【作者】 曲景学；

【导师】 杨永全；

【作者基本信息】 四川大学 ， 水力学及河流动力学， 2001， 博士

【摘要】 空化与空蚀是水工泄水建筑物设计中必须考虑的一个重要因素，国内外对此问题的研究虽有近百年的历史，但由于问题的复杂性，尚有许多关键问题有待进一步研究。孔板式泄洪洞作为一种新型消能方式，自从被小浪底工程采用以来，其水力特性，特别是空化特性，引起了国内外学者的高度重视。本文在对国内外空化研究的基本理论和方法进行系统全面总结的基础上，对孔板泄洪洞初生空化问题进行了试验和数值模拟研究。主要研究内容及成果如下： 1．对空化现象、空化机理和研究方法等进行了较为全面的总结，对国内外的最新研究成果进行了分析、综述。详细分析了空化初生的各种影响因素。 2．首次揭示出对于同一过流体型，空化噪声声压级差最大值、平均值和相对能量三者之间存在良好的对应关系这一重要结论，从而使噪声判别法的不同判别指标得到了统一，同时也为空化初生判别标准的统一提供了前提条件。 3．进行了孔板泄洪洞减压模型试验，得出了研究对象的空化噪声声压级差最大值、平均值和相对能量三者之间的量化关系。试验成果表明：这些关系对同一体型的细小差别并不十分敏感；对不同的过流体型，三者之间的对应关系会有所不同。通过将这些成果应用于消能孔板空化初生的判别，表明其应用情况是合理和有效的，具有良好的实用价值。试验中还详细测量、研究了不同条件下的孔板空化特性和消能特性。 4．采用轴对称的K～ε紊流数学模型，对减压试验中所采用的孔板泄洪洞的时均流场，特别是消能情况进行了数值模拟。详细地给出了减压模型试验中较难量测的时均流场特征量和紊动参数的全场分布，计算所得的孔板消能的压力分布与试验结果相吻合，从而达到了与物理模型相互补充、印证的目的。 5．建立了微可压缩流理论和大涡模拟方法相结合的空化流数学模型，为 四川大学工学博士学位论文孔板泄洪洞空化初生的研究开辟了一条新途径。由于本文所建立的空化流方程考虑了液体的可压缩性，因此对空化的描述更符合实际情况。由于数学模型不受比尺效应影响，可以直接模拟原型，因此有着广阔的应用前景。同时，数学模型对于研究空化初生比尺效应的研究也具有重要价值。 6．首次对孔板泄洪洞的空化初生进行了数值模拟。其中，采用大涡模拟方法计算了孔板消能的流场，获得了详细的流场特征，将计算所得的压力分布与实测值进行了比较，符合良好。通过数值模拟还获得了孔板消能流场瞬时压力的全场分布以及相应的低压区位置。据此，采用微压缩流理论计算出了各级 在孔板的空化发生点位置，所预测的空化发生情况与减压模型试验结果一致。由此表明，本文所建立的数学模型是合理、可靠的。更多还原

【Abstract】 The cavitation is an important factor in the design of hydraulic engineering. It has been studied for nearly a century by many scholars in the world, however, because of its complexity, a large amount of problems still need to be studied further. The orifice dissipator, as a new energy dissipation type, has been paid much attention since it was adopted in the Xiaolangdi project. In this dissertation, author summarized the existing results about the cavitation phenomena, its mechanism and method, studied the cavitation inception in the flood-discharge tunnel by experimental and numerical methods. The main contents and conclusions are as follows:1.Summarized the existing results about the cavitation phenomena, its mechanism and method. Analyzed the factors affecting the cavitation inception.2.Reveal the following important laws for the first time: a correlation exists among the maximum sound pressure level difference, the averaged sound pressure level difference and the relative energy of the cavitation noise for a given structure. It is very useful to unify the different noise index.3.Made the cavitation experiment of the flood-discharge tunnel with orifices in a pressure variable tank. The correlation among the maximum sound pressure level difference, the averaged sound pressure level difference and the relative energy of the cavitation noise was obtained. This correlation was used to determine the cavitation inception of the orifices and achieved good results.4.Simulate the time-averaged turbulent flow fields in the flood-discharge tunnel by using the axis-symmetric K turbulence mathematical model. The detailIII-2distributions of time-averaged parameters of the turbulent flow fields were obtained. The calculated pressure distributions were compared with the measured data and in reasonable agreement.5.Established a mathematical model to simulate the instantaneous flow fields and cavitation by combining the weakly compressible fluid theory and the Large Eddy Simulation method. Because the compressibility of fluid was taken into consideration, it is in better agreement with the true situation. It is valuable for simulating directly the cavitation in the prototype structures and studying the scale effects.6.Simulate numerically the cavitation in the flood-discharge tunnel with orifices for the first time. The Large Eddy Simulation method was used to give the detail flow feature. The calculated pressure distributions were compared with the measured data and in reasonable agreement. On the calculated instantaneous pressure distribution, the positions of cavitation inception were obtained. The predicted cavitation is in good agreement with the experimental results, which shows that the mathematical model given in this dissertation is reasonable.更多还原