Linear-Frequency-Domain Predictions of Dynamic-Response Data for Viscous Transonic Flows

AIAA Journal ◽  
2013 ◽  
Vol 51 (11) ◽  
pp. 2540-2557 ◽  
Author(s):  
Reik Thormann ◽  
Markus Widhalm
Keyword(s):  
Dynamic Response ◽  
Frequency Domain ◽  
Transonic Flows ◽  
Linear Frequency ◽  
Response Data

scholarly journals Dynamic Response of Bridge-Ship Collision Considering Pile-Soil Interaction

2017 ◽  
Vol 3 (10) ◽  
pp. 965 ◽  
Author(s):  
Hussein Yousif Aziz ◽  
HE Yun Yong ◽  
Baydaa Hussain Mauls
Keyword(s):  
Dynamic Response ◽  
Frequency Domain ◽  
Integral Transform ◽  
Simulation Models ◽  
Bridge Piers ◽  
Inverse Transformation ◽  
Winkler Foundation ◽  
Transient Vibration ◽  
Ship Collision ◽  
Shearing Strain

According to most countries’ norms, and to find the effect of the bridge collision the equivalent static method was designed for bridge-ship collision, ignoring the dynamic effects of shocks. It is sharply different from actual situation. So based on the theory of Winkler foundation, shearing strain theory of Timoshenko and potential energy variation functional principle of Hamilton, the simulation models of bridge piers was built considering the pile–soil interaction. Lateral transient vibration equation of bridge piers was concluded. Based on the theory of integral transform, the differential equation of the collision system and the boundary conditions were transformed with Laplace transformation; the analytical solution of the stress wave in frequency domain was concluded. And then the inversion of solution in frequency domain was carried out using Matlab based on the Crump inverse transformation. Finally the dynamic response law of displacement, normal stress and the shear stress of bridge piers were obtained.

Dynamics of Closed Circuit Hydraulic Model Loops

2002 ◽  
Author(s):  
Bjo̸rnar Svingen ◽  
Morten Kjeldsen ◽  
Roger E. A. Arndt
Keyword(s):  
Theoretical Analysis ◽  
Dynamic Response ◽  
Theoretical Work ◽  
Current Theory ◽  
Water Tunnel ◽  
Post Processing ◽  
Global System ◽  
Pressure Transducers ◽  
Response Data ◽  
Cavitating Hydrofoil

This paper reviews the issue of making unsteady measurements involving cavitating flow in traditional test loops. Measurements of the dynamic response of a water tunnel during testing of a partially cavitating hydrofoil are presented and reviewed in the context of current theory. Data were collected from an array of pressure transducers that were distributed around the tunnel loop. In the post processing of these data, gain and phase response data were calculated. Theoretical analysis consisted of splitting the system into different elements, and included the compressibility of water in the physics used to describe each element. While solving the global system an eigenvalue solution was found, thus no node specific solution is obtained. This work is currently being extended with the aim of obtaining node specific values such that a more direct comparison between the experimental and theoretical work can be made.

Dynamic Response of 3D Surface/Embedded Rigid Foundations of Arbitrary Shapes on Multi-Layered Soils in Time Domain

2019 ◽  
Vol 19 (09) ◽  
pp. 1950106 ◽  
Author(s):  
Zejun Han ◽  
Mi Zhou ◽  
Xiaowen Zhou ◽  
Linqing Yang
Keyword(s):  
Dynamic Response ◽  
Frequency Domain ◽  
Time Domain ◽  
Dynamic Stiffness ◽  
Dynamic Responses ◽  
Rigid Foundation ◽  
Layered Soils ◽  
Stiffness Matrices ◽  
The Time Domain ◽  
Arbitrary Shapes

Significant differences between the predicted and measured dynamic response of 3D rigid foundations on multi-layered soils in the time domain were identified due to the existence of uncertainties, which makes the issue a complicated one. In this study, a numerical method was developed to determine the dynamic responses of 3D rigid surfaces and embedded foundations of arbitrary shapes that are bonded to a multi-layered soil in the time domain. First, the dynamic stiffness matrices of the rigid foundations in the frequency domain are calculated via integral domain transformation. Secondly, a dynamic stiffness equation for rigid foundations in the time domain is established via the mixed variables formulation, which is based on the discrete dynamic stiffness matrices in the frequency domain. The proposed method can be applied to the treatment of systems with multiple degrees of freedom without losing the true information that concerns the coupling characteristics. Numerical examples are presented to demonstrate the accuracy of the proposed method for predicting the horizontal, vertical, rocking, and torsional vibrations. Further, a parametric study was carried out to provide insight into the dynamic behavior of the soil–foundation interaction (SFI) while considering soil nonhomogeneity. The results indicate that the elastic modulus of the soil has a significant impact on the dynamic responses of the rigid foundation. Finally, a numerical example of a rigid foundation resting on a six-layered, semi-infinite soil demonstrates that the proposed method can be used to deal with multi-layered media in the time domain in a relatively easy way.

A Frequency-Domain INS/GPS Dynamic Response Method for Bridging GPS Outages

2010 ◽  
Vol 63 (4) ◽  
pp. 627-643 ◽  
Author(s):  
Mohammed El-Diasty ◽  
Spiros Pagiatakis
Keyword(s):  
Neural Network ◽  
Transfer Function ◽  
Dynamic Response ◽  
Dynamic System ◽  
Least Squares ◽  
Frequency Domain ◽  
Impulse Response ◽  
Time Domain ◽  
Response Model ◽  
Response Method

We develop a new frequency-domain dynamic response method to model integrated Inertial Navigation System (INS) and Global Positioning System (GPS) architectures and provide an accurate impulse-response-based INS-only navigation solution when GPS signals are denied (GPS outages). The input to such a dynamic system is the INS-only solution and the output is the INS/GPS integration solution; both are used to derive the transfer function of the dynamic system using Least Squares Frequency Transform (LSFT). The discrete Inverse Least Squares Frequency Transform (ILSFT) of the transfer function is applied to estimate the impulse response of the INS/GPS system in the time domain. It is shown that the long-term motion dynamics of a DQI-100 IMU/Trimble BD950 integrated system are recovered by 72%, 42%, 75%, and 40% for north and east velocities, and north and east positions respectively, when compared with the INS-only solution (prediction mode of the INS/GPS filter). A comparison between our impulse response model and the current state-of-the-art time-domain feed-forward neural network shows that the proposed frequency-dependent INS/GPS response model is superior to the neural network model by about 26% for 2D velocities and positions during GPS outages.

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