初生空化数公式的优化研究

初生空化数是衡量过流体型是否发生空化的判别标准。传统的托马公式认为液流负压值达到液体饱和蒸汽压时即发生空化。近来研究表明,气核和液体抗拉强度等对初生空化有重要影响。有学者认为把托马公式中的液体饱和蒸汽压替换为临界压强更为合理。本文在已有研究的基础上,对空化初生机理和影响空化初生的因素进行分析。认为空化仅是气核克服表面张力和液体饱和蒸汽压膨胀而形成的,并没有克服液体抗拉强度,且在空化源附近的液体几乎不具有抗拉强度,并基于此提出新的初生空化数公式。     

基于ADV的推流式曝气池流场特性研究

曝气池内横向水流对气泡的生成过程有明显的影响,曝气对池内流场也有明显影响。为进一步研究曝气池内流场特性,采用声学多普勒流速仪（ADV）对大尺度Orbal曝气池模型内的流场特性进行了实验研究。结果表明：水流经过弯道后流速分布呈现出内侧小、外侧大的特点,且存在横向流速;进入直段后,流速分布不断调整,内、外侧水流流速差减小,且较浅水深时,流速调整较快。开启曝气盘后与清水时相比,曝气盘上游断面,近水面处流速减小,水面下较深处流速增大;曝气盘下游断面,近水面处流速增大,水面下较深处流速减小;曝气盘下游紊动强度明显增强。     

Cavitation bubbles collapse characteristics behind a convex body

Cavitation bubbles behind a convex body were experimentally studied by a high speed camera and a hydrophone synchronously. The experiments were conducted in a circulating water tunnel with five various contraction ratios： β = 0.497, β= 0.6, β= 0.697, β= 0.751, and β= 0.799. The distributions of the cavitation bubble collapse positions behind the five different convex bodies were obtained by combining the images taken by the high speed camera. According to the collapse positions, it was found that no cavitation bubble was collapsed in the region near the wall until the ratio of the water head loss over the convex body height was larger than 20, which can be used to predict if the cavitation damage would occur in the tunnel with orifice energy dissipaters.     

文档图像屏幕适配方法中的行切问题研究

针对当前使用嵌入式设备阅读文档图像时存在的不便,提出一种基于图像处理的文档适配的方法.该方法以数字图像处理技术为核心,根据设备屏幕尺寸对采集的文档图像进行切割重排,达到适应屏幕大小的目的.对于汉字结构带来的分割误差问题进行重点研究和分析,提出基于前后检测的方法以解决该问题.最后通过实例对该方法进行验证与分析,证明该方法具有一定可行性,并在切割文字的正确率方面有较好表现.