| 词汇 | example_english_vortex |
| 释义 | Examples of vortexThese examples are from corpora and from sources on the web. Any opinions in the examples do not represent the opinion of the Cambridge Dictionary editors or of Cambridge University Press or its licensors. Is it just that there were too many vortices in the wake ? One is to keep the analysis as simple as possible to explain the cigar-like shape of the vortices found in the three-dimensional computations. The vortices decrease in diameter as they travel downstream. The mechanism through which the vortices generate sound is of general interest in aeroacoustics. Beyond the existence of hairpin vortices, the data also show individual hairpins commonly aligned behind each other in the x-direction to form a group. The waves propagate away and the vortices ultimately reach an equilibrium, which is discussed below. In the case of finite-core vortices, the problem of the stability of this state needs special examination. Reported first are the results of 234 moderate-resolution calculations used to determine the margin of apparent nonlinear stability for strained, initially circular vortices. The existence of these counter-rotating vortices within the sublayer has been demonstrated by several techniques. While the exact reasons for the formation of these vortices are not known, several theories have been proposed. In this case, the intense perturbation of the upper boundary favours the generation of downstream patches of vortices travelling with high phase velocity. Upper vortices are at the surface and their interaction is effectively strengthened owing to the influence of their 'images' with respect to the boundary. The localized suction and induced streamwise vortices introduce strong distortions of the streamwise velocity. The motion thus started continued downstream in the form of a pair of trailing vortices. When the transverse vortices convected downstream, an ejection sequence occurred near the wall. Around these filaments, or vortices, the superconducting properties are partially destroyed. At this timescale, however, near-surface vortices are affected by external currents, bottom topography, wind, etc., and the whole approach has to be revised. The nonlinear solution of the partial differential equations in the form of dipolar vortices is found. In these works the waves and vortices were assumed to be uncorrelated. The pinning effect of the vortices due to impurities was also established [25-27, 34]. The final state comprises two counter-rotating vortices which dissipate. Owing to the induced velocity field, the three vortices start to rotate around each other. The role of these potentials is to hold down the vortices from moving as a result of mutual interactions. We restrict attention to axially symmetric solutions and consider models with and without vortices. They relate this question to the formation of vortices in the medium, a phenomenon that cannot be seen in the one-dimensional model. We study a mean-field model of superconducting vortices in one and two dimensions. Each point in figure 7 represents the average strength of the three or four most recently formed vortices in one photograph. About a third of the 33 papers presented concentrated on theoretical aspects and the majority of these were concerned with the 'method of discrete vortices'. During the other half of the cycle these vortices were convected back past the cylinder by their own mutually-induced velocity. I n this case the reduction was effected by removing vortices, justified as accounting for three-dimensional effects which would occur in a real flow. The vortices were then convected without difficulty into the separating shear layer. The energetics of a linear array of hollow or stagnant-cored vortices of finite crosssection in an ideal fluid is studied in this paper. Namely, we should discuss the reduction of the degree of freedom in vortices in connection with ap/ay > 0 near the wall surface. An extremely beautiful photographic record of a row of vortices in the case of 8 = 75" is shown in figure 15. The common assumption made by the aforementioned authors in their theory is that the lattice of line vortices is infinite. In general, however, vortices are generated during inflow and expelled during outflow. Given the initial position of the vortices their motion can be calculated with help of this relation. The vortices are shed from the pipe during outflow. I n aerodynamic contexts, the global flow field causes impressed forcing on concentrated vortices embedded in it. The results for the point vortices are in the bottom row. Analysis of the results is directed towards the properties of large-scale spanwise vortices and shear-aligned double-roller vortices and the relationship between them. The pictures in figures 4-7 suggest that the vortices scatter more and more about the midline as 0 increases. They use 750 point vortices and an algorithm (the 'centre-to-centre method') that restricts the vortices to the sites of a grid a t every time-step. The adjustment of the spanwise lengthscale with streamwise wavelength indicates that the formation of the streamwise vortices is an instability process. Near the origin of the mixing layer, the secondary vortices had short wavelengths. They found streamwise vortices in the trailingedge region. Their results support the experimental observations regarding spikes, high-shear layer and hairpin vortices. A number of different flow regimes have been observed involving separation and the generation of vortices. The lines pass through the centres of the heads of the hairpin vortices. The consequences of such an encounter are expected to lead to a complex pattern of vortices owing to cut and connect processes and pairing processes. The numbers refer to the initial locations of the point vortices. The transverse phase variation is responsible for the formation of hairpin vortices. The numbers refer to initial locations of point vortices. A phase-locked flow-visualization technique was adopted for determining the convection velocities of the two types of vortices during the pairing event. The smoke traces in such a case may occasionally reveal an organized train of vortices but most of the time do not show any structure. However, the periodic nature of the vortices is more or less maintained. The presence of such vortices is consistent with the distribution of fluctuation intensity in figures 20 and 21. The spatial and temporal properties of the vortices are analysed. Just as in the direct summation scheme the computation time scales as the square of the number of vortices. We further found that the random fine eddies were produced by the interactions of the merging spanwise structures and the streamwise vortices. The success of the present model in elliptic flows has led to its use in the investigation of the decay mechanisms in trailing vortices. The next transition, which takes the system into a state of nonaxisymmetric drifting vortices, shows hysteresis. We bypassed this enormous data taking task by measuring the passage frequency of the vortices. In the two-dimensional region both quasi-streamwise vortices and arches can be observed. The third, which is finite (type 3), includes the movement of upper and lower layer vortices along closed trajectories in directions corresponding to their cyclonicity. Two-dimensional excitation may, interact and detract from the coherence of the streamwise vortices. The distance between cyclonic and anticyclonic vortices in a tilted heton will not remain constant if it interacts with other hetons. All vortices forming the hetons rotate in a region of finite size. As the horizontal separation between hetons increases, the induced velocity also increases and the interaction between upper and lower layer vortices becomes more important. Finally, the two two-layer vortices are assumed to be vertically tilted. We shall proceed to look at the circulation strengths of the shed vortices in these repeatable wake modes, as shown in figure 15. While the vortices in the upper row are swept along the edge with minor distortion, those in the lower row are rapidly distorted, or distended. With decreasing angle, the waves become stronger, while the vortices tend to weaken. The oscillations in this case are presumably partly due to transients set up by the impulsive generation of the rather shallow point vortices. The larger dispersion in figure 6 (a) is because the streamwise range within which vortices were selected is greater than their lateral deviation. An important inference is that the growth process and the process of turbulence production probably involve secondary vortices wrapped around the core in azimuthal planes. The sketches in figure 4 show a frequently observed interaction between two toroidal vortices. In order to demonstrate this surprising result, let us consider a semi-infinite strip of trailing vortices of width dy. Perhaps the most striking advances have occurred in the understanding of coherent structures (vortices) in rotating flows. A t the same time, the interface is rapidly pulled down in front of the vortices. The result was a distinct pattern of vortices with circulation in (x, 2)-planes and a scale one half that of the basic spanwise vortices. The convection of these vortices out of the flow domain renders the specification of proper inflow/outflow boundary conditions difficult. The spanwise wavelength of the rib vortices was found to be about 2-3 cylinder side lengths in the near wake. At the outflow, vortices produced at the cylinder are expected to leave the domain. In figure 11(b) the curvature of the potential isolines, which corresponds to the curvature of the vortices, can be seen. The simultaneous excitation by counter-rotating, (+), modes ensured the generation of steady streamwise vortices that are of great importance to the transition mechanism. The hairpin vortices were generated by a hemispheric protuberance and the injection of fluid into the boundary layer. The vortices soon transformed into very turbulent motion within the horizontal layers, which grew continuously in a cellular pattern. At t = 13 and 14 min, there are four vortices in a row, surprisingly pentagonal in cross-section. Putting in more vortices would not improve spatial resolution. There is also considerable fundamental interest in these flows and in the ways in which vortices are generated and shed. First, the vortices could pair to form larger vortices, creating a discrete hierarchy of vortices throughout the boundary layer. There are two counter-rotating vortices with fluid sinking toward the crest and rising above the trough. As the number of discrete vortices becomes large, their interaction becomes very complex. Even if the turbulent character of the incident wake is ignored, the interaction of highly coherent vortices with the body remains an unclarified problem. Within two vortices (one wavelength) density variations are weak, except in the local fluid exchange region. Instead, the iso-surfaces indicate that the flow is dominated by streamwise oriented vortices. The production of strong, isolated vortices has been identified, and these bear striking resemblances to structures observed in curved flows. Interaction between vortices that are initially far apart is possible because of their ability to propel themselves, even in the absence of external influences. The tendency of close, like-sign vorticity patches to merge is another characteristic feature of finite-core vortices. These examples are from corpora and from sources on the web. Any opinions in the examples do not represent the opinion of the Cambridge Dictionary editors or of Cambridge University Press or its licensors. |
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