The experiment lays pressure sensors to measure the pressure of the discharge system, and the measure results show that cavitation erosion will never happen during outflow.

The phenomena occurring in high speed water flow, such as cavitation, aeration, fluttering pressure and energy loss etc, are all related with the development and behaviour of the turbulent boundarylayer.

Aiming at minimizing the flow loss of the cascade surface boundary layer and airfoil cavitation erosion,a unified objective function was established by using Distance Method and the best bone line was worked out by applying the genetic algorithm.

Part two: Study on the cavitation noise. The extend work of my doctoral research is introduced in the part. Problems of cavitation noise are investigated with three methods such as theory analysis, numerical simulation and experiment research.

The cavitation erosion damage process of dynamically loaded journal bearings

The cavitation damage model was built using finite element analysis software MSC.Marc.

This paper attempted to numerically analyze the action process based on damage mechanics when a jet created by bubble collapse acted on the bearing surface in the process of cavitation erosion.

The strain history and damage evolvement of bearing material acted on by jet impact load can be calculated efficiently using the proposed method, which develops a new method of analyzing cavitation erosion failure of the bearing surface.

Based on the variational constraint approach, the variational form of Reynolds equation in hydrodynamic lubrication is revised continuously to satisfy certain constraints in the cavitation zone of oil film field.

The paper begins with a theoretical analysis of potential flow for the two-di- mensional conduit inlet,and after the boundary curve of constant pressure is obtained, it is transformed to the case of axial symmetry.It is hoped that the pressure along the new boundary,be nearly constant.The method of transformation is mainly that for equal distance ratios(i.e.,distance divided by entrance width in the two-dimen- sional case and that divided by entrance diameter in the axially symmetrical case), area ratios(i.e.sectional...

The paper begins with a theoretical analysis of potential flow for the two-di- mensional conduit inlet,and after the boundary curve of constant pressure is obtained, it is transformed to the case of axial symmetry.It is hoped that the pressure along the new boundary,be nearly constant.The method of transformation is mainly that for equal distance ratios(i.e.,distance divided by entrance width in the two-dimen- sional case and that divided by entrance diameter in the axially symmetrical case), area ratios(i.e.sectional area divided by entrance area in both cases)are equal. The pressure distribution along the curved wall of an axially symmetric inlet so obtained was calculated by the relaxation method,and that of another was measured from an air-flow model test.The results as given in Figures 10 and 13 of the paper show that although the pressure along the wall is not constant,the variation is not great.The paper finally suggests that as for to reduce the possibility of cavitation, the forms of the axially symmetric inlets given by Equations(5)and(6)of the paper may be considered as adequate for practical cngineering use,with the restriction that the value of k which appears in the two equations not be greater than 0.05,in order to prevent the possible separation of flow from the inlet wall.

文中给出了隧洞进水口曲线为等压的二元分析结果,然后将此二元进水口的曲线形式转变为轴对称进水口的曲面形式。所用的转变方法是:当 x/D=(x_1)/B时,d/D=(b/B)~(1/2),其中 d、x和 D 分别为轴对称进水口段中某断面的直径,由起始断面至该断面的距离和起始断面的直径;b、x 和 B 分别为相应二元情形的某断面的宽度,由起始断面至该断面的距离和起始断面的宽度。对用这种方法得到的一个轴对称进水口曲面上压力分布,进行了松弛法计算,还对另一个进行了气流模型试验。结果如文中图10及图13指明,曲面上压力虽然不是等值的,但变化不大。文中建议,就减蚀的意义而言,式(5)和式(6)所给轴对称进水口曲面的形式是可以考虑来作为实际工程上应用的,但为了避免可能发生水流从边壁上脱离的现象,式中 k 值应取小于或等于0.05。

Applying the laboratory test data obtained by J. W. Holl and D. Colgate, this paper tries to estimate the required control of surface irregularities for high overflow dams so as to avoid the incipiency of cavitation damage. By plotting the prototype observation data of five overflow dams, an empirical equation of the velocity coefficient φ as a function of H/q~(2/3) is first established. Thereby, with given H and q, the various valuesof the surface shooting flow for the non-aerated case, such as depth,...

Applying the laboratory test data obtained by J. W. Holl and D. Colgate, this paper tries to estimate the required control of surface irregularities for high overflow dams so as to avoid the incipiency of cavitation damage. By plotting the prototype observation data of five overflow dams, an empirical equation of the velocity coefficient φ as a function of H/q~(2/3) is first established. Thereby, with given H and q, the various valuesof the surface shooting flow for the non-aerated case, such as depth, mean velocity,Froude number, and cavitation index may be determined. The experimental data given by Colgate have been analysed and the cavitationindices of the two test specimens have been calculated. The four “σ_i～△/δ” chartsas given by Holl are put into a single diagram, in which the results of Colgate are alsoincorporated. Based upon the prototype observation data of the Norris Dam, Glennmaggie Dam, nd Werribee Weir, an empirical equation for the boundary layer thickness is established, and a comparison of the equation with those given by W. J. Bauer—V. T. Chow and G. Halbronn is made. With the diagrams and equations so obtained, the incipient cavitation index and the corresponding allowable maximum surface irregularities can be estimated. In the final part of the paper, the limit of the cavitation index has been suggested below which special treatment of the concrete surface such as used in the Hungry Horse Dam should be adopted.

The present investigation is concerned with the determination of pressure distribution along curved boundaries formed by circular arcs often found in hydraulic structures. The boundary geometry considered are: (1) Semi-infinite pier in closed conduit with head part formed by two circular arcs, (2) Isolated circular-arc irregularity on the wall of closed conduit. Analytical results. found by means of conformal transformation were compared with experimental data from wind tunnel and water tunnel tests, and with...

The present investigation is concerned with the determination of pressure distribution along curved boundaries formed by circular arcs often found in hydraulic structures. The boundary geometry considered are: (1) Semi-infinite pier in closed conduit with head part formed by two circular arcs, (2) Isolated circular-arc irregularity on the wall of closed conduit. Analytical results. found by means of conformal transformation were compared with experimental data from wind tunnel and water tunnel tests, and with those obtained in previous investigations. Data on incipient cavitation number found from water tunnel tests and from published papers were compared with some of the calculated—C_(pmin). Agreement is good.