scholarly journals The preferred mode of incompressible jets: linear frequency response analysis

2013 ◽  
Vol 716 ◽  
pp. 189-202 ◽  
Author(s):  
X. Garnaud ◽  
L. Lesshafft ◽  
P. J. Schmid ◽  
P. Huerre
Keyword(s):  
Excitation Frequency ◽  
Operating Conditions ◽  
Jet Flows ◽  
Response Analysis ◽  
Frequency Response Analysis ◽  
Potential Core ◽  
External Perturbations ◽  
Flow Response ◽  
Numerical Studies ◽  
Local Shear

AbstractThe linear amplification of axisymmetric external forcing in incompressible jet flows is investigated within a fully non-parallel framework. Experimental and numerical studies have shown that isothermal jets preferably amplify external perturbations for Strouhal numbers in the range $0. 25\leq {\mathit{St}}_{D} \leq 0. 5$, depending on the operating conditions. In the present study, the optimal forcing of an incompressible jet is computed as a function of the excitation frequency. This analysis characterizes the preferred amplification as a pseudo-resonance with a dominant Strouhal number of around $0. 45$. The flow response at this frequency takes the form of a vortical wavepacket that peaks inside the potential core. Its global structure is characterized by the cooperation of local shear-layer and jet-column modes.

scholarly journals Stereo-DIC Measurements of a Vibrating Bladed Disk: In-Depth Analysis of Full-Field Deformed Shapes

2021 ◽  
Vol 11 (12) ◽  
pp. 5430
Author(s):  
Paolo Neri ◽  
Alessandro Paoli ◽  
Ciro Santus
Keyword(s):  
Single Point ◽  
Excitation Frequency ◽  
Phase Variation ◽  
Operating Conditions ◽  
Image Correlation ◽  
Response Analysis ◽  
Full Field ◽  
Low Speed ◽  
Bladed Disk ◽  
Depth Analysis

Vibration measurements of turbomachinery components are of utmost importance to characterize the dynamic behavior of rotating machines, thus preventing undesired operating conditions. Local techniques such as strain gauges or laser Doppler vibrometers are usually adopted to collect vibration data. However, these approaches provide single-point and generally 1D measurements. The present work proposes an optical technique, which uses two low-speed cameras, a multimedia projector, and three-dimensional digital image correlation (3D-DIC) to provide full-field measurements of a bladed disk undergoing harmonic response analysis (i.e., pure sinusoidal excitation) in the kHz range. The proposed approach exploits a downsampling strategy to overcome the limitations introduced by low-speed cameras. The developed experimental setup was used to measure the response of a bladed disk subjected to an excitation frequency above 6 kHz, providing a deep insight in the deformed shapes, in terms of amplitude and phase distributions, which could not be feasible with single-point sensors. Results demonstrated the system’s effectiveness in measuring amplitudes of few microns, also evidencing blade mistuning effects. A deeper insight into the deformed shape analysis was provided by considering the phase maps on the entire blisk geometry, and phase variation lines were observed on the blades for high excitation frequency.

Experimental and Numerical Studies of Violin Bridge Vibration Mechanism

2013 ◽  
Vol 579-580 ◽  
pp. 536-541
Author(s):  
Cheng Zhong Zhang ◽  
Bang Yan Ye ◽  
Li Dong Liang ◽  
Xiong Jia ◽  
Guang Ming Zhang
Keyword(s):  
Frequency Response ◽  
Three Dimensional ◽  
Response Analysis ◽  
Frequency Response Analysis ◽  
Mechanical Behaviors ◽  
Numerical Studies ◽  
Vibration Mechanism ◽  
Modeling And Experiments ◽  
Isolated Bridge ◽  
Potential Tool

A violin bridge kept in place by the pressure of the four strings has a powerful effect on the tone of the instrument. Its dynamic mechanical behaviors are investigated using finite elemental modeling and experiments in this paper. Modal and frequency response analysis of an isolated bridge are carried out. Numerical results show that the frequency responses are related to the vibration modes of the bridge. Particularly, the bridge hill is due to the bridge itself, and linked to the in-plane rocking mode of the bridge near the bridge hill peak. Three-dimensional dynamic forces exerted to the violin plates by the strings and bridge are then experimentally measured using a dynamometer. The experimental results are then analyzed and correlated to the simulation. The frequency response analysis of an isolated bridge is demonstrated to be a potential tool to study the mechanical behaviors of the violin bridge.

Estimation and Reduction of Motor Input Surge Voltage using Frequency Response Analysis

2012 ◽  
Vol 132 (8) ◽  
pp. 630-637
Author(s):  
Toru Wakimoto ◽  
Yoshimitsu Takahashi ◽  
Norihito Kimura ◽  
Yukitoshi Narumi ◽  
Naoki Hayakawa
Keyword(s):  
Frequency Response ◽  
Response Analysis ◽  
Frequency Response Analysis

Identification of Trouble of Transformer by Frequency Response Analysis

2009 ◽  
Vol 129 (4) ◽  
pp. 517-525 ◽  
Author(s):  
Satoru Miyazaki ◽  
Yoshinobu Mizutani ◽  
Hiroshi Suzuki ◽  
Michiharu Ichikawa
Keyword(s):  
Frequency Response ◽  
Response Analysis ◽  
Frequency Response Analysis

Diagnosis Criterion of Abnormality of Transformer Winding by Frequency Response Analysis (FRA)

2016 ◽  
Vol 136 (7) ◽  
pp. 654-662
Author(s):  
Satoru Miyazaki ◽  
Yoshinobu Mizutani ◽  
Akira Taguchi ◽  
Junichi Murakami ◽  
Naokazu Tsuji ◽  
...  
Keyword(s):  
Frequency Response ◽  
Response Analysis ◽  
Frequency Response Analysis ◽  
Transformer Winding ◽  
Diagnosis Criterion

MODAL FREQUENCY RESPONSE ANALYSIS OF HUMAN SUBJECT USING FEM

2018 ◽  
Vol 11 (5) ◽  
Author(s):  
Sahil Savara ◽  
Ishbir Singh ◽  
Sachin Kalsi
Keyword(s):  
Frequency Response ◽  
Human Subject ◽  
Response Analysis ◽  
Frequency Response Analysis ◽  
Modal Frequency
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