Advanced Natural Circulation Reduced-Order Model With Inclined Channel for Low Pressure Conditions

2020 ◽  
Vol 6 (2) ◽  
Author(s):  
René Manthey ◽  
Alexander Knospe ◽  
Carsten Lange ◽  
Christoph Schuster ◽  
Antonio Hurtado
Keyword(s):  
Reference Model ◽  
Nonlinear Dynamical Systems ◽  
Natural Circulation ◽  
Dynamical Behavior ◽  
Low Pressure ◽  
Reduced Order Model ◽  
Circulation System ◽  
Order Model ◽  
Two Phase ◽  
Reduced Order

Abstract Natural circulation with two-phase flow is a nonlinear dynamical systems, which can show a very complex and strange behavior under specific conditions. The application of stability analysis requires a large computational effort and is cumbersome in case of prediction the dynamical behavior by system codes alone. Therefore, model-order reduction techniques are used to compensate this disadvantage by coupling with a bifurcation code such as MatCont. A reduced-order model is derived by employing the proper orthogonal decomposition (POD) to analyze the stability landscape of a low pressure natural circulation system representing passive safety systems such as the containment cooling condenser. The required full-order model contains a classical natural circulation loop with a heated section and a riser. The two-phase region is modeled by a drift–flux mixture model. The reliability of the full-order model is investigated by comparison with a reference model by the validated system code ATHLET.

Advanced Natural Circulation Reduced Order Model With Inclined Channel for Low Pressure Conditions

2018 ◽  
Author(s):  
René Manthey ◽  
Alexander Knospe ◽  
Carsten Lange ◽  
Christoph Schuster ◽  
Antonio Hurtado
Keyword(s):  
Reference Model ◽  
Nonlinear Dynamical Systems ◽  
Natural Circulation ◽  
Dynamical Behavior ◽  
Low Pressure ◽  
Reduced Order Model ◽  
Circulation System ◽  
Order Model ◽  
Two Phase ◽  
Reduced Order

Natural circulation with two-phase flow is a nonlinear dynamical systems, which can show a very complex and strange behavior under specific conditions. The application of stability analysis requires a large computational effort and is cumbersome in case of prediction the dynamical behavior by system codes alone. Therefore, model order reduction techniques are used to compensate this disadvantage by coupling with a bifurcation code such as MatCont. A reduced order model is derived by employing the POD-method to analyze the stability landscape of a low pressure natural circulation system representing passive safety systems such as the containment cooling condenser. The required full order model contains a classical natural circulation loop with a heated section and a riser. The two-phase region is modeled by a drift-flux mixture model. The reliability of the FOM is investigated by comparison with a reference model by the validated system code ATHLET.

The Static and Dynamic Behavior of MEMS Arches Under Electrostatic Actuation

2009 ◽  
Author(s):  
Hassen M. Ouakad ◽  
Mohammad I. Younis ◽  
Fadi M. Alsaleem ◽  
Ronald Miles ◽  
Weili Cui
Keyword(s):  
Multiple Scales ◽  
Perturbation Technique ◽  
Dynamical Behavior ◽  
Primary Resonance ◽  
Reduced Order Model ◽  
Harmonic Load ◽  
Order Model ◽  
Reduced Order ◽  
Electrostatically Actuated ◽  
Model Equations

In this paper, we investigate theoretically and experimentally the static and dynamic behaviors of electrostatically actuated clamped-clamped micromachined arches when excited by a DC load superimposed to an AC harmonic load. A Galerkin based reduced-order model is used to discretize the distributed-parameter model of the considered shallow arch. The natural frequencies of the arch are calculated for various values of DC voltages and initial rises of the arch. The forced vibration response of the arch to a combined DC and AC harmonic load is determined when excited near its fundamental natural frequency. For small DC and AC loads, a perturbation technique (the method of multiple scales) is also used. For large DC and AC, the reduced-order model equations are integrated numerically with time to get the arch dynamic response. The results show various nonlinear scenarios of transitions to snap-through and dynamic pull-in. The effect of rise is shown to have significant effect on the dynamical behavior of the MEMS arch. Experimental work is conducted to test polysilicon curved microbeam when excited by DC and AC loads. Experimental results on primary resonance and dynamic pull-in are shown and compared with the theoretical results.

scholarly journals Reduced-Order Model of Rotor Cage in Multiphase Induction Machines: Application on the Prediction of Torque Pulsations

2020 ◽  
Vol 25 (1) ◽  
pp. 11 ◽  
Author(s):  
Abdelhak Mekahlia ◽  
Eric Semail ◽  
Franck Scuiller ◽  
Hussein Zahr
Keyword(s):  
Induction Machine ◽  
Induction Machines ◽  
Reduced Order Model ◽  
Order Model ◽  
Two Phase ◽  
Reduced Order ◽  
Three Phase ◽  
Torque Pulsations ◽  
Sinusoidal Current ◽  
Rotor Cage

For three-phase induction machines supplied by sinusoidal current, it is usual to model the n-bar squirrel-cage by an equivalent two-phase circuit. For a multiphase induction machine which can be supplied with different harmonics of current, the reduced-order model of the rotor must be more carefully chosen in order to predict the pulsations of torque. The proposed analysis allows to avoid a wrong design with non-sinusoidal magnetomotive forces. An analytical approach is proposed and confirmed by Finite-Element modelling at first for a three-phase induction machine and secondly for a five-phase induction machine.

Investigating the Stability Characteristics of Natural-Circulation Boiling Water Reactors Using Root Loci of a Reduced-Order Model

2001 ◽  
Vol 136 (3) ◽  
pp. 301-314 ◽  
Author(s):  
Robert Zboray ◽  
Wilhelmus J. M. de Kruijf ◽  
Tim H. J. J. van der Hagen ◽  
Hugo van Dam
Keyword(s):  
Natural Circulation ◽  
Reduced Order Model ◽  
Boiling Water ◽  
Boiling Water Reactors ◽  
Order Model ◽  
Reduced Order ◽  
Water Reactors ◽  
The Stability

scholarly journals An Error Indicator-Based Adaptive Reduced Order Model for Nonlinear Structural Mechanics—Application to High-Pressure Turbine Blades

2019 ◽  
Vol 24 (2) ◽  
pp. 41
Author(s):  
Fabien Casenave ◽  
Nissrine Akkari
Keyword(s):  
High Pressure ◽  
Reference Model ◽  
Turbine Blades ◽  
Reduced Order Model ◽  
High Fidelity ◽  
Order Model ◽  
High Pressure Turbine ◽  
Time Step ◽  
Reduced Order ◽  
Error Indicator

The industrial application motivating this work is the fatigue computation of aircraft engines’ high-pressure turbine blades. The material model involves nonlinear elastoviscoplastic behavior laws, for which the parameters depend on the temperature. For this application, the temperature loading is not accurately known and can reach values relatively close to the creep temperature: important nonlinear effects occur and the solution strongly depends on the used thermal loading. We consider a nonlinear reduced order model able to compute, in the exploitation phase, the behavior of the blade for a new temperature field loading. The sensitivity of the solution to the temperature makes the classical unenriched proper orthogonal decomposition method fail. In this work, we propose a new error indicator, quantifying the error made by the reduced order model in computational complexity independent of the size of the high-fidelity reference model. In our framework, when the error indicator becomes larger than a given tolerance, the reduced order model is updated using one time step solution of the high-fidelity reference model. The approach is illustrated on a series of academic test cases and applied on a setting of industrial complexity involving five million degrees of freedom, where the whole procedure is computed in parallel with distributed memory.

Sign in / Sign up

Export Citation Format

Share Document