To see the other types of publications on this topic, follow the link: Wave flows.
Journal articles on the topic 'Wave flows'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Wave flows.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Choi, J. E., M. K. Sreedhar, and F. Stern. "Stokes Layers in Horizontal-Wave Outer Flows." Journal of Fluids Engineering 118, no. 3 (September 1, 1996): 537–45. http://dx.doi.org/10.1115/1.2817792.
Full textAbstract:
Results are reported of a computational study investigating the responses of flat plate boundary layers and wakes to horizontal wave outer flows. Solutions are obtained for temporal, spatial, and traveling waves using Navier Stokes, boundary layer, and perturbation expansion equations. A wide range of parameters are considered for all the three waves. The results are presented in terms of Stokes-layer overshoots, phase leads (lags), and streaming. The response to the temporal wave showed all the previously reported features. The magnitude and nature of the response are small and simple such that it is essentially a small disturbance on the steady solution. Results are explainable in terms of one parameter ξ (the frequency of oscillation). For the spatial wave, the magnitude and the nature of the response are significantly increased and complex such that it cannot be considered simply a small disturbance on the without-wave solution. The results are explainable in terms of the two parameters λ−1 and x/λ (where λ is the wavelength). A clear asymmetry is observed in the wake response for the spatial wave. An examination of components of the perturbation expansion equations indicates that the asymmetry is a first-order effect due to nonlinear interaction between the steady and first-harmonic velocity components. For the traveling wave, the responses are more complex and an additional parameter, c (the wave speed), is required to explain the results. In general, for small wave speeds the results are similar to a spatial wave, whereas for higher wave speeds the response approaches the temporal wave response. The boundary layer and perturbation expansion solutions compares well with the Navier Stokes solution in their range of validity.
2
MILES, JOHN. "Gravity waves on shear flows." Journal of Fluid Mechanics 443 (September 25, 2001): 293–99. http://dx.doi.org/10.1017/s0022112001005043.
Full textAbstract:
The eigenvalue problem for gravity waves on a shear flow of depth h and non-inflected velocity profile U(y) (typically parabolic) is revisited, following Burns (1953) and Yih (1972). Complementary variational formulations that provide upper and lower bounds to the Froude number F as a function of the wave speed c and wavenumber k are constructed. These formulations are used to improve Burns's long-wave approximation and to determine Yih's critical wavenumber k∗, for which the wave is stationary (c = 0) and to which k must be inferior for the existence of an upstream running wave.
3
KAGHASHVILI, EDISHER KH. "Alfvén waves in shear flows: Driven wave formalism." Journal of Plasma Physics 79, no. 5 (May 16, 2013): 797–804. http://dx.doi.org/10.1017/s0022377813000500.
Full textAbstract:
AbstractThe driven wave formalism, as it was later applied to the solar coronal plasma processes, was first developed in our earlier work (Kaghashvili, E. Kh. 2007 Alfvén wave-driven compressional fluctuations in shear flows. Phys. Plasmas14, 44502) that presented the analytical solutions for the plasma density fluctuations. In the driven-wave formalism, we look for the short-term changes in the initial waveform due to the linear interaction of the initial natural mode of the system and the flow inhomogeneity. This formalism allows us to obtain the analytical solutions for the driven waves that are excited in the system. While a full set of driven wave solutions for magnetohydrodynamic variables in the cold plasma case were presented earlier (Kaghashvili, E. 2012c Driven wave-generated electric field in the solar corona. J. Geophys. Res. 117, A10103, doi:10.1029/2012JA018120), the purpose of this paper is to remove the cold-plasma restriction and to present the formal solutions for the initial linearly polarized Alfvén wave-driven fluctuations.
4
Johnson, E. R., and G. G. Vilenski. "Two-dimensional leaps in near-critical flow over isolated orography." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 461, no. 2064 (September 20, 2005): 3747–63. http://dx.doi.org/10.1098/rspa.2005.1530.
Full textAbstract:
This paper describes steady two-dimensional disturbances forced on the interface of a two-layer fluid by flow over an isolated obstacle. The oncoming flow speed is close to the linear longwave speed and the layer densities, layer depths and obstacle height are chosen so that the equations of motion reduce to the forced two-dimensional Korteweg–de Vries equation with cubic nonlinearity, i.e. the forced extended Kadomtsev–Petviashvili equation. The distinctive feature noted here is the appearance in the far lee-wave wake behind obstacles in subcritical flow of a ‘table-top’ wave extending almost one-dimensionally for many obstacles widths across the flow. Numerical integrations show that the most important parameter determining whether this wave appears is the departure from criticality, with the wave appearing in slightly subcritical flows but being destroyed by two-dimensional effects behind even quite long ridges in even moderately subcritical flow. The wave appears after the flow has passed through a transition from subcritical to supercritical over the obstacle and its leading and trailing edges resemble dissipationless leaps standing in supercritical flow. Two-dimensional steady supercritical flows are related to one-dimensional unsteady flows with time in the unsteady flow associated with a slow cross-stream variable in the two-dimensional flows. Thus the wide cross-stream extent of the table-top wave appears to derive from the combination of its occurrence in a supercritical region embedded in the subcritical flow and the propagation without change of form of table-top waves in one-dimensional unsteady flow. The table-top wave here is associated with a resonant steepening of the transition above the obstacle and a consequent twelve-fold increase in drag. Remarkably, the table-top wave is generated equally strongly and extends laterally equally as far behind an axisymmetric obstacle as behind a ridge and so leads to subcritical flows differing significantly from linear predictions.
5
Kandaswamy, Palani G., B. Tamil Selvi, and Lokenath Debnath. "Propagation of Rossby waves in stratified shear flows." International Journal of Mathematics and Mathematical Sciences 12, no. 3 (1989): 547–57. http://dx.doi.org/10.1155/s0161171289000682.
Full textAbstract:
A study is made of the propagation of Rossby waves in a stably stratified shear flows. The wave equation for the Rossby waves is derived in an isothermal atmosphere on a beta plane in the presence of a latitudinally sheared zonal flow. It is shown that the wave equation is singular at five critical levels, but the wave absorption takes place only at the two levels where the local relative frequency equals in magnitude to the Brunt Vaisala frequency. This analysis also reveals that these two levels exhibit valve effect by allowing the waves to penetrate them from one side only. The absorption coefficient exp(2πμ)is determined at these levels. Both the group velocity approach and single wave treatment are employed for the investigation of the problem.
6
WEBB, G. M., E. Kh KAGHASHVILI, and G. P. ZANK. "Magnetohydrodynamic wave mixing in shear flows: Hamiltonian equations and wave action." Journal of Plasma Physics 73, no. 1 (February 2007): 15–68. http://dx.doi.org/10.1017/s0022377806004399.
Full textAbstract:
Abstract.Magnetohydrodynamic wave interactions in a linear shear flow are investigated using the Lagrangian fluid displacement ξ and entropy perturbation Δ S, in which a spatial Fourier solution is obtained in the frame of the background shear flow (Kelvin's method). The equations reduce to three coupled oscillator equations, with time-dependent coefficients and with source terms proportional to the entropy perturbation. In the absence of entropy perturbations, the system admits a wave action conservation integral consisting of positive and negative energy waves. Variational and Hamiltonian forms of the equations are obtained. Examples of wave amplification phenomena and sharp resonant-type wave interactions are obtained. Implications for the interaction of magnetohydrodynamic waves in the shear flow between fast, polar coronal-hole solar wind and slow, streamer belt solar wind are discussed.
7
Yuan, Jing, Ole Madsen, and Eng Soon Chan. "EXPERIMENTAL STUDY OF TURBULENT OSCILLATORY BOUNDARY LAYERS IN A NEW OSCILLATORY WATER TUNNEL." Coastal Engineering Proceedings 1, no. 33 (October 18, 2012): 24. http://dx.doi.org/10.9753/icce.v33.waves.24.
Full textAbstract:
A new oscillatory water tunnel has been built in the Civil and Environmental Engineering Department’s Hydraulic Laboratory at the National University of Singapore. It can accurately produce oscillatory flows that correspond to full-scale sea waves. Tests including pure sinusoidal waves and combined wave-current flows over smooth and rough bottoms have been performed. High quality measurements of the boundary layer flow fields are obtained using a PIV system. The PIV measured flow field is phase and spatially averaged to give a mean vertical velocity profile. It is found that the logarithmic profile can accurately approximate the near-bottom first-harmonic amplitude of sinusoidal waves and give highly accurate determinations of the hydrodynamic roughness and the theoretical bottom location. The bottom shear stress obtained from momentum integral is in general agreement with results from log-profile fitting. The current profiles of combined wave-current flows indicate a two-log-profile structure as suggested by simple combined wave-current flow theory. The difference between the two current shear velocities obtained from combined wave-current flows, as well as a small but meaningful third harmonic embedded in a pure sinusoidal wave, suggest the existence of a time-varying turbulent eddy viscosity.
8
YAO, LUN-SHIN. "A resonant wave theory." Journal of Fluid Mechanics 395 (September 25, 1999): 237–51. http://dx.doi.org/10.1017/s0022112099005832.
Full textAbstract:
Analysis is used to show that a solution of the Navier–Stokes equations can be computed in terms of wave-like series, which are referred to as waves below. The mean flow is a wave of infinitely long wavelength and period; laminar flows contain only one wave, i.e. the mean flow. With a supercritical instability, there are a mean flow, a dominant wave and its harmonics. Under this scenario, the amplitude of the waves is determined by linear and nonlinear terms. The linear case is the target of flow-instability studies. The nonlinear case involves energy transfer among the waves satisfying resonance conditions so that the wavenumbers are discrete, form a denumerable set, and are homeomorphic to Cantor's set of rational numbers. Since an infinite number of these sets can exist over a finite real interval, nonlinear Navier–Stokes equations have multiple solutions and the initial conditions determine which particular set will be excited. Consequently, the influence of initial conditions can persist forever. This phenomenon has been observed for Couette–Taylor instability, turbulent mixing layers, wakes, jets, pipe flows, etc. This is a commonly known property of chaos.
9
FRACCAROLLO, L., and H. CAPART. "Riemann wave description of erosional dam-break flows." Journal of Fluid Mechanics 461 (June 25, 2002): 183–228. http://dx.doi.org/10.1017/s0022112002008455.
Full textAbstract:
This work examines the sudden erosional flow initiated by the release of a dam-break wave over a loose sediment bed. Extended shallow-water equations are formulated to describe the development of the surge. Accounting for bed material inertia, a transport layer of finite thickness is introduced, and a sharp interface view of the morphodynamic boundary is adopted. Approximations are sought for an intermediate range of wave evolution, in which equilibration of the sediment load can be assumed instantaneous but momentum loss due to bed friction has not yet been felt. The resulting homogeneous hyperbolic equations are mathematically tractable using the Riemann techniques of gas dynamics. Dam-break initial conditions give rise to self-similar flow profiles. The wave structure features piecewise constant states, two smoothly varied simple waves, and a special type of shock: an erosional bore forming at the forefront of the wave. Profiles are constructed through a semi-analytical procedure, yielding a geomorphic generalization of the Stoker solution for dam-break waves over rigid bed. For most flow properties, the predictions of the theoretical treatment compare favourably with experimental tests visualized using particle imaging techniques.
10
TAM, CHRISTOPHER K. W., and LAURENT AURIAULT. "The wave modes in ducted swirling flows." Journal of Fluid Mechanics 371 (September 25, 1998): 1–20. http://dx.doi.org/10.1017/s0022112098002043.
Full textAbstract:
The small-amplitude wave modes inside a ducted inviscid compressible swirling flow are investigated. In order to avoid possible mathematical ambiguities arising from the use of an inviscid flow model, the wave modes are cast as the solution of an initial boundary value problem. Two families of propagating waves are found. The acoustic modes are supported by the compressibility effect of the flow. The rotational modes are sustained by the centrifugal force field associated with the mean flow rotation. Two cases, one with a free-vortex swirl and the other with a rigid-body swirl, are investigated in some depth. Numerical results are provided.
11
Campbell, Bryce K., Kelli Hendrickson, and Yuming Liu. "Nonlinear coupling of interfacial instabilities with resonant wave interactions in horizontal two-fluid plane Couette–Poiseuille flows: numerical and physical observations." Journal of Fluid Mechanics 809 (November 14, 2016): 438–79. http://dx.doi.org/10.1017/jfm.2016.636.
Full textAbstract:
We investigate mechanisms governing the initial growth and nonlinear evolution of interfacial waves in horizontal two-fluid plane Couette–Poiseuille flows. Nonlinear coupling of the Kelvin–Helmholtz interfacial instability with resonant wave interactions has been shown to be capable of rapidly generating long waves through the transfer of energy from linearly unstable short waves to stable long-wave components within the context of potential flow theory. The objective of this work is to determine whether that coupled mechanism persists in laminar and turbulent viscous flows. Utilizing both theoretical and computational methods, we analyse the initial Orr–Sommerfeld instability to quantify the frequencies and growth/decay rates of each wave mode for two-fluid laminar and turbulent channel flows. The obtained dispersion relation allows for the identification of resonant and/or near-resonant triads among (unstable and damped) wave components in an interfacial wave spectrum. We perform direct numerical simulations (DNS) of the two-phase Navier–Stokes equations with a fully nonlinear interface to formally establish the validity of our theoretical predictions for viscous flows. DNS results show the existence of a nonlinear energy cascade from unstable short- to damped long-wavelength waves due to resonant subharmonic and/or triadic interactions in both laminar Couette and turbulent Poiseuille flows. Spectral analysis of the interfacial evolution confirms that the combined instability–resonance mechanism persists in the presence of viscosity despite being derived under the assumption of potential flow theory. Finally, we perform a detailed examination of experimentally measured wave power spectra from Jurman et al. (J. Fluid Mech., vol. 238, 1992, pp. 187–219) and carry out a numerical sensitivity study of the flow conditions to demonstrate and verify the existence of the coupled instability–resonance mechanism in physical systems. Our analysis accurately predicts the initial instability and the resulting nonlinear energy cascade through subharmonic and triadic interfacial wave resonances.
12
Rubina, L. I., and O. N. Ulyanov. "On double wave type flows." Sibirskii matematicheskii zhurnal 60, no. 4 (June 30, 2019): 859–73. http://dx.doi.org/10.33048/smzh.2019.60.412.
Full text
13
Riley, N. "Wave interactions and fluid flows." Contemporary Physics 28, no. 1 (January 1987): 71–73. http://dx.doi.org/10.1080/00107518708211042.
Full text
14
Rubina, L. I., and O. N. Ulyanov. "On Double Wave Type Flows." Siberian Mathematical Journal 60, no. 4 (July 2019): 673–84. http://dx.doi.org/10.1134/s0037446619040128.
Full text
15
Busse, F. H. "Wave interactions and fluid flows." Physics of the Earth and Planetary Interiors 46, no. 4 (July 1987): 390–91. http://dx.doi.org/10.1016/0031-9201(87)90096-3.
Full text
16
Csanady, G. T. "Wave interactions and fluid flows." Limnology and Oceanography 32, no. 5 (September 1987): 1177. http://dx.doi.org/10.4319/lo.1987.32.5.1177.
Full text
17
MONISMITH, S. G., E. A. COWEN, H. M. NEPF, J. MAGNAUDET, and L. THAIS. "Laboratory observations of mean flows under surface gravity waves." Journal of Fluid Mechanics 573 (February 2007): 131–47. http://dx.doi.org/10.1017/s0022112006003594.
Full textAbstract:
In this paper we present mean velocity distributions measured in several different wave flumes. The flows shown involve different types of mechanical wavemakers, channels of differing sizes, and two different end conditions. In all cases, when surface waves, nominally deep-water Stokes waves, are generated, counterflowing Eulerian flows appear that act to cancel locally, i.e. not in an integral sense, the mass transport associated with the Stokes drift. No existing theory of wave–current interactions explains this behaviour, although it is symptomatic of Gerstner waves, rotational waves that are exact solutions to the Euler equations. In shallow water (kH ≈ 1), this cancellation of the Stokes drift does not hold, suggesting that interactions between wave motions and the bottom boundary layer may also come into play.
18
VLACHOGIANNIS, M., and V. BONTOZOGLOU. "Observations of solitary wave dynamics of film flows." Journal of Fluid Mechanics 435 (May 25, 2001): 191–215. http://dx.doi.org/10.1017/s0022112001003688.
Full textAbstract:
Experimental results are reported on non-stationary evolution and interactions of waves forming on water and water–glycerol solution flowing along an inclined plane. A nonlinear wave generation process leads to a large number of solitary humps with a wide variety of sizes. A uorescence imaging method is applied to capture the evolution of film height in space and time with accuracy of a few microns. Coalescence – the inelastic interaction of solitary waves resulting in a single hump – is found to proceed at a timescale correlated to the difference in height between the interacting waves. The correlation indicates that waves of similar height do not merge. Transient phenomena accompanying coalescence are reported. The front-running ripples recede during coalescence, only to reappear when the new hump recovers its teardrop shape. The tail of the resulting solitary wave develops an elevated substrate relative to the front, which decays exponentially in time; both observations about the tail confirm theoretical predictions. In experiments with water, the elevated back substrate is unstable, yielding to a tail oscillation with wavelength similar to that of the front-running ripples. This instability plays a key role in two complex interaction phenomena observed: the nucleation of a new crest between two interacting solitary humps and the splitting of a large hump (that has grown through multiple coalescence events) into solitary waves of similar size.
19
Makarenko, Nikolay, Janna Maltseva, Eugene Morozov, Roman Tarakanov, and Kseniya Ivanova. "Internal waves in marginally stable abyssal stratified flows." Nonlinear Processes in Geophysics 25, no. 3 (September 5, 2018): 659–69. http://dx.doi.org/10.5194/npg-25-659-2018.
Full textAbstract:
Abstract. The problem on internal waves in a weakly stratified two-layer fluid is studied semi-analytically. We discuss the 2.5-layer fluid flows with exponential stratification of both layers. The long-wave model describing travelling waves is constructed by means of a scaling procedure with a small Boussinesq parameter. It is demonstrated that solitary-wave regimes can be affected by the Kelvin–Helmholtz instability arising due to interfacial velocity shear in upstream flow.
20
Kribus, A., and S. Leibovich. "Instability of strongly nonlinear waves in vortex flows." Journal of Fluid Mechanics 269 (June 25, 1994): 247–64. http://dx.doi.org/10.1017/s0022112094001540.
Full textAbstract:
Weakly nonlinear descriptions of axisymmetric cnoidal and solitary waves in vortices recently have been shown to have strongly nonlinear counterparts. The linear stability of these strongly nonlinear waves to three-dimensional perturbations is studied, motivated by the problem of vortex breakdown in open flows. The basic axisymmetric flow varies both radially and axially, and the linear stability problem is therefore nonseparable. To regularize the generalization of a critical layer, viscosity is introduced in the perturbation problem. In the absence of the waves, the vortex flows are linearly stable. As the amplitude of a wave constituting the basic flow increases owing to variation in the level of swirl, stability is first lost to non-axisymmetric ‘bending’ modes. This instability occurs when the wave amplitude exceeds a critical value, provided that the Reynolds number is larger enough. The critical wave amplitudes for instability typically are large, but not large enough to create regions of closed streamlines. Examination of the most-amplified eigenvectors shows that the perturbations tend to be concentrated downstream of the maximum streamline displacement in the wave, in a position consistent with the observed three-dimensional perturbations in the interior of a bubble type of vortex breakdown.
21
Delale, Can F., Günter H. Schnerr, and Jürgen Zierep. "Asymptotic solution of shock tube flows with homogeneous condensation." Journal of Fluid Mechanics 287 (March 25, 1995): 93–118. http://dx.doi.org/10.1017/s0022112095000875.
Full textAbstract:
The asymptotic solution of shock tube flows with homogeneous condensation is presented for both smooth, or subcritical, flows and flows with an embedded shock wave, or supercritical flows. For subcritical flows an analytical expression, independent of the particular theory of homogeneous condensation to be employed, that determines the condensation wave front in the rarefaction wave is obtained by the asymptotic analysis of the rate equation along pathlines. The complete solution is computed by an algorithm which utilizes the classical nucleation theory and the Hertz–Knudsen droplet growth law. For supercritical flows four distinct flow regimes are distinguished along pathlines intersecting the embedded shock wave analogous to supercritical nozzle flows. The complete global solution for supercritical flows is discussed only qualitatively owing to the lack of a shock fitting technique for embedded shock waves. The results of the computations obtained by the subcritical algorithm show that most of the experimental data available exhibit supercritical flow behaviour and thereby the predicted onset conditions in general show deviations from the measured values. The causes of these deviations are reasoned by utilizing the qualitative global asymptotic solution of supercritical flows.
22
Thomas, Jim, K. Shafer Smith, and Oliver Bühler. "Near-inertial wave dispersion by geostrophic flows." Journal of Fluid Mechanics 817 (March 22, 2017): 406–38. http://dx.doi.org/10.1017/jfm.2017.124.
Full textAbstract:
We investigate theoretically and numerically the modulation of near-inertial waves by a larger-amplitude geostrophically balanced mean flow. Because the excited wave is initially trapped in the mixed layer, it projects onto a broad spectrum of vertical modes, each mode $n$ being characterized by a Burger number, $Bu_{n}$, proportional to the square of the vertical scale of the mode. Using numerical simulations of the hydrostatic Boussinesq equations linearized about a prescribed balanced background flow, we show that the evolution of the wave field depends strongly on the spectrum of $Bu_{n}$ relative to the Rossby number of the balanced flow, $\unicode[STIX]{x1D716}$, with smaller relative $Bu_{n}$ leading to smaller horizontal scales in the wave field, faster accumulation of wave amplitude in anticyclones and faster propagation of wave energy into the deep ocean. This varied behaviour of the wave may be understood by considering the dynamics in each mode separately; projecting the linearized hydrostatic Boussinesq equations onto modes yields a set of linear shallow water equations, with $Bu_{n}$ playing the role of the reduced gravity. The wave modes fall into two asymptotic regimes, defined by the scalings $Bu_{n}\sim O(1)$ for low modes and $Bu_{n}\sim O(\unicode[STIX]{x1D716})$ for high modes. An amplitude equation derived for the former regime shows that vertical propagation is weak for low modes. The high-mode regime is the basis of the Young & Ben Jelloul (J. Mar. Res., vol. 55, 1997, pp. 735–766) theory. This theory is here extended to $O(\unicode[STIX]{x1D716}^{2})$, from which amplitude equations for the subregimes $Bu_{n}\sim O(\unicode[STIX]{x1D716}^{1/2})$ and $Bu_{n}\sim O(\unicode[STIX]{x1D716}^{2})$ are derived. The accuracy of each approximation is demonstrated by comparing numerical solutions of the respective amplitude equation to simulations of the linearized shallow water equations in the same regime. We emphasize that since inertial wave energy and shear are distributed across vertical modes, their overall modulation is due to the collective behaviour of the wave field in each regime. A unified treatment of these regimes is a novel feature of this work.
23
Viroulet, S., J. L. Baker, F. M. Rocha, C. G. Johnson, B. P. Kokelaar, and J. M. N. T. Gray. "The kinematics of bidisperse granular roll waves." Journal of Fluid Mechanics 848 (June 13, 2018): 836–75. http://dx.doi.org/10.1017/jfm.2018.348.
Full textAbstract:
Small perturbations to a steady uniform granular chute flow can grow as the material moves downslope and develop into a series of surface waves that travel faster than the bulk flow. This roll wave instability has important implications for the mitigation of hazards due to geophysical mass flows, such as snow avalanches, debris flows and landslides, because the resulting waves tend to merge and become much deeper and more destructive than the uniform flow from which they form. Natural flows are usually highly polydisperse and their dynamics is significantly complicated by the particle size segregation that occurs within them. This study investigates the kinematics of such flows theoretically and through small-scale experiments that use a mixture of large and small glass spheres. It is shown that large particles, which segregate to the surface of the flow, are always concentrated near the crests of roll waves. There are different mechanisms for this depending on the relative speed of the waves, compared to the speed of particles at the free surface, as well as on the particle concentration. If all particles at the surface travel more slowly than the waves, the large particles become concentrated as the shock-like wavefronts pass them. This is due to a concertina-like effect in the frame of the moving wave, in which large particles move slowly backwards through the crest, but travel quickly in the troughs between the crests. If, instead, some particles on the surface travel more quickly than the wave and some move slower, then, at low concentrations, large particles can move towards the wave crest from both the forward and rearward sides. This results in isolated regions of large particles that are trapped at the crest of each wave, separated by regions where the flow is thinner and free of large particles. There is also a third regime arising when all surface particles travel faster than the waves, which has large particles present everywhere but with a sharp increase in their concentration towards the wave fronts. In all cases, the significantly enhanced large particle concentration at wave crests means that such flows in nature can be especially destructive and thus particularly hazardous.
24
Sutherland, B. R. "Rayleigh Wave–Internal Wave Coupling and Internal Wave Generation above a Model Jet Stream." Journal of the Atmospheric Sciences 63, no. 3 (March 1, 2006): 1042–55. http://dx.doi.org/10.1175/jas3658.1.
Full textAbstract:
Abstract Linear theory for modes in a nonuniformly stratified, semi-infinite shear flow demonstrates that Rayleigh waves (stable waves propagating in fluid with spatially varying shear) couple with evanescent internal waves. If the bulk Richardson number (the squared ratio of the buoyancy frequency and shear) lies between 1/4 and 1, the waves have infinite e-folding depth for waves with critical relative horizontal wavenumbers. Fully nonlinear numerical simulations examine the effect of Rayleigh wave–internal wave coupling when the shear layer is localized and is thus Kelvin–Helmholtz unstable. Diagnostics examining profiles of the wave-induced mean flow show that if the bulk Richardson number is of order unity, significant momentum is extracted from a shear layer as a consequence of transport by waves. The work is extended to the study of unstable jet flows and applications of this work for internal wave generation by dynamic instability of the upper flank of the jet stream are discussed.
25
Delisi, Donald P., and Timothy J. Dunkerton. "Laboratory Observations of Gravity Wave, Critical Layer Flows Using Single and Double Wave Forcing." Applied Mechanics Reviews 47, no. 6S (June 1, 1994): S113—S117. http://dx.doi.org/10.1115/1.3124384.
Full textAbstract:
Laboratory measurements of gravity wave, critical layer flows are presented. The measurements are obtained in a salt-stratified annular tank, with a vertical shear profile. Internal gravity waves are generated at the floor of the tank and propagate vertically upward into the fluid. At a depth where the phase speed of the wave equals the mean flow speed, defined as a critical level, the waves break down, under the right forcing conditions, generating small scale turbulence. Two cases are presented. In the first case, the wave forcing is a single, monochromatic wave. In this case, the early wave breaking is characterized as Kelvin-Helmholtz breaking at depths below the critical level. Later wave breaking is characterized by weak overturning in the upper part of the tank and regular, internal mixing regions in the lower part of the tank. In the second case, the wave forcing is two monochromatic waves, each propagating with a different phase speed. In this case, the early wave breaking is again Kelvin-Helmholtz in nature, but later wave breaking is characterized by sustained overturning in the upper part of the tank with internal mixing regions in the lower part of the tank. Mean velocity profiles are obtained both before and during the experiments.
26
Katsis, C., and T. R. Akylas. "Wind-Generated Surface Waves on a Viscous Fluid." Journal of Applied Mechanics 52, no. 1 (March 1, 1985): 208–12. http://dx.doi.org/10.1115/1.3168999.
Full textAbstract:
The excitation of surface waves on a viscous fluid by shear flows is studied. Turbulent and laminar air flows over oil of low and high viscosity are considered. It is found that the dominant wave-generation mechanism depends crucially on the shear-flow profile: for a turbulent flow, long surface waves are generated at low wind speeds due to the work done by the stress components in phase with the surface slope, while Kelvin-Helmholtz instability is responsible for the excitation of short waves at higher wind speeds. On the other hand, for a laminar shear flow, direct resonance between surface waves and Tollmien-Schlichting waves in the shear flow is the dominant wave-generation mechanism.
27
SHATS, MICHAEL, HORST PUNZMANN, NICOLAS FRANCOIS, and HUA XIA. "WAVE-GENERATED FLOWS ON THE WATER SURFACE." International Journal of Modern Physics: Conference Series 42 (January 2016): 1660179. http://dx.doi.org/10.1142/s2010194516601794.
Full textAbstract:
Predicting trajectories of fluid parcels on the water surface perturbed by waves is a difficult mathematical and theoretical problem. It is even harder to model flows generated on the water surface due to complex three-dimensional wave fields, which commonly result from the modulation instability of planar waves. We have recently shown that quasi-standing, or Faraday, waves are capable of generating horizontal fluid motions on the water surface whose statistical properties are very close to those in two-dimensional turbulence. This occurs due to the generation of horizontal vortices. Here we show that progressing waves generated by a localized source are also capable of creating horizontal vortices. The interaction between such vortices can be controlled and used to create stationary surface flows of desired topology. These results offer new methods of surface flow generation, which allow engineering inward and outward surface jets, large-scale vortices and other complex flows. The new principles can be also be used to manipulate floaters on the water surface and to form well-controlled Lagrangian coherent structures on the surface. The resulting flows are localized in a narrow layer near the surface, whose thickness is less than one wavelength.
28
Bell, M. J. "The nonlinear evolution of a slowly growing wave on a laterally sheared baroclinic flow." Journal of Fluid Mechanics 241 (August 1992): 615–43. http://dx.doi.org/10.1017/s0022112092002179.
Full textAbstract:
Wave disturbances to baroclinic flows produce cyclones in the atmosphere and eddies in the oceans and have been extensively studied in laboratory experiments with differentially heated annuli of rotating fluid. Related analytical studies have concentrated mainly on the development of slowly growing waves on laterally uniform zonal flows. Neutral inviscid waves on such flows do not advect their own potential vorticity field whereas neutral waves on most laterally sheared baroclinic flows do. Scaling arguments suggest that on these laterally sheared flows the harmonics generated by the neutral waves play the dominant role in arresting the initial growth of weakly unstable waves. The arrest of a wave is chiefly accomplished by fully nonlinear advection within a critical layer centred on the wave's steering level whose depth is proportional to the wave's amplitude. Explicit numerical solutions illustrating these points are presented for a case in which the critical level is non-singular and the inviscid calculations comparatively straightforward. The stability of the solutions and the effects of diffusive fluxes on them are discussed. Potential vorticity diagnostics for a numerical simulation of a wave flow in a rotating annulus near the axisymmetric transition show that distortion of the wave's potential vorticity field is mainly confined to the vicinity of the steering level. Assumptions and approximations made in the explicit calculations which are of doubtful validity for this flow are highlighted.
29
JALIKOP, SHREYAS V., and ANNE JUEL. "Steep capillary-gravity waves in oscillatory shear-driven flows." Journal of Fluid Mechanics 640 (November 10, 2009): 131–50. http://dx.doi.org/10.1017/s0022112009991509.
Full textAbstract:
We study steep capillary-gravity waves that form at the interface between two stably stratified layers of immiscible liquids in a horizontally oscillating vessel. The oscillatory nature of the external forcing prevents the waves from overturning, and thus enables the development of steep waves at large forcing. They arise through a supercritical pitchfork bifurcation, characterized by the square root dependence of the height of the wave on the excess vibrational Froude number (W, square root of the ratio of vibrational to gravitational forces). At a critical valueWc, a transition to a linear variation inWis observed. It is accompanied by sharp qualitative changes in the harmonic content of the wave shape, so that trochoidal waves characterize the weakly nonlinear regime, but ‘finger’-like waves form forW≥Wc. In this strongly nonlinear regime, the wavelength is a function of the product of amplitude and frequency of forcing, whereas forW<Wc, the wavelength exhibits an explicit dependence on the frequency of forcing that is due to the effect of viscosity. Most significantly, the radius of curvature of the wave crests decreases monotonically withWto reach the capillary length forW=Wc, i.e. the lengthscale for which surface tension forces balance gravitational forces. ForW<Wc, gravitational restoring forces dominate, but forW≥Wc, the wave development is increasingly defined by localized surface tension effects.
30
Ma, Peifeng, and Ole Secher Madsen. "A 3D SEDIMENT TRANSPORT MODEL FOR COMBINED WAVE-CURRENT FLOWS." Coastal Engineering Proceedings 1, no. 33 (October 18, 2012): 21. http://dx.doi.org/10.9753/icce.v33.sediment.21.
Full textAbstract:
Accurate prediction of current velocity and bottom shear stress, which both can be significantly influenced by wind waves, is essential for sediment transport predictions in the coastal environment. Consequently wind-wave effects must be taken into account in a numerical sediment transport model for application in coastal waters. In the present study, elements of a large-scale 3D numerical coastal circulation and sediment transport model are developed to predict net, i.e. the wave-period-averaged, sediment transport rates. The sediment transport components considered are (i) bed-load transport; (ii) mean suspended load sediment transport within the wave boundary layer, which is obtained from an analytical solution; and (iii) suspended load sediment transport above the wave bottom boundary layer, which is obtained from a numerical model. In all model components wind wave effects are accounted for through simple analytical models. Thus, the roughness prescribed for the hydrodynamic part of the numerical coastal circulation model is the apparent roughness, i.e. the roughness experienced by a slowly varying current in the presence of waves. Similarly, the reference concentration specified for the sediment transport part of the numerical model is obtained from analytical solutions for suspended sediment concentrations within the combined wave-current bottom boundary layer. Stratification effects caused by suspended sediment are included in the large-scale numerical sediment transport model. Results of idealized tests suggest that wind wave effects can be pronounced, e.g. in some typical coastal scenarios sediment can only be mobilized when wind waves are present and accounted for. It is also shown that stratification can significantly affect suspended sediment transport rates of fine sediments.
31
LIU, PHILIP L. F., YONG SUNG PARK, and JAVIER L. LARA. "Long-wave-induced flows in an unsaturated permeable seabed." Journal of Fluid Mechanics 586 (August 14, 2007): 323–45. http://dx.doi.org/10.1017/s0022112007007057.
Full textAbstract:
We present both analytical and numerical solutions describing seepage flows in an unsaturated permeable seabed induced by transient long waves. The effects of compressibility of pore water in the seabed due to a small degree of unsaturation are considered in the investigation. To make the problem tractable analytically, we first focus our attention on situations where the horizontal scale of the seepage flow is much larger than the vertical scale. With this simplification the pore-water pressure in the soil column is governed by a one-dimensional diffusion equation with a specified pressure at the water–seabed interface and the no-flux condition at the bottom of the seabed. Analytical solutions for pore-water pressure and velocity are obtained for arbitrary transient waves. Special cases are studied for periodic waves, cnoidal waves, solitary waves and bores. Numerical solutions are also obtained by simultaneously solving the Navier–Stokes equations for water wave motions and the exact two-dimensional diffusion equation for seepage flows in the seabed. The analytical solutions are used to check the accuracy of the numerical methods. On the other hand, numerical solutions extend the applicability of the analytical solutions. The liquefaction potential in a permeable bed as well as the energy dissipation under various wave conditions are then discussed.
32
Gao, Jie, Ming Wei, Yunning Liu, Qun Zheng, and Ping Dong. "Experimental and numerical investigations of hole injection on the suction side throat of transonic turbine vanes in a cascade with trailing edge injection." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 232, no. 8 (February 27, 2017): 1454–66. http://dx.doi.org/10.1177/0954410017694918.
Full textAbstract:
Trailing-edge mixing flows associated with coolant injection are complex, in particular at transonic flows, and result in significant aerodynamics losses. The objective of this paper is to evaluate the impacts of hole injection near the suction side throat on shock wave control and aerodynamic losses. A series of tests and calculations on effects of hole injection on the suction-side throat of a high-pressure turbine vane cascade with and without trailing-edge injection were conducted. Wake traverses with a five-hole probe and tests of pressure distributions on the turbine profile were taken for total injection mass flow ratios of 0% and 1.2% under test Mach numbers of 0.7, 0.78, and 0.87. Meantime, numerical predictions are carried out for exit isentropic Mach numbers of 0.7, 0.78, 0.87, and 1.1 and hole-injection mass flow ratios of 0%, 0.17%, 0.3%, and 0.89%. Numerical predictions show a reasonable agreement with the experimental data, and wake total pressure losses and flow angles as well as pressure distributions on the turbine profile were compared to calculations without hole injection, indicating a significant effect of hole injection on the profile wake development and its blockage effect on the shock-wave flow in the vane cascade passage. At subsonic flows, the hole injection on the suction side throat thickens the suction-side boundary layer, and increases the flow mixing, thus causing increased wake losses and flow angles. At transonic flows, while the trailing-edge injection reduces the strength of the shock wave at the trailing-edge pressure side, the hole injection on the suction side throat alters the local pressure fields, and then tends to enhance the shock-wave at the trailing-edge pressure-side; however, it seems to reduce the strength of the shock-wave at the trailing-edge suction side.
33
NIKORA, VLADIMIR I., ALEXANDER N. SUKHODOLOV, and PAWEL M. ROWINSKI. "Statistical sand wave dynamics in one-directional water flows." Journal of Fluid Mechanics 351 (November 25, 1997): 17–39. http://dx.doi.org/10.1017/s0022112097006708.
Full textAbstract:
Moving sand waves and the overlying tubulent flow were measured on the Wilga River in Poland, and the Tirnava Mica and Buzau Rivers in Romania. Bottom elevations and flow velocities were measured at six points simultaneously by multi-channel measuring systems. From these data, the linear and two-dimensional sections of the three-dimensional correlation and structure functions and various projections of sand wave three-dimensional spectra were investigated.It was found that the longitudinal wavenumber spectra of the sand waves in the region of large wavenumbers followed Hino's −3 law (S(Kx) ∝K−3x) quite satisfactorily, confirming the theoretical predictions of Hino (1968) and Jain & Kennedy (1974). However, in contrast to Hino (1968), the sand wave frequency spectrum in the high-frequency region was approximated by a power function with the exponent −2, while in the lower-frequency region this exponent is close to −3.A dispersion relation for sand waves has been investigated from analysis of structure functions, frequency spectra and the cross-correlation functions method. For wavelengths less than 0.15–0.25 of the flow depth, their propagation velocity C is inversely proportional to the wavelength λ. When the wavelengths of spectral components are as large as 3–4 times the flow depth, no dispersion occurs. These results proved to be in good qualitative agreement with the theoretical dispersion relation derived from the potential-flow-based analytical models (Kennedy 1969; Jain & Kennedy 1974). We also present another, physically-based, explanation of this phenomenon, introducing two types of sand movement in the form of sand waves. The first type (I) is for the region of large wavenumbers (small wavelengths) and the second one (II) is for the region of small wavenumbers (large wavelengths). The small sand waves move due to the motion of individual sand particles (type I, C∝λ−1) while larger sand waves propagate as a result of the motion of smaller waves on their upstream slopes (type II, C∝λ0). Like the sand particles in the first type, these smaller waves redistribute sand from upstream slopes to downstream ones. Both types result in sand wave movement downstream but with a different propagation velocity.The main characteristics of turbulence, as well as the quantitative values characterizing the modulation of turbulence by sand waves, are also presented.
34
Savva, Miles A. C., and Jacques Vanneste. "Scattering of internal tides by barotropic quasigeostrophic flows." Journal of Fluid Mechanics 856 (October 5, 2018): 504–30. http://dx.doi.org/10.1017/jfm.2018.694.
Full textAbstract:
Oceanic internal tides and other inertia–gravity waves propagate in an energetic turbulent flow whose length scales are similar to the wavelengths. Advection and refraction by this flow cause the scattering of the waves, redistributing their energy in wavevector space. As a result, initially plane waves radiated from a source such as a topographic ridge become spatially incoherent away from the source. To examine this process, we derive a kinetic equation which describes the statistics of the scattering under the assumptions that the flow is quasigeostrophic, barotropic and well represented by a stationary homogeneous random field. Energy transfers are quantified by computing a scattering cross-section and shown to be restricted to waves with the same frequency and identical vertical structure, hence the same horizontal wavelength. For isotropic flows, scattering leads to an isotropic wave field. We estimate the characteristic time and length scales of this isotropisation, and study their dependence on parameters including the energy spectrum of the flow. Simulations of internal tides generated by a planar wavemaker carried out for the linearised shallow-water model confirm the pertinence of these scales. A comparison with the numerical solution of the kinetic equation demonstrates the validity of the latter and illustrates how the interplay between wave scattering and transport shapes the wave statistics.
35
Yang, Di, and Lian Shen. "Direct numerical simulation of scalar transport in turbulent flows over progressive surface waves." Journal of Fluid Mechanics 819 (April 18, 2017): 58–103. http://dx.doi.org/10.1017/jfm.2017.164.
Full textAbstract:
The transport of passive scalars in turbulent flows over progressive water waves is studied using direct numerical simulation. A combined pseudo-spectral and finite-difference scheme on a wave-surface-fitted grid is used to simulate the flow and scalar fields above the wave surface. Three representative wave ages (i.e. wave-to-wind speed ratios) are considered, corresponding to slow, intermediate and fast wind-waves, respectively. For each wave condition, four Schmidt numbers are considered for the scalar transport. The presence of progressive surface waves is found to induce significant wave-phase-correlated variation to the scalar field, with the phase dependence varying with the wave age. The time- and plane-averaged profiles of the scalar over waves of various ages exhibit similar vertical structures as those found in turbulence over a flat wall, but with the von Kármán constant and effective wave surface roughness for the mean scalar profile exhibiting considerable variation with the wave age. The profiles of the root-mean-square scalar fluctuations and the horizontal scalar flux exhibit good scaling in the viscous sublayer that agrees with the scaling laws previously reported for flat-wall turbulence, but with noticeable wave-induced variation in the viscous wall region. The profiles of the vertical scalar flux in the viscous sublayer exhibit apparent discrepancies from the reported scaling law for flat-wall turbulence, due to a negative vertical flux region above the windward face of the wave crest. Direct observation and quadrant-based conditional averages indicate that the wave-dependent distributions of the scalar fluctuations and fluxes are highly correlated with the coherent vortical structures in the turbulence, which exhibit clear wave-dependent characteristics in terms of both shape and preferential location.
36
Zhang, Rui Jin, Hong Yue Sun, Hong Zhan Zhang, and Hosoyamada Tokuzo. "Numerical Study for Water Waves Generated by Debris Flow." Advanced Materials Research 671-674 (March 2013): 388–92. http://dx.doi.org/10.4028/www.scientific.net/amr.671-674.388.
Full textAbstract:
Earthquake or rainfall can arouse landslide, which will cause debris flow. Free surface water waves generated by plunging of debris flow cause devastating damage on human life. In this study, a numerical scheme for debris flow and free surface water wave was developed based on shallow water approximation, in which the interaction between these two flows was included newly. Generation of waves by plunging of debris flow is highly non-linear phenomena. Original CIP method and first order up-wind scheme mixed with second order central derivative scheme were adopted to simulate collision of two initially separated fluids (debris flow and still water). Six cases have been adopted to simulate the generation, propagation and run-up of water waves generated by debris flow. The time series of these two flows for these six calculating cases show the interaction of these two flows. Numerical results for interaction of debris flow and generated water wave are quite satisfactory and reasonable.
37
Constantin, Adrian. "Some Three-Dimensional Nonlinear Equatorial Flows." Journal of Physical Oceanography 43, no. 1 (January 1, 2013): 165–75. http://dx.doi.org/10.1175/jpo-d-12-062.1.
Full textAbstract:
Abstract This study presents some explicit exact solutions for nonlinear geophysical ocean waves in the β-plane approximation near the equator. The solutions are provided in Lagrangian coordinates by describing the path of each particle. The unidirectional equatorially trapped waves are symmetric about the equator and propagate eastward above the thermocline and beneath the near-surface layer to which wind effects are confined. At each latitude the flow pattern represents a traveling wave.
38
HALL, PHILIP, and SPENCER SHERWIN. "Streamwise vortices in shear flows: harbingers of transition and the skeleton of coherent structures." Journal of Fluid Mechanics 661 (August 16, 2010): 178–205. http://dx.doi.org/10.1017/s0022112010002892.
Full textAbstract:
The relationship between asymptotic descriptions of vortex–wave interactions and more recent work on ‘exact coherent structures’ is investigated. In recent years immense interest has been focused on so-called self-sustained processes in turbulent shear flows where the importance of waves interacting with streamwise vortex flows has been elucidated in a number of papers. In this paper, it is shown that the so-called ‘lower branch’ state which has been shown to play a crucial role in these self-sustained processes is a finite Reynolds number analogue of a Rayleigh vortex–wave interaction with scales appropriately modified from those for external flows to Couette flow, the flow of interest here. Remarkable agreement between the asymptotic theory and numerical solutions of the Navier–Stokes equations is found even down to relatively small Reynolds numbers, thereby suggesting the possible importance of vortex–wave interaction theory in turbulent shear flows. The relevance of the work to more general shear flows is also discussed.
39
Ligrani, P. M., C. Saumweber, A. Schulz, and S. Wittig. "Shock Wave–Film Cooling Interactions in Transonic Flows." Journal of Turbomachinery 123, no. 4 (February 1, 2001): 788–97. http://dx.doi.org/10.1115/1.1397305.
Full textAbstract:
Interactions between shock waves and film cooling are described as they affect magnitudes of local and spanwise-averaged adiabatic film cooling effectiveness distributions. A row of three cylindrical holes is employed. Spanwise spacing of holes is 4 diameters, and inclination angle is 30 deg. Free-stream Mach numbers of 0.8 and 1.10–1.12 are used, with coolant to free-stream density ratios of 1.5–1.6. Shadowgraph images show different shock structures as the blowing ratio is changed, and as the condition employed for injection of film into the cooling holes is altered. Investigated are film plenum conditions, as well as perpendicular film injection crossflow Mach numbers of 0.15, 0.3, and 0.6. Dramatic changes to local and spanwise-averaged adiabatic film effectiveness distributions are then observed as different shock wave structures develop in the immediate vicinity of the film-cooling holes. Variations are especially evident as the data obtained with a supersonic Mach number are compared to the data obtained with a free-stream Mach number of 0.8. Local and spanwise-averaged effectiveness magnitudes are generally higher when shock waves are present when a film plenum condition (with zero crossflow Mach number) is utilized. Effectiveness values measured with a supersonic approaching free-stream and shock waves then decrease as the injection crossflow Mach number increases. Such changes are due to altered flow separation regions in film holes, different injection velocity distributions at hole exits, and alterations of static pressures at film hole exits produced by different types of shock wave events.
40
Smith, Jerome A. "A Bistatic Phased-Array Doppler Sonar for Wave–Current Research." Journal of Atmospheric and Oceanic Technology 31, no. 7 (July 1, 2014): 1628–41. http://dx.doi.org/10.1175/jtech-d-13-00187.1.
Full textAbstract:
Abstract Wave breaking and wave-forced flows are important to air–sea interactions and to the transport and dispersal of materials at sea. But recent measurements have shown a discrepancy in the Eulerian response to wave groups compared to scientists’ current theoretical understanding of wave–current interactions. Flow structures on scales of centimeters to meters occur underneath breaking waves, and larger-scale flows are driven by wave–current interactions (e.g., Langmuir circulation, alongshore flows). Such details of the vertically resolved flow are just beginning to be modeled, and observational guidance is needed. Here a new instrument is described that is intended to measure waves and currents over a 2D vertical plane underwater, resolving two components of velocity on this plane. Initial observations were made near the Scripps Pier (La Jolla, California), where steep waves and strong currents can be reliably found, yet logistics are not too burdensome. To get the spatial resolution desired using 200-kHz sound, ping-to-ping “coherent processing” would have be used for Doppler estimation; however, near shore the reverberations remain too strong for far too long to get any coherence, unlike the previous experience in deep water. In view of this, using much higher frequencies (>1 MHz) with “incoherent processing” is suggested; the increased attenuation at higher frequencies then would subdue the reverberation problem, but with comparable space–time resolution.
41
RUYER-QUIL, C., P. TREVELEYAN, F. GIORGIUTTI-DAUPHINÉ, C. DUPRAT, and S. KALLIADASIS. "Modelling film flows down a fibre." Journal of Fluid Mechanics 603 (April 30, 2008): 431–62. http://dx.doi.org/10.1017/s0022112008001225.
Full textAbstract:
Consider the gravity-driven flow of a thin liquid film down a vertical fibre. A model of two coupled evolution equations for the local film thickness h and the local flow rate q is formulated within the framework of the long-wave and boundary-layer approximations. The model accounts for inertia and streamwise viscous diffusion. Evolution equations obtained by previous authors are recovered in the appropriate limit. Comparisons to experimental results show good agreement in both linear and nonlinear regimes. Viscous diffusion effects are found to have a stabilizing dispersive effect on the linear waves. Time-dependent computations of the spatial evolution of the film reveal a strong influence of streamwise viscous diffusion on the dynamics of the flow and the wave selection process.
42
KALADZE, T. D., D. J. WU, O. A. POKHOTELOV, R. Z. SAGDEEV, L. STENFLO, and P. K. SHUKLA. "Rossby-wave driven zonal flows in the ionospheric E-layer." Journal of Plasma Physics 73, no. 1 (February 2007): 131–40. http://dx.doi.org/10.1017/s0022377806004351.
Full textAbstract:
Abstract.A novel mechanism for the generation of large-scale zonal flows by small-scale Rossby waves in the Earth's ionospheric E-layer is considered. The generation mechanism is based on the parametric excitation of convective cells by finite amplitude magnetized Rossby waves. To describe this process a generalized Charney equation containing both vector and scalar (Korteweg–de Vries type) nonlinearities is used. The magnetized Rossby waves are supposed to have arbitrary wavelengths (as compared with the Rossby radius). A set of coupled equations describing the nonlinear interaction of magnetized Rossby waves and zonal flows is obtained. The generation of zonal flows is due to the Reynolds stresses produced by finite amplitude magnetized Rossby waves. It is found that the wave vector of the fastest growing mode is perpendicular to that of the magnetized Rossby pump wave. Explicit expression for the maximum growth rate as well as for the optimal spatial dimensions of the zonal flows are obtained. A comparison with existing results is carried out. The present theory can be used for the interpretation of the observations of Rossby-type waves in the Earth's ionosphere.
43
WEBB, G. M., A. ZAKHARIAN, and G. P. ZANK. "Wave mixing and instabilities in cosmic-ray-modified shocks and flows." Journal of Plasma Physics 61, no. 4 (May 1999): 553–99. http://dx.doi.org/10.1017/s0022377898007466.
Full textAbstract:
Wave mixing equations describing the interaction of short-wavelength sound waves and entropy waves in two-fluid cosmic ray hydrodynamics in a non-uniform, large-scale, background flow in one Cartesian space dimension are investigated. The wave interaction coefficients depend on large-scale gradients in the background flow, and consist of two physically distinct components. The first component consists of wave-damping terms due to the diffusing cosmic rays, plus squeezing instability terms associated with the large-scale cosmic ray pressure gradient. These effects were first investigated by Drury and Dorfi in a study of the propagation of short-wavelength WKB sound waves in cosmic-ray-modified flows and shocks. The second component describes gas dynamical wave mixing effects due to gradients of the gas entropy S and the gas dynamical Riemann invariants (R±) of the background flow. A Green function solution is used to illustrate the coupling of the backward and forward sound waves for the case of a uniform background flow, in which the coupling coefficients depend on the parameter α = a2c/2κ, where ac is the cosmic-ray ‘sound speed’ and κ is the hydrodynamical cosmic-ray diffusion coefficient. Analytical WKB approximation methods and numerical simulations are used to investigate the modifications of the cosmic ray squeezing instability by wave mixing in cosmic-ray-modified shocks and pressure balance structures. Astrophysical applications to instabilities in supernova remnant shocks are discussed.
44
Erwina, Novry, Didit Adytia, Sri Redjeki Pudjaprasetya, and Toni Nuryaman. "Staggered Conservative Scheme for 2-Dimensional Shallow Water Flows." Fluids 5, no. 3 (August 31, 2020): 149. http://dx.doi.org/10.3390/fluids5030149.
Full textAbstract:
Simulating discontinuous phenomena such as shock waves and wave breaking during wave propagation and run-up has been a challenging task for wave modeller. This requires a robust, accurate, and efficient numerical implementation. In this paper, we propose a two-dimensional numerical model for simulating wave propagation and run-up in shallow areas. We implemented numerically the 2-dimensional Shallow Water Equations (SWE) on a staggered grid by applying the momentum conserving approximation in the advection terms. The numerical model is named MCS-2d. For simulations of wet–dry phenomena and wave run-up, a method called thin layer is used, which is essentially a calculation of the momentum deactivated in dry areas, i.e., locations where the water thickness is less than the specified threshold value. Efficiency and robustness of the scheme are demonstrated by simulations of various benchmark shallow flow tests, including those with complex bathymetry and wave run-up. The accuracy of the scheme in the calculation of the moving shoreline was validated using the analytical solutions of Thacker 1981, N-wave by Carrier et al., 2003, and solitary wave in a sloping bay by Zelt 1986. Laboratory benchmarking was performed by simulation of a solitary wave run-up on a conical island, as well as a simulation of the Monai Valley case. Here, the embedded-influxing method is used to generate an appropriate wave influx for these simulations. Simulation results were compared favorably to the analytical and experimental data. Good agreement was reached with regard to wave signals and the calculation of moving shoreline. These observations suggest that the MCS method is appropriate for simulations of varying shallow water flow.
45
Grisouard, Nicolas, and Oliver Bühler. "Forcing of oceanic mean flows by dissipating internal tides." Journal of Fluid Mechanics 708 (August 8, 2012): 250–78. http://dx.doi.org/10.1017/jfm.2012.303.
Full textAbstract:
AbstractWe present a theoretical and numerical study of the effective mean force exerted on an oceanic mean flow due to the presence of small-amplitude internal waves that are forced by the oscillatory flow of a barotropic tide over undulating topography and are also subject to dissipation. This extends the classic lee-wave drag problem of atmospheric wave–mean interaction theory to a more complicated oceanographic setting, because now the steady lee waves are replaced by oscillatory internal tides and, most importantly, because now the three-dimensional oceanic mean flow is defined by time averaging over the fast tidal cycles rather than by the zonal averaging familiar from atmospheric theory. Although the details of our computation are quite different, we recover the main action-at-a-distance result from the atmospheric setting, namely that the effective mean force that is felt by the mean flow is located in regions of wave dissipation, and not necessarily near the topographic wave source. Specifically, we derive an explicit expression for the effective mean force at leading order using a perturbation series in small wave amplitude within the framework of generalized Lagrangian-mean theory, discuss in detail the range of situations in which a strong, secularly growing mean-flow response can be expected, and then compute the effective mean force numerically in a number of idealized examples with simple topographies.
46
Guha, Anirban, and Firdaus E. Udwadia. "Nonlinear dynamics induced by linear wave interactions in multilayered flows." Journal of Fluid Mechanics 816 (March 6, 2017): 412–27. http://dx.doi.org/10.1017/jfm.2017.84.
Full textAbstract:
Using simple kinematics, we propose a general theory of linear wave interactions between the interfacial waves of a two-dimensional (2D), inviscid, multilayered fluid system. The strength of our formalism is that one does not have to specify the physics of the waves in advance. Wave interactions may lead to instabilities, which may or may not be of the familiar ‘normal-mode’ type. Contrary to intuition, the underlying dynamical system describing linear wave interactions is found to be nonlinear. Specifically, a saw-tooth jet profile with three interfaces possessing kinematic and geometric symmetry is explored. Fixed points of the system for different ranges of a Froude number like control parameter $\unicode[STIX]{x1D6FE}$ are derived, and their stability evaluated. Depending upon the initial condition and $\unicode[STIX]{x1D6FE}$, the dynamical system may reveal transient growth, weakly positive Lyapunov exponents, as well as different nonlinear phenomena such as the formation of periodic and pseudo-periodic orbits. All these occur for those ranges of $\unicode[STIX]{x1D6FE}$ where normal-mode theory predicts neutral stability. Such rich nonlinear phenomena are not observed in a 2D dynamical system resulting from the two-wave problem, which reveals only stable and unstable nodes.
47
Campbell, Bryce K., and Yuming Liu. "Nonlinear resonant interactions of interfacial waves in horizontal stratified channel flows." Journal of Fluid Mechanics 717 (February 1, 2013): 612–42. http://dx.doi.org/10.1017/jfm.2012.598.
Full textAbstract:
AbstractWe consider the problem of nonlinear resonant interactions of interfacial waves with the presence of a linear interfacial instability in an inviscid two-fluid stratified flow through a horizontal channel. The resonant triad consists of a (linearly) unstable wave and two stable waves, one of which has a wavelength that can be much longer than that of the unstable component. Of special interest is the development of the long wave by energy transfer from the base flow due to the coupled effect of nonlinear resonance and interfacial instability. By use of the method of multiple scales, we derive the interaction equations which govern the time evolution of the amplitudes of the interacting waves including the effect of interfacial instability. The solution of the evolution equations shows that depending on the flow conditions, the (stable) long wave can achieve a bi-exponential growth rate through the resonant interaction with the unstable wave. Moreover, the unstable wave can grow unboundedly even when the nonlinear self-interaction effect is included, as do the stable waves in the associated resonant triad. For the verification of the theoretical analysis and the practical application involving a broadbanded spectrum of waves, we develop an effective direct simulation method, based on a high-order pseudo-spectral approach, which accounts for nonlinear interactions of interfacial waves up to an arbitrary high order. The direct numerical simulations compare well with the theoretical analysis for all of the characteristic flows considered, and agree qualitatively with the experimental observation of slug development near the entrance of two-phase flow into a pipe.
48
DELALE, C. F., and D. G. CRIGHTON. "Prandtl–Meyer flows with homogeneous condensation. Part 1. Subcritical flows." Journal of Fluid Mechanics 359 (March 25, 1998): 23–47. http://dx.doi.org/10.1017/s0022112097008379.
Full textAbstract:
Prandtl–Meyer flows with heat addition from homogeneous condensation not exceeding a critical value (subcritical flows) are investigated by an asymptotic method in the double limit of a large nucleation time followed by a small droplet growth time. The physically distinct condensation zones, with detailed analytical structure, are displayed along streamlines and the flow field in each zone is determined utilizing the asymptotic solution of the rate equation along streamlines. In particular the nucleation wave front, which corresponds to states of maximum nucleation along streamlines, is accurately located independently of the particular condensation model employed. Results obtained using the classical nucleation equation together with the Hertz–Knudsen droplet growth law show, despite qualitative agreement, considerable differences between the nucleation wave fronts and measured onset conditions for the experiments of Smith (1971), because of intersecting characteristics in the heat addition zones. This shows the necessity of including an embedded oblique shock wave in the expansion fan of corner expansion flows for the cases investigated.
49
Wargula, Anna, Britt Raubenheimer, Steve Elgar, Jia-Lin Chen, and Fengyan Shi. "TIME-VARYING WAVE EFFECTS ON FLOWS AND DYNAMICS AT AN UNSTRATIFIED INLET." Coastal Engineering Proceedings, no. 36 (December 30, 2018): 45. http://dx.doi.org/10.9753/icce.v36.currents.45.
Full textAbstract:
Surface gravity waves alter discharge and circulation near and within coastal inlets, affecting the exchange and transport of water masses, nutrients, sediments, and pollutants between inland waters and the ocean. Field observations and numerical simulations suggest that, during storms, wave forcing (radiation-stress gradients) owing to wave dissipation across the ebb shoal can enhance fluxes into the inlet (Bertin et al. 2009; Wargula et al. 2014). As a result, water levels may increase inside the bay (Olabarrieta et al. 2011; Dodet et al. 2013), creating an offshore-directed pressure gradient that may balance onshore fluxes during energetic waves, and may enhance offshore fluxes after the waves decrease. Spatial and tidal variability in water depths on the ebb shoal lead to complex wave breaking patterns that drive spatially and tidally asymmetric flows. Here, field observations and numerical simulations are used to evaluate the effects of waves on discharge and circulation, and the relative importance of wave radiation-stress and pressure gradients at an unstratified inlet during and following energetic waves.
50
Thompson, Alex C. "NUMERICAL MODEL OF BREAKWATER WAVE FLOWS." Coastal Engineering Proceedings 1, no. 21 (January 29, 1988): 149. http://dx.doi.org/10.9753/icce.v21.149.
Full textAbstract:
A mathematical model of flow on a sloping breakwater face is described and results of calculations compared with some experimental results to show how the model can be calibrated. Flow above the surface of the slope is represented by the shallow water wave equations solved by a finite difference method. Flow within the breakwater is calculated by one of two methods. A solution of the linear seepage flow equations, again using finite differences or a simplified model of inflow can be used. Experimental results for runup and reflection coefficient are from tests performed at HRL Wallingford.