| 1. |
- Bagheri, Shervin, et al.
(author)
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Input-Output Analysis and Control Design Applied to a Linear Model of Spatially Developing Flows
- 2009
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In: Applied Mechanics Review. - : ASME International. - 0003-6900 .- 1088-8535 .- 2379-0407. ; 62:2
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Journal article (peer-reviewed)abstract
- This review presents a framework for the input-output analysis, model reduction, and control design for fluid dynamical systems using examples applied to the linear complex Ginzburg-Landau equation. Major advances in hydrodynamics stability, such as global modes in spatially inhomogeneous systems and transient growth of non-normal systems, are reviewed. Input-output analysis generalizes hydrodynamic stability analysis by considering a finite-time horizon over which energy amplification, driven by a specific input (disturbances/actuator) and measured at a specific output (sensor), is observed. In the control design the loop is closed between the output and the input through a feedback gain. Model reduction approximates the system with a low-order model, making modern control design computationally tractable for systems of large dimensions. Methods from control theory are reviewed and applied to the Ginzburg-Landau equation in a manner that is readily generalized to fluid mechanics problems, thus giving a fluid mechanics audience an accessible introduction to the subject.
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| 2. |
- Boström, Anders E, 1951
(author)
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Review of hypersingular integral equation method for crack scattering and application to modeling of ultrasonic nondestructive evaluation
- 2003
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In: Applied Mechanics Reviews. - : ASME International. - 1088-8535 .- 0003-6900 .- 2379-0407. ; 56:4, s. 383-405
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Journal article (peer-reviewed)abstract
- The scattering of elastic waves by cracks in isotropic and anisotropic solids has important applications in various areas of mechanical engineering and geophysics, in particular in ultrasonic nondestructive testing and evaluation. The scattering by cracks can be investigated by integral equation methods, eg, boundary elements methods, but here we are particularly concerned with more analytically oriented hypersingular integral equation methods. In these methods, which are only applicable to very simple crack shapes, the unknown crack opening displacement in the integral equation is expanded in a set of Chebyshev functions, or the like, and the integral equation is projected onto the same set of functions. This procedure automatically takes care of the hypersingularity in the integral equation. The methods can be applied to cracks in 2D and 3D, and to isotropic or anisotropic media. The crack can be situated in an unbounded space or in a layered structure, including the case with an interface crack. Also, problems with more than one crack can be treated. We show how the crack scattering procedures can be combined with models for transmitting and receiving ultrasonic probes to yield a complete model of ultrasonic nondestructive testing. We give a few numerical examples showing typical results that can be obtained, also comparing with some experimental results. This review article cites 78 references.
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| 3. |
- Dankowicz, Harry, et al.
(author)
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Untitled
- 2014
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In: Applied Mechanics Review. - : ASME International. - 0003-6900 .- 1088-8535 .- 2379-0407. ; 66:2, s. 020201-
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Journal article (peer-reviewed)
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| 4. |
- Fabbiane, Nicolò, 1986-, et al.
(author)
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Adaptive and model-based control theory applied to convectively unstable flows
- 2014
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In: Applied Mechanics Review. - : ASME International. - 0003-6900 .- 1088-8535 .- 2379-0407. ; 66:6, s. 060801-
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Research review (peer-reviewed)abstract
- Research on active control for the delay of laminar-turbulent transition in boundary layers has made a significant progress in the last two decades, but the employed strategies have been many and dispersed. Using one framework, we review model-based techniques, such as linear-quadratic regulators, and model-free adaptive methods, such as least-mean square filters. The former are supported by a elegant and powerful theoretical basis, whereas the latter may provide a more practical approach in the presence of complex disturbance envi- ronments, that are difficult to model. We compare the methods with a particu- lar focus on efficiency, practicability and robustness to uncertainties. Each step is exemplified on the one-dimensional linearized Kuramoto-Sivashinsky equa- tion, that shows many similarities with the initial linear stages of the transition process of the flow over a flat plate. Also, the source code for the examples are provided.
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| 5. |
- Juniper, Matthew P., et al.
(author)
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Modal Stability Theory : Lecture notes from the FLOW-NORDITA Summer School on Advanced Instability Methods for Complex Flows, Stockholm, Sweden, 2013
- 2014
-
In: Applied Mechanics Review. - : ASME Press. - 0003-6900 .- 1088-8535 .- 2379-0407. ; 66:2, s. 024804-
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Research review (peer-reviewed)abstract
- This article contains a review of modal stability theory. It covers local stability analysis of parallel flows including temporal stability, spatial stability, phase velocity, group velocity, spatio-temporal stability, the linearized Navier-Stokes equations, the Orr-Sommerfeld equation, the Rayleigh equation, the Briggs-Bers criterion, Poiseuille flow, free shear flows, and secondary modal instability. It also covers the parabolized stability equation (PSE), temporal and spatial biglobal theory, 2D eigenvalue problems, 3D eigenvalue problems, spectral collocation methods, and other numerical solution methods. Computer codes are provided for tutorials described in the article. These tutorials cover the main topics of the article and can be adapted to form the basis of research codes.
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| 6. |
- Kalpakli Vester, A., et al.
(author)
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Turbulent flows in curved pipes : Recent advances in experiments and simulations
- 2016
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In: Applied Mechanics Review. - : American Society of Mechanical Engineers (ASME). - 0003-6900 .- 1088-8535 .- 2379-0407. ; 68:5
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Journal article (peer-reviewed)abstract
- Curved pipes are essential components of nearly all the industrial process equipments, ranging from power production, chemical and food industries, heat exchangers, nuclear reactors, or exhaust gas ducts of engines. During the last two decades, an interest on turbulent flows in such conduits has revived, probably due to their connection to technical applications such as cooling systems of nuclear reactors (e.g., safety issues due to flowinduced fatigue) and reciprocating engines (e.g., efficiency optimization through exhaust gas treatment in pulsatile turbulent flows). The present review paper, therefore, is an account on the state-of-the-art research concerning turbulent flow in curved pipes, naturally covering mostly experimental work, while also analytical and numerical works are reviewed. This paper starts with a historical review on pipe flows in general and specifically on flows through curved conduits. In particular, research dealing with the effect of curvature on transition to turbulence, work dealing with pressure losses in curved pipes, as well as turbulence statistics are summarized. The swirl-switching phenomenon, a specific structural phenomenon occurring in turbulent curved pipe flows, which has interesting fundamental as well as practical implications, is reviewed. Additional complications, with respect to flow through bends, namely, entering swirling flow and pulsating flow, are reviewed as well. This review closes with a summary on the main literature body as well as an outlook on future work that should be performed in order to tackle open questions remaining in the field.
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| 7. |
- Lingwood, Rebecca, et al.
(author)
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Instabilities of the von Karman Boundary Layer
- 2015
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In: Applied Mechanics Review. - : ASME International. - 0003-6900 .- 1088-8535 .- 2379-0407. ; 67:3
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Research review (peer-reviewed)abstract
- Research on the von Karman boundary layer extends back almost 100 years but remains a topic of active study, which continues to reveal new results; it is only now that fully non-linear direct numerical simulations (DNS) have been conducted of the flow to compare with theoretical and experimental results. The von Karman boundary layer, or rotating-disk boundary layer, provides, in some senses, a simple three-dimensional boundary-layer model with which to compare other more complex flow configurations but we will show that in fact the rotating-disk boundary layer itself exhibits a wealth of complex instability behaviors that are not yet fully understood.
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| 8. |
- Olofsson, Ulf, et al.
(author)
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Open System Tribology in the Wheel-Rail Contact-A Literature Review
- 2018
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In: Applied Mechanics Review. - : ASME Press. - 0003-6900 .- 1088-8535 .- 2379-0407. ; 69:6
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Research review (peer-reviewed)abstract
- The tiny contact zone (approximately 1 cm2) where steel wheel meets steel rail is fundamental to rail transport. This work is a comprehensive presentation of recent research in wheel-rail contact tribology. It stresses that, unlike gears or rolling bearings which are sealed contacts with reduced exposure to the surrounding environment, a wheel-rail contact is an open system that is exposed to dirt and particles as well as to applied and natural lubrication (the latter category includes rain, dew, and biological materials such as leaves). As an open system contact, it also radiates sound and airborne wear particles. These characteristics of an open system underscore the need for special studies of open system tribology. Areas requiring study include airborne particle emissions and the environmental effects of applied lubrication and friction modification. Given that adhesion, wear, and sound and particle emission are closely related in an open system, these should be studied together rather than independently.
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| 9. |
- Schmid, Peter J., et al.
(author)
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Analysis of Fluid Systems : Stability, Receptivity, Sensitivity
- 2014
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In: Applied Mechanics Review. - : ASME International. - 0003-6900 .- 1088-8535 .- 2379-0407. ; 66:2, s. 024803-
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Research review (peer-reviewed)abstract
- This article presents techniques for the analysis of fluid systems. It adopts an optimization-based point of view, formulating common concepts such as stability and receptivity in terms of a cost functional to be optimized subject to constraints given by the governing equations. This approach differs significantly from eigenvalue-based methods that cover the time-asymptotic limit for stability problems or the resonant limit for receptivity problems. Formal substitution of the solution operator for linear time-invariant systems results in the matrix exponential norm and the resolvent norm as measures to assess the optimal response to initial conditions or external harmonic forcing. The optimization-based approach can be extended by introducing adjoint variables that enforce governing equations and constraints. This step allows the analysis of far more general fluid systems, such as time-varying and nonlinear flows, and the investigation of wavemaker regions, structural sensitivities, and passive control strategies.
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| 10. |
- Soltani Dehkharqani, Arash, et al.
(author)
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A Review of Available Methods for the Assessment of Fluid Added Mass, Damping, and Stiffness With an Emphasis on Hydraulic Turbines
- 2018
-
In: Applied Mechanics Review. - : American Society for Mechanical Engineers (ASME). - 0003-6900 .- 1088-8535 .- 2379-0407. ; 70:5
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Journal article (peer-reviewed)abstract
- Fluid added mass, damping, and stiffness are highly relevant parameters to consider when evaluating the dynamic response of a submerged structure in a fluid. The prediction of these parameters for hydraulic turbines has been approached relatively recently. Complex fluid-structure analyses including three-dimensional flow and the need for experiments during operation are the main challenges for the numerical and experimental approaches, respectively. The main objective of this review is to address the impact of different parameters, for example, flow velocity, cavitation, nearby solid structure, and rotational speed on the fluid added mass and damping of Kaplan/Propeller and Francis turbine runners. The fluid added stiffness is also discussed in the last section of the paper. Although studies related to hydraulic turbines are the main objective of this paper, the literature on hydrofoils is also taken into consideration to provide valuable information on topics such as individual runner blades. In this literature survey, the analytical, numerical, and experimental approaches used to determine fluid added parameters are discussed, and the pros and the cons of each method are addressed.
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