Experimental study of temperature effect on the growth and collapse of cavitation bubbles near a rigid boundary

The effect of temperature on the dynamics of a laser-induced cavitation bubble is studied experimentally. The growth and collapse of the cavitation bubble are measured by two sensitive fiber-optic sensors based on optical beam deflection (OBD). Cavitation bubble tests are performed in water at different temperatures, and the temperature ranges from freezing point (0 °C) to near boiling point. The results indicate that both the maximum bubble radius and bubble lifetime are increased with the increase of temperature. During the stage of bubble rapidly collapsing in the vicinity of a solid surface, besides laser ablation effect, both the first and second liquid-jet-induced impulses are also observed. They are both increased with liquid temperature increasing, and then reach a peak, followed by a decrease. The peak appears at the temperature which is approximately the average of freezing and boiling points. The mechanism of liquid temperature influence on cavitation erosion is also discussed.     

磁流变液颗粒成链过程的理论和实验研究

通过计算机模拟及实验研究了磁流变液颗粒在渐变磁场作用下的成链过程。首先从理论上建立了磁流变液成链过程的物理模型,采用蒙特卡罗方法模拟了其在渐变磁场作用下成链的详细过程。其次,采用光学显微镜观察了磁流变液在渐变磁场作用下的成链过程。数值模拟和实验结果表明,在平行磁场中,当外部磁场为零时,磁流变液的磁性颗粒处于随机分布状态。随着磁场强度的增加,磁性颗粒产生磁团聚形成链状絮凝体,进而由二连体或三连体发展到多连体,甚至网状及柱状结构;在倾斜磁场中,磁流变液中的聚合链也同时旋转,磁性颗粒沿着磁场方向从小链逐渐增大到大链,最后全部沿着磁场方向呈链状或柱状排列。研究结果对优化磁流变液材料的配置和设计高性能磁流变液装置具有重要意义。     

<774A>和<774B>型红外变象管设计定型鉴定会议在北京召开

由211研究所设计、211所与5808厂研制的<774A>、<774B>两种红外变象管设计定型鉴定会议于1980年2月25日至2月28日在北京举行。会议由五机部科研局主持。参加会议的代表来自有关的部队领导机关、工厂、研究所、高等院校,共39人,代表22个单位。     

节流阀小开度下空化特性的数值分析

基于计算流体动力学方法,数值研究了节流阀开度变化对节流阀内压力场、速度场及空化区域的影响。结果表明:随着开度的减小,下游槽(尤其是节流口处)流体的流速会迅速增大,空化区域逐步增大且空蚀程度逐渐加深,但当开度很小即节流阀阀口接近于闭合时,空化程度反而减弱,且空化区域向节流口移动。此外,阀内压力较大的区域位于上流道,压力较小的区域位于下流道,随着开度的减小,阀内的低压区逐步向阀口处转移。