ON THE HIGH ACCURACY NS-ALPHA-DECONVOLUTION TURBULENCE MODEL

2010 ◽  
Vol 20 (04) ◽  
pp. 611-633 ◽  
Author(s):  
LEO G. REBHOLZ ◽  
MYRON M. SUSSMAN
Keyword(s):  
Complete Resolution ◽  
Numerical Experiments ◽  
Degrees Of Freedom ◽  
High Accuracy ◽  
Zeroth Order ◽  
Order Model ◽  
Regular Solutions ◽  
Fluid Turbulence ◽  
Approximate Deconvolution ◽  
Consistency Error

We analyze the mathematical and physical properties of, and present numerical experiments for, the recently proposed NS-α-deconvolution model of fluid turbulence. This family of models has the well-known NS-α model as its zeroth-order model, and applies the Nth van Cittert deconvolution operator to the filtered terms in NS-α to create the Nth-order NS-α-deconvolution model. This model is proposed in Ref. 29, where it is shown to have consistency error O(α2N + 2). Herein we prove that the model admits unique regular solutions, is frame invariant, and improves the consistency error of NS-α from O(α2) to O(α2N + 2) while requiring (N + 1)1/2 times more (typically 1 ≤ N ≤ 5) degrees of freedom for complete resolution. Numerical experiments show that adding approximate deconvolution to NS-α significantly improves accuracy in computations.

scholarly journals Diagonal scaling of stiffness matrices in the Galerkin boundary element method

2000 ◽  
Vol 42 (1) ◽  
pp. 141-150 ◽  
Author(s):  
Mark Ainsworth ◽  
Bill McLean ◽  
Thanh Tran
Keyword(s):  
Integral Equation ◽  
Stiffness Matrix ◽  
Numerical Experiments ◽  
Degrees Of Freedom ◽  
Boundary Integral ◽  
Piecewise Constant ◽  
Stiffness Matrices ◽  
Diagonal Scaling ◽  
Mesh Ratio ◽  
Galerkin Boundary Element Method

AbstractA boundary integral equation of the first kind is discretised using Galerkin's method with piecewise-constant trial functions. We show how the condition number of the stiffness matrix depends on the number of degrees of freedom and on the global mesh ratio. We also show that diagonal scaling eliminates the latter dependence. Numerical experiments confirm the theory, and demonstrate that in practical computations involving strong local mesh refinement, diagonal scaling dramatically improves the conditioning of the Galerkin equations.

scholarly journals A Reduced Order Model of Mistuning Using a Subset of Nominal System Modes

1999 ◽  
Author(s):  
M.-T. Yang ◽  
J. H. Griffin
Keyword(s):  
Degrees Of Freedom ◽  
Reduced Order Model ◽  
Reduced Order Models ◽  
Order Model ◽  
Disk System ◽  
Element Analysis ◽  
Reduced Order ◽  
Nominal System ◽  
Harmonic Response ◽  
Bladed Disk

Reduced order models have been reported in the literature that can be used to predict the harmonic response of mistuned bladed disks. It has been shown that in many cases they exhibit structural fidelity comparable to a finite element analysis of the full bladed disk system while offering a significant improvement in computational efficiency. In these models the blades and disk are treated as distinct substructures. This paper presents a new, simpler approach for developing reduced order models in which the modes of the mistuned system are represented in terms of a sub-set of nominal system modes. It has the following attributes: the input requirements are relatively easy to generate; it accurately predicts mistuning effects in regions where frequency veering occurs; as the number of degrees of freedom increases it converges to the exact solution; it accurately predicts stresses as well as displacements; and it accurately models the deformation and stresses at the blades’ bases.

A fractional order model for electrochemical impedance of IPMC actuators based on constant phase element

2020 ◽  
pp. 1045389X2097443
Author(s):  
Mohammad Javad Doregiraei ◽  
Hossein Moeinkhah ◽  
Jafar Sadeghi
Keyword(s):  
Fractional Order ◽  
Electrical Impedance ◽  
Constant Phase Element ◽  
Electrochemical Impedance ◽  
High Accuracy ◽  
Metal Composite ◽  
Order Model ◽  
Unknown Parameters ◽  
Fractional Order Model ◽  
Wide Range

The accurate modeling of electrical impedance over a wide range of frequency is essential for precise dynamic modeling and control problems of Electroactive Polymer (EAP) actuators. Recently, fractional order modeling has attracted more attention due to the high accuracy. This paper deals with a fractional order electrical impedance model and its identification procedure for a class of EAP actuator named Ionic Polymer Metal Composite (IPMC). To take IPMC’s fractional characteristic into account, constant phase element (CPE) is used to construct a model structure according to Electrochemical Impedance Spectroscopy (EIS). By employing the Levy’s method in combination with genetic optimization algorithm, the unknown parameters of the resulting fractional transfer function are identified. Finally the proposed model is verified, by comparing with experimental EIS data. The results show that the fractional order model has high accuracy for representing the electrical impedance of IPMC actuator. The proposed modeling procedure is general and can also be used for any type of EAPs.

Identification of Structural Systems With Limited Number of Sensors and Actuators

2004 ◽  
Author(s):  
Jun Yu ◽  
Maura Imbimbo ◽  
Raimondo Betti
Keyword(s):  
Degrees Of Freedom ◽  
Dynamic Models ◽  
Solution Space ◽  
Order Model ◽  
Sensors And Actuators ◽  
Common Assumption ◽  
Reduced Order ◽  
Different Types ◽  
The Common ◽  
Inverse Vibration

The common assumption in the so-called linear inverse vibration problem, which provides the mass/stiffness/damping matrices of second order dynamic models, is the availability of a full set of sensors and actuators. In “reduced-order” problems (with limited number of instrumentation), only the components of the eigenvector matrix regarding the measured degrees of freedom can be successfully identified while nothing can be said about the components connected to the unmeasured degrees of freedom. This paper presents a recently developed “reduced-order” model and expands such a model to a “full-order” one that is quite useful in damage detection. The five representative categories of “reduced-order” problems, defined by considering different types of geometrical conditions, are analyzed and a discussion on their solution space has been performed. The effectiveness and robustness of this approach is shown by means of a numerical example.

Distributed Feedback Control of the Benjamin-Bona-Mahony-Burgers Equation by a Reduced-Order Model

2015 ◽  
Vol 5 (1) ◽  
pp. 61-74 ◽  
Author(s):  
Guang-Ri Piao ◽  
Hyung-Chun Lee
Keyword(s):  
Feedback Control ◽  
Numerical Experiments ◽  
Burgers Equation ◽  
Distributed Feedback ◽  
Reduced Order Model ◽  
Order Model ◽  
Reduced Order ◽  
Order Case ◽  
Functional Gain ◽  
Proper Orthogonal

AbstractA reduced-order model for distributed feedback control of the Benjamin-Bona-Mahony-Burgers (BBMB) equation is discussed. To retain more information in our model, we first calculate the functional gain in the full-order case, and then invoke the proper orthogonal decomposition (POD) method to design a low-order controller and thereby reduce the order of the model. Numerical experiments demonstrate that a solution of the reduced-order model performs well in comparison with a solution for the full-order description.

Comparison of Constraint-Handling Mechanisms for the (1,λ)-ES on a Simple Constrained Problem

2016 ◽  
Vol 24 (1) ◽  
pp. 1-23 ◽  
Author(s):  
Michael Hellwig ◽  
Dirk V. Arnold
Keyword(s):  
Linear Constraint ◽  
Constraint Handling ◽  
Theoretical Knowledge ◽  
Zeroth Order ◽  
Order Model ◽  
Step Size ◽  
Constrained Problem ◽  
Repair Mechanisms ◽  
Handling Methods ◽  
Feasible Solutions

This paper investigates constraint-handling techniques used in nonelitist single-parent evolution strategies for the problem of maximizing a linear function with a single linear constraint. Two repair mechanisms are considered, and the analytical results are compared to those of earlier repair approaches in the same fitness environment. The first algorithm variant applies reflection to initially infeasible candidate solutions, and the second repair method uses truncation to generate feasible solutions from infeasible ones. The distributions describing the strategies’ one-generation behavior are calculated and used in a zeroth-order model for the steady state attained when operating with fixed step size. Considering cumulative step size adaptation, the qualitative differences in the behavior of the algorithm variants can be explained. The approach extends the theoretical knowledge of constraint-handling methods in the field of evolutionary computation and has implications for the design of constraint-handling techniques in connection with cumulative step size adaptation.

Compensation of geometric and elastic errors in large manipulators with an application to a high accuracy medical system

Robotica ◽  
2002 ◽  
Vol 20 (3) ◽  
pp. 341-352 ◽  
Author(s):  
Ph. Drouet ◽  
S. Dubowsky ◽  
S. Zeghloul ◽  
C. Mavroidis
Keyword(s):  
Degrees Of Freedom ◽  
High Accuracy ◽  
Medical Robot ◽  
Serial Manipulators ◽  
High Position ◽  
Six Degrees Of Freedom ◽  
Position Accuracy ◽  
End Point ◽  
Compensation Process ◽  
Very High

A method is presented that compensates for manipulator end-point errors in order to achieve very high position accuracy. The measured end-point error is decomposed into generalized geometric and elastic error parameters that are used in an analytical model to calibrate the system as a function of its configuration and the task loads, including any payload weight. The method exploits the fundamental mechanics of serial manipulators to yield a non-iterative compensation process that only requires the identification of parameters that are function only of one variable. The resulting method is computationally simple and requires far less measured data than might be expected. The method is applied to a six degrees-of-freedom (DOF) medical robot that positions patients for cancer proton therapy to enable it to achieve very high accuracy. Experimental results show the effectiveness of the method.

scholarly journals Design and modeling of a high accuracy three degrees of freedom MEMS manipulator

2005 ◽  
Author(s):  
Shyam Venugopal ◽  
Lun-Chen Hsu ◽  
Smitha Malalur-Nagaraja-Rao ◽  
B. P. Wang ◽  
Mu Chiao ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
High Accuracy ◽  
Three Degrees Of Freedom
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