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The influence of the length-to-depth aspect ratio and of wall asymmetry on the main vortical flow structures evolving in rectangular two-dimensional deep cavities is studied experimentally using wall-pressure and particle image velocimetry (PIV) measurements. Wall-pressure and cavity flow statistics have been analyzed and shown that the flow features are strongly affected especially by the asymmetry. An emphasis is given concerning the behavior of the shear layer oscillations that are compared to the analytical deep-cavity model prediction proposed by P.J.W. Block (NASA Tech. Note. 1976). The results show good agreement with Block's model if the value of the convection velocity is properly adjusted. Stochastic estimation of the cavity flows demonstrates that convective structures are involved downstream of the cavity along the wall and highlights the physical nature of the pressure-producing flow structures. Key words: vortex dynamics, asymmetric deep cavity, self-sustain oscillations, simultaneous PIV and pressure measurements. En utilisant des mesures de la pression du mur et de PIV, nous etudions experimentalement l'influence du rapport de forme longueur versus profondeur et de l'asymetrie du mur sur la structure d'ecoulement tourbillonnant principal evoluant dans des cavites profondes a deux dimensions rectangulaires. La pression du mur et la statistique d'ecoulement dans la cavite sont analysees et montrent que les caracteristiques d'ecoulement sont fortement affectees surtout par l'asymetrie. Nous mettons l'emphase sur le comportement des oscillations de la couche cisaillee, qui sont alors comparees aux predictions du modele analytique pour cavite profonde propose par P.J.W. Block (NASA Tech. Note. 1976). Les resultats montrent un bon accord avec le modele de Block, si la valeur de la vitesse de convexion est ajustee de facon appropriee. L'estime stochastique des ecoulements dans la cavite montre que les structures convectives existent en aval de la cavite le long du mur et souligne la nature physique des structures d'ecoulement produisant de la pression. [Traduit par la Redaction] Mots-cles: tourbillon, dynamique, cavite profonde asymetrique, oscillations auto-entretenues, mesures simultanees de PIV et de la pression., 1. Introduction Understanding the unsteady features of cavity flows presents great interest for the design of many engineering applications. Modelling these dynamics can be used to design and enhance feedback [...]

Tailings may undergo desiccation stress history under varied climatic and depositional parameters. While tailings substantially dewatered prior to deposition may experience desiccation under the greatest range of climatic variation, even conventionally deposited tailings may desiccate in arid climates at lower rates of rise. Bench-scale research has shown that the stress history imparted by desiccation substantially improves strength in gold tailings. The present study further investigates this phenomenon by simulating multi-layer deposition of high-density tailings using a modular drying box, 0.7 m by 1 min plan. The box is instrumented for directly measuring evaporation, drainage, water content, vertical volume change, and matric suction. Additional measurements included total suction at the surface as well as observations of crack development. The dewatering behaviour conforms to that predicted by previously published generic modelling, specifically that the presence of partially desiccated tailings initially accelerates, but then decelerates dewatering of fresh tailings. The shear behaviour of samples obtained using buried tubes and by driving thin-wall tubes into the multi-layer simulation are compared with shear behaviour of samples from bench-scale experiments. Shear strength of samples from the multi-layer simulation is independent of the sampling method, and shows higher strength than the bench-scale samples. The higher strength may be due to the greater number of wet-dry cycles or other age-related processes. Key words: tailings, desiccation, drying box, simple shear, cyclic. Les refus peuvent subir une etude des contraintes deja subies de dessiccation sous des parametres climatiques et sedimentaires varies. Malgre que des residus deshydrates en grande partie avant le depot peuvent eprouver la dessiccation sous la plus grande portee de variations climatiques, meme les residus conventionnellement deposes peuvent se dessecher dans les climats arides a des taux inferieurs d'elevation. Des recherches a l'echelle de banc d'essai ont montre que l'etude des contraintes deja subie conferee par la dessiccation ameliore considerablement la resistance dans les residus d'or. La presente etude examine davantage ce phenomene en simulant des depots de residus a multicouche a haute densite a l'aide d'une boite de sechage modulaire, 0,7 m par 1 m en plan. La boite est instrumentee pour mesurer directement l'evaporation, le drainage, la teneur en eau, le changement de volume vertical et la succion matricielle. Des mesures supplementaires inclus la succion totale a la surface et des observations du developpement de la fissure. Le comportement de deshydratation est conforme a celle predite par la modelisation generique deja publiee, plus precisement que la presence de residus desseches partiellement accelere initialement, mais puis ralentit la deshydratation des residus frais. Le comportement en cisaillement d'echantillons obtenus a l'aide de tubes enterres, en enfoncant des tubes a paroi mince dans la simulation a multicouche, est compare avec le comportement en cisaillement des experimentations a l'echelle de banc d'essai. La resistance au cisaillement des echantillons de la simulation a multicouches est independante de la methode d'echantillonnage, et montre une plus grande resistance que les echantillons a l'echelle de banc d'essai. La resistance la plus elevee peut etre a cause du plus grand nombre de cycles de mouillage- sechage ou d'autres processus lies a l'age. [Traduit par la Redaction] Mots-cles: residus, dessiccation, boite de sechage, cisaillement simple, cyclique., Introduction In the last few decades, more than 50 tailings impoundments have failed due to seismic activity, liquefaction, foundation failure, etc. Many of these failures have been attributed to liquefaction [...]

This paper examines the role of waves in the development of the instability of an unbounded transverse mixing layer in shallow waters. In supercritical state waves become significant. The matching of the wave-like asymptotic solution in the far field to the solutions near the inflection and the returning surfaces poses a difficult mathematical problem. We therefore conducted numerical simulations to find solutions directly from the shallow water equations. The simulations found that the growing waves in the unstable current had a consistent structure throughout the linear stage of the instability's development. The excitation, reflection, and transmission of waves produced a modulating instability that maintained a consistent structure as the amplitude of the instability increased over many orders of magnitude. This role of the waves on the supercritical instability, as delineated by our numerical simulations, is not solely describable by the classical analytical method. Key words: shear instabilities, shallow flow, waves in currents, direct numerical simulations. Cet article examine le role des vagues dans le developpement de l'instabilite d'une couche de melange transversal illimitee en eaux peu profondes. En etat supercritique, les vagues deviennent importantes. L'adequation de la solution asymptotique d'ondulation en champ lointain avec les solutions pres de l'inflexion et des surfaces de retour pose un probleme mathematique difficile. Nous avons donc effectue des simulations numeriques afin de trouver des solutions a meme les equations d'eau peu profonde. Les simulations ont revele que les vagues croissantes dans un courant instable avaient une structure coherente au long de la phase lineaire du developpement de l'instabilite. L'excitation, la reflexion et la transmission des vagues ont genere une instabilite qui a maintenu une structure coherente alors que l'amplitude de l'instabilite augmentait sur plusieurs ordres de grandeur. Ce role des vagues en matiere de l'instabilite supercritique, tel que defini dans nos simulations numeriques, n'est pas represente uniquement par la methode analytique classique. [Traduit par la Redaction] Mots-cles: instabilites causees par le cisaillement, debit en eau peu profonde, vagues dans les courants, simulations numeriques directes., Introduction The transverse mixing layer in shallow waters is a shear flow developed between free streams of different velocities. The mixing layer in deep water is unstable according to Rayleigh's [...]

The sudden appearance of localized turbulent patches in an otherwise quiescent flow was first observed by Osborne Reynolds for pipe flow (1) and has since been found to be the [...], Over a century of research into the origin of turbulence in wall-bounded shear flows has resulted in a puzzling picture in which turbulence appears in a variety of different states competing with laminar background flow (1-6). At moderate flow speeds, turbulence is confined to localized patches; it is only at higher speeds that the entire flow becomes turbulent. The origin of the different states encountered during this transition, the front dynamics of the turbulent regions and the transformation to full turbulence have yet to be explained. By combining experiments, theory and computer simulations, here we uncover a bifurcation scenario that explains the transformation to fully turbulent pipe flow and describe the front dynamics of the different states encountered in the process. Key to resolving this problem is the interpretation of the flow as a bistable system with nonlinear propagation (advection) of turbulent fronts. These findings bridge the gap between our understanding of the onset of turbulence (7) and fully turbulent flows (8,9).

This paper presents a fully developed nonlinear analytical (exact) model for analyzing composite beams under transverse bending load. The model reproduces the elements responsible for the relative slip between the layers (shear connectors and interface) with an elastoplastic strain-softening interlayer. Further than the slip, the model predicts stresses due to a given load and ultimate load for debonding of bilayered composite beams. All the details on the mathematical development are presented. This paper advances the state of the art, since the last development available in literature is an analytical (nonexact) linear model. A number of parametric studies are conducted to evaluate the influence of various geometrical and material parameters, the main results of which are presented together with the interpretation, e.g., the dependence of load-carrying capacity, stresses, and deflection on the local nonlinear load-slip relationship. The research proves as well that the shear connection lower and upper bounds (respectively, totally flexible and infinite rigid shear connectors) do not imply any lower and upper bound for the response. DOI: 10.1061/(ASCE)EM.1943-7889.0000043 CE Database subject headings: Composite beams; Inelasticity; Connections; Shear flow; Slip; Elastoplasticity; Analytical techniques.

To further the understanding of secondary, flow loss, a set of surface measurements is presented for a planar turbine cascade tested at low Mach number (maximum of 0.23) and at an inlet axial chord Reynolds number of 5.9 x [10.sup.5]. The endwall and airfoil surface measurements are of skin friction, limiting streamline direction, and static pressure. An oil film interferometry measurement technique applied to the endwall and airfoil surfaces (at some 2000 locations) provides an extensive passage surface map of skin friction values and limiting streamline topology. Measurements of pressures on the same passage surfaces are also presented, resulting in a complete picture of endwall and airfoil surface pressure and shear. [DOI: 10.1115/1.2988168]

In this paper, we discuss the motion of a vesicle in a linear shear flow. It is known that deformable vesicles such as liposomes show the so-called tank-treading and tumbling motions depending on the viscosity ratio between the inside and outside of the vesicle, the swelling ratio, and so on. First, we have conducted numerical simulations on the tank-treading motion of a liposome in a linear shear flow and compared the results with other numerical and experimental results. It is confirmed that the inclination angle of the vesicle becomes smaller when the viscosity ratio becomes larger or the swelling ratio becomes smaller and that the present results show quantitatively good agreement with other results. Then, the effects of membrane modeling are discussed from the mechanics point of view. There are two types of modeling for the lipid bilayer biomembrane. One is a two-dimensional fluid membrane, which reflects the fluidity of the lipid molecules. The other is a hyperelastic membrane, which reflects the stiffness of cytoskeleton structure. Liposome is usually modeled as a fluid membrane and red blood cell (RBC) is modeled as a hyperelastic one. We discuss how these differences of membrane models affect the behaviors of vesicles under the presence of shear flow. It is shown that the hyperelastic membrane model for RBC shows a less inclination angle of tank-treading motion and early transition from tank-treading to tumbling. [DOI: 10.1115/1.3062966] Keywords: immersed boundary method, liposome, red blood cell, tank-treading, tumbling, membrane

Shallow orographic convection embedded in an unstable cap cloud can organize into convective bands. Previous research has highlighted the important role of small-amplitude topographic variations in triggering and organizing banded convection. Here, the underlying dynamical mechanisms are systematically investigated by conducting three-dimensional simulations of moist flows past a two-dimensional mountain ridge using a cloud-resolving numerical model. Most simulations address a sheared environment to account for the observed wind profiles. Results confirm that small-amplitude topographic variations can enhance the development of embedded convection and anchor quasi-stationary convective bands to a fixed location in space. The resulting precipitation patterns exhibit tremendous spatial variability, since regions receiving heavy rainfall can be only kilometers away from regions receiving little or no rain. In addition, the presence of banded convection has important repercussions on the area-mean precipitation amounts. For the experimental setup here, the gravity wave response to small-amplitude topographic variations close to the upstream edge of the cap cloud (which is forced by the larger-scale topography) is found to be the dominant triggering mechanism. Small-scale variations in the underlying topography are found to force the location and spacing of convective bands over a wide range of scales. Further, a self-sufficient mode of unsteady banded convection is investigated that does not dependent on external perturbations and is able to propagate against the mean flow. Finally, the sensitivity of model simulations of banded convection with respect to horizontal computational resolution is investigated. Consistent with predictions from a linear stability analysis, convective bands of increasingly smaller scales arc favored as the horizontal resolution is increased. However, small-amplitude topographic roughness is found to trigger banded convection and to control the spacing and location of the resulting bands. Thereby, the robustness of numerical simulations with respect to an increase in horizontal resolution is increased in the presence of topographic variations.

There is lively debate on whether Asian plate material was involved in southward flow of mid-lower crust in a ductile channel beneath southern Tibet. One argument against such involvement is the apparent absence of material derived from Asian lithosphere within the High Himalayan Series (Indian plate) that could represent the putative channel. A north-south--trending mid-Miocene dike swarm that intrudes the Tethyan sedimentary cover of the Sakya gneiss dome (Indian plate) yields new Sr-Nd isotopic data ([sup.87]Sr/[sup.86]Sr = 0.7071-0.7079;[[epsilon].sub.Nd]-4 to-6) indicating that these melts share the same source as Miocene dacitic dikes from north of the Indus-Tsangpo suture. Moreover, dikes on both sides of this suture represent crustal melts derived largely from mid-lower crust of the Asian plate, exposed today as the Nyainqentanglha gneisses that underlie the Gangdese batholith. We infer that melting of the Asian lithosphere extended south of the surface trace of the suture, requiring southward propagation of anatectic Asian middle crustal material during the Miocene. The emplacement ages of the southern dike swarm (12-9 Ma) thus delimit the timing of active southward ductile flow of Asian material. Keywords: Himalaya, isotope geochemistry, tectonics, channel flow.

The linear analysis of the instability due to vertical shear in the dust layer of the solar nebula is performed. The following assumptions are adopted throughout this paper: (1) The self-gravity of the dust layer is neglected. (2) One fluid model is adopted, where the dust aggregates have the same velocity with the gas due to strong coupling by the drag force. (3) The gas is incompressible. The calculations with both the Coriolis and the tidal forces show that the tidal force has a stabilizing effect. The tidal force causes the radial shear in the disk. This radial shear changes the wave number of the mode which is at first unstable, and the mode is eventually stabilized. Thus the behavior of the mode is divided into two stages: (1) the first growth of the unstable mode which is similar to the results without the tidal force, and (2) the subsequent stabilization due to an increase of the wave number by the radial shear. If the midplane dust/gas density ratio is smaller than 2, the stabilization occurs before the unstable mode grows largely. On the other hand, the mode grows faster by one hundred orders of magnitude, if this ratio is larger than 20. Because the critical density of the gravitational instability is a few hundreds times as large as the gas density, the hydrodynamic instability investigated in this paper grows largely before the onset of the gravitational instability. It is expected that the hydrodynamic instability develops turbulence in the dust layer and the dust aggregates are stirred up to prevent from settling further. The formation of planetesimals through the gravitational instabilities is difficult to occur as long as the dust/gas surface density ratio is equal to that for the solar abundance. On the other hand, the shear instability is suppressed and the planetesimal formation through the gravitational instability may occur, if dust/gas surface density ratio is hundreds times as large as that for the solar abundance. Keywords: Planetary formation; Solar nebula

A qualitative and quantitative comparison between unforced flows emanating from equivalent geometries of axisymmetric (circular) and square coaxial nozzles is presented. The initial state of the jets is turbulent, as in nozzles relevant to practical applications. Flow visualization and velocity measurements were performed at a coflow-jet Reynolds number of 1.9 x [10.sup.4] and at an inner-to-outer jet velocity ratio of 0.3. Scaling of mean velocity and turbulence profiles has been examined for the three shear layers formed in the near field of axisymmetric and square coaxial flows. Visualizations and local velocity measurements have indicated modest mixing enhancement when square nozzles are used compared to the axisymmetric ones, and this is largely attributed to differences in initial velocity profiles between these two configurations. Low-coherence, large-scale periodic structures were observed for both nozzle configurations in the midfield of the inner mixing region, which has wake characteristics. The outer mixing region, which is initially highly turbulent, shows no signs of an 'indigenous' organized structure. The spectral characteristics of the circular and square nozzle combinations are qualitatively similar. However, the discrete frequency peaks associated with the wake of the inner mixing region are much broader in the case of the square nozzles. More important, the dominant frequency at the end of the midfield within the inner mixing region is lower in the case of the square nozzles compared to that of the circular ones. Spectra from the turbulent shear layers of the middle mixing region in the near field indicate the presence of a short-lived shear layer preferred mode at a much higher frequency than the one associated with the subsequent development of the wake downstream. The existence of axis switching, a phenomenon observed in single nonaxisymmetric nozzles, is not evident from visualizations and measurements in the square coaxial nozzle, presumably due to the initial low coherence of large-scale structures in the shear layers.

A simple model is presented that predicts many features of the shear banding in steady shear and pipe flows. The model employs six parameters, all of which can be obtained from independent rheological experiments, and then they could be used to predict other rheological data.

Atmospheric conditions such as crosswind, stratification and turbulence can influence aircraft trailing vortices. Numerical simulations of vortex/shear interactions with ground effects have been undertaken by several groups. A two dimensional flow is considered, suggesting that the mechanism responsible for the asymmetric deflection in the trailing vortices, could be deduced from inviscid interactions between the vortex pair and shear layers. Such a method is faster than the Navier-Stokes numerical simulations, and could be useful in real-time predictions.

Shear waves traversing the deep mantle southeast of Hawaii from earthquakes in the Tonga-Fiji region, were examined. The reflections were analyzed from the core-mantle boundary (CMB), and signals were selected to minimize uncertainties involved in the measurement of arrival times. The strong lateral gradients in velocity and anisotropic shear wave polarization ae interpreted as representing small-scale dynamical structure within the thermal boundary layer.

A counter-rotating vortex pair in a cross-stream shear flow effects the three-dimensional stability and the growth rates of unstable perturbations. Three long-wave instabilities result from a mutual interaction between the vortices, an interaction between the shear flow and the mutual interaction, and an interaction of the vortex self-induced velocity with the shear flow. The instabilities have qualitatively different nonlinear evolution of the vortex pair. The wave-number range and the growth rate of short-wave perturbations increase if the shearing rate is large.

The multiple jets in a crossflow consist of a complex three-dimensional scarf vortex that is present around each impinging jet and a fountain upwash flow resulting from the collision of the wall jets. The shear layer surrounding the jets experiences intense velocity fluctuations in the regions having high mean velocity gradients. This study helps in understanding complex flowfields such as those in industrial environments where impinging jets compete on crosswind and the flow created under a take-off and landing aircraft.

A leading-edge suction technique facilitates the study of the effect of shear-layer control on leading-edge vortices over delta wings. The direction of the shear layer, and the location and structure of the main vortex undergo modifications due to the application of suction near the separation point. Suction induces a drop in the maximum swirl angle in the core and overall circulation, thereby moving the vortex breakdown location downstream. The swirl angle increases and the breakdown location moves upstream when the suction slot is positioned inboard. Rolling moment generation is discussed.

A study of the flowfield and noise properties of a supersonic diamond-shaped jet reveals many structures in the shear layers that are not detected in these layers of expanded axisymmetric and rectangular jets. These structures express the streamwise vorticity in the layers, which may not affect the overall mixing and noise fields in these jets. Narrow-band spectral studies of the diamond jet demonstrate a moderate reduction of the mixing noise as compared to that of an equivalent axisymmetric jet. The shear layer global growth rates are similar for different jet geometries.

Numerical studies of the unsteady boundary-layer separation from an Eppler 387 airfoil at low Reynolds number reveal the effects of Reynolds number and angle of attack on the growth of unsteady flow. Linear stability analysis suggests that the cause of the shear layer turbulence is a Kelvin-Helmholtz instability. Vortex shedding, related to the unsteady large-scale structures, controls the low-Reynolds-number separation bubble reattachment. Computational results are favorably compared with time-averaged experimental ones to present the boundary-layer separation characterization.

The measurements of Mach number profiles for two stream conditions provide insights into the instabilities present in supersonic shear layers. An artificial excitation for two-dimensional (2-D) waves produces 2-D instabilities in both the cases. The excited three-dimensional waves create oblique instability waves for different excitation angles. The growth rate of waves for low Mach number conditions remain unaffected by excitation, whereas enhanced mixing is observed for the higher Mach number profiles.

Twin-fin buffeting occurs when the leading-edge vortex shear layers overlap the fins to reattach near the inboard face. Another mechanism for buffeting involves the mixing of shear layers between the fins themselves. The layer mixing causes extra inboard excitation. The two methods involve modified frequency parameters. The results of an experimental investigation on three 60 degree cropped generic delta wings of 0.5 m span are given.

Planar supersonic base flow visualizations show that large-scale turbulent structures exist in compressible shear layers. The structures interact vigorously with recirculation region. The shear layer gives rise to Mach and shock waves. An eddy shocklet formation may be due to the shock waves. The structures are elliptical and have an inclination towards mean flow direction. The coherent eddies cause shear layer formation, recompression and reattachment processes which lead to a flattening and tilting in the streamwise direction.

A cinematic particle image velocimetry technique determines the velocity field in a two-stream, high-Reynolds-number turbulent free shear layer. The shear layer shows complex three-dimensional clusters with vortices of both signs. The velocity field has stronger temporal variations and less spatial coherency than that of a passive scalar field. The experiment yields temporal and spatial correlations of the two-dimensional velocity and spanwise vorticity fields.

Skin-friction measurements on a two-dimensional airfoil at a Mach number of 0.2, for different Reynolds numbers and angles of attack, involve the use of a shear-stress-transport turbulence model. The method, also using a Navier-Stokes code, provides data on a range of laminar and turbulent shear stresses. The results reveal the effects of Reynolds number and pressure gradient on boundary-layer transition. The data is in good agreement with numerical simulations.

A direct numerical simulation explains the interaction between an imposed monochromatic, time-dependent acoustic disturbance and a steady state shear flow in a two-dimensional duct. Oblique waves originate above a certain critical frequency. The amplitudes of acoustic pressure vary due to interactions between oblique and axially travelling waves. The oblique waves amplify at a higher rate as compared to the axially travelling waves. The numerically simulated thickness of the acoustic boundary layer is comparable to theoretical predictions.

The growth and symmetry of small-scale vortices in opposing shear layers affects the location and shape of the large-scale Karman vortices formed in the near wake. Experiments with a horizontal cylinder placed above a free-surface water channel involve the measurement of instantaneous velocity using a laser-scanning version of high-image-density particle image velocimetry. The formation of Karman vortices downstream of the cylinder is observed over a range of Reynolds numbers. The Karman vortices form further downstream as the shear-layer vortices attain large values of circulation.

Particle image velocimetry and flow visualization are used to study a laminar wall jet, disturbed from an external source. Under external disturbance, vortical structure in outer shear layer is improved. Collection and ejection of wall vorticity into outer flow is caused by convecting shear layer vortical structure. Wall jet flow is totally thrown out due to strong interaction between inner and outer vortex structures, and the flow becomes turbulent.

The steadiness and convolution of the interface between the freestream and recirculating/wake core regions in an axisymmetric, separated supersonic flow were studied using planar imaging. Five regions along the shear layer/wake boundary were investigated in detail to quantify the effects that key phenomena, such as the recompression and reattachment processes, have on the development of large-scale unsteady motions and interfacial convolution. These studies show that flapping motions, when viewed from the side, generally increase in magnitude, in relation to the local shear layer thickness, with downstream distance, except at the mean reattachment point, where they are slightly suppressed. When viewed from the end, the area-based (pulsing) fluctuations increase monotonically downstream as a percentage of the local area, whereas the position-based (flapping) motions show pronounced peaks in magnitude in the recompression region and in the developing wake. The interface convolution increases monotonically with downstream distance in both the side- and end-view orientations.

The transient, linear response of a stably stratified atmosphere to thermal forcing in the presence of a critical level is investigated analytically using the Green's function method. The prescribed thermal forcing is located below or across a critical level. The target solution is for the finite-depth steady forcing, but intermediate solutions to the line-type pulse forcing, finite-depth pulse forcing, and line-type steady forcing are analyzed in some detail because these solutions give some insight into the basic dynamics of the response to the target forcing. The responses to the pulse forcings exhibit the moving mode whose center travels downstream with a speed of the basic-state wind. In the vicinity of the initial forcing, gravity waves are attenuated across the critical level. In response to the line-type pulse forcing, after some time the magnitude of the perturbation vertical velocity at the center of the moving mode remains almost unchanged with time. The transient critical level is a function of the horizontal location and time. In response to the finite-depth pulse forcing, after some time the magnitude of the perturbation vertical velocity at the line that connects the centers of the moving modes at the forcing top and bottom decreases with time due to the geometric expansion of the line. In responses to the steady forcings, the stationary mode as well as the moving mode appear. The origin of the stationary mode is very small-amplitude waves with zero or near-zero horizontal phase velocities in the pulse forcings. These waves work constructively to be perceptible in response to the steady forcings. The stationary mode is almost entirely absorbed at the critical level, and the dynamics of the moving modes in the pulse and steady forcing cases are similar to each other. It is shown that adding a widespread heating (cooling) term eventually yields a steady-state field in the stationary mode. Unlike the steady-state case, there is a gradual decrease of the momentum flux from the thermal forcing top to the critical level. The moving mode can transport a small amount of the momentum flux above the critical level.