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Zeitschriftenartikel zum Thema „Turbulence suppression“

Autor: Grafiati

Veröffentlicht am 28. Juni 2021

Zuletzt aktualisiert am 13. Februar 2022

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1

Reis, J. C., und C. H. Kruger. „Turbulence suppression in combustion-driven magnetohydrodynamic channels“. Journal of Fluid Mechanics 188 (März 1988): 147–57. http://dx.doi.org/10.1017/s0022112088000679.

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The effects of a magnetic field on core turbulence, mean-velocity boundary-layer profiles, turbulence-intensity boundary-layer profiles and turbulent spectral-energy distributions have been experimentally determined for combustion-driven magneto-hydrodynamic (MHD) flows. The turbulence suppression of the core was found to be similar to that of liquid-metal MHD flows, even though the turbulent structure was entirely different. The mean-velocity and turbulence-intensity boundary-layer profiles were affected much less than those of liquid-metal flows, primarily because the low-temperature thermal boundary layer reduced the electrical conductivity near the wall. No spectral dependence of turbulence suppression was observed in the core.

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2

VAITHIANATHAN, T., ASHISH ROBERT, JAMES G. BRASSEUR und LANCE R. COLLINS. „Polymer mixing in shear-driven turbulence“. Journal of Fluid Mechanics 585 (07.08.2007): 487–97. http://dx.doi.org/10.1017/s0022112007007033.

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We investigate numerically the influence of polymer mixing on shear-driven turbulence. Of particular interest is the suppression of mixing that accompanies drag reduction with dilute polymer solutions. The simulations use the finite extensible nonlinear elastic model with the Peterlin closure (FENE-P) to describe the polymer stresses in the momentum equation, with polymer concentration allowed to vary in space and time. A thin slab of concentrated polymer was placed in an initially Newtonian homogeneous turbulent shear flow on a plane perpendicular to the mean velocity gradient, and allowed to mix in the gradient direction while actively altering the turbulence. The initially higher concentration of polymer near the centreplane suppressed production of turbulent kinetic energy and Reynolds stress in that region, while turbulence outside the polymer-rich region remained shear-dominated Newtonian turbulence. The rate of mixing in the shear direction was severely damped by the action of the polymer compared to a passive scalar in the corresponding Newtonian turbulent shear flow. This, in part, was a result of the same damping of vertical velocity fluctuations by the polymer that leads to the suppression of momentum flux. However, the cross-correlation between the polymer concentration and vertical velocity fluctuations was also suppressed, indicating that the explanation for the reduction in polymer mixing involves both the suppression of vertical velocity fluctuations and an alteration of turbulence structure by the polymer–turbulence interactions.

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3

Dai, Qi, Kun Luo, Tai Jin und Jianren Fan. „Direct numerical simulation of turbulence modulation by particles in compressible isotropic turbulence“. Journal of Fluid Mechanics 832 (26.10.2017): 438–82. http://dx.doi.org/10.1017/jfm.2017.672.

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In this paper, a systematic investigation of turbulence modulation by particles and its underlying physical mechanisms in decaying compressible isotropic turbulence is performed by using direct numerical simulations with the Eulerian–Lagrangian point-source approach. Particles interact with turbulence through two-way coupling and the initial turbulent Mach number is 1.2. Five simulations with different particle diameters (or initial Stokes numbers, $St_{0}$) are conducted while fixing both their volume fraction and particle densities. The underlying physical mechanisms responsible for turbulence modulation are analysed through investigating the particle motion in the different cases and the transport equations of turbulent kinetic energy, vorticity and dilatation, especially the two-way coupling terms. Our results show that microparticles ($St_{0}\leqslant 0.5$) augment turbulent kinetic energy and the rotational motion of fluid, critical particles ($St_{0}\approx 1.0$) enhance the rotational motion of fluid, and large particles ($St_{0}\geqslant 5.0$) attenuate turbulent kinetic energy and the rotational motion of fluid. The compressibility of the turbulence field is suppressed for all the cases, and the suppression is more significant if the Stokes number of particles is close to 1. The modifications of turbulent kinetic energy, the rotational motion and the compressibility are all related with the particle inertia and distributions, and the suppression of the compressibility is attributed to the preferential concentration and the inertia of particles.

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4

KANEDA, YUKIO, und TAKAKI ISHIDA. „Suppression of vertical diffusion in strongly stratified turbulence“. Journal of Fluid Mechanics 402 (10.01.2000): 311–27. http://dx.doi.org/10.1017/s0022112099007041.

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A spectral approximation for diffusion of passive scalar in stably and strongly stratified turbulence is presented. The approximation is based on a linearized approximation for the Eulerian two-time correlation and Corrsin's conjecture for the Lagrangian two-time correlation. For strongly stratified turbulence, the vertical component of the turbulent velocity field is well approximated by a collection of Fourier modes (waves) each of which oscillates with a frequency depending on the direction of the wavevector. The proposed approximation suggests that the phase mixing among the Fourier modes having different frequencies causes the decay of the Lagrangian two-time vertical velocity autocorrelation, and the highly oscillatory nature of these modes results in the suppression of single-particle dispersion in the vertical direction. The approximation is free from any ad hoc adjusting parameter and shows that the suppression depends on the spectra of the velocity and fluctuating density fields. It is in good agreement with direct numerical simulations for strongly stratified turbulence.

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5

ROBERT, ASHISH, T. VAITHIANATHAN, LANCE R. COLLINS und JAMES G. BRASSEUR. „Polymer-laden homogeneous shear-driven turbulent flow: a model for polymer drag reduction“. Journal of Fluid Mechanics 657 (28.06.2010): 189–226. http://dx.doi.org/10.1017/s0022112010001394.

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Drag reduction (DR) under a turbulent boundary layer implies the suppression of turbulent momentum flux to the wall, a large-eddy phenomenon. Our hypothesis is that the essential mechanisms by which dilute concentrations of long-chain polymer molecules reduce momentum flux involve only the interactions among turbulent velocity fluctuations, polymer molecules and mean shear. Experiments indicate that these interactions dominate in a polymer-active ‘elastic layer’ outside the viscous sublayer and below a Newtonian inertial layer in a polymer-laden turbulent boundary layer. We investigate our hypothesis by modelling the suppression of momentum flux with direct numerical simulation (DNS) of homogeneous turbulent shear flow (HTSF) and the finite extensible nonlinear elastic with Peterlin approximation (FENE-P) model for polymer stress. The polymer conformation tensor equation was solved using a new hyperbolic algorithm with no artificial diffusion. We report here on the equilibrium state with fixed mean shear rate S, where progressive increases in non-dimensional polymer relaxation time WeS (shear Weissenberg number) or concentration parameter 1 − β produced progressive reductions in Reynolds shear stress, turbulence kinetic energy and turbulence dissipation rate, concurrent with increasing polymer stress and elastic potential energy. The changes in statistical variables underlying polymer DR with 1 − β, WeS, %DR and polymer-induced changes to spectra are similar to experiments in channel and pipe flows and show that the experimentally measured increase in normalized streamwise velocity variance is an indirect consequence of DR that is true only at lower DR. Comparison of polymer stretch and elastic potential energy budgets with channel flow DNS showed qualitative correspondence when distance from the wall was correlated to WeS. As WeS increased, the homogeneous shear flow displayed low-DR, high-DR and maximum-DR (MDR) regimes, similar to experiments, with each regime displaying distinctly different polymer–turbulence physics. The suppression of turbulent momentum flux arises from the suppression of vertical velocity fluctuations primarily by polymer-induced suppression of slow pressure–strain rate correlations. In the high-Weissenberg-number MDR-like limit, the polymer nearly completely blocks Newtonian inter-component energy transfer to vertical velocity fluctuations and turbulence is maintained by the polymer contribution to pressure–strain rate. Our analysis from HTSF with the FENE-P representation of polymer stress and its comparisons with experimental and DNS studies of wall-bounded polymer–turbulence supports our central hypothesis that the essential mechanisms underlying polymer DR lie directly in the suppression of momentum flux by polymer–turbulence interactions in the presence of mean shear and indirectly in the presence of the wall as the shear-generating mechanism.

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6

Reiser, D., und M. Z. Tokar. „Turbulence Suppression in Transport Barriers“. Fusion Science and Technology 45, Nr. 2T (März 2004): 346–53. http://dx.doi.org/10.13182/fst04-a500.

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7

Farrell, Brian F., und Petros J. Ioannou. „Turbulence suppression by active control“. Physics of Fluids 8, Nr. 5 (Mai 1996): 1257–68. http://dx.doi.org/10.1063/1.868897.

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8

KOMOSHVILI, K., S. CUPERMAN und C. BRUMA. „Plasma-turbulence suppression and transport-barrier formation by externally driven radiofrequency waves in spherical tokamaks“. Journal of Plasma Physics 65, Nr. 3 (April 2001): 235–53. http://dx.doi.org/10.1017/s0022377801001015.

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Turbulent transport of heat and particles is the principle obstacle confronting controlled fusion today. We investigate quantitatively the suppression of turbulence and formation of transport barriers in spherical tokamaks by sheared electric fields generated by externally driven radiofrequency (RF) waves, in the frequency range ωA ∼ ω < ωci (where ωA and ωci are the Alfvén and ion cyclotron frequencies).This investigation consists of the solution of the full-wave equation for a spherical tokamak in the presence of externally driven fast waves and the evaluation of the power dissipation by the mode-converted Alfvén waves. This in turn provides a radial flow shear responsible for the suppression of plasma turbulence. Thus a strongly nonlinear equation for the radial sheared electric field is solved, and the turbulent transport suppression rate is evaluated and compared with the ion temperature gradient (ITG) instability increment.

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9

Zhilenko, D. Yu, und O. E. Krivonosova. „Suppression of Turbulence in Rotational Flows“. Technical Physics Letters 45, Nr. 9 (September 2019): 870–73. http://dx.doi.org/10.1134/s1063785019090141.

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10

Minnie, J., J. W. Bieber, W. H. Matthaeus und R. A. Burger. „Suppression of Particle Drifts by Turbulence“. Astrophysical Journal 670, Nr. 2 (Dezember 2007): 1149–58. http://dx.doi.org/10.1086/522026.

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11

Lai, J. C. S. „Turbulence suppression in an elliptic jet“. International Journal of Heat and Fluid Flow 13, Nr. 1 (März 1992): 93–96. http://dx.doi.org/10.1016/0142-727x(92)90064-g.

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12

Zhang, Qi, und Robert A. Handler. „Active suppression of buoyancy driven turbulence“. International Journal of Heat and Mass Transfer 75 (August 2014): 207–12. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2014.03.012.

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13

Shringarpure, Mrugesh, Mariano I. Cantero und S. Balachandar. „Dynamics of complete turbulence suppression in turbidity currents driven by monodisperse suspensions of sediment“. Journal of Fluid Mechanics 712 (25.09.2012): 384–417. http://dx.doi.org/10.1017/jfm.2012.427.

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AbstractTurbidity currents derive their motion from the excess density imposed by suspended sediments. The settling tendency of sediments is countered by flow turbulence, which expends energy to keep them in suspension. This interaction leads to downward increasing concentration of suspended sediments (stable stratification) in the flow. Thus in a turbidity current sediments play the dual role of sustaining turbulence by driving the flow and damping turbulence due to stable stratification. By means of direct numerical simulations, it has been shown previously that stratification above a threshold can substantially reduce turbulence and possibly extinguish it. This study expands the simplified model by Cantero et al. (J. Geophys. Res., vol. 114, 2009a, C03008), and puts forth a proposition that explains the mechanism of complete turbulence suppression due to suspended sediments. In our simulations it is observed that suspensions of larger sediments lead to stronger stratification and, above a threshold size, induce an abrupt transition in the flow to complete turbulence suppression. It has been widely accepted that hairpin and quasi-streamwise vortices are key to sustaining turbulence in wall-bounded flows, and that only vortices of sufficiently strong intensity can spawn the next generation of vortices. This auto-generation mechanism keeps the flow populated with hairpin and quasi-streamwise vortical structures and thus sustains turbulence. From statistical analysis of Reynolds stress events and visualization of flow structures, it is observed that settling sediments damp the Reynolds stress events (Q2 events), which means a reduction in both the strength and spatial distribution of vortical structures. Beyond the threshold sediment size, the existing vortical structures in the flow are damped to an extent where they lose their ability to regenerate the subsequent generation of turbulent vortical structures, which ultimately leads to complete turbulence suppression.

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14

Holguin, F., M. Ruszkowski, A. Lazarian, R. Farber und H.-Y. K. Yang. „Role of cosmic-ray streaming and turbulent damping in driving galactic winds“. Monthly Notices of the Royal Astronomical Society 490, Nr. 1 (16.09.2019): 1271–82. http://dx.doi.org/10.1093/mnras/stz2568.

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ABSTRACT Large-scale galactic winds driven by stellar feedback are one phenomenon that influences the dynamical and chemical evolution of a galaxy, redistributing material throughout the circumgalatic medium. Non-thermal feedback from galactic cosmic rays (CRs) – high-energy charged particles accelerated in supernovae and young stars – can impact the efficiency of wind driving. The streaming instability limits the speed at which they can escape. However, in the presence of turbulence, the streaming instability is subject to suppression that depends on the magnetization of turbulence given by its Alfvén Mach number. While previous simulations that relied on a simplified model of CR transport have shown that super-Alfvénic streaming of CRs enhances galactic winds, in this paper we take into account a realistic model of streaming suppression. We perform three-dimensional magnetohydrodynamic simulations of a section of a galactic disc and find that turbulent damping dependent on local magnetization of turbulent interstellar medium (ISM) leads to more spatially extended gas and CR distributions compared to the earlier streaming calculations, and that scale heights of these distributions increase for stronger turbulence. Our results indicate that the star formation rate increases with the level of turbulence in the ISM. We also find that the instantaneous wind mass loading is sensitive to local streaming physics with the mass loading dropping significantly as the strength of turbulence increases.

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15

Жиленко, Д. Ю., und О. Э. Кривоносова. „Подавление турбулентности в течениях с вращением“. Письма в журнал технической физики 45, Nr. 17 (2019): 20. http://dx.doi.org/10.21883/pjtf.2019.17.48218.17740.

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The possibilities of turbulence control in spherical Couette flow were examined experimentally. It was shown, that with increasing of outer sphere rotational rate modulation amplitude, the suppression of turbulence is possible with transition to laminar flow state. The reverse process - turbulence recovery - is available with amplitude decreasing. It was established that turbulence breaking and recovering is accompanied by hysteresis. It was shown, that at small values of modulation amplitude, suppression of turbulence is available only in narrow frequency band.

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16

Stamenkovic, Zivojin, Milos Kocic und Jelena Petrovic. „The CFD modeling of two-dimensional turbulent MHD channel flow“. Thermal Science 21, suppl. 3 (2017): 837–50. http://dx.doi.org/10.2298/tsci160822093s.

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In this paper, influence of magnetic field on turbulence characteristics of twodimensional flow is investigated. The present study has been undertaken to understand the effects of a magnetic field on mean velocities and turbulence parameters in turbulent 2-D channel flow. Several cases are considered. First laminar flow in a channel and MHD laminar channel flow are analyzed in order to validate model of magnetic field influence on electrically conducting fluid flow. Main part of the paper is focused on MHD turbulence suppression for 2-D turbulent flow in a channel and around the flat plate. The simulations are performed using ANSYS CFX software. Simulations results are obtained with BSL Reynolds stress model for turbulent and MHD turbulent flow around flat plate. The nature of the flow has been examined through distribution of mean velocities, turbulent fluctuations, vorticity, Reynolds stresses and turbulent kinetic energy.

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17

Borque, Paloma, Edward P. Luke, Pavlos Kollias und Fan Yang. „Relationship between Turbulence and Drizzle in Continental and Marine Low Stratiform Clouds“. Journal of the Atmospheric Sciences 75, Nr. 12 (09.11.2018): 4139–48. http://dx.doi.org/10.1175/jas-d-18-0060.1.

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Abstract Turbulence and drizzle-rate measurements from a large dataset of marine and continental low stratiform clouds are presented. Turbulence peaks at cloud base over land and near cloud top over the ocean. For both regions, eddy dissipation rate values of 10−5–10−2 m2 s−3 are observed. Surface-based measurements of cloud condensation nuclei number concentration NCCN and liquid water path (LWP) are used to estimate the precipitation susceptibility S0. Results show that positive S0 values are found at low turbulence, consistent with the principle that aerosols suppress precipitation formation, whereas S0 is smaller, and can be negative, in a more turbulent environment. Under similar macrophysical conditions, especially for medium to high LWP, high (low) turbulence is likely to lessen (promote) the suppression effect of high NCCN on precipitation. Overall, the turbulent effect on S0 is stronger in continental than marine stratiform clouds. These observational findings are consistent with recent analytical prediction for a turbulence-broadening effect on cloud droplet size distribution.

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18

Umlauf, Lars. „The Description of Mixing in Stratified Layers without Shear in Large-Scale Ocean Models“. Journal of Physical Oceanography 39, Nr. 11 (01.11.2009): 3032–39. http://dx.doi.org/10.1175/2009jpo4006.1.

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Abstract Large-scale geophysical flows often exhibit layers with negligible vertical shear and infinite gradient Richardson number Ri. It is well known that these layers may be regions of active mixing, even in the absence of local shear production of turbulence because, among other processes, turbulence may be supplied by vertical turbulent transport from neighboring regions. This observation is contrasted by the behavior of most turbulence parameterizations used in ocean climate modeling, predicting the collapse of mixing of mass and matter if the Richardson number exceeds a critical threshold. Here, the performance of a simple model without critical Richardson number is evaluated, taking into account the diffusion of turbulence into layers without shear production and therefore avoiding the suppression of mixing at large values of Ri. The model is based on the framework of second-moment turbulence closures, focusing on the consistent modeling of the turbulent length scale for strongly stratified turbulence. Results are compared to eddy-resolving simulations of stratified shear flows that have recently become available. The model is simple enough for inclusion in ocean climate models.

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Daschiel, G., V. Krieger, J. Jovanović und A. Delgado. „Numerical simulation of turbulent flow through Schiller’s wavy pipe“. Journal of Fluid Mechanics 761 (19.11.2014): 241–60. http://dx.doi.org/10.1017/jfm.2014.619.

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AbstractThe development of incompressible turbulent flow through a pipe of wavy cross-section was studied numerically by direct integration of the Navier–Stokes equations. Simulations were performed at Reynolds numbers of $4.5\times 10^{3}$ and $10^{4}$ based on the hydraulic diameter and the bulk velocity. Results for the pressure resistance coefficient ${\it\lambda}$ were found to be in excellent agreement with experimental data of Schiller (Z. Angew. Math. Mech., vol. 3, 1922, pp. 2–13). Of particular interest is the decrease in ${\it\lambda}$ below the level predicted from the Blasius correlation, which fits almost all experimental results for pipes and ducts of complex cross-sectional geometries. Simulation databases were used to evaluate turbulence anisotropy and provide insights into structural changes of turbulence leading to flow relaminarization. Anisotropy-invariant mapping of turbulence confirmed that suppression of turbulence is due to statistical axisymmetry in the turbulent stresses.

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20

Yoshizawa, Akira, Sanae-I. Itoh, Kimitaka Itoh und Nobumitsu Yokoi. „Dynamos and MHD theory of turbulence suppression“. Plasma Physics and Controlled Fusion 46, Nr. 3 (12.02.2004): R25—R94. http://dx.doi.org/10.1088/0741-3335/46/3/r01.

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21

Gemmrich, Johannes. „Bubble-induced turbulence suppression in Langmuir circulation“. Geophysical Research Letters 39, Nr. 10 (17.05.2012): n/a. http://dx.doi.org/10.1029/2012gl051691.

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22

Serizawa, Akimi, und Isao Kataoka. „Turbulence suppression in bubbly two-phase flow“. Nuclear Engineering and Design 122, Nr. 1-3 (September 1990): 1–16. http://dx.doi.org/10.1016/0029-5493(90)90193-2.

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23

Kataoka, Isao, Akimi Serizawa und D. C. Besnard. „Prediction of turbulence suppression and turbulence modeling in bubbly two-phase flow“. Nuclear Engineering and Design 141, Nr. 1-2 (Juni 1993): 145–58. http://dx.doi.org/10.1016/0029-5493(93)90099-u.

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24

Garg, Rajat P., Joel H. Ferziger, Stephen G. Monismith und Jeffrey R. Koseff. „Stably stratified turbulent channel flows. I. Stratification regimes and turbulence suppression mechanism“. Physics of Fluids 12, Nr. 10 (2000): 2569. http://dx.doi.org/10.1063/1.1288608.

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25

Pan, J. C., W. J. Schmoll und D. R. Ballal. „Turbulent Combustion Properties Behind a Confined Conical Stabilizer“. Journal of Engineering for Gas Turbines and Power 114, Nr. 1 (01.01.1992): 33–38. http://dx.doi.org/10.1115/1.2906304.

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Turbulence properties were investigated in and around the recirculation zone produced by a 45 deg conical flame stabilizer of 25 percent blockage ratio confined in a pipe supplied with a turbulent premixed methane-air mixture at a Reynolds number of 5.7×104. A three-component LDA system was used for measuring mean velocities, turbulence intensities, Reynolds stresses, skewness, kurtosis, and turbulent kinetic energy. It was found that wall confinement elongates the recirculation zone by accelerating the flow and narrows it by preventing mean streamline curvature. For confined flames, turbulence production is mainly due to shear stress-mean strain interaction. In the region of maximum recirculation zone width and around the stagnation point, the outer stretched flame resembles a normal mixing layer and gradient-diffusion closure for velocity holds. However, and in the absence of turbulent heat flux data, countergradient diffusion cannot be ruled out. Finally, and because of the suppression of mean streamline curvature by confinement, in combusting flow, the production of turbulence is only up to 33 percent of its damping due to dilatation and dissipation.

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Hurther, D., und U. Lemmin. „Improved Turbulence Profiling with Field-Adapted Acoustic Doppler Velocimeters Using a Bifrequency Doppler Noise Suppression Method“. Journal of Atmospheric and Oceanic Technology 25, Nr. 3 (01.03.2008): 452–63. http://dx.doi.org/10.1175/2007jtecho512.1.

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Abstract A novel noise reduction method and corresponding technique are presented for improving turbulence measurements with acoustic Doppler velocimeters (ADVs) commonly used in field studies of coastal and nearshore regions, rivers, lakes, and estuaries. This bifrequency method is based on the decorrelation of the random and statistically independent Doppler noise terms contained in the Doppler signals at two frequencies. It is shown through experiments in an oscillating grid turbulence (OGT) tank producing diffusive isotropic turbulence that a shift in carrier frequency of less than 10% is sufficient to increase the resolved frequency range by a decade in the turbulent velocity spectra. Over this spectral range, the slope of the velocity spectra agrees well with the universal inertial range value of −5/3. The limit due to spatial averaging effects over the sample volume can be determined from the abrupt deviation of the spectral slope from the −5/3 value. As a result, the relative error of the turbulent intensity estimate and the turbulent kinetic energy (TKE) dissipation rate, measured by two different methods, does not exceed 10% in the case of isotropic turbulence. Furthermore, the bifrequency method allows accurate estimates of the turbulent microscales as shown by the good agreement of the ratio between the Taylor and Kolmogorov microscales and an Re1/4t power law. Compared to previous Doppler noise reduction methods (Garbini et al.), an increase in time resolution by a factor of 4 is achieved. The proposed method also avoids the loss of TKE energy contained in isotropic flow structures of size equal to and smaller than the sample volume. Different from Doppler noise methods proposed by Hurther and Lemmin and Blanckaert and Lemmin, this method does not require additional hardware components, electronic circuitry, or sensors because the redundant instantaneous velocity field information is captured with the same transducer. The required shift in carrier frequency is small enough for the bifrequency method to be easily implemented in commercial ADVs.

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Rastigejev, Yevgenii, und Sergey A. Suslov. „E–ε Model of Spray-Laden Near-Sea Atmospheric Layer in High Wind Conditions“. Journal of Physical Oceanography 44, Nr. 2 (01.02.2014): 742–63. http://dx.doi.org/10.1175/jpo-d-12-0195.1.

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Abstract In-depth understanding and accurate modeling of the interaction between ocean spray and a turbulent flow under high wind conditions is essential for improving the intensity forecasts of hurricanes and severe storms. Here, the authors consider the E–ε closure for a turbulent flow model that accounts for the effects of the variation of turbulent energy and turbulent mixing length caused by spray stratification. The obtained analytical and numerical solutions show significant differences between the current E–ε model and the lower-order turbulent kinetic energy (TKE) model considered previously. It is shown that the reduction of turbulent energy and mixing length above the wave crest level, where the spray droplets are generated, that is not accounted for by the TKE model results in a significant suppression of turbulent mixing in this near-wave layer. In turn, suppression of turbulence causes an acceleration of flow and a reduction of the drag coefficient that is qualitatively consistent with field observations if spray is fine (even if its concentration is low) or if droplets are large but their concentration is sufficiently high. In the latter case, spray inertia may become important. This effect is subsequently examined. It is shown that spray inertia leads to the reduction of wind velocity in the close proximity of the wave surface relative to the reference logarithmic profile. However, at higher altitudes the suppression of flow turbulence by the spray still results in the wind acceleration and the reduction of the local drag coefficient.

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Dillon, Jeremy, Len Zedel und Alex E. Hay. „Simultaneous Velocity Ambiguity Resolution and Noise Suppression for Multifrequency Coherent Doppler Sonar“. Journal of Atmospheric and Oceanic Technology 29, Nr. 3 (01.03.2012): 450–63. http://dx.doi.org/10.1175/jtech-d-11-00069.1.

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Abstract Coherent Doppler sonar is a useful tool for noninvasive measurement of ocean currents, sediment transport, and turbulence in coastal environments. Various methods have been proposed to separately address two of its inherent limitations: velocity ambiguity and measurement noise. However, in energetic turbulent flows, both factors may be present simultaneously. The presence of measurement noise complicates velocity ambiguity resolution, and conversely velocity ambiguity presents a challenge for existing noise suppression methods. A velocity estimator based on maximum a posteriori (MAP) estimation has been developed to resolve velocity ambiguity and suppress measurement noise simultaneously rather than separately. The estimator optimally combines measurements from multiple acoustic carrier frequencies and multiple transducers. Data fusion is achieved using a probabilistic approach, whereby measurements are combined numerically to derive a velocity likelihood function. The MAP velocity estimator is evaluated using a high-fidelity coherent Doppler sonar simulation of oscillating flow and data from a towing tank grid turbulence experiment where both velocity ambiguity and backscatter decorrelation were present. Time series and spectra from MAP velocity estimation are compared to those obtained with conventional Doppler signal processing. In addition to robustly resolving velocity ambiguity, the MAP velocity estimator is shown to reduce high-frequency noise in turbulence spectra.

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29

Hussain, A. K. M. F., und M. A. Z. Hasan. „Turbulence suppression in free turbulent shear flows under controlled excitation. Part 2. Jet-noise reduction“. Journal of Fluid Mechanics 150 (Januar 1985): 159–68. http://dx.doi.org/10.1017/s0022112085000076.

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It is shown that reduction of broadband (even total) far-field jet noise can be achieved via controlled excitation of a jet at a frequency in the range 0.01 < Stθ < 0.02, where Stθ is the Strouhal number based on the exit momentum thickness of the shear layer. Hot-wire measurements in the noise-producing region of the jet reveal that the noise suppression is a direct consequence of turbulence suppression, produced by early saturation and breakdown of maximally growing instability modes.

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Boedo, J. A., D. S. Gray, P. W. Terry, S. Jachmich, G. R. Tynan und R. W. Conn. „Scaling of plasma turbulence suppression with velocity shear“. Nuclear Fusion 42, Nr. 2 (01.02.2002): 117–21. http://dx.doi.org/10.1088/0029-5515/42/2/301.

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31

Parmananda, P., und M. Eiswirth. „Suppression of Chemical Turbulence Using Feedbacks and Forcing“. Journal of Physical Chemistry A 103, Nr. 28 (Juli 1999): 5510–14. http://dx.doi.org/10.1021/jp990451+.

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32

Terry, P. W. „Suppression of turbulence and transport by sheared flow“. Reviews of Modern Physics 72, Nr. 1 (01.01.2000): 109–65. http://dx.doi.org/10.1103/revmodphys.72.109.

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33

Itoh, K., T. Ohkawa, S.-I. Itoh, M. Yagi und A. Fukuyama. „Suppression of plasma turbulence by asymmetric hot ions“. Plasma Physics and Controlled Fusion 40, Nr. 5 (01.05.1998): 661–64. http://dx.doi.org/10.1088/0741-3335/40/5/018.

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34

Di Siena, A., T. Görler, E. Poli, A. Bañón Navarro, A. Biancalani und F. Jenko. „Electromagnetic turbulence suppression by energetic particle driven modes“. Nuclear Fusion 59, Nr. 12 (17.09.2019): 124001. http://dx.doi.org/10.1088/1741-4326/ab4088.

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35

Boué, Laurent, Victor L'vov und Itamar Procaccia. „Temperature suppression of Kelvin-wave turbulence in superfluids“. EPL (Europhysics Letters) 99, Nr. 4 (01.08.2012): 46003. http://dx.doi.org/10.1209/0295-5075/99/46003.

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36

Murphy, P. J., J. T. Tough und W. Fiszdon. „The suppression of superfluid turbulence in helium II“. Journal of Low Temperature Physics 86, Nr. 5-6 (März 1992): 423–31. http://dx.doi.org/10.1007/bf00121507.

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37

Leddy, J., und B. Dudson. „Intrinsic suppression of turbulence in linear plasma devices“. Plasma Physics and Controlled Fusion 59, Nr. 12 (07.11.2017): 125011. http://dx.doi.org/10.1088/1361-6587/aa9297.

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38

Biskamp, D., und M. Walter. „Suppression of shear damping in drift wave turbulence“. Physics Letters A 109, Nr. 1-2 (Mai 1985): 34–38. http://dx.doi.org/10.1016/0375-9601(85)90386-x.

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39

Yokoi, N., K. Higashimori und M. Hoshino. „Transport enhancement and suppression in turbulent magnetic reconnection: A self-consistent turbulence model“. Physics of Plasmas 20, Nr. 12 (Dezember 2013): 122310. http://dx.doi.org/10.1063/1.4851976.

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40

Wang, Yannan, Lingling Cao, Zhongfu Cheng, Bart Blanpain und Muxing Guo. „Mathematical Methodology and Metallurgical Application of Turbulence Modelling: A Review“. Metals 11, Nr. 8 (17.08.2021): 1297. http://dx.doi.org/10.3390/met11081297.

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This paper focusses on three main numerical methods, i.e., the Reynolds-Averaged Navier-Stokes (RANS), Large Eddy Simulation (LES), and Direct Numerical Simulation (DNS) methods. The formulation and variation of different RANS methods are evaluated. The advantage and disadvantage of RANS models to characterize turbulent flows are discussed. The progress of LES with different subgrid scale models is presented. Special attention is paid to the inflow boundary condition for LES modelling. Application and limitation of the DNS model are described. Different experimental techniques for model validation are given. The consistency between physical experimentation/modelling and industrial cases is discussed. An emphasis is placed on the model validation through physical experimentation. Subsequently, the application of a turbulence model for three specific flow problems commonly encountered in metallurgical process, i.e., bubble-induced turbulence, supersonic jet transport, and electromagnetic suppression of turbulence, is discussed. Some future perspectives for the simulation of turbulent flow are formulated.

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Itsweire, E. C., und K. N. Helland. „Spectra and energy transfer in stably stratified turbulence“. Journal of Fluid Mechanics 207 (Oktober 1989): 419–52. http://dx.doi.org/10.1017/s0022112089002648.

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The influence of stabilizing buoyancy forces on the spectral characteristics and spectral energy transfer of grid-generated turbulence was studied in a ten-layer closed-loop stratified water channel. The results are compared to the limiting ideal cases of the three-dimensional turbulence and two-dimensional turbulence theories. The velocity power spectra evolve from a classical isotropic shape to a shape of almost k−2 after the suppression of the net vertical mixing. This final spectral shape is rather different from the k−3 to k−4 predicted by the theory of two-dimensional turbulence and could result from the interaction between small-scale internal waves and quasi-two-dimensional turbulent structures as well as some Doppler shift of advected waves. Several lengthscales are derived from the cospectra of the vertical velocity and density fluctuations and compared with the buoyancy, overturning and viscous lengthscales measured in previous studies, e.g. Stillinger, Helland & Van Atta (1983) and Itsweire, Helland & Van Atta (1986). The smallest turbulent scale, defined when the buoyancy flux goes to zero, can be related to the peak of the cospectra of the buoyancy flux. This new relationship can be used to provide a measure of the smallest turbulent scale in cases where the buoyancy flux never goes to zero, i.e. a growing turbulent stratified shear flow. Finally, the one-dimensional energy transfer term computed from the bispectra shows evidence of a reverse energy cascade from the small scales to the large scales far from the grid where buoyancy forces dominate inertial forces. The observed reverse energy transfer could be produced by the development of quasi-two-dimensional eddies as the original three-dimensional turbulence collapses.

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Wei, Wei, Hongsheng Zhang, Bingui Wu, Yongxiang Huang, Xuhui Cai, Yu Song und Jianduo Li. „Intermittent turbulence contributes to vertical dispersion of PM<sub>2.5</sub> in the North China Plain: cases from Tianjin“. Atmospheric Chemistry and Physics 18, Nr. 17 (10.09.2018): 12953–67. http://dx.doi.org/10.5194/acp-18-12953-2018.

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Abstract. Heavy particulate pollution events have frequently occurred in the North China Plain over the past decades. Due to high emissions and poor dispersion conditions, issues are becoming increasingly serious during cold seasons. Although early studies have explored some potential reasons for air pollution, there are few works focusing on the effects of intermittent turbulence. This paper draws upon two typical PM2.5 (particulate matter with diameter less than 2.5 mm) pollution cases from the winter of 2016–2017. After several days of gradual accumulation, the concentration of PM2.5 near the surface reached the maximum as a combined result of strong inversion layer, stagnant wind, and high ambient humidity and then sharply decreased to a very low level within a few hours. In order to identify the strength of turbulent intermittency, an effective index, called the intermittency factor (IF), was proposed by this work. The results show that the turbulence is very weak during the cumulative stage due to the suppression by strongly stratified layers, while for the stage of dispersion, the turbulence is highly intermittent and not locally generated. The vertical structure of turbulence and wind profiles confirms the generation and downward transport of intermittent turbulence associated with low-level jets. The intermittent turbulent fluxes contribute positively to the vertical transport of particulate matter and improve the air quality near the surface. This work has demonstrated a possible mechanism of how intermittent turbulence affects the dispersion of particulate matter.

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BELGHERRAS, S., T. BENOUAZ und S. M. A. BEKKOUCHE. „Intermittent transport of nonlinear reduced models in tokomak plasmas turbulence“. Journal of Plasma Physics 78, Nr. 6 (01.05.2012): 607–15. http://dx.doi.org/10.1017/s0022377812000426.

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AbstractUnderstanding the origin and nature of turbulent transport in tokomak plasmas is one of the major challenges of a successful magnetic confinement fusion. The aim of this work is to study instability associated with the ion-temperature gradient (ITG)-driven turbulence in the core of the plasma, which is the seat of fusion reactions. We used a low degree of freedom model composed of 18 ordinary differential equations. When the system is slightly above the stability threshold of the ITG mode, it is considered to be in the convection regime and convective heat transport of the system is time-independent, or oscillates periodically. As ITG is increased further, the system bifurcates to the turbulent regime. In a strongly turbulent regime, intermittent bursts (the so-called avalanches) are observed. This intermittency is a result of the competition among the following three factors: generation of sheared flows and suppression of ITG turbulence, gradual reduction of the sheared flows due to viscosity, and rapid regrowth of ITG modes due to reduction of sheared flows.

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Lei, Jiao, Naian Liu und Ran Tu. „Flame height of turbulent fire whirls: A model study by concept of turbulence suppression“. Proceedings of the Combustion Institute 36, Nr. 2 (2017): 3131–38. http://dx.doi.org/10.1016/j.proci.2016.06.080.

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45

LANDA, P. S., A. A. ZAIKIN, A. S. GINEVSKY und YE V. VLASOV. „TURBULENCE AND COHERENT STRUCTURES IN SUBSONIC SUBMERGED JETS: CONTROL OF THE TURBULENCE“. International Journal of Bifurcation and Chaos 09, Nr. 02 (Februar 1999): 397–414. http://dx.doi.org/10.1142/s0218127499000262.

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The onset of turbulence and formation of large-scale patterns (coherent structures) in subsonic submerged jets are considered from the standpoint of noise-induced nonequilibrium phase transitions of the second kind. It is shown by the example of noise-induced oscillations of a pendulum with a randomly vibrating suspension axis that such a transition can be controlled by an additional harmonic action. The known possibility of notable suppression or intensification of turbulence in jets and free shear layers by means of a slight acoustic action at one or another frequency can be attributable to such control.

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46

Shringarpure, Mrugesh, Mariano I. Cantero und S. Balachandar. „Analysis of Turbulence Suppression in Sediment-laden Saline Currents“. Procedia Engineering 126 (2015): 16–23. http://dx.doi.org/10.1016/j.proeng.2015.11.170.

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47

Zaman, Ehsan, Ali Vakil, Mark Martinez und James Olson. „An integral criterion for turbulence suppression in swirling flows“. Canadian Journal of Chemical Engineering 96, Nr. 9 (22.02.2018): 2025–34. http://dx.doi.org/10.1002/cjce.23145.

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48

Müller, A. J., A. E. Sáez und J. A. Odell. „Turbulence suppression by polymer solutions in opposed jets flow“. AIChE Journal 41, Nr. 5 (Mai 1995): 1333–36. http://dx.doi.org/10.1002/aic.690410530.

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49

Lazarian, A. „Enhancement and Suppression of Heat Transfer by MHD Turbulence“. Astrophysical Journal 645, Nr. 1 (22.06.2006): L25—L28. http://dx.doi.org/10.1086/505796.

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50

Bennett, Sean J., Yinting Hou und Joseph F. Atkinson. „Turbulence suppression by suspended sediment within a geophysical flow“. Environmental Fluid Mechanics 14, Nr. 4 (17.11.2013): 771–94. http://dx.doi.org/10.1007/s10652-013-9323-2.

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