Comparison of Unsteady Aerodynamics Approximations for Time-Domain Representation of Frequency-Independent Aeroelastic State-Space Models

2015 ◽  
Author(s):  
Ezra A. Tal ◽  
Nhan T. Nguyen ◽  
Eric Ting
Keyword(s):  
State Space ◽  
Time Domain ◽  
Unsteady Aerodynamics ◽  
State Space Models ◽  
Frequency Independent

scholarly journals Time Domain Modelling of Frequency Dependent Wind and Wave Forces on a Three-Span Suspension Bridge With Two Floating Pylons Using State Space Models

2017 ◽  
Author(s):  
Yuwang Xu ◽  
Ole Øiseth ◽  
Torgeir Moan
Keyword(s):  
State Space ◽  
Time Domain ◽  
Rational Functions ◽  
Suspension Bridge ◽  
State Space Models ◽  
Suspension Bridges ◽  
Wave Forces ◽  
Frequency Dependent ◽  
Main Challenge ◽  
Frequency Domain Approach

Floating suspension bridges, one of several new designs to make it possible to cross deep and wide fjords, consist of three spans and supported by two tension leg platforms and two fixed traditional concrete pylons. Geometric nonlinearities, nonlinear aerodynamic and hydrodynamic forces and nonlinear mooring systems can become of high importance. Time domain methods are commonly applied when nonlinearities need to be considered. The main challenge in time domain simulation of the floating suspension bridge is the modelling of frequency-dependent aerodynamic self-excited forces and hydrodynamic radiation forces. This paper shows how rational functions fitted to aerodynamic derivatives and hydrodynamic added mass and potential damping can be converted to state space models to transform the frequency-dependent forces to time-domain. A user element is implemented in the software ABAQUS to be able to include the self-excited forces in the dynamic analysis. The element is developed as a one node element that is included in the nodes along the girder and the tension leg platforms. The responses of the floating suspension bridge under turbulent wind forces and first-order wave excitation forces are calculated in a comprehensive case study and compared with results obtained using a multi-mode frequency domain approach to illustrate the performance of the presented time-domain methodology.

Synthetic seismograms using the state‐space approach

Geophysics ◽  
1979 ◽  
Vol 44 (5) ◽  
pp. 880-895 ◽  
Author(s):  
J. M. Mendel ◽  
N. E. Nahi ◽  
M. Chan
Keyword(s):  
State Space ◽  
Time Domain ◽  
State Space Model ◽  
Layered Media ◽  
State Space Models ◽  
State Equations ◽  
Space Model ◽  
Domain State ◽  
The Time Domain ◽  
Treat All

We develop time‐domain state‐space models for lossless layered media which are described by the wave equation and boundary conditions. We develop state‐space models for two cases: (1) source and sensor at the surface, and (2) source and sensor in the first layer. Our models are for nonequal one‐way traveltimes; hence, they are more general than most existing models of layered media which are usually for layers of equal one‐way traveltimes. A notable exception to this is the work of Wuenschel (1960); however, most of the useful results even in his paper are developed only for the uniform traveltime case. Our state‐space model treat all of the equations that describe a layered‐media system together in the time domain. Earlier approaches (e.g., Wuenschel, 1960; Robinson, 1968) recursively connect adjacent layers by means of frequency‐domain relationships. We refer to our state equations as “causal functional equations.” They actually represent a new class of equations. Why are we interested in a different class of models for what appears to be a well‐studied system? As is well known, there is a vast literature associated with systems which are described by time‐domain state‐space models. Most recent results in estimation and identification theories, for example, require a state‐space model. These time‐domain techniques have proven very beneficial outside of the geophysics field and we feel should also be beneficial in the geophysics field. In fact, our ultimate objective is to apply those theories to the layered‐media problem; but, to do so, of course, requires state‐space models—hence, this paper.

scholarly journals Time-Domain Absorbing Boundary Terminations for Waveguide Ports Based on State-Space Models

2014 ◽  
Vol 50 (2) ◽  
pp. 145-148 ◽  
Author(s):  
Thomas Flisgen ◽  
Johann Heller ◽  
Ursula van Rienen
Keyword(s):  
State Space ◽  
Time Domain ◽  
State Space Models ◽  
Absorbing Boundary

Parameter Estimation Using a Modified Version of SPSA Algorithm Applied to State Space Models

2009 ◽  
Vol 129 (12) ◽  
pp. 1187-1194 ◽  
Author(s):  
Jorge Ivan Medina Martinez ◽  
Kazushi Nakano ◽  
Kohji Higuchi
Keyword(s):  
Parameter Estimation ◽  
State Space ◽  
State Space Models

Heat transfer modeling and identification using fractional order state space models

2008 ◽  
Vol 42 (6-8) ◽  
pp. 939-951 ◽  
Author(s):  
Tounsia Jamah ◽  
Rachid Mansouri ◽  
Saïd Djennoune ◽  
Maâmar Bettayeb
Keyword(s):  
Heat Transfer ◽  
State Space ◽  
Fractional Order ◽  
State Space Models ◽  
Heat Transfer Modeling ◽  
Order State
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