积冰算法对SLD环境中的结冰进行了模拟,验证了模型的有效性,证明其能提高对SLD结冰的模拟能力。从翼面收集率及冰型生长两方面对SLD的结冰过程和水滴动力学过程产生的效应进行了分析。展开更多
SLD(Supercooled large droplets,超大直径过冷水滴)为超过100微米的过冷水滴,这种结冰环境其在目前的适航规范中没有相应规定。和小直径水滴相比(小于50微米),SLD结冰是多个动力学(破碎,撞击飞溅,流动)和热力学过程的组合,各个环节对...SLD(Supercooled large droplets,超大直径过冷水滴)为超过100微米的过冷水滴,这种结冰环境其在目前的适航规范中没有相应规定。和小直径水滴相比(小于50微米),SLD结冰是多个动力学(破碎,撞击飞溅,流动)和热力学过程的组合,各个环节对冰型也有不同的作用。本文参照TAB破碎模型建立了SLD破碎模型,并对破碎过程的主要环节的影响进行了分析,分析了水滴在翼型附近的运动情况,并结合飞溅模型对SLD环境中的冰型生长进行了数值模拟。模拟结果和冰风洞实验结果符合的较好。展开更多
Ice jams and ice dams in rivers will cause significant rises of water levels. Under extreme conditions, the ice flooding during winter or early spring may occur. In this paper, by considering the fluid-solid coupling ...Ice jams and ice dams in rivers will cause significant rises of water levels. Under extreme conditions, the ice flooding during winter or early spring may occur. In this paper, by considering the fluid-solid coupling effect caused by the water and the ice cover, the mechanisms of the mechanical breakup of the river ice cover are studied. A formula is obtained for determining whether or not the mechanical breakup process would happen under the hydraulic pressure of the flow. Combined with the hydraulic model under the ice covered flow, a numerical model is built and the interaction between the discharge, the hydraulic pressure under the ice cover and the date for the mechanical breakup of the river ice cover is simulated. The simulated results of the dates for the mecha- nical breakup of the river ice cover agree very well with the field observations of the breakups of the river ice cover in the Hequ Reach of the Yellow River. Therefore, the numerical model might serve as a good preliminary step in studying the breakup of the river ice-cover, evidencing many important parameters that affect the ice-cover process,展开更多
The effects of breakup reactions on elastic and α-production channels for the ^6Li＋^116Sn system have been investigated at energies below and near the Coulomb barrier. The angular distributions of α-particle produc...The effects of breakup reactions on elastic and α-production channels for the ^6Li＋^116Sn system have been investigated at energies below and near the Coulomb barrier. The angular distributions of α-particle production differential cross sections have been obtained at several projectile energies between 22 and 40 MeV. The measured breakup α-particle differential cross sections and elastic scattering angular distributions have been compared with the predictions of continuum-discretized coupled channels（CDCC） calculations. The influence of breakup coupling has also been investigated by extracting dynamic polarization potentials（DPP） from the CDCC calculations. From the predictions of CDCC calculations the relative importance of the nuclear, Coulomb, and total breakup contributions have also been investigated. The nuclear breakup couplings are observed to play an important role in comparison to the Coulomb breakup for the direct breakup mechanisms associated in the reaction of ~6Li projectile with ^（116）Sn target nuclei. The influence of strong nuclear breakup coupling exhibits suppression in the Coulomb-nuclear interference peak. The direct breakup cross sections from the CDCC calculations under-predict the measured α-particle differential cross sections at all energies. This suggests that the measured α particles may also have contributions from other possible breakup reaction channels.展开更多
文摘目前的民机结冰适航规范中,大粒径过冷水滴(supercooled large droplet,SLD)环境尚未得到规定,是一个重大的飞行安全隐患。由于SLD的粒径较大(大于50μm),在研究其结冰时需要考虑水滴动力学过程。针对SLD成冰模拟中破碎模型的不足,根据对破碎机理的认识提出了多因素破碎(multifactor-effected breakup,MEB)判定模型,并结合积冰算法对SLD环境中的结冰进行了模拟,验证了模型的有效性,证明其能提高对SLD结冰的模拟能力。从翼面收集率及冰型生长两方面对SLD的结冰过程和水滴动力学过程产生的效应进行了分析。
文摘SLD(Supercooled large droplets,超大直径过冷水滴)为超过100微米的过冷水滴,这种结冰环境其在目前的适航规范中没有相应规定。和小直径水滴相比(小于50微米),SLD结冰是多个动力学(破碎,撞击飞溅,流动)和热力学过程的组合,各个环节对冰型也有不同的作用。本文参照TAB破碎模型建立了SLD破碎模型,并对破碎过程的主要环节的影响进行了分析,分析了水滴在翼型附近的运动情况,并结合飞溅模型对SLD环境中的冰型生长进行了数值模拟。模拟结果和冰风洞实验结果符合的较好。
基金supported by the National Natural Science Foundation of China (Grant No. 50979021)the Natural Science Foundation of Anhui Province (Grant No. 090415217)supported by the Hefei University of Technology (Grant No. GDBJ2008-020-Seed Grant for Ph. D.)
文摘Ice jams and ice dams in rivers will cause significant rises of water levels. Under extreme conditions, the ice flooding during winter or early spring may occur. In this paper, by considering the fluid-solid coupling effect caused by the water and the ice cover, the mechanisms of the mechanical breakup of the river ice cover are studied. A formula is obtained for determining whether or not the mechanical breakup process would happen under the hydraulic pressure of the flow. Combined with the hydraulic model under the ice covered flow, a numerical model is built and the interaction between the discharge, the hydraulic pressure under the ice cover and the date for the mechanical breakup of the river ice cover is simulated. The simulated results of the dates for the mecha- nical breakup of the river ice cover agree very well with the field observations of the breakups of the river ice cover in the Hequ Reach of the Yellow River. Therefore, the numerical model might serve as a good preliminary step in studying the breakup of the river ice-cover, evidencing many important parameters that affect the ice-cover process,
基金DAE-BRNS for financial assistance through a major research projectsupported by National Natural Science Foundation of China (U1432247,11575256,U1632138,11605253)+2 种基金China Postdoctoral Science Foundation (2016M602906)CNPqFAPERJ for partial financial support
文摘The effects of breakup reactions on elastic and α-production channels for the ^6Li＋^116Sn system have been investigated at energies below and near the Coulomb barrier. The angular distributions of α-particle production differential cross sections have been obtained at several projectile energies between 22 and 40 MeV. The measured breakup α-particle differential cross sections and elastic scattering angular distributions have been compared with the predictions of continuum-discretized coupled channels（CDCC） calculations. The influence of breakup coupling has also been investigated by extracting dynamic polarization potentials（DPP） from the CDCC calculations. From the predictions of CDCC calculations the relative importance of the nuclear, Coulomb, and total breakup contributions have also been investigated. The nuclear breakup couplings are observed to play an important role in comparison to the Coulomb breakup for the direct breakup mechanisms associated in the reaction of ~6Li projectile with ^（116）Sn target nuclei. The influence of strong nuclear breakup coupling exhibits suppression in the Coulomb-nuclear interference peak. The direct breakup cross sections from the CDCC calculations under-predict the measured α-particle differential cross sections at all energies. This suggests that the measured α particles may also have contributions from other possible breakup reaction channels.
