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Maxwell Wolfinger - One of the best experts on this subject based on the ideXlab platform.
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Transformation of Flow Structure on a rotating wing due to variation of radius of gyration
Experiments in Fluids, 2015Co-Authors: Maxwell Wolfinger, Donald RockwellAbstract:The Flow Structure on a rotating wing (rectangular plate) is characterized over a range of travel distance at different radii of gyration. Travel distance is defined as the length of the arc subtended by the radius of gyration. Stereoscopic particle image velocimetry is employed to determine the volumetric Flow Structure, in the form of three-dimensional surfaces of the q -criterion, helical density, and downwash velocity. These representations are complemented by sectional patterns of vorticity and tangential velocity. An increase in the radius of gyration reduces the influence of rotation on the Flow Structure. At small radius of gyration, a coherent leading-edge vortex develops rapidly and then persists over a range of travel distance. At moderate radius of gyration, this leading-edge vortex is replaced by an arch vortex, which develops relatively slowly over a larger travel distance, and is eventually swept into the wake of the wing. The foregoing classes of vortical Structures are associated with distinctive patterns of: helical density, which represents the axial vorticity flux through the three-dimensional vortex system; downwash related to the strengths of the components of the vortex system; and tangential velocity associated with the extent of reverse Flow, or stall.
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Flow Structure on a rotating wing effect of radius of gyration
Journal of Fluid Mechanics, 2014Co-Authors: Maxwell WolfingerAbstract:The Flow Structure on a rotating wing (flat plate) is characterized over a range of Rossby number $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}\mathit{Ro} = r_g/C$ , in which $r_g$ and $C$ are the radius of gyration and chord of the wing, as well as travel distance $\mathit{Ro} = r_g \Phi /C$ , where $\Phi $ is the angle of rotation. Stereoscopic particle image velocimetry (SPIV) is employed to determine the Flow patterns on defined planes, and by means of reconstruction, throughout entire volumes. Images of the $Q$ -criterion and spanwise vorticity, velocity and vorticity flux are employed to represent the Flow Structure. At low Rossby number, the leading-edge, tip and root vortices are highly coherent with large dimensionless values of $Q$ in the interior regions of all vortices and large downwash between these components of the vortex system. For increasing Rossby number, however, the vortex system rapidly degrades, accompanied by loss of large $Q$ within its interior and downstream displacement of the region of large downwash. These trends are accompanied by increased deflection of the leading-edge vorticity layer away from the surface of the wing, and decreased spanwise velocity and vorticity flux in the trailing region of the wing, which are associated with the degree of deflection of the tip vortex across the wake region. Combinations of large Rossby number $\mathit{Ro} =r_g/C$ and travel distance $r_g \Phi /C$ lead to separated Flow patterns similar to those observed on rectilinear translating wings at high angle of attack $\alpha $ . In the extreme case where the wing travels a distance corresponding to a number of revolutions, the highly coherent Flow Structure is generally preserved if the Rossby number is small; it degrades substantially, however, at larger Rossby number.
Justin T. Webster - One of the best experts on this subject based on the ideXlab platform.
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ACC - Long-time dynamics and control of subsonic Flow-Structure interactions
2012 American Control Conference (ACC), 2012Co-Authors: Irena Lasiecka, Justin T. WebsterAbstract:In this paper we present recent results concerning nonlinear (von Karman and Berger) Flow-Structure interactions with a focus on stability, long-time dynamics, and convergence to equilibria. Flow-Structure interactions describe the interaction of a Flow of gas over a flexible plate. In particular, we (1) outline well-posedness results via nonlinear semigroup methods, (b) analyze damping mechanisms in the plate (interior and boundary), (c) discuss approaches to the study of long-time behavior of solutions (i.e. global compact attracting sets), and (d) present preliminary results concerning the asympototic smoothness of both the von Karman and Berger Flow-Structure systems with boundary damping. We conclude with an assessment of several open problems for both the von Karman and Berger Flow-Structure interactions.
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weak and strong solutions of a nonlinear subsonic Flow Structure interaction semigroup approach
Nonlinear Analysis-theory Methods & Applications, 2011Co-Authors: Justin T. WebsterAbstract:Abstract We consider a non-rotational, subsonic Flow–Structure interaction describing the Flow of gas above a flexible plate. A perturbed wave equation describes the Flow, and a second-order nonlinear plate equation describes the plate’s displacement. It is shown that the linearization of the model generates a strongly continuous semigroup with respect to the topology generated by “finite energy” considerations. An interesting feature of the problem is that linear perturbed Flow–Structure interaction is not monotone with respect to the standard norm describing the finite energy space. The main tool used in overcoming this difficulty is the construction of a suitable inner product on the finite energy space which allows the application of ω -maximal monotone operator theory. The obtained result allows us to employ suitable perturbation theory in order to discuss well-posedness of weak and strong solutions corresponding to several classes of nonlinear dynamics including the full Flow–Structure interaction with von Karman, Berger’s and other semilinear plate equations.
Chao Zhu - One of the best experts on this subject based on the ideXlab platform.
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Modeling of Axial-Symmetric Flow Structure in Gas–Solids Risers
Journal of Fluids Engineering, 2015Co-Authors: Dawei Wang, Rajesh Patel, Chao ZhuAbstract:Pneumatic transport of solids in a riser has a unique nonuniform Flow Structure, characterized by the core solids acceleration and the wall solids deceleration along the riser, which causes the down-Flow of solids and hence back mixing. To predict this nonuniform Flow Structure, this paper presents a mechanistic model that includes two controlling mechanisms: the interparticle collision damping for axial transport of solids and the effects of collision-induced diffusion and turbulent convection for radial transport of solids. The model predictions are partially validated against available measurements, such as axial and radial distributions of concentration and velocity of solids.
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Entrance Effects on Gas−Solid Riser Flow Structure
Industrial & Engineering Chemistry Research, 2008Co-Authors: Jun You, Dawei Wang, Chao ZhuAbstract:The gas−solid Flow in a riser has strong inherent nonuniformities both in the Flow Structure and in the dynamic phases. The Flow Structure in a riser can be altered with the implementation of different solids feeding devices, and hence may affect the reactor performance. This paper is aimed at investigating the effect of various riser entrances on the overall Flow Structure and its stability at different operation conditions. Three riser entrances are selected to simulate the common solids feeding devices of risers, namely, the J-bend feeder, the L-valve feeder with a distributor, and the L-valve feeder after a taper section. The study is first focused on the Flow dynamics in the riser entrance region. This is to identify the characteristic height of the entrance region as well as to obtain the radial distributions of phase transport properties at the end of the entrance region. These radial profiles are then used as the Flow inlet conditions in the mechanistic model for the study of overall Flow structur...
Donald Rockwell - One of the best experts on this subject based on the ideXlab platform.
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Transformation of Flow Structure on a rotating wing due to variation of radius of gyration
Experiments in Fluids, 2015Co-Authors: Maxwell Wolfinger, Donald RockwellAbstract:The Flow Structure on a rotating wing (rectangular plate) is characterized over a range of travel distance at different radii of gyration. Travel distance is defined as the length of the arc subtended by the radius of gyration. Stereoscopic particle image velocimetry is employed to determine the volumetric Flow Structure, in the form of three-dimensional surfaces of the q -criterion, helical density, and downwash velocity. These representations are complemented by sectional patterns of vorticity and tangential velocity. An increase in the radius of gyration reduces the influence of rotation on the Flow Structure. At small radius of gyration, a coherent leading-edge vortex develops rapidly and then persists over a range of travel distance. At moderate radius of gyration, this leading-edge vortex is replaced by an arch vortex, which develops relatively slowly over a larger travel distance, and is eventually swept into the wake of the wing. The foregoing classes of vortical Structures are associated with distinctive patterns of: helical density, which represents the axial vorticity flux through the three-dimensional vortex system; downwash related to the strengths of the components of the vortex system; and tangential velocity associated with the extent of reverse Flow, or stall.
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Flow Structure on a rotating plate
Experiments in Fluids, 2011Co-Authors: C. A. Ozen, Donald RockwellAbstract:The Flow Structure on a rotating plate of low aspect ratio is characterized well after the onset of motion, such that transient effects are not significant, and only centripetal and Coriolis accelerations are present. Patterns of vorticity, velocity contours, and streamline topology are determined via quantitative imaging, in order to characterize the leading-edge vortex in relation to the overall Flow Structure. A stable leading-edge vortex is maintained over effective angles of attack from 30° to 75°, and at each angle of attack, its sectional Structure at midspan is relatively insensitive to Reynolds number over the range from 3,600 to 14,500. The streamline topology, vorticity distribution, and circulation of the leading-edge vortex are determined as a function of angle of attack, and related to the velocity field oriented toward, and extending along, the leeward surface of the plate. The Structure of the leading-edge vortex is classified into basic regimes along the span of the plate. Images of these regimes are complemented by patterns on crossFlow planes, which indicate the influence of root and tip swirl, and spanwise Flow along the leeward surface of the plate. Comparison with the equivalent of the purely translating plate, which does not induce the foregoing Flow Structure, further clarifies the effects of rotation.
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Unsteady Flow Structure on Low Aspect Ratio Wings
2011Co-Authors: Donald RockwellAbstract:Abstract : The overall objective of this investigation was to determine the quantitative Flow Structure on low aspect ratio wings subjected to basic classes of maneuvers, in order to provide a basis for interpretation of induced forces. Techniques of particle image velocimetry were employed for critical planes of the Flow field, and a technique of stereo particle image velocimetry was developed for water-based systems. Post-processing of the acquired images allowed determination of the vorticity and streamline topology, and construction of space-time volumes of the Flow Structure. These approaches led to characterization of the three-dimensional Flow Structure on flapping wings, as well as wings in rectilinear motion, and determination of patterns of spanwise- and streamwise-oriented vorticity. Passive control in the form of a sinusoidal leading-edge, which mimics the protuberances on the flipper of the humpback whale, and active open-loop control, in the form of small-amplitude perturbations of a wing can effectively can effectively manipulate the Structure of the classes of Flows investigated herein.
Gianluca Blois - One of the best experts on this subject based on the ideXlab platform.
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Wall effects on the Flow Structure around a rectangular cylinder
Meccanica, 2012Co-Authors: Stefano Malavasi, Gianluca BloisAbstract:The mean Flow Structure around an elongated rectangular cylinder near a solid wall was quantitatively characterized. The Flow fields were experimentally measured by means of a 2D PIV technique. The Flow pattern was extracted for each experimental condition and the effect of the solid wall was investigated by varying the distance of the cylinder from the wall. We used a detection algorithm able to extract a series of significant points on 2D velocity fields. The cataloguing of these points made it possible to trace, in the measurement plane, a series of characteristic lines depicting the architectural state of Flow. Finally, the parametric description of the morphological state of Flow allowed quantification of the effects of the boundary (wall proximity) conditions on the Flow Structure. The parameterization of the Flow Structure enabled the identification of significant kinematic parameters, which were compared with the force coefficients on the obstacle.
