循环水槽船模阻力试验不确定度分析

Uncertainty analysis of ship model resistance measurement in circulating water channel

[目的]采用试验流体力学(EFD)和计算流体力学(CFD)方法研究流体力学,都存在不确定度分析的问题。针对循环水槽船模阻力试验开展不确定度研究,分别分析精度极限、天平标定和数据采集过程中引起的不确定度。[方法]针对循环水槽所特有的、来流不均匀度和湍流强度难以通过EFD方法求解不确定度的敏感系数,根据上海交通大学循环水槽的实际情况建立相关数学模型,采用CFD模拟得到来流不均匀度和湍流强度对总阻力的影响,应用不确定度理论得到相应的不确定度分量,对CFD计算的不确定度进行专门分析。[结果]结果显示:在CFD不确定度分析中,修正和未修正的计算结果均得到了有效确认,表明利用CFD模拟开展研究可行;循环水槽船模阻力试验合成相对不确定度为1.91%,湍流强度对阻力的影响最大,起主导作用,在设计循环水槽时应尽可能降低湍流强度;由不均匀度引起的不确定度分量,以及由精度极限、天平标定和数据采集过程引起的不确定度分量均不大。[结论]采用CFD方法分析EFD不确定度的一些分量,具备可行性和一定的借鉴意义。

[Objectives]Experimental fluid dynamics(EFD)and computational fluid dynamics(CFD)are the two main methods for studying fluid mechanics problems,and they both have uncertainty analysis problems.The uncertainty of ship model resistance testing in circulating water channels is studied,and the uncertainty caused by the precision limit,balance calibration and data acquisition process are analyzed respectively.[Methods]It is difficult to solve the sensitivity coefficient of uncertainty using the EFD method because of the specific inflow unevenness and turbulence intensity of circulating water channels.According to the actual situation of circulating water channels at Shanghai Jiao Tong University,a related mathematical model is established,and the influence of inflow unevenness and turbulence intensity on total resistance is obtained via CFD simulation.The corresponding uncertainty component is obtained by applying the uncertainty theory,and the uncertainty of the CFD calculation is also specially analyzed.[Results]The results show that in the uncertainty analysis of CFD,the corrected and uncorrected calculation results are effectively confirmed,which indicates the feasibility of using CFD simulation to carry out research.The relative uncertainty of ship model resistance testing in a circulating water tank is 1.91%.Turbulence intensity has the greatest influence on resistance and plays a leading role;it should be considered in order to reduce turbulence intensity as much as possible when designing circulating water channels.The second most influential aspect is the uncertainty component caused by unevenness.The uncertainty components caused by the precision limit,balance calibration and data acquisition process are not significant.[Conclusions]Using the CFD method to analyze certain components of EFD uncertainty is feasible and has certain reference significance.