Streamlines, streaklines, and pathlines

About: Streamlines, streaklines, and pathlines is a research topic. Over the lifetime, 6118 publications have been published within this topic receiving 133556 citations.

Linear theory of stratified hydrostatic flow past an isolated mountain

Abstract: The stratified hydrostatic flow over a bell-shaped isolated mountain is examined using linear theory. Solutions for various parts of the flow field are obtained using analytical and numerical Fourier analysis. The flow aloft is composed of vertically propagating mountain waves. The maximum amplitude of these waves occurs directly over the mountain but there is also considerable wave energy trailing downstream along the parabolas y 2 = Nzax/U Near the ground, the asymmetric pressure field causes the incoming streamlines to split to avoid the mountain and this lateral deflection persists downstream. The horizontal divergence associated with this lateral deflection is balanced by the descent of potentially warmer air from aloft. The relationship of linear theory to other three-dimensional models is discussed. The approach to the two-dimensional infinite ridge limit and non-hydrostatic effects are also discussed. DOI: 10.1111/j.2153-3490.1980.tb00962.x

How rapidly is a passive scalar mixed within closed streamlines

Abstract: The homogenization of a passive ‘tracer’ in a flow with closed mean streamlines occurs in two stages: first, a rapid phase dominated by shear-augmented diffusion over a time ≈P1/3(L/U), where the Peclet number P=LU/κ (L,U and κ are lengthscale, velocity scale and diffusivity), in which initial values of the tracer are replaced by their (generalized) average about a streamline; second, a slow phase requiring the full diffusion time ≈ L2/κ. The diffusion problem for the second phase, where tracer isopleths are held to streamlines by shear diffusion, involves a generalized diffusivity which is proportional to κ, but exceeds it if the streamlines are not circular. Expressions are also given for flow fields that are oscillatory rather than steady.

Image-guided streamline placement

Abstract: Accurate control of streamline density is key to producing several effective forms of visualization of two-dimensional vector fields. We introduce a technique that uses an energy function to guide the placement of streamlines at a specified density. This energy function uses a low-pass filtered version of the image to measure the difference between the current image and the desired visual density. We reduce the energy (and thereby improve the placement of streamlines) by (1) changing the positions and lengths of streamlines, (2) joining streamlines that nearly abut, and (3) creating new streamlines to fill sufficiently large gaps. The entire process is iterated to produce streamlines that are neither too crowded nor too sparse. The resulting streamlines manifest a more hand-placed appearance than do regularlyor randomly-placed streamlines. Arrows can be added to the streamlines to disambiguate flow direction, and flow magnitude can be represented by the thickness, density, or intensity of the lines. CR Categories: I.3.3 [Computer Graphics]: Picture/Image generation; I.4.3 [Image Processing]: Enhancement. Additional

Creating Evenly-Spaced Streamlines of Arbitrary Density

Abstract: This paper presents a new evenly-spaced streamlines placement algorithm to visualize 2D steady flows. The main technical contribution of this work is to propose a single method to compute a wide variety of flow field images, ranging from texture-like to hand-drawing styles. Indeed the control of the density of the field is very easy since the user only needs to set the separating distance between adjacent streamlines, which is related to the overall density of the image. We show that our method produces images of a quality at least as good as other methods but that it is computationally less expensive and offers a better control on the rendering process.

Steady solutions of the Navier-Stokes equations by selective frequency damping

Abstract: A new method, enabling the computation of steady solutions of the Navier-Stokes equations in globally unstable configurations, is presented. We show that it is possible to reach a steady state by damping the unstable (temporal) frequencies. This is achieved by adding a dissipative relaxation term proportional to the high-frequency content of the velocity fluctuations. Results are presented for cavity-driven boundary-layer separation and a separation bubble induced by an external pressure gradient.