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Journal articles on the topic 'Oscillating Flow'
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1
Blevins, R. D. "Application of the Discrete Vortex Method to Fluid-Structure Interaction." Journal of Pressure Vessel Technology 113, no. 3 (August 1, 1991): 437–45. http://dx.doi.org/10.1115/1.2928779.
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The discrete vortex method for numerical simulation of two-dimensional flows is applied to six problems in fluid-structure interaction: steady flow over bluff and streamlined sections, flow with transverse oscillations of the free stream, oscillation in otherwise still reservoir, vibration induced by steady flow, flow-induced vibration in oscillating flow, and impulsively started flow. Direct comparison is made with various formulations and with experimental data.
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Fabrikant, A. L. "Harbour oscillations generated by shear flow." Journal of Fluid Mechanics 282 (January 10, 1995): 203–17. http://dx.doi.org/10.1017/s0022112095000103.
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A new mechanism that could be responsible for excitation of long-period oscillations in partially enclosed harbours is discussed. This mechanism is based on the interaction between a shear flow and the harbour-basin natural mode and does not suppose any external exciting forces caused by wind waves, tsunami, etc. The growth rate of harbour oscillations is found in terms of a plane-wave reflection coefficient integrated on the wavenumber spectrum of the oscillating outflow field near the harbour entrance. Analytical considerations for simple shear flows (vortex sheet and jet) show that the growth rate changes its sign depending on the ratio of oscillation frequency to flow speed.
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Alassar, R. S., and H. M. Badr. "OSCILLATING VISCOUS FLOW OVER PROLATE SPHEROIDS." Transactions of the Canadian Society for Mechanical Engineering 23, no. 1A (March 1999): 83–93. http://dx.doi.org/10.1139/tcsme-1999-0006.
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The axisymmetric viscous oscillating flow over a prolate spheroid is considered. The oscillations are harmonic and the free stream is always parallel to the spheroid major axis. The flow is governed by the Strouhal and the Reynolds numbers as well as the spheroid axis ratio. In the present paper, we only investigate the effect of Reynolds number while keeping the Strouhal number and the axis ratio unchanged. The results are presented in terms of the periodic variation of the drag coefficient, pressure, surface vorticity, separation angle, the wake length, and the streamline and vorticity patterns for Reynolds numbers ranging from 5 to 100. Upon averaging the stream function and vorticity over one complete oscillation, the double boundary-layer structure observed in the case of a sphere is confirmed for the range of parameters considered.
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Bauer, Ronald J., and C. H. von Kerczek. "Stability of Liquid Film Flow Down an Oscillating Wall." Journal of Applied Mechanics 58, no. 1 (March 1, 1991): 278–82. http://dx.doi.org/10.1115/1.2897164.
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The stability of a liquid film flowing down an inclined oscillating wall is analyzed. First, the linear theory growth rates of disturbances are calculated to second order in a disturbance wave number. It is shown that this growth rate is simply the sum of the same growth rate expansions for a nonoscillating film on an inclined plate and an oscillating film on a horizontal plate. These growth rates were originally calculated by Yih (1963, 1968). The growth rate formula derived here shows that long wavelength disturbances to a vertical falling film, which are unstable at all nonzero values of the Reynolds number when the wall is stationary, can be stabilized by sufficiently large values of wall oscillation in certain frequency ranges. Second, the full time-dependent stability equations are solved in terms of a wall oscillation amplitude expansion carried to about 20 terms. This expansion shows that for values of mean flow Reynolds number less than about ten, the wall oscillations completely stabilize the film against all the unstable disturbances of the steady film.
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Yeung, R. W., and M. Vaidhyanathan. "Flow Past Oscillating Cylinders." Journal of Offshore Mechanics and Arctic Engineering 115, no. 4 (November 1, 1993): 197–205. http://dx.doi.org/10.1115/1.2920112.
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The phenomenon of vortex shedding by oscillating cylinders is a complex one. Its understanding is, however, of utmost importance in marine-related engineering, particularly in connection with motions of deep submersibles and marine risers. In this paper, computational results are presented so that the behavior of the shedding as a function of certain parameter space can be elucidated. A methodology based on the random vortex method and a complex-variable boundary-integral formulation is used to study both forced and vortex-induced oscillations of a circular cylinder. Preliminary evaluation of this method indicates that it has been successful in predicting a number of experimentally observed behavior, among which the phenomena of “lock-in” associated with oscillations of the cylinder are well captured.
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Tozzi, J. T., and C. H. von Kerczek. "The Stability of Oscillatory Hagen-Poiseuille Flow." Journal of Applied Mechanics 53, no. 1 (March 1, 1986): 187–92. http://dx.doi.org/10.1115/1.3171709.
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The linear stability theory of the nonzero mean, sinusoidally oscillating flow in a tube of circular cross section is examined. It is found that the relevant axisymmetric disturbances in the oscillatory flow are more stable (i.e., have larger decay rates) than the axisymmetric disturbances of the mean flow alone. This result holds for values of the cross-sectional average oscillation velocity amplitude at least as large as seven-tenths the average mean-flow velocity amplitude. Although the instantaneous velocity profile contains generalized inflection rings for a substantial portion of the oscillation period, the disturbances do not become instantaneously unstable at any time, even for very low frequency oscillations.
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Chen, C. K., L. Wang, J. T. Yang, and L. T. Chen. "Experimental and Computational Analysis of Periodic Flow Structure in Oscillatory Gas Flow Meters." Journal of Mechanics 22, no. 2 (June 2006): 137–44. http://dx.doi.org/10.1017/s1727719100004433.
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AbstractThe oscillatory characteristics and dynamic structure of periodic flow in an oscillatory gas flow meter were studied experimentally and numerically. The flow oscillations were triggered by the Coanda effect and an universal correlation between Strouhal number and Reynolds number, Str = 1.09 × 10−3 for ReHD >800, was deduced based on spectral analysis of the pressure fluctuations in the flow channel. Numerical simulation indicated that the evolution of the flow patterns was classified into stages of induction and sustainable periodic oscillation. The transformation between the two stages was noticeably affected by the design of the feedback channels. The results further revealed that the development of the main vortex in the oscillating chamber and the small vortices at the entrance of the feedback channels concurrently modulate the mechanism of oscillation. The small vortices located at both entrances of the feedback channels play the role of a pair of modulating valves, which alternatively switch on and off the bypass flow through each feedback channel, thus reinforcing the periodic oscillation.
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Loewenberg, Michael. "Axisymmetric unsteady stokes flow past an oscillating finite-length cylinder." Journal of Fluid Mechanics 265 (April 25, 1994): 265–88. http://dx.doi.org/10.1017/s0022112094000832.
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The flow field generated by axial oscillations of a finite-length cylinder in an incompressible viscous fluid is described by the unsteady Stokes equations and computed with a first-kind boundary-integral formulation. Numerical calculations were conducted for particle oscillation periods comparable with the viscous relaxation time and the results are contrasted to those for an oscillating sphere and spheroid. For high-frequency oscillations, a two-term boundary-layer solution is formulated that involves two, sequentially solved, second-kind integral equations. Good agreement is obtained between the boundary-layer solution and fully numerical calculations at moderate oscillation frequencies. The flow field and traction on the cylinder surface display several features that are qualitatively distinct from those found for smooth particles. At the edges, where the base joins the side of the cylinder, the traction on the cylinder surface exhibits a singular behaviour, characteristic of steady two-dimensional viscous flow. The singular traction is manifested by a sharply varying pressure profile in a near-field region. Instantaneous streamline patterns show the formation of three viscous eddies during the decelerating portion of the oscillation cycle that are attached to the side and bases of the cylinder. As deceleration proceeds, the eddies grow, coalesce at the edges of the particle, and thus form a single eddy that encloses the entire particle. Subsequent instantaneous streamline patterns for the remainder of the oscillation cycle are insensitive to particle geometry: the eddy diffuses outwards and vanishes upon particle reversal; a simple streaming flow pattern occurs during particle acceleration. The evolution of the viscous eddies is most apparent at moderate oscillation frequencies. Qualitative results are obtained for the oscillatory flow field past an arbitrary particle. For moderate oscillation frequencies, pathlines are elliptical orbits that are insensitive to particle geometry; pathlines reduce to streamline segments in constant-phase regions close to and far from the particle surface.
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Hicks, Peter D., and Pierre Ricco. "Laminar streak growth above a spanwise oscillating wall." Journal of Fluid Mechanics 768 (March 6, 2015): 348–74. http://dx.doi.org/10.1017/jfm.2015.98.
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The use of spanwise wall oscillations to attenuate the growth of laminar streaks within the incompressible Blasius boundary layer is investigated. As in the case of the flow above a stationary flat plate, studied by Leib et al. (J. Fluid Mech., vol. 380, 1999, pp. 169–203), free-stream convected gusts interact with the boundary layer to drive the streak growth. Spanwise wall oscillations can either reduce or increase the total energy of the laminar streaks, depending upon the wall oscillation amplitude and frequency, as well as the free-stream gust properties. Reductions in streak energies of up to 90 % are obtained, indicating that spanwise wall oscillations are an effective technique for attenuating the laminar streak growth. Therefore they may suppress secondary boundary-layer instabilities and delay transition. The laminar boundary-layer base flow matches the Blasius profile in the streamwise and wall-normal directions, while in the spanwise direction a generalized version of the classical Stokes layer profile (generated by a wall oscillating beneath a quiescent fluid) occurs, which evolves downstream due to non-parallel flow effects. Via a Wentzel–Kramers–Brillouin–Jeffreys analysis, this generalized Stokes layer is shown to approach the classical Stokes layer in the limit of large downstream distances or high-frequency plate oscillations. The laminar streaks forced by the generalized and the classical Stokes flows differ significantly, which implies that the choice of the spanwise base flow may affect the secondary instability and transition in this flow. The analysis also proves that the use of the classical Stokes layer as spanwise base flow, as employed by Hack & Zaki (Phys. Fluids. vol. 24 (3), 2012, 034101), is inappropriate.
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Huang, Yangyang, Monika Nitsche, and Eva Kanso. "Hovering in oscillatory flows." Journal of Fluid Mechanics 804 (September 9, 2016): 531–49. http://dx.doi.org/10.1017/jfm.2016.535.
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We investigate the hovering dynamics of rigid bodies with up-down asymmetry placed in oscillating background flows. Recent experiments on inanimate pyramid-shaped objects in oscillating flows with zero mean component demonstrate that the resulting aerodynamic forces are sufficient to keep the object aloft. The mechanisms responsible for this lift production are fundamentally unsteady and depend on the shed vorticity. Here, we consider a model system of a two-dimensional flyer and compute the unsteady, two-way coupling between the flyer and the surrounding fluid in the context of the vortex sheet model. We examine in detail the flow properties (frequency and speed) required for hovering and their dependence on the flyer’s characteristics (mass and geometry). We find that, at low oscillation frequencies, a flyer of a fixed mass and shape requires a constant amount of flow acceleration to hover, irrespective of the frequency and speed of the oscillating flow. Meanwhile, at high oscillation frequencies, the flow speed required to hover is constant. In either case, the aerodynamic requirements to hover (flow acceleration or flow speed) are an intrinsic property of the flyer itself. This physical insight could potentially have significant implications on the design of unmanned air vehicles as well as on understanding active hovering of live organisms that can manipulate their flapping motion to favour a larger oscillation amplitude or frequency.
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Pariz, Aref, Ingo Fischer, Alireza Valizadeh, and Claudio Mirasso. "Transmission delays and frequency detuning can regulate information flow between brain regions." PLOS Computational Biology 17, no. 4 (April 15, 2021): e1008129. http://dx.doi.org/10.1371/journal.pcbi.1008129.
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Brain networks exhibit very variable and dynamical functional connectivity and flexible configurations of information exchange despite their overall fixed structure. Brain oscillations are hypothesized to underlie time-dependent functional connectivity by periodically changing the excitability of neural populations. In this paper, we investigate the role of the connection delay and the detuning between the natural frequencies of neural populations in the transmission of signals. Based on numerical simulations and analytical arguments, we show that the amount of information transfer between two oscillating neural populations could be determined by their connection delay and the mismatch in their oscillation frequencies. Our results highlight the role of the collective phase response curve of the oscillating neural populations for the efficacy of signal transmission and the quality of the information transfer in brain networks.
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Fu, H. L., K. C. Leong, X. Y. Huang, and C. Y. Liu. "An Experimental Study of Heat Transfer of a Porous Channel Subjected to Oscillating Flow." Journal of Heat Transfer 123, no. 1 (July 12, 2000): 162–70. http://dx.doi.org/10.1115/1.1336510.
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Experiments have been conducted to study the heat transfer of a porous channel subjected to oscillating flow. The surface temperature distributions for both steady and oscillating flows were measured. The local and length-averaged Nusselt numbers were analyzed. The experimental results revealed that the surface temperature distribution for oscillating flow is more uniform than that for steady flow. Due to the reversing flow direction, there are two thermal entrance regions for oscillating flow. The length-averaged Nusselt number for oscillating flow is higher than that for steady flow. The length-averaged Nusselt number for both steady and oscillating flows increase linearly with a dimensionless grouping parameter k*/kfDe/L1/2Pe*1/2. The porous channel heat sink subjected to oscillating flow can be considered as an effective method for cooling high-speed electronic devices.
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Wise, Daniel J., and Pierre Ricco. "Turbulent drag reduction through oscillating discs." Journal of Fluid Mechanics 746 (April 4, 2014): 536–64. http://dx.doi.org/10.1017/jfm.2014.122.
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AbstractThe changes in a turbulent channel flow subjected to sinusoidal oscillations of wall flush-mounted rigid discs are studied by means of direct numerical simulations (DNS). The Reynolds number is ${Re}_{\tau }=180$, based on the friction velocity of the stationary-wall case and the half-channel height. The primary effect of the wall forcing is the sustained reduction of wall-shear stress, which reaches a maximum of 20 %. A parametric study on the disc diameter, maximum tip velocity, and oscillation period is presented, with the aim of identifying the optimal parameters which guarantee maximum drag reduction and maximum net energy saving, the latter computed by taking into account the power spent to actuate the discs. This may be positive and reaches 6 %. The Rosenblat viscous pump flow, namely the laminar flow induced by sinusoidal in-plane oscillations of an infinite disc beneath a quiescent fluid, is used to predict accurately the power spent for disc motion in the fully developed turbulent channel flow case and to estimate localized and transient regions over the disc surface subjected to the turbulent regenerative braking effect, for which the wall turbulence exerts work on the discs. The Fukagata–Iwamoto–Kasagi identity is employed effectively to show that the wall-friction reduction is due to two distinguished effects. One effect is linked to the direct shearing action of the near-wall oscillating-disc boundary layer on the wall turbulence, which causes the attenuation of the turbulent Reynolds stresses. The other effect is due to the additional disc-flow Reynolds stresses produced by the streamwise-elongated structures which form between discs and modulate slowly in time. The contribution to drag reduction due to turbulent Reynolds stress attenuation depends on the penetration thickness of the disc-flow boundary layer, while the contribution due to the elongated structures scales linearly with a simple function of the maximum tip velocity and oscillation period for the largest disc diameter tested, a result suggested by the Rosenblat flow solution. A brief discussion on the future applicability of the oscillating-disc technique is also presented.
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Mohler, F. S., and J. E. Heath. "Oscillating heat flow from rabbit's pinna." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 255, no. 3 (September 1, 1988): R464—R469. http://dx.doi.org/10.1152/ajpregu.1988.255.3.r464.
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Thermal characteristics of the pinnae of the ears of New Zealand White rabbits (Oryctolagus cuniculus) were measured with an infrared imaging system, and vasomotor oscillations were observed to occur spontaneously in the pinnae of all rabbits at an ambient temperature of 20 degrees C. Measured fluctuations in surface temperature were used to characterize the observed vasomotor oscillations, whereas heat loss from the pinnae was calculated using the mean pinna temperatures. The pulsing related to thermoregulation had a mean frequency of approximately 0.025 Hz with a mean amplitude of approximately 0.35 degrees C. When surface temperature was measured simultaneously from both pinnae of individual rabbits, the thermal pulsing was synchronous in the two pinnae. Many of the characteristics of the vasomotor rhythm measured in the pinnae of rabbits were consistent with an active and controlled oscillation, and a possible thermoregulatory role for a controlled vasomotor oscillation is discussed.
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Oberleithner, Kilian, Lothar Rukes, and Julio Soria. "Mean flow stability analysis of oscillating jet experiments." Journal of Fluid Mechanics 757 (September 19, 2014): 1–32. http://dx.doi.org/10.1017/jfm.2014.472.
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AbstractLinear stability analysis (LSA) is applied to the mean flow of an oscillating round jet with the aim of investigating the robustness and accuracy of mean flow stability wave models. The jet’s axisymmetric mode is excited at the nozzle lip through a sinusoidal modulation of the flow rate at amplitudes ranging from 0.1 % to 100 %. The instantaneous flow field is measured via particle image velocimetry (PIV) and decomposed into a mean and periodic part utilizing proper orthogonal decomposition (POD). Local LSA is applied to the measured mean flow adopting a weakly non-parallel flow approach. The resulting global perturbation field is carefully compared with the measurements in terms of spatial growth rate, phase velocity, and phase and amplitude distribution. It is shown that the stability wave model accurately predicts the excited flow oscillations during their entire growth phase and during a large part of their decay phase. The stability wave model applies over a wide range of forcing amplitudes, showing no pronounced sensitivity to the strength of nonlinear saturation. The upstream displacement of the neutral point and the successive reduction of gain with increasing forcing amplitude is very well captured by the stability wave model. At very strong forcing ($\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}{>}40\, \%$), the flow becomes essentially stable to the axisymmetric mode. For these extreme cases, the prediction deteriorates from the measurements due to an interaction of the forced wave with the geometric confinement of the nozzle. Moreover, the model fails far downstream in a region where energy is transferred from the oscillation back to the mean flow. This study supports previously conducted mean flow stability analysis of self-excited flow oscillations in the cylinder wake and in the vortex breakdown bubble and extends the methodology to externally forced convectively unstable flows. The high accuracy of mean flow stability wave models as demonstrated here is of great importance for the analysis of coherent structures in turbulent shear flows.
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Wakeland, Ray Scott, and Robert M. Keolian. "Measurements of Resistance of Individual Square-Mesh Screens to Oscillating Flow at Low and Intermediate Reynolds Numbers." Journal of Fluids Engineering 125, no. 5 (September 1, 2003): 851–62. http://dx.doi.org/10.1115/1.1601254.
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Measurements are reported of pressure losses across single screens subjected to low-frequency oscillating flow for 0.002≲Red≲400, where Red is Reynolds number based on wire diameter and peak approach velocity. Several correlation methods are examined. Extensive comparisons are made between present oscillating-flow results and previous reports of the resistance of screens to steady flow. Defining oscillating results in terms of peak amplitudes, the oscillating and steady-flow resistances are found to be the same, including behavior in the intermediate Reynolds number region that departs from correlations of the form ARe−1+B. The friction factor is also found to depend on Reynolds number, but not independently on oscillation amplitude, over the range of conditions measured.
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Xue, ZL, XS Wang, FJ Hong, P. Zhang, and H. H. Qiu. "INTERFACIAL FILM DYNAMICS OF OSCILLATING PLUG/SLUG FLOWS IN MINI/MICRO CHANNELS(Liquid Flow)." Proceedings of the International Conference on Jets, Wakes and Separated Flows (ICJWSF) 2005 (2005): 131–36. http://dx.doi.org/10.1299/jsmeicjwsf.2005.131.
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LARRIEU, E., E. J. HINCH, and F. CHARRU. "Lagrangian drift near a wavy boundary in a viscous oscillating flow." Journal of Fluid Mechanics 630 (July 10, 2009): 391–411. http://dx.doi.org/10.1017/s002211200900682x.
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The formation of sand ripples in oscillating flows is thought to be due to a steady streaming current which near the bottom is towards the crests. We present quantitative observations of this mean flow over self-formed and artificial ripples, by observing the displacement of a coloured filament after a number of oscillations in the simple situation of viscous Couette flow. Confusingly, the filament moves in the ‘wrong’ direction, because it follows the Lagrangian mean flow. We calculate the Lagrangian mean flow. A complication is that the amplitudes of the oscillations in the experiments are not small. We compare the predictions with the experimental observations of displacements of the filament, showing good agreement.
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Tatsios, Giorgos, Alexandros Tsimpoukis, and Dimitris Valougeorgis. "The Half-Range Moment Method in Harmonically Oscillating Rarefied Gas Flows." Fluids 6, no. 1 (January 1, 2021): 17. http://dx.doi.org/10.3390/fluids6010017.
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The formulation of the half-range moment method (HRMM), well defined in steady rarefied gas flows, is extended to linear oscillatory rarefied gas flows, driven by oscillating boundaries. The oscillatory Stokes (also known as Stokes second problem) and the oscillatory Couette flows, as representative ones for harmonically oscillating half-space and finite-medium flow setups respectively, are solved. The moment equations are derived from the linearized time-dependent BGK kinetic equation, operating accordingly over the positive and negative halves of the molecular velocity space. Moreover, the boundary conditions of the “positive” and “negative” moment equations are accordingly constructed from the half-range moments of the boundary conditions of the outgoing distribution function, assuming purely diffuse reflection. The oscillatory Stokes flow is characterized by the oscillation parameter, while the oscillatory Couette flow by the oscillation and rarefaction parameters. HRMM results for the amplitude and phase of the velocity and shear stress in a wide range of the flow parameters are presented and compared with corresponding results, obtained by the discrete velocity method (DVM). In the oscillatory Stokes flow the so-called penetration depth is also computed. When the oscillation frequency is lower than the collision frequency excellent agreement is observed, while when it is about the same or larger some differences are present. Overall, it is demonstrated that the HRMM can be applied to linear oscillatory rarefied gas flows, providing accurate results in a very wide range of the involved flow parameters. Since the computational effort is negligible, it is worthwhile to consider the efficient implementation of the HRMM to stationary and transient multidimensional rarefied gas flows.
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Morris, G. J., J. T. Jurewicz, and G. M. Palmer. "Gas-Solid Flow in a Fluidically Oscillating Jet." Journal of Fluids Engineering 114, no. 3 (September 1, 1992): 362–66. http://dx.doi.org/10.1115/1.2910038.
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The motion of air and solid particles is examined in a fluidically oscillating slot jet using time-averaged and cycle-resolved laser Doppler anemometry measurements. These measurements reveal the time dependent relative velocity magnitudes between the phases as well as the detailed nature of the flulidcally oscillating slot jet. Temporal phase differences between the gas and solid phases ranged up to 40 degrees for jet oscillation frequencies up to 50 Hz. The results indicate that the fluidic nozzle is an effective particle spreading device and the fuel injector attributes are inherently present such as enhanced mixing and low velocity regions for flame anchoring.
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Chen, S. S. "Flow-Induced Vibrations in Two-Phase Flow." Journal of Pressure Vessel Technology 113, no. 2 (May 1, 1991): 234–41. http://dx.doi.org/10.1115/1.2928751.
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Two-phase flow exists in many shell-and-tube heat exchangers and power generation components. The flowing fluid is a source of energy that can induce small-amplitude subcritical oscillations and large-amplitude dynamic instabilities. In fact, many practical system components have experienced excessive flow-induced vibrations. This paper reviews the current understanding of vibration of circular cylinders in quiescent fluid, cross-flow, and axial flow, with emphasis on excitation mechanisms, mathematical models, and available experimental data. A unified theory is presented for cylinders oscillating under different flow conditions.
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Hara, Tetsu, and Chiang C. Mei. "Oscillating flows over periodic ripples." Journal of Fluid Mechanics 211 (February 1990): 183–209. http://dx.doi.org/10.1017/s0022112090001549.
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Oscillating flows over periodic ripples are of practical as well as scientific interest because of their relevance to beach processes. When either the ripples are sufficiently steep or the amplitude of ambient oscillations large, streamlines of a viscous flow are no longer parallel to the ripple surface. Circulation cells are formed which can help redistribute suspended sediments. Here we study theoretically these cells for a low-viscosity fluid such as pure water over rigid ripples. In particular we have calculated cells whose dimensions are as large as the ripple wavelength and therefore represent viscous effects far above the usual Stokes boundary layer. An idea of Stuart which was originated for stationary mean circulations around a cylinder is extended here. For large ambient amplitude, large oscillating vortices drifting with the ambient flow are found by seeking the stationary cells in a moving coordinate system.
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Shklyaev, Oleg E., and Anna C. Balazs. "Resonant amplification of enzymatic chemical oscillations by oscillating flow." Chaos: An Interdisciplinary Journal of Nonlinear Science 31, no. 9 (September 2021): 093125. http://dx.doi.org/10.1063/5.0061927.
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Dehkordi, Behzad Ghadiri, and Ali Mehrabadir. "Analyzing Oscillating Input Flow around a Circular Cylinder." Applied Mechanics and Materials 110-116 (October 2011): 644–52. http://dx.doi.org/10.4028/www.scientific.net/amm.110-116.644.
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2D fluid flow around a circular cylinder is numerically studied where the input flow is oscillating at different values of forcing frequency. The input section of domain has constant horizontal velocity except a region in the middle of this section which has an oscillating transverse velocity. The uniform fluid flow around an oscillating circular cylinder is also studied. The results are obtained for these two cases and compared with other experimental and numerical results. A comparison of the numerical results with the experimental data indicates that the 2D simulation has excellent agreement with literature. The effect of oscillation on the flow field, wake pattern and drag coefficient has been studied. The results show that the lift coefficient diagram is pure sinusoidal for forcing frequency f=0.85 and is lied in the lock-in zone. The mean drag coefficient has a maximum value in this forcing frequency.
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Jesudhas, Vimaldoss, Frédéric Murzyn, and Ram Balachandar. "IDDES Evaluation of Oscillating Hydraulic Jumps." E3S Web of Conferences 40 (2018): 05067. http://dx.doi.org/10.1051/e3sconf/20184005067.
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This paper presents the results of three-dimensional, unsteady, Improved Delayed Detached Eddy Simulations of an oscillating and a stable hydraulic jump at Froude numbers of 3.8 and 8.5, respectively. The different types of oscillations characterised in a hydraulic jump are analysed by evaluating the instantaneous flow field. The instability caused by the flapping wall-jet type flow in an oscillating jump is distinct compared to the jump-toe fluctuations caused by the spanwise vortices in the shear layer of a stable jump. These flow features are accurately captured by the simulations and are presented with pertinent discussions. The near-bed vortical structures in an oscillating jump is extracted and analysed using the λ2 criterion.
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Box, F., K. Singh, and T. Mullin. "The interaction between rotationally oscillating spheres and solid boundaries in a Stokes flow." Journal of Fluid Mechanics 849 (June 26, 2018): 834–59. http://dx.doi.org/10.1017/jfm.2018.354.
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We present the results of an experimental and theoretical investigation into the influence of proximate boundaries on the motion of an rotationally oscillating sphere in a viscous fluid. The angular oscillations of the sphere are controlled using the magnetic torque generated by a spatially uniform, oscillatory magnetic field which interacts with a small magnet embedded within the sphere. We study the motion of the sphere in the vicinity of stationary walls that are parallel and perpendicular to the rotational axis of the sphere, and near a second passive sphere that is non-magnetic and free to move. We find that rigid boundaries introduce viscous resistance to motion that acts to suppress the oscillations of the driven sphere. The amount of viscous resistance depends on the orientation of the wall with respect to the axis of rotation of the oscillating sphere. A passive sphere also introduces viscous resistance to motion, but for this case the rotational oscillations of the active sphere establish a standing wave that imparts vorticity to the fluid and induces oscillations of the passive sphere. The standing wave is analogous to the case of an oscillating plate in a viscous fluid; the amplitude of the wave decays exponentially with radial distance from the surface of the oscillating sphere. The standing wave introduces a phase lag between the motion of the active sphere and the response of the passive sphere which increases linearly with separation distance.
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Lanets, O. S., V. T. Dmytriv, V. M. Borovets, I. A. Derevenko, and I. M. Horodetskyy. "Analytical Model of the Two-Mass Above Resonance System of the Eccentric-Pendulum Type Vibration Table." International Journal of Applied Mechanics and Engineering 25, no. 4 (December 1, 2020): 116–29. http://dx.doi.org/10.2478/ijame-2020-0053.
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AbstractThe article deals with atwo-mass above resonant oscillatory system of an eccentric-pendulum type vibrating table. Based on the model of a vibrating oscillatory system with three masses, the system of differential equations of motion of oscillating masses with five degrees of freedom is compiled using generalized Lagrange equations of the second kind. For given values of mechanical parameters of the oscillatory system and initial conditions, the autonomous system of differential equations of motion of oscillating masses is solved by the numerical Rosenbrock method. The results of analytical modelling are verified by experimental studies. The two-mass vibration system with eccentric-pendulum drive in resonant oscillation mode is characterized by an instantaneous start and stop of the drive without prolonged transient modes. Parasitic oscillations of the working body, as a body with distributed mass, are minimal at the frequency of forced oscillations.
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Staubli, T. "Entrainment of Self-Sustained Flow Oscillations: Phaselocking or Asynchronous Quenching?" Journal of Applied Mechanics 54, no. 3 (September 1, 1987): 706–12. http://dx.doi.org/10.1115/1.3173093.
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Asynchronous quenching and phaselocking are two different mechanisms leading to the onset of synchronization of flow instabilities with externally excited oscillations. Experimental evidence for asynchronous quenching as well as for phaselocking is given from response measurements of representative pressures, velocities, or of forces for the following types of flow - forcing interactions: an oscillating circular cylinder in crossflow; interaction of an unstable, planar jet with an oscillating leading edge; a forced mixing layer between parallel streams; and a thermally forced cavity shear-layer.
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Lu, Liang, Shirang Long, and Kangwu Zhu. "A Numerical Research on Vortex Street Flow Oscillation in the Double Flapper Nozzle Servo Valve." Processes 7, no. 10 (October 11, 2019): 721. http://dx.doi.org/10.3390/pr7100721.
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The oscillating flow field of the double nozzle flapper servo valve pre-stage is numerically analyzed through Large Eddy Simulation (LES) turbulent modeling with the previous grid independence verification. The vortex street flow phenomenon can be observed when the flow passes through the nozzle flapper channel, the vortex alternating in each side produces the periodical flow oscillation. The structural and flow parameter effects on the oscillating flow are emphasized, and it could be determined that the pressure on the flapper is nearly proportional to the flow velocity and inversely proportional to the actual distance between the flapper and the nozzle. On the other hand, the main frequency of oscillation decreases with the velocity and increases with the distance between the nozzle flapper. The main stage movement is further considered with a User Defined Function (UDF), and it could be determined that the influences of the structural and flow parameters on the flow oscillation are rarely changed, but the main frequencies drop, generally.
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Zhang, Zhen, and Dong-hyuk Shin. "Effect of ambient pressure oscillation on the primary breakup of cylindrical liquid jet spray." International Journal of Spray and Combustion Dynamics 12 (January 2020): 175682772093555. http://dx.doi.org/10.1177/1756827720935553.
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The present simulation study investigates the effects of ambient pressure oscillation on cylindrical liquid jet sprays, using the volume of fluid method. The research is motivated by combustion instability in combustion engines, where strong harmonic pressure oscillation can damage internal structures. Oscillating pressure modulates not only the fuel mass flow rate but also the ambient gas density and liquid surface tension, and in liquid sprays, the ambient fluid density and surface tension can have substantial effects on spray breakup. In order to investigate the multiple property changes with ambient pressure oscillation, therefore, a new solver in OpenFOAM is developed. In the solver, liquid mass flow rate, ambient gas density, and liquid surface tension change simultaneously as a result of pressure oscillation. Simulations were conducted at a Reynolds number of 2000 and Weber number over 2000, conditions that are conducive to primary breakup in laminar flows. The simulations show that oscillations in ambient pressure significantly strengthen the surface instability of the liquid ligament, which depends on the surface tension–pressure coefficient, the mean pressure, and the amplitude of oscillation.
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Jester, W., and Y. Kallinderis. "Numerical Study of Incompressible Flow About Transversely Oscillating Cylinder Pairs." Journal of Offshore Mechanics and Arctic Engineering 126, no. 4 (November 1, 2004): 310–17. http://dx.doi.org/10.1115/1.1834618.
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A numerical investigation of incompressible flow about transversely oscillating cylinder pairs is performed. Both tandem and side-by-side arrangements undergoing both flow-induced and forced transverse oscillations are considered. A second-order projection scheme is used to solve the 2-D incompressible Navier Stokes equations and a staggered approach is used to couple flow and structural response. Automatic mesh deformation and adaptation are used to handle arbitrary motion of the bodies. Comparisons with experimental results indicate that the present numerical method can capture complex interference and flow–structure interaction phenomena. Specifically, results are presented that demonstrate wake galloping effects, in which a cylinder in the wake of another experiences large flow-induced vibration over a wide range of flow velocities, and the presence of an experimentally observed secondary peak in the flow-induced vibration of rigidly connected cylinders in a tandem arrangement. An explanation of this secondary peak is provided by employing appropriate visualization of the unsteady flow. Results for forced oscillation of a pair of cylinders in a side-by-side arrangement are also presented that show the effect of phase angle on the wake structure behind the cylinder pair.
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Yokoi, Yoshifumi, and Hiromi Fukuta. "Numerical Experiment of a Symmetrical Airfoil with Attack Angle of 5 Degrees in Fluctuating Relative Flow Velocity." Advanced Materials Research 1016 (August 2014): 490–94. http://dx.doi.org/10.4028/www.scientific.net/amr.1016.490.
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In this study, a numerical experiment was performed as what obtains relative velocity fluctuation by oscillating an object with comparatively large amplitude in the direction of flow. Follow pattern and instantaneous fluid force around an In-line forced oscillating symmetrical airfoil (NACA0012) with attack angle of 5 degrees caused not separation in stationary situation were investigated using a vortex method at the Reynolds numberRe=4.05×105, in ranges of the oscillation amplitude ratio 2a/c=0.5,1.0,1.5 and 2.0 and the oscillation frequency ratiof/fK=0.25,0.5,1.0 and 2.0 (here,a:half-amplitude of oscillation,c:chord-length,f:oscillation frequency,fK:natural Karman vortex shedding frequency from a stationary airfoil with the attack angle of 90 degrees). As a result of calculations, Separation was observed by oscillating condition even if it was the airfoil of attack angle not separating. It is found that the separation was dependent on the velocity ratio. The characteristics of fluid force are changed by oscillation.
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Tian, Xing, Jian Yang, Zhigang Guo, and Qiuwang Wang. "Numerical Investigation of Gravity-Driven Granular Flow around the Vertical Plate: Effect of Pin-Fin and Oscillation on the Heat Transfer." Energies 14, no. 8 (April 14, 2021): 2187. http://dx.doi.org/10.3390/en14082187.
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In this paper, the heat transfer of pin-fin plate unit (PFPU) under static and oscillating conditions are numerically studied using the discrete element method (DEM). The flow and heat transfer characteristics of the PFPU with sinusoidal oscillation are investigated under the conditions of oscillating frequency of 0–10 Hz, amplitude of 0–5 mm and oscillating direction of Y and Z. The contact number, contact time, porosity and heat transfer coefficient under the above conditions are analyzed and compared with the smooth plate. The results show that the particle far away from the plate can transfer heat with the pin-fin of PFPU, and the oscillating PFPU can significantly increase the contact number and enhance the temperature diffusion and heat transfer. The heat transfer coefficient of PFPU increases with the increase of oscillating frequency and amplitude. When the PFPU oscillates along the Y direction with the amplitude of 1 mm and the frequency of 10 Hz, the heat transfer coefficient of PFPU is increased by 28% compared with that of the smooth plate. Compared with the oscillation along the Z direction, the oscillation along the Y direction has a significant enhancement on the heat transfer of PFPU.
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CHOI, B. I., and H. D. SHIN. "Flame/Flow Interaction in Oscillating Flow Field." Combustion Science and Technology 159, no. 1 (October 2000): 87–107. http://dx.doi.org/10.1080/00102200008935778.
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Oz, Furkan, and Kursat Kara. "Jet Oscillation Frequency Characterization of a Sweeping Jet Actuator." Fluids 5, no. 2 (May 14, 2020): 72. http://dx.doi.org/10.3390/fluids5020072.
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The time-resolved flow field of a spatially oscillating jet emitted by a sweeping jet (SWJ) actuator is investigated numerically using three-dimensional Reynolds-averaged Navier–Stokes (3D-URANS) equations. Numerical simulations are performed for a range of mass flow rates providing flow conditions varying from incompressible to subsonic compressible flows. After a detailed mesh study, the computational domain is represented using two million hexagonal control volumes. The jet oscillation frequency is predicted by analyzing velocity time histories at the actuator exit, and a linear relationship between the jet oscillation frequency and time-averaged exit nozzle Mach number is found ( f = 511.22 M + 46.618 , R² = 0.97). The results of our numerical model are compared with data from the literature, and a good agreement is found. In addition, we confirmed that the Strouhal number is almost constant with the Mach number for the subsonic oscillating jet and has an average value of St = 0.0131. The 3D-URANS model that we presented here provides a computationally inexpensive yet accurate alternative to the researchers to investigate jet oscillation characteristics.
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SEWATKAR, C. M., ATUL SHARMA, and AMIT AGRAWAL. "Simulation of flow across a row of transversely oscillating square cylinders." Journal of Fluid Mechanics 680 (May 31, 2011): 361–97. http://dx.doi.org/10.1017/jfm.2011.167.
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A numerical study of flow across a row of transversely oscillating square cylinders (of diameter d) has been undertaken using the lattice Boltzmann method, for a better understanding of fluid–structure interaction problems. The effects of cylinder oscillation frequency ratio (fe/fo, where fe is the cylinder oscillation frequency and fo is the corresponding vortex shedding frequency for stationary row of cylinders), amplitude ratio (A/d), non-dimensional spacing between the cylinders (s/d) and Reynolds number (Re) on ensuing flow regimes and flow parameters have been studied to understand the flow physics. Six different flow regimes observed in this study are the quasi-periodic non-lock-on-I, synchronous lock-on, quasi-periodic lock-on, quasi-periodic non-lock-on-II, synchronous non-lock-on and chaotic non-lock-on. It is observed that the range of the lock-on regime depends upon the relative dominance of incoming flow and cylinder motion. Although the lock-on regime in the case of Re = 80, s/d = 4 and A/d = 0.2 is substantially larger as compared to that for a single oscillating cylinder, the range of the lock-on regime shrinks with a reduction in the cylinder spacing, increase in the Reynolds number or decrease in the oscillation amplitude. It is also observed that the wake interaction behind the cylinders weakens with an increase in fe/fo, Re, A/d or s/d, leading to the formation of independent wakes and synchronous nature of the flow. For fe/fo ≥ 1.2, independent and intact oscillating wakes are noted and an additional frequency (wake oscillation frequency) is obtained in the time series of the lift coefficient. Although it was expected that the complexity in the wake interaction would increase with cylinder oscillation or amplitude ratio, an opposite effect (that is, formation of independent wakes) is noted from the results.
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Kirollos, Ramy, Robert S. Allison, and Stephen Palmisano. "Cortical Correlates of the Simulated Viewpoint Oscillation Advantage for Vection." Multisensory Research 30, no. 7-8 (2017): 739–61. http://dx.doi.org/10.1163/22134808-00002593.
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Behavioural studies have consistently found stronger vection responses for oscillating, compared to smooth/constant, patterns of radial flow (the simulated viewpoint oscillation advantage for vection). Traditional accounts predict that simulated viewpoint oscillation should impair vection by increasing visual–vestibular conflicts in stationary observers (as this visual oscillation simulates self-accelerations that should strongly stimulate the vestibular apparatus). However, support for increased vestibular activity during accelerating vection has been mixed in the brain imaging literature. This fMRI study examined BOLD activity in visual (cingulate sulcus visual area — CSv; medial temporal complex — MT+; V6; precuneus motion area — PcM) and vestibular regions (parieto-insular vestibular cortex — PIVC/posterior insular cortex — PIC; ventral intraparietal region — VIP) when stationary observers were exposed to vection-inducing optic flow (i.e., globally coherent oscillating and smooth self-motion displays) as well as two suitable control displays. In line with earlier studies in which no vection occurred, CSv and PIVC/PIC both showed significantly increased BOLD activity during oscillating global motion compared to the other motion conditions (although this effect was found for fewer subjects in PIVC/PIC). The increase in BOLD activity in PIVC/PIC during prolonged exposure to the oscillating (compared to smooth) patterns of global optical flow appears consistent with vestibular facilitation.
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Lim, Tae Gyu, and Jae Min Hyun. "Flow Driven by a Torsionally-Oscillating Shrouded Endwall Disk." Journal of Fluids Engineering 119, no. 1 (March 1, 1997): 115–21. http://dx.doi.org/10.1115/1.2819096.
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A study is made of time-dependent flow of a viscous fluid driven by an oscillating shrouded disk in finite geometry. Numerical solutions to the Navier-Stokes equations are obtained for the flow in a cylindrical cavity with its upper endwall disk executing torsional oscillation at a velocity Ω cos λt. Details of the three-component velocity field are examined at high Reynolds number. The value of the nondimensional amplitude of disk oscillation, ε = Ω/λ, encompasses a range up to ε ≳ O(1). The numerical results for the azimuthal flow for ε ≪ 1 are consistent with the predictions of the earlier analytical model. The azimuthal flow is largely confined to the Stokes layer thickness. The analytical predictions of the meridional flow, based on a straightforward expansion technique, display discrepancies from the numerical results. The steady meridional streaming at finite values of ε is exhibited. The qualitative patterns of meridional steady streaming are verified by laboratory flow visualizations. The explicit effect of Re on the overall flow character is scrutinized. The numerical data are processed to describe the behavior of the torque coefficient at the oscillating disk.
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Taslim, Taslim, and Mohd Sabri Takriff. "Oscillatory Flow Mixer for Pulp Bleaching." ASEAN Journal of Chemical Engineering 2, no. 1 (October 20, 2008): 47. http://dx.doi.org/10.22146/ajche.50802.
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This paper reports the results of an investigation on the use of oscillatory baffled column as a mixer for pulp bleaching. Unbleached hardwood kraft pulp was bleached using hydrogen peroxide. Variables studied were oscillation frequency, oscillation amplitude, and pulp consistency. The mixing process was achieved by oscillating pulp suspension in a periodically baffled column at a certain frequency and amplitude. The mixing quality of pulp bleaching was quantified using mixing index. The results showed that mixing quality improved with oscillation frequency and amplitude, but decreased with pulp consistency. This typical device is very promising as a mixer for pulp bleaching.
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THO, PAUL, RICHARD MANASSEH, and ANDREW OOI. "Cavitation microstreaming patterns in single and multiple bubble systems." Journal of Fluid Mechanics 576 (March 28, 2007): 191–233. http://dx.doi.org/10.1017/s0022112006004393.
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Cavitation microstreaming is a well-known phenomenon; however, few flow visualizations or measurements of the velocity fields have been conducted. In this paper micro-PIV (particle image velocimetry) measurements and streak photography were used to study the flow field around a single and two oscillating bubbles resting on a solid boundary. The mode of oscillation of the bubble was also measured in terms of the variation in the radius of the bubble and the movement of the bubble's centroid so that the streaming flow field could be accurately related to the bubble's oscillatory motion. The mode of oscillation was found to vary primarily with the applied acoustic frequency. Several modes of oscillation were investigated, including translating modes where the bubble's centroid moves along either a single axis, an elliptical orbit or a circular orbit. The flow field resulting from these oscillation modes contains closed streamlines representing vortical regions in the vicinity of the bubble. The translating modes were observed to occur in sequential order with the acoustic excitation frequency, changing from a translation along a single axis, to an elliptical orbit and finally to a circular orbit, or vice versa. Following this sequence, there is a corresponding transformation of the streaming pattern from a symmetrical flow structure containing four vortices to a circular vortex centred on the bubble. Despite some inconsistencies, there is general agreement between these streaming patterns and those found in existing theoretical models. Volume and shape mode oscillations of single bubbles as well as several different cases of multiple bubbles simultaneously oscillating with the same frequency and phase were also investigated and show a rich variety of streaming patterns.
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Aboutalebi, Payam, Fares M’zoughi, Itziar Martija, Izaskun Garrido, and Aitor J. Garrido. "Switching Control Strategy for Oscillating Water Columns Based on Response Amplitude Operators for Floating Offshore Wind Turbines Stabilization." Applied Sciences 11, no. 11 (June 5, 2021): 5249. http://dx.doi.org/10.3390/app11115249.
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In this article, a new strategy for switching control has been proposed with the aim of reducing oscillations in floating offshore wind turbines. Such oscillations lead to a shortage in the system’s efficiency, lifespan and harvesting capability of wind and wave energies. In order to study the decreasing of undesired oscillations in the system, particularly in pitch and top tower fore-aft movements, a square-shaped platform barge equipped with four symmetric oscillating water columns has been considered. The oscillating water columns’ air flux valves allow to operate the air columns so that to control the barge movements caused by oscillatory motion of the waves. In order to design the control scheme, response amplitude operators have been used to evaluate the performance of the system for a range of wave frequency profiles. These response amplitude operators analysis makes it possible to implement a switching control strategy to adequately regulate the valves opening/closing transition. The obtained results show that the proposed controlled oscillating water column-based barge present a better performance compared to the traditional barge one. In the case study with the period of 10 s, the results indicate the significant oscillation reduction for the controlled oscillating water column-based system compared to the standard barge system by 30.8% in pitch angle and 25% in fore-aft displacement.
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ASO, Shigeru, Noriyuki KANEHIRA, and Atsuhiro SAKAMOTO. "Flow Visualization of Separated Flows around Oscillating Airfoil." Journal of the Visualization Society of Japan 11, Supplement2 (1991): 311–14. http://dx.doi.org/10.3154/jvs.11.supplement2_311.
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Kabi, Prasenjit, Vishank Razdan, Durbar Roy, Lalit Bansal, Sumita Sahoo, Rabibrata Mukherjee, Swetaprovo Chaudhuri, and Saptarshi Basu. "Evaporation-induced alterations in oscillation and flow characteristics of a sessile droplet on a rose-mimetic surface." Soft Matter 17, no. 6 (2021): 1487–96. http://dx.doi.org/10.1039/d0sm02106g.
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Bolaños-Jiménez, Rocío, Massimiliano Rossi, David Fernandez Rivas, Christian J. Kähler, and Alvaro Marin. "Streaming flow by oscillating bubbles: quantitative diagnostics via particle tracking velocimetry." Journal of Fluid Mechanics 820 (May 10, 2017): 529–48. http://dx.doi.org/10.1017/jfm.2017.229.
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Oscillating microbubbles can be used as microscopic agents. Using external acoustic fields they are able to set the surrounding fluid into motion, erode surfaces and even to carry particles attached to their interfaces. Although the acoustic streaming flow that the bubble generates in its vicinity has been often observed, it has never been measured and quantitatively compared with the available theoretical models. The scarcity of quantitative data is partially due to the strong three-dimensional character of bubble-induced streaming flows, which demands advanced velocimetry techniques. In this work, we present quantitative measurements of the flow generated by single and pairs of acoustically excited sessile microbubbles using a three-dimensional particle tracking technique. Using this novel experimental approach we are able to obtain the bubble’s resonant oscillating frequency, study the boundaries of the linear oscillation regime, give predictions on the flow strength and the shear in the surrounding surface and study the flow and the stability of a two-bubble system. Our results show that velocimetry techniques are a suitable tool to make diagnostics on the dynamics of acoustically excited microbubbles.
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Bilanin, Alan J. "Flow-Driven Oscillating Acoustic Attenuator." Journal of the Acoustical Society of America 129, no. 3 (2011): 1667. http://dx.doi.org/10.1121/1.3573326.
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Stern, C., S. P. R. Czitrom, and R. Godoy. "Oscillating Flow through a Funnel." Physics of Fluids 11, no. 9 (September 1999): S3. http://dx.doi.org/10.1063/1.4739153.
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Petzoldt, Ronald W. "Oscillating Liquid Flow ICF Reactor." Fusion Technology 19, no. 3P2A (May 1991): 758–62. http://dx.doi.org/10.13182/fst91-a29436.
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Kolev, Spas D., Christopher W. K. Chow, David E. Davey, and Dennis E. Mulcahy. "Oscillating flow injection stripping potentiometry." Analytica Chimica Acta 309, no. 1-3 (June 1995): 293–99. http://dx.doi.org/10.1016/0003-2670(95)00091-d.
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Alassar, R. S., and H. M. Badr. "Oscillating flow over oblate spheroids." Acta Mechanica 137, no. 3-4 (September 1999): 237–54. http://dx.doi.org/10.1007/bf01179212.
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Chon, Ki H., Ramakrishna Raghavan, Yu-Ming Chen, Donald J. Marsh, and Kay-Pong Yip. "Interactions of TGF-dependent and myogenic oscillations in tubular pressure." American Journal of Physiology-Renal Physiology 288, no. 2 (February 2005): F298—F307. http://dx.doi.org/10.1152/ajprenal.00164.2004.
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We have previously shown that there are two oscillating components in spontaneously fluctuating single-nephron blood flow obtained from Sprague-Dawley rats (Yip K-P, Holstein-Rathlou NH, and Marsh DJ. Am J Physiol Renal Physiol 264: F427–F434, 1993). The slow oscillation (20–30 mHz) is mediated by tubuloglomerular feedback (TGF), whereas the fast oscillation (100 mHz) is probably related to spontaneous myogenic activity. The fast oscillation is rarely detected in spontaneous tubular pressure because of its small magnitude and the fact that tubular compliance filters pressure waves. We detected myogenic oscillation superimposed on TGF-mediated oscillation when ambient tubular flow was interrupted. Two well-defined peaks are present in the mean power spectrum of stop-flow pressure (SFP) centering at 25 and 100 mHz ( n = 13), in addition to a small peak at 125–130 mHz. Bispectral analysis indicates that two of these oscillations (30 and 100 mHz) interact nonlinearly to produce the third oscillation at 125–130 mHz. The presence of nonlinear interactions between TGF and myogenic oscillations indicates that estimates of the relative contribution of each of these mechanisms in renal autoregulation need to account for this interaction. The magnitude of myogenic oscillations was considerably smaller in the SFP measured from spontaneously hypertensive rats (SHR, n = 13); consequently, nonlinear interactions were not observed with bispectral analysis. Reduced augmentation of myogenic oscillations in SFP of SHR might account for the failure in detecting nonlinear interactions in SHR.