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Xie L.,Shanghai JiaoTong University | Jin S.-Y.,Shanghai JiaoTong University | Jin S.-Y.,Shanghai Marine Equipment Research Institute | Wang Y.-Z.,Shanghai JiaoTong University | Yu J.-G.,Shanghai JiaoTong University
Shiyan Liuti Lixue/Journal of Experiments in Fluid Mechanics | Year: 2012

Through the established re-circulation water channel, the inner flow field in 90° bending duct of circular-section with a fore-end valve was measured by particle image velocimetry. Massive high-resolution data of transient flow field were obtained at different observation sections under diverse velocities. The transient and time-averaged flow fields after adaptive correlation calculation were analyzed. The POD modes were obtained after proper orthogonal decomposition of the flow fields, and the structural properties of vortex were further analyzed through the reconstruction of fluctuation field. Conclusions are drawn out that there exists Kármán vortex street in the bend after the butterfly valve, the vortex information is included in low proper orthogonal decomposition modes, and the flow properties of vortex can be restored through the reconstruction of fluctuation field. Source

Shi J.,Shanghai Marine Equipment Research Institute | Li X.,Shanghai JiaoTong University | Lu T.,Shanghai JiaoTong University | Zhang J.,Shanghai JiaoTong University
International Journal of Automotive Technology | Year: 2012

A traction control system (TCS) is used to improve the acceleration performance on slippery roads by preventing excessive wheel slip. In this paper, a new traction control system using the integrated control of gear shifting and throttle actuation is developed for vehicles with automatic transmissions. In the design of the slip controller, by means of a differential manifold transformation, a slip control system with nonlinearities and uncertainties is transformed into a linear system, and a sliding mode controller is applied for the purpose of increasing the robustness of the system. Next, to achieve the required driving torque, the optimal throttle and gear position, maps are constructed based on dynamic programming. The simulation results indicate that the present traction control system can improve the acceleration performance of an automatic transmission vehicle for various types of road conditions. © 2012 The Korean Society of Automotive Engineers and Springer-Verlag Berlin Heidelberg. Source

Wu H.,Shanghai JiaoTong University | Jiang W.,Shanghai JiaoTong University | Zhang Y.,Shanghai JiaoTong University | Lu W.,Shanghai Marine Equipment Research Institute
Journal of the Acoustical Society of America | Year: 2014

Application of modal expansion approach for the exterior acoustic field has drawn wide research interests in recent years. This is primarily due to the acoustic radiation modes (ARM) that can diagonalize the impedance matrix, hence significantly simplifying the computation of radiated sound power. The orthogonal ARM are typically calculated via a standard eigenvalue analysis of the impedance matrix, which normally leads to numerical difficulties especially for wideband frequency and large scale problems. In this paper, a theory of mapped ARM is proposed to avoid the cumbersome computation of ARM for convex structures. A mapping relationship between the ARM on the surface of an equivalent spherical source and the mapped ARM on the surface of a convex structure is obtained based on the equivalent source method, multipole expansion method, and boundary integral method. Furthermore, analytical expressions for the radiated sound power of structures vibrating in its mapped ARM as well as that of spheres are derived. Finally, a simple method is proposed to approximate the radiated sound power based on the modal decomposition method and the mapping relationship. Numerical simulations are conducted to validate the accuracy and efficiency of the proposed approach, and different vibrating structures with various geometries are considered. Results demonstrate that the proposed methodology for calculating the radiated sound power of convex structures is very efficient and accurate as compared with the traditional approach. © 2014 Acoustical Society of America. Source

Hu J.,Shanghai Marine Equipment Research Institute | Qiu Z.,Beihang University | Su T.C.,Florida Atlantic University
Journal of Sound and Vibration | Year: 2011

Axisymmetric vibrations of a viscous-fluid-filled piezoelectric sphere, with radial polarization, submerged in a compressible viscous fluid medium are investigated. The oscillations are harmonically driven by an axisymmetrically applied electric potential difference across the surface of the shell. A theoretical formulation cast the piezoelectric shell problem into a corresponding problem of an elastic shell with the contribution of piezoelectricity confined to slightly modified in vacuum natural frequencies and their associated mode shapes. It is noted that the fluid inside the shell will have a dominating influence on the vibrational characteristics of the submerged shell. The circular components of the natural frequency spectra closely follow those of the fluid-filled shell in vacuo. Furthermore, the corresponding damping components of those natural frequencies are rather small, making acoustic radiation and under-damped oscillation possible for an infinite number of natural frequencies. The characteristics of natural frequencies are elucidated using a fluid-filled polyvinglindene fluoride (PVDF) shell submerged in both air and water as an example. It is found that the piezoelectric parameters that contribute to the shells natural frequencies is of a small order for thin PVDF shells, and is thereby negligible. It is noted that, with the mechanical constant typically associated with piezoelectric materials, fluid viscosity could have a significant effect on some vibrations. In certain cases, a natural frequency associated with a minimum viscous damping and a maximum of total damping (indicating highly efficient acoustic radiation) is possible with such a frequency. The vibrational characteristics, fluid loading, and energy flow are evaluated for a fluid-filled PVDF shell submerged in air and water. The inclusion of fluid inside the shell is shown to produce various narrow band peaks responses, vibrational absorbing frequencies, and non-dissipating frequencies. Those vibrational characteristics could have many potential applications. For example, the interior fluid could offer the option of generating a desired narrow band near resonant sound radiation while keeping power dissipation due to fluid viscosity to a minimum. Those well-defined narrow band characteristics also open up possibilities of using a vibrating, fluid-filled shell as a micro scale sensor for sensing and detection applications. © 2011 Elsevier Ltd. All rights reserved. Source

Shao D.,Harbin Engineering University | Hu F.,Shanghai Marine Equipment Research Institute | Wang Q.,Harbin Engineering University | Pang F.,Harbin Engineering University | Hu S.,Harbin Engineering University
Composite Structures | Year: 2016

The aim of this work is to present a unified and analytical solution for the transient response analysis of moderately thick general cross-ply composite laminated rectangular plates with general boundary restraints by using the method of reverberation ray matrix (MRRM). The wave solutions are constructed by the exact closed form solutions of the governing differential equations on the basis of the first-order shear deformation theory (FSDT). The reverberation ray matrix can be easily obtained by using the MRRM together with the wave solutions, boundary conditions and dual coordinates of the composite plate. As one merit of this paper, the spring boundary technology is applied to imitate the general boundary restraints and eliminate the barrier of the reverberation ray matrix. Then, the early short time transient responses of the composite laminated rectangular plate with general boundary restraints are obtained by using the Fast-Fourier transform (FFT) algorithm. The excellent accuracy, reliability and efficiency of the current solution are fully demonstrated and verified through numerical examples involving plates with different boundary conditions. A variety of new parameter studies for the composite laminated rectangular plate with different elastic restraint parameters, layer numbers, orthotropic ratios as well as various impact load types are analyzed. © 2016 Elsevier Ltd. Source

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