To obtain a universal model solving the uncertain acoustic field in shallow water, a non-intrusive model coupled polynomial chaos expansion （PCE） method with Helmholtz equa- tion is established, in which the polynom...To obtain a universal model solving the uncertain acoustic field in shallow water, a non-intrusive model coupled polynomial chaos expansion （PCE） method with Helmholtz equa- tion is established, in which the polynomial coefficients are solved by probabilistic collocation method （PCM）. For the cases of Pekeris waveguide which have uncertainties in depth of water column, in both sound speed profile and depth of water column, and for the case of thermocline with lower limit depth uncertain, probability density functions （PDF） of transmission loss （TL） are calculated. The results show that the proposed model is universal for the acoustic propa- gation codes with high computational efficiency and accuracy, and can be applied to study the uncertainty of acoustic propagation in the shallow water en^-ironment with multiple parameters uncertain.展开更多
针对随机不确定性可能带来翼吊式飞机严重气动性能波动的问题,提出了一种基于主动学习加点策略的Gauss过程回归(Gaussian process regression,GPR)代理模型方法用于不确定性分析,该主动学习加点策略能够有效地降低模型不确定性,提高不...针对随机不确定性可能带来翼吊式飞机严重气动性能波动的问题,提出了一种基于主动学习加点策略的Gauss过程回归(Gaussian process regression,GPR)代理模型方法用于不确定性分析,该主动学习加点策略能够有效地降低模型不确定性,提高不确定预测的精度。关注来流不确定性输入,分别使用Smolyak稀疏网格多项式混沌展开(polynomial chaos expansion,PCE)方法和基于主动学习加点策略的GPR代理模型方法,结合Sobol灵敏度分析对翼-身-短舱-挂架几何进行了不确定性分析。结果表明,在跨声速条件下,攻角和Mach数的不确定性会引起翼吊式飞机升力系数和阻力系数的剧烈波动,其中升力系数的波动同时受攻角和Mach数的影响,阻力系数的波动主要由Mach数决定。展开更多
Sensitivity analysis is used to quantify the contribution of the uncertainty of input variables to the uncertainty of systematic output responses.For tolerance design in manufacturing and assembly,sensitivity analysis...Sensitivity analysis is used to quantify the contribution of the uncertainty of input variables to the uncertainty of systematic output responses.For tolerance design in manufacturing and assembly,sensitivity analysis is applied to help designers allocate tolerances optimally.However,different sensitivity indices derived from different sensitivity analysis methods will always lead to conflicting results.It is necessary to find a sensitivity index suitable for tolerance allocation to transmission mechanisms so that the sensitivity results can truly reflect the effects of tolerances on kinematic and dynamic performances.In this paper,a variety of sensitivity indices are investigated and compared based on hybrid simulation.Firstly,the hybrid simulation model of the crank-slider mechanism is established.Secondly,samples of the kinematic and dynamic responses of the mechanism with joint clearances and link length errors are obtained,and the surrogate model established using polynomial chaos expansion(PCE).Then,different sensitivity indices are calculated based on the PCE model and are further used to evaluate the effect of joint clearances and link length errors on the output response.Combined with the tolerance-cost function,the corresponding tolerance allocation schemes are obtained based on different sensitivity analysis results.Finally,the kinematic and dynamic responses of the mechanism adopting different tolerance allocation schemes are simulated,and the sensitivity index corresponding to the optimal response is determined as the most appropriate index.展开更多
文摘To obtain a universal model solving the uncertain acoustic field in shallow water, a non-intrusive model coupled polynomial chaos expansion （PCE） method with Helmholtz equa- tion is established, in which the polynomial coefficients are solved by probabilistic collocation method （PCM）. For the cases of Pekeris waveguide which have uncertainties in depth of water column, in both sound speed profile and depth of water column, and for the case of thermocline with lower limit depth uncertain, probability density functions （PDF） of transmission loss （TL） are calculated. The results show that the proposed model is universal for the acoustic propa- gation codes with high computational efficiency and accuracy, and can be applied to study the uncertainty of acoustic propagation in the shallow water en^-ironment with multiple parameters uncertain.
文摘针对随机不确定性可能带来翼吊式飞机严重气动性能波动的问题,提出了一种基于主动学习加点策略的Gauss过程回归(Gaussian process regression,GPR)代理模型方法用于不确定性分析,该主动学习加点策略能够有效地降低模型不确定性,提高不确定预测的精度。关注来流不确定性输入,分别使用Smolyak稀疏网格多项式混沌展开(polynomial chaos expansion,PCE)方法和基于主动学习加点策略的GPR代理模型方法,结合Sobol灵敏度分析对翼-身-短舱-挂架几何进行了不确定性分析。结果表明,在跨声速条件下,攻角和Mach数的不确定性会引起翼吊式飞机升力系数和阻力系数的剧烈波动,其中升力系数的波动同时受攻角和Mach数的影响,阻力系数的波动主要由Mach数决定。
基金This work is supported by the National Natural Science Foundation of China(Nos.52075480 and 52105279)the High-Level Talent Special Support Plan of Zhejiang Province(No.2020R52004)the Ningbo Natural Science Foundation(No.2021J163),China.
文摘Sensitivity analysis is used to quantify the contribution of the uncertainty of input variables to the uncertainty of systematic output responses.For tolerance design in manufacturing and assembly,sensitivity analysis is applied to help designers allocate tolerances optimally.However,different sensitivity indices derived from different sensitivity analysis methods will always lead to conflicting results.It is necessary to find a sensitivity index suitable for tolerance allocation to transmission mechanisms so that the sensitivity results can truly reflect the effects of tolerances on kinematic and dynamic performances.In this paper,a variety of sensitivity indices are investigated and compared based on hybrid simulation.Firstly,the hybrid simulation model of the crank-slider mechanism is established.Secondly,samples of the kinematic and dynamic responses of the mechanism with joint clearances and link length errors are obtained,and the surrogate model established using polynomial chaos expansion(PCE).Then,different sensitivity indices are calculated based on the PCE model and are further used to evaluate the effect of joint clearances and link length errors on the output response.Combined with the tolerance-cost function,the corresponding tolerance allocation schemes are obtained based on different sensitivity analysis results.Finally,the kinematic and dynamic responses of the mechanism adopting different tolerance allocation schemes are simulated,and the sensitivity index corresponding to the optimal response is determined as the most appropriate index.
