海洋鱼类经过数百万年的自然进化,获得了非凡的水动力性能,人类迄今为止研发的任何水下航行体尚难以超越.仿生已成为提高水下航行体水动力性能的重要技术途径.本文对仿生水动力学的研究进展进行了梳理,重点评述了仿生水动力学理论研究、仿生推进/操纵和仿生减阻三个方面的国内外研究现状和发展趋势,并对仿生水动力学研究亟需突破的瓶颈问题和技术路线给出了若干建议.

船舶水动力学领域中,数值水池虚拟试验结果的可信度是制约其应用与发展的关键因素之一.目前常用的CFD不确定度分析,经实践证明不完全适用于虚拟试验置信度评估,因而需要建立一种新的置信度评估方法,以确保针对"属性细分"后的一类问题,虚拟试验结果可信且达到工程实用精度要求.为此,文中提出了一种新的船舶水动力数值水池试验置信度评估方法,该方法的核心是"不确定度分析、最优解确认、大子样验证"三重验证流程,其中:不确定度分析基于正交试验设计、方差分析和统计推断理论;最优解确认基于正交试验设计的效应分析方法和残差最小原理;大子样验证则基于大量数值水池试验结果和相应模型试验数据的对比与统计分析.文中以船模阻力虚拟试验为例开展了实践,证明了该置信度评估方法的合理性和有效性.

The boundary layer integral solution theory is adopted to model thick boundary layer around un-derwater vehicle at maneuvering condition.The corresponding calculation code is developed.The computa-tion of characteristic parameters of boundary layer around SUBOFF submarine is carried out. The comput-ed results including boundary layer thickness, shape factor, momentum thickness and friction coefficient are analyzed. The variation of characteristic parameter is obtained at maneuvering condition. The result shows that the calculation code developed in this paper can be applied to analyze the underwater vehicle's 3D boundary layer characteristics and evaluate hydrodynamic performance.

An innovative methodology of confidence level assessment for virtual test of ship model hydrodynamics is presented in this paper. The methodology is based on the procedure of "uncertainty analysis, validation of optimal solution, validation by big sample data". In which the uncertainty analysis is based on orthogonal design and variance analysis methods and statistic inference theory, the validation of optimal solution is based on effect analysis in orthogonal design and principle of minimum deviation; the virtual test method is validated by statistical analysis of comparison with a large numbers of experimental data. The procedure is applied to practice with virtual test of ship model resistance, and shows that the methodology of confidence level assessment is reasonable and effective.

Numerical simulation of wall pressure fluctuations and flow induced noise of submarine has be-come vigorous in the field of flow-acoustic coupling. The fairwater of a submarine is optimized by two shapes, one is the fairwater with fillet, and another is three-dimensional canopy-like fairwater. Numerical investigation by LES and acoustic analogy is carried out to analyze the vortical flow fields (horse-shoe vor-tex) and acoustic characteristics of the three fairwaters, and the effect of optimization is studied to describe the quantitative change of pressure fluctuations and flow induced noise. This study shows that the optimiza-tion of fairwater is able to improve the flow quality around fairwater especially in the junction of fairwater and hull, and the wall pressure fluctuations and flow induced noise can be suppressed obviously. The work is beneficial to the research in the field of flow-acoustic coupling and the design of the submarine with a new type.

With respect to the measurement uncertainty, this paper discusses the definition, the sources, the classification and the expressions of the CFD uncertainty. Based on the orthogonal design and the statistics inference theory, a new verification and validation method and the related procedures in the CFD simulation are developed. With the method, two examples of the CFD verification and validation are studied for the drag coefficient and the nominal wake fraction, and the calculation factors and their interactions which would significantly affect the simulation results are obtained. Moreover, the sizes of all uncertainty components resulting from the controlled and un-controlled calculation factors are determined, and the optimal combination of the calculation factors is obtained by an effect estimation in the orthogonal experiment design. It is shown that the new method can be used for the verification in the CFD uncertainty analysis, and can reasonably and definitely judge the credibility of the simulative result. As for CFD simulation of the drag coefficient and the nominal wake fraction, the results predicted can be validated. Although there is still some difference between the simulation results and the experiment results, its approximate level and credibility can be accepted.

Wall Pressure Fluctuations (WPF) represent the unsteady feature of turbulence. It is a significant hydrodynamic acoustic source. The study of WPF has become vigorous in the field of flow-acoustic cou-pling. The wall pressure fluctuations of wing/plate junctions (two shapes) under different velocities are sim-ulated numerically by large eddy simulation with dynamic Smagorinsky subgrid model. And the horse-shoe vortical field around wing/plate junction is captured and displayed. It shows that the computed wall pres-sure fluctuations agree well with experimental measurements. And the numerical computation approach for WPF is validated. These works are beneficial for understanding the physical mechanism of unsteady flow around wing/plate junction.

Basing on the principle of the self propulsion model test, the calculation of the underwater self propulsion points in the forced self propulsion model tests was discussed. Considering the relationship between the constraining force with the resistance allowance, it is suggested to carry out an after-hull interaction curve to make up the narrow range of the forced self propulsion model tests when the resistance allowance is difficult to be exactly confirmed. And the relationship between self propulsion factors with the resistance allowance was also found. Furthermore, a new method was discussed in this paper by combining the two self propulsion manners mentioned above. By the new method test data is less scattered, which is helpful to enhance the model test precision.

In industrial practice, the cavity-type oscillation is undesirable from the perspective of inducement of structure vibration and fatigue, generation of noise and drastic increase in drag on the body. A numerical work for the prediction of wall pressure fluctuations and flow-induced noise of cavity is performed in the paper. Firstly, the wall pressure fluctuations of a plate are computed and compared with experimental results of Small Anechoic Flow Facility in CSSRC. The robustness of large eddy simulation (LES) in unsteady flow calculation is analyzed. Secondly, the calculations of wall pressure fluctuations of shuttle holes are accomplished. The power spectra of wall pressure fluctuations are analyzed. The numerical predictions are compared with measured data. Finally, the flow induced noises of three cavities are predicted through LES and FW-H acoustic analogy. The computed results including flow pattern in cavity, vorticity distribution and radiated sound spectrum are analyzed. The computed results are compared with experimental data of Large Circulation Channel in CSSRC, and the numerical prediction method is validated. It shows that the numerical prediction method in the paper is credible. Key words: wall pressure fluctuations; flow induced noise; Large eddy simulation; FW-H acoustic analogy; cavity

The resistance model tests for an underwater vessel operating close to the bottom or near surface were carried out. In the tests the analytical methods were established and the rules on the additional resistance coefficients were achieved. The model tests prove that the additional resistance induced by surface and bottom could be obtained by a low-speed shallow-immersed test method. The model test results indicate that only when the underwater vessel submersed depth reaches 1/3 length, the sea-surface effects disappeared. When the distance between the underwater vessel and the seabed surpassed 1/4 length, the seabed could not effected the underwater vessel resistance. If considering the sea-surface and seabed synchronously, then the underwater vessel must navigate at a depth exceeding 1/3 length, at the same time the distance between the underwater vessel and the seabed should be 1/2 times the underwater vessel length at least.

The characteristic parameters of boundary layer are inputs for the flow noise calculation, their change influence the power spectra of wall pressure fluctuations, so as to affect the analysis of the flow radiation noise. In this paper Hess-Smith boundary element method was adopted to model thick boundary layer for body of revolution. The corresponding code is developed. The computation of characteristic parameters of boundary layer for a body of revolution is carried out. The computed results including boundary layer thickness, shape factor, momentum thickness and friction coefficient are analyzed. The variation of characteristic parameter is obtained. The result showed that the code developed in this paper can be applied to the analysis of the body of revolution's 3D boundary layer calculation, which can offer input parameter for flow noise calculation. Key words: flow noise, characteristic parameter, boundary layer, body of revolution, Hess-Smith boundary element

Cavity flow and flow induced noise are two important issues in the field of flow-acoustic coupling.The mechanism of cavity flow induced noise in water is studied by the large eddy simulation(LES) and Kirchhoff integral in this paper.The cavity flow oscillation analysis shows that the fluid-resonance mode is impossible in the condition of low Mach number in water,and the fluid-dynamic oscillation determines the generation of cavity flow induced noise.After that,the effects of dipole and quadrupole sources on the acoustic spectrum are identified according to Kirchhoff control surface integral and body surface integral.With the analysis of mathematical expression of acoustic source,the power spectrum of Lighthill stress tensor and wall influence,the radiation of flow induced noise should be attributed to the vortex transportation of the acoustic effect in fluctuations of unsteady flow.

CFD simulation of submarine powering performance in the numerical towing tank of CSSRC is described in detail in this paper.The computation approach for resistance,flow field and hydrodynamic forces in open-water and self-propulsion(body-propulsor interaction) conditions are defined.Meanwhile,the various computation cases for submarine powering performance are analyzed.And the prediction accuracy is presented.These models consist of fifteen bodies of revolution(series models),ten submarine models of all appendages(series models),SUBOFF model,several submarine models and propeller models for method validation.The research result is an important component of numerical tank and can be adopted for the numerical simulation of flow around submarine in future.

The CFD uncertainty definition,source,classification and expression were elaborated,where the CFD simulation results were regarded as a random variable in the light of the uncertainty in measurements.Basing on the orthogonal experiment design and variance analysis methods,the concepts and procedures of CFD varification were developed.And based on statistic inference theory,the criterions and judgement pro-cess for CFD validation were also established.Using the commercial soft Fluent and the present methods,uncertainty analysis and assessment in CFD simulation on the resistance coeffcient and nominal wake fraction were illustrated,and significant calculation factors and their interaction which have strong effects on calculated results and all uncertainty components were obtained.The study shows that,for the state of the CFD art,the results’ fidelity or confidence could be accepted in spite of the discrety or uncertainty multiple times than the experiment.

Using the structured-grid technology and the flow model around one blade passage,the hydro-dynamic performance of the stock propeller was numerically computed with commercial RANS methods.According to the uncertainty analysis methology and procedure in CFD recommended by ITTC and the benchmark database,the numerical hydrodynamic results were verified and validated.In this paper,grid studies were conducted using three grids(m=3) with grid refinement ratio rk=2~(1/2),and SST k-ω and RNG k-e turbulent models were solved respectively to analyze the turbulent-model effects on the grid-conver-gence characteristics.The objectives are to promote the numerical simulation levels in the practice of the open-water performance of the propeller.

The predictions of cavity flow and flow-induced noise are two important and complex issues in fluid-acoustic coupling field. Numerical studies for these issues are performed in the paper by large eddy simulation (LES) and FW-H acoustic analogy. Firstly, the wall pressure fluctuations of plate, foil, shutter hole are computed and compared with experimental results. The robustness of large eddy simulation in unsteady flow calculation is analyzed. Secondly, the calculation of a 2-D cavity flow are accomplished. The power spectrum of pressure fluctuations is compared with measured data and the vorticity distribution is analyzed. Finally, the flow induced noises of two 3D cavities are predicted. The computed results are compared with experimental data of Large Circulation Channel in CSSRC. It shows that the numerical prediction method in the paper is credible.

In industrial practice,the cavity-type oscillation is undesirable from the perspective of induce-ment of structure vibration and fatigue,generation of noise and drastic increase in drag on the body.In this paper,the flow induced noise in water of rectangular cavities of five sizes is predicted through large eddy simulation and FW-H acoustic analogy.Firstly,the international research works in predicting flow gener-ated sound with LES and FW-H analogy are summarized.Secondly,the method of LES,the dynamic Smagorinsky subgrid model and the approach of FW-H analogy are described in details.Finally,the com-puted results including flow pattern in cavity,vorticity distribution and radiated sound spectrum are ana-lyzed.The computed results are compared with experimental data,and the numerical prediction method is validated.

Using the structured-grid technology and the flow model around one blade passage,the hydro-dynamic performance and wake characteristics of the high-skew stock propeller were numerically analyzed with commercial RANS methods.Among the advanced ratio J 0.33 to 0.95,the differences between the CFD results and experiments about the open-water performance are within 3%.Through the comparison of the flow fields around the propeller computed by CFD and the actuator-disk theory with viscous effect,it is in-dicated that: the effect of propeller suction occurs in front of the propeller;in the near field,X/Dp4,be-hind the propeller,the effect of the propeller is confined to the slipstream,and the circumferentially-aver-aged axial velocity profiles along the radial direction mainly depend on the propeller loading conditions;in the intermediate region,4X/Dp15,the swirling wake brings the axial high-speed velocity a more quickly decay along the lognitudinal direction and a larger region in the radial direction;in the developed wake,X/Dp15,there results in a single shear flow.

Wall pressure fluctuation beneath a turbulent boundary layer is an important source of hydrodynamic noise. It is necessary to carry out computational and experimental research. The wall pressure fluctuations of an underwater vehicle are numerically predicted under the theoretical framework of large eddy simulation (LES) with fine grid generated technique. Firstly, the equations of LES, the dynamic Smagorinsky subgrid model and numerical approach for discretization are described in details. Secondly, the pressure distribution on hull and appendages of SUBOFF model are computed by LES and validated by measured data. The robustness of LES in steady flow calculation is analyzed. Thirdly, the wall pressure fluctuations of a plate are computed and compared with experimental results of Small Anechoic Flow Facility in CSSRC. And the robustness of LES in unsteady flow calculation is analyzed. Finally, the wall pressure fluctuations on the hull (3 positions) and sail (4 positions) of an underwater vehicle are simulated by LES. The I/3 OCT spectrum are given. The frequency and decay characteristics of the spectnims are studied. The computed results are validated by experimental results. It shows that the numerical prediction method in the paper is credible.

The viscous flows around two submarine models SUBOFF and SubB are numerically simulated by solving RANS equations with five turbulence models(k-e、RNG k-e、k-ω、SST k-ω、RSM).The predicted flow fields with five turbulence models are compared with experimental measured data,so the prediction accuracy of different turbulence models are researched.The predicted flow field with Reynolds stress model is best among them.The effect of Reynolds number on the flow around submarine SUBOFF is studied.The flow fields of SUBOFF at different Reynolds numbers are numerically simulated.Then the variation of nondimensional axial velocity profiles,the wake flow contours,the boundary layer thicknesses and the vortex distributions at the root of appendages along with Reynolds number are analyzed in details.