Resampling strategies to improve surrogate model‐based uncertainty quantification: Application to LES of LS89

Uncertainty quantification (UQ) is receiving more and more attention for engineering applications particularly from robust optimization. Indeed, running a computer experiment only provides a limited knowledge in terms of uncertainty and variability of the input parameters. These experiments are often computationally expensive, and surrogate models can be constructed to address this issue. The outcome of an uncertainty quantification study is, in this case, directly correlated to the surrogate's quality. Thus, attention must be devoted to the design of experiments to retrieve as much information as possible. This work presents 2 new strategies for parameter space resampling to improve a Gaussian process surrogate model. These techniques indeed show an improvement of the predictive quality of the model with high‐dimensional analytical input functions. Finally, the methods are successfully applied to a turbine blade large‐eddy simulation application: the aerothermal flow around the LS89 blade cascade.     

Processing of Gasdynamic Numerical Solutions in Similarity Parameters

The distinctive features of the application of similarity parameters (those of Tsien and Hayes, Sychev, Messiter, the linear theory, and hypersonic theory of the flow past slender bodies) are considered with reference to examples of the supersonic flow past sharp bodies of revolution, thin delta wings, and blunt bodies (ellipsoids of revolution and elliptical cylinders). Approaches to the construction of generalizing dependences on the basis of numerical solutions are discussed. These dependences can simplify the overview of numerous solutions and the search for optimal shapes in certain classes of bodies; they give preliminary design estimates and can also be used in complicated problems in which the gasdynamic results are only part of a more general, for example, dynamic problem.     

高负荷后掠风扇设计若干基本问题

1单级风扇ATS－2（Ad、ncedTransonicStage）设计概述目的是探索总增压比为4．3的两级风扇的设计技术。指标为：设计后掠风扇进口级的缩尺实验件;级增压比2．2;级绝热效率不小于85％;喘振裕度不小于12％。取进口级增压比为2．2,意味着这类单级的增压比已超过大多数于50～80年代设计并服役的涡喷、涡扇发动机前两级轴流级的总增压比,例如WP7发动机。这就需要选用更高的叶尖线速度（相对来流马赫数）。于是这类高性能跨音级的技术特征为级压比高,线速度高,单位迎面流量大,转子叶片后掠或前掠。这时效率的维持主要受到两方面的制约…     

昆虫运动机理的研究

昆虫运动机理研究是一门交叉学科的前沿基础研究。旨在完善现有的空气动力学理论,为微机械设计寻找新思想、新概念。本文重点介绍目前在昆虫运动参数测量中的一些关键问题和研究进展情况,并对如何分析这些参数进行一些简单说明     

Asymmetric vortices flow over slender body and its active control at high angle of attack

The studies of asymmetric vortices flow over slender body and its active control at high angles of attack have significant importance for both academic field and engineering area. This paper attempts to provide an update state of art to the investigations on the fields of forebody asymmetric vortices. This review emphasizes the correlation between micro-perturbation on the model nose and its response and evolution behaviors of the asymmetric vortices. The critical issues are discussed, which include the formation and evolution mechanism of asymmetric multi-vortices; main behaviors of asymmetric vortices flow including its deterministic feature and vortices flow structure; the evolution and development of asymmetric vortices under the perturbation on the model nose; forebody vortex active control especially discussed micro-perturbation active control concept and technique in more detail. However present understanding in this area is still very limited and this paper tries to identify the key unknown problems in the concluding remarks. The project supported by the National Natural Science Foundation of China (10172017), Aeronautical Science Foundation of China (02A51048) and Foundation of National Key Laboratory of Aerodynamic Design and Research (51462020504HK0101)     

叶轮机械数值计算与设计方法进展及其在汽轮机中的应用──第一部分:数值计算及设计方法进展

本文对多级汽轮机通流部分气动热力学数值计算方法与设计体系研究所取得的进展进行了回顾，主要内容包括通流部分气动热力准三维、全三维计算方法进展、程序的校准方法、多级轴流透平气动热力设计体系研制等，并提出了今后进一步开发的设想．     

Numerical simulation of plate autorotation in a viscous fluid flow

A general formulation of the plane coupled dynamical and aerodynamical problem of the motion of a rigid body with a rotational degree of freedom in a viscous incompressible fluid flow is given. A computation technique for solving the Navier-Stokes equations based on the meshless viscous vortex domain method is used. The autorotation of a single plate and a pair of plates is investigated. The effect of the reduced moment of inertia and the Reynolds number on the angular rotation velocity is determined. The time dependences of the hydrodynamic loads are compared with the corresponding instantaneous flow patterns. The increased the autorotation velocity of two plates in tandem is detected.     

Analytic Representation of Volume Flow as a Function of Geometry and Pressure in a Static Physical Model of the Glottis

A static physical model of the larynx (model M5) was used to obtain a large set of volume flows as a function of symmetric glottal geometry and transglottal pressure. The measurements cover ranges of these variables relevant to human phonation. A generalized equation was created to accurately estimate the glottal volume flow given specific glottal geometries and transglottal pressures. Both the data and the generalized formula give insights into the flow behavior for different glottal geometries, especially the contrast between convergent and divergent glottal angles at different glottal diameters. The generalized equation produced a fit to the entire M5 dataset (267 points) with an average accuracy of 3.4%. The accuracy was about seven times better than that of the Ishizaka-Flanagan approach to glottal flow and about four times better than that of a pressure coefficient approach. Thus, for synthesis purposes, the generalized equation presented here should provide more realistic glottal flows (based on steady flow conditions) as suitable inputs to the vocal tract, for given values of transglottal pressure and glottal geometry. Applications of the generalized formula to pulses generated by vocal fold motions typical of those produced by the Ishizaka-Flanagan coupled-oscillator model and the more recent body-cover model of Story and Titze are also included.     

由两个风扇转子设计得到的启示

本文对两个风扇转子设计进行了总结,从设计过程突破问题的关键以及流动的组织方面看,得到了几点有益启示,值得在新型叶轮机设计及有关问题研究中引以借鉴。     

Objective Voice Quality Analysis Before and After Onset of Unilateral Vocal Fold Paralysis

This study was designed to investigate objective voice quality measurements in unilateral vocal fold paralysis (UVFP) by eliminating intersubject variability. To our knowledge this is the first report objectively analyzing paralytic dysphonia as compared to the same voice before onset of UVFP. The voices of two male subjects were prospectively recorded before and after the onset of iatrogenic UVFP (thoracic surgery).The following acoustic measurements of the vowel /a/ were performed using the CSL and MDVP (Kay Elemetrics): jitter, shimmer, harmonics-to-noise ratio, cepstral peak prominence, the relative energy levels of the first harmonic, the first formant and the third formant, the spectral slope in the low-frequency zone (0-1 kHz and 0-2 kHz), and the relative level of energy above 6 kHz. Distribution of spectral energy was analyzed from a long-term average spectrum of 40 seconds of text. Laryngeal aerodynamic measurements were obtained for one patient before and after onset of paralysis using the Aerophone II (Kay Elemetrics). Pitch and amplitude perturbation increased secondary to UVFP, while the harmonics-to-noise ratio and the cepstral peak prominence decreased. A relative increase in the mid-frequency and high-frequency ranges and a decrease in the low-frequency spectral slope were observed. Mean airflow rate and intraoral pressure increased, and glottal resistance and vocal efficiency decreased secondary to UVFP. The findings of this self-paired study confirm some but not all the results of previous studies. Measures involving the fundamental and the formants did not corroborate previous findings. Further investigation with vocal tract modeling is warranted.