测量不确定度评定及应用

对测量误差和测量不确定度的基本概念作了介绍，并举例说明了测量不确定度A类和B类评定以及测量结果给出的方法，为测量不确定度评定提供参考。     

基于延迟分离涡模型的潜艇突出体流场数值计算结果不确定度分析

基于国际船模水池会议(ITTC)的计算流体力学(CFD)不确定度分析推荐规程,采用延迟分离涡模型对简化潜艇Suboff主艇体突出体非稳态流场进行了数值模拟,并对自研软件(HUST-Ship)数值结果的不确定度进行了分析.采用结构化重叠网格技术和三重解(三种网格量)对突出体阻力结果进行稳态流场的不确定度分析,稳态流场的计...     

电能表示值误差检定结果的不确定度分析与评定

简述了不确定度的分类、产生电能表测量不确定度的原因、产生电能表不确定度的来源、电能表测量不确定度评定程序。     

测量不确定度分析及应用举例

依据 1 999年国家质量技术监督局计量司颁布的JJF 1 0 59- 1 999《测量不确定度评定与表示》 ,对测量误差和测量不确定度的基本概念作了简单介绍 ,并举例说明了测量不确定度A类和B类评定的方法。     

水质分析中不确定度评定的应用

合理的分析评定不确定度是实验室内部质量控制和评价检测质量非常重要的程序之一,文章通过测量水中的氨氮含量为例,使用校准曲线这一类型的不确定度计算方法和基本步骤,介绍其测量方法、检测结果的计算方法、计算标准不确定度,并评定出分析数据的准确性和可靠性。     

水位观测不确定度的分析计算

文章探讨了水位观测误差不确定度的计算方法,分析了测量误差对被测量值不能确定的程度,以及被测量真值所处的量值的评定,随机误差分量和未定系统误差的联合分布范围等,对于水文资料分析和指导今后测验工作都有实际的意义。     

热轧带肋钢筋抗拉强度检测结果的影响因素及不确定度评定分析

分析了影响钢筋抗拉强度检测结果的各种因素和产生测量结果不确定度的来源.以HRB335钢筋为例开展试验研究,通过建立数学模型,系统分析了影响钢筋抗拉强度检测结果的不确定度分量及其贡献率,阐述了不确定度评定在钢筋抗拉强度检测中的应用情况,以期提高钢筋抗拉强度检测结果的准确性.     

铬酸钡分光光度法测定水样中硫酸盐的测量不确定度评定

硫酸盐是天然水体中的主要化学成份。本文通过对铬酸钡分光光度法(冷法)测定水样中硫酸盐不确定度来源的分析,找出影响测量的各种因素,计算不确定度分量及合成不确定度,以确定测量结果的可信度和准确度,建立测量不确定度的方法。     

水位观测的不确定度计算

文章以西峡水文站2008年11月12日和2008年11月15日的水位观测资料为例,阐述一般风浪和较大风浪情况下水位观测不确定度的计算方法,以验证实际观测资料的精度,从而指导水文测验工作。     

磷酸盐标准溶液不确定度的分析

通过对《水质总磷的测定（GB11893-1989）》中磷酸盐标准溶液配制的各步的不确定度的分析,找到影响其不确定度的主要因素,结果表明影响标的不确定度的主要因素是标液稀释带来的不确定度。     

A NOVEL DESIGN OF COMPOSITE WATER TURBINE USING CFD

This paper presents computational investigation of a novel design of composite material axial water turbine using Computational Fluid Dynamics(CFD).Based on three-dimensional numerical flow analysis,the flow characteristics through the water turbine with nozzle,wheel and diffuser are predicted.The extract power and torque of a composite water turbine at different rotating speeds were calculated and analyzed for a specific flow speed.The simulation results show that using nozzle and diffuser can increase the pressure drop across the turbine and extract more power from available water energy.These results provide a fundamental understanding of the composite water turbine,and this design and analysis method is used in the design process.     

IMPROVEMENT OF BUBBLE MODEL FOR CAVITATING FLOW SIMULATIONS

In the present research,a bubble dynamics based model for cavitating flow simulations is extended to higher void fraction region for wider range of applications.The present bubble model is based on the so-called Rayleigh-Plesset equation that calculates a temporal bubble radius with the surrounding liquid pressure and is considered to be valid in an area below a certain void fraction.The solution algorithm is modified so that the Rayleigh-Plesset equation is no more solved once the bubble radius(or void fraction)reaches at a certain value till the liquid pressure recovers above the vapor pressure in order to overcome this problem.This procedure is expected to stabilize the numerical calculation.The results of simple two-dimensional flow field are presented compared with the existing bubble model.     

大涡模拟在水下航行体周围黏性流场计算中的初步应用

在空间过滤得到的不可压缩流动的大涡模拟控制方程基础上,利用基于三阶迎风偏置格式的混合差分及二阶中心差分离散控制方程的对流项及耗散项,离散得到的线性方程组通过无矩阵计算的隐式LU-SGS（Lower-Upper Symmetric Gauss Seidel）分步迭代方法求解.利用大涡模拟（Large Eddy Simulation-LES）方法对水下航行体周围的黏性流场及水动力进行了定常数值模拟,计算得到的速度、压力分布及阻力值与试验吻合较好.     

NUMERICAL PREDICTION OF PROPELLER EXCITED ACOUSTIC RESPONSE OF SUBMARINE STRUCTURE BASED ON CFD,FEM AND BEM

A mesh-less Refined Integral Algorithm (RIA) of Boundary Element Method (BEM) is proposed to accurately solve the Helmholtz Integral Equation (HIE).The convergence behavior and the practicability of the method are validated.Computational Fluid Dynamics (CFD),Finite Element Method (FEM) and RIA are used to predict the propeller excited underwater noise of the submarine hull structure.Firstly the propeller and submarine’s flows are independently validated,then the self propulsion of the "submarine+propeller" system is simulated via CFD and the balanced point of the system is determined as well as the self propulsion factors.Secondly,the transient response of the "submarine+ propeller" system is analyzed at the balanced point,and the propeller thrust and torque excitations are calculated.Thirdly the thrust and the torque excitations of the propeller are loaded on the submarine,respectively,to calculate the acoustic response,and the sound power and the main peak frequencies are obtained.Results show that:(1) the thrust mainly excites the submarine axial mode and the high frequency area appears at the two conical-type ends,while the torque mainly excites the circumferential mode and the high frequency area appears at the broadside of the cylindrical section,but with rather smaller sound power and radiation efficiency than the former,(2) the main sound source appears at BPF and 2BPF and comes from the harmonic propeller excitations.So,the main attention should be paid on the thrust excitation control for the sound reduction of the propeller excited submarine structure.     

Numerical Simulation of Unsteady Turbulent Flow Induced by Two-Dimensional Elevator Car and Counter Weight System

A two-dimensional model of unsteady turbulent flow induced by high-speed elevator system was established in the present study. The research was focused on the instantaneous variation of the aerodynamic force on the car structure during traversing motion of the counter weight in the hoistway. A dynamic meshing method was employed to treat the multi-body motion system to avoid poor distortion of meshes. A comprehensive understanding of this significant aspect was obtained by varying the horizontal gap (δ =0.1m, 0.2m, and 0.3m) between the elevator car and the counter weight, and the moving speed ( U 0= 2m/s, 6m/s, and 10m/s) of the elevator system. A pulsed intensification of the aerodynamic force on the elevator car and subsequent appearance of large valley with negative aerodynamic force were clearly observed in the numerical results. In parameters studied ( δ =0.1m, U 0= 2m/s, 6m/s, 10m/s), the peaked horizontal and vertical forces are respectively 7-11 and 4.3-5.65 times of that when the counter weight is far from the car. These results demonstrated the prominent influence of the traversing counter weight on aerodynamic force on the elevator car, which is of great significance to designers of high-speed elevator system.     

A new methodology for the CFD uncertainty analysis

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.     

NUMERICAL ANALYSIS OF LEAKAGE FLOW THROUGH TWO LABYRINTH SEALS

The leakage flow through two labyrinth seals, e.g the interlocking seal and the stepped seal, was numerically investigated. Preliminary calculation of the seal-cavity averaged pressure by using the one-dimensional control volume method showed favorable agreement with the experimental measurements. Subsequently, in-depth understanding of the fluid flow through the labyrinth seals was obtained by employing Computational Fluid Dynamics (CFD) and k ?ε turbulence model, which resulted in a potential wealth of information like the streamline pattern, velocity vector field, and distribution of turbulent kinetic energy and static pressure. At the clearance of the seal the turbulent kinetic energy reached the peak value, while in the bulk region of the cavities it decayed fast. The static pressure rapidly dropped as the fluid flow went through the clearance; no distinct difference of the static pressure was inspected in the cavities. Also noted from the numerical results was that the stepped seal showed better sealing performance than the interlocking seal.     

非定常流弯肘型尾水管不规则压力脉动预测

尾水管内螺旋状涡带引起的压力脉动是造成混流式水轮机机组振动的主要原因之一,直接威胁机组的安全运行。为此,提出一种基于CFD数值计算的水轮机尾水管压力脉动数字化预测法,并利用此法对一大型混流式水轮机偏工况下尾水管内水流流动进行了长时间非定常流计算,讨论该工况下尾水管内死水域与涡带的运动规律,预测了尾水管的不规则压力脉动,压力脉动分析结果表明,其波形、频率、相位与实际基本一致。     

WEAKLY SWIRLING TURBULENT FLOW IN TURBID WATER HYDRAULIC SEPARATION DEVICE

This article deals with the characteristics of weakly swirling turbulent flow field in a Turbid Water Hydraulic Separation Device （TWHSD） through experimental and numerical researches. The flow field was measured by PIV, which provided streamlines, vortex structure, vorticity and velocity distribution in different test planes in the TWHSD. On the basis of the experimental results, the tangential and radial velocity distributions of the swirling flow field were obtained. Meanwhile, the numerical simulations were conducted with the RNG κ-ε and RSM turbulence models, respectively. According to the experimental and numerical results, the characteristics of the clear water flow field inside the TWHSD were determined. In view of simulation accuracy and time consumption, it is suggested to apply the RNG κ-ε model instead of the RSM model, which is more time consuming, to make further study on two-phases flow fields in the device.     

CFD simulation of a container ship in random waves using a coupled level-set and volume of fluid method

The coupled level-set and volume of fluid(CLSVOF)method is an advanced interface-capturing method that has been extended to handle overset grid systems.However,artificial uneven interface may be observed across block boundaries of different sizes and geometries.We present an improved inter-grid VOF interpolation and mass correction scheme to address the issue.To demonstrate the capability of the improved CLSVOF method,it is applied to the simulation of a container ship in pitch and heave motions under both head sea and following sea irregular wave conditions.Our simulation proves that the improved CLSVOF method is capable of revealing detailed physics difficult to see with other methods.Those phenomena simulated in our work include the extensive greenwater propagation on the ship deck,the breakup of overtopping waves into small droplets,and the formation and collapse of air pockets in sudden bow and stern slamming which cause strong and highly localized impacts on the ship bow,stern,and rudder.