FYFD

Search results for: “jet”

  • Rocket Engine Test

    [original media no longer available]

    In this static test of XCOR Aerospace’s Lynx rocket engine, Mach diamonds (shown at the top of the frame) are visible in the rocket exhaust. The distinctive pattern is a result of the over- or under-expansion of the exhaust jet with respect to the ambient air; in other words, the gases exiting the rocket are either too high or too low in pressure relative to the surrounding air. A series of shock waves and expansion fans forms in the exhaust jet until the pressure is equalized to ambient. It is these compressions and expansions that form the diamond pattern. (Video credit: XCOR Aerospace)

  • Floral Still Life

    Floral Still Life

    Fluid motion is captured as a floral still life in these high-speed photos by Jack Long. The artist keeps mum about his set-up but notes that these are single capture events, not constructed composites. It looks as if the blossoms are created from the impact of a falling fluid with the upward jet that forms the stem. The leaves and vase appear to be created from upward splashes, but whether those are generated by vibration or dropping an object is unclear. See Long’s Flickr page for more. (Photo credit: Jack Long via Gizmodo)

  • Featured Video Play Icon

    Egg Spinning

    Spin a hard boiled egg in a puddle of milk and you get a sprinkler. But how? The science starts at the surface. When the egg spins, the fluid touching its surface is dragged along due to friction, and, because of the fluid’s viscosity, other parts of the fluid will also be spun. Dynamics tells us that the velocity at the surface of the object varies with radius; the velocity at the bottom of a spinning sphere is much smaller than that at its equator because a particle at the equator traverses a larger distance in a single rotation. Likewise, the fluid touching the bottom of the egg is spun slower than the fluid just above it. Bernoulli’s principle tells us that, for an incompressible fluid, the pressure decreases as velocity increases, meaning that a favorable pressure gradient exists along the spinning convex surface. It is this pressure gradient that draws the fluid up the sides of the object. Near the equator, the pressure gradient is weakest and centrifugal force flings the the fluid outward. Surface tension, angular velocity, and viscosity all play a role in the jets and sheets created by the sprinklers. (Video credit: NPR Science Friday with Tadd Truscott et al)

  • Reader Question: Fire as a Fluid?

    Reader Question: Fire as a Fluid?

    Reader David L asks:

    I understand that fire is a form of energy rather than a fluid in the physical/tangible sense. However, is it possible for fire to exhibit fluid-like behaviours to a certain extent.

    In other words, could the dynamic properties of fire be described with pseudo-variables analogical to variables that describe a physical fluid (i.e. viscosity, density, Re, etc.)?

    Actually, combustion is a major topic of research among fluid dynamicists. Since the part of fire that we identify as visible flame is a reacting mixture of gas and some solid particles, it moves according to the same equations of motion as any other gas. However, when studying combustion thermodynamical equations and chemical reactions must also be tracked in addition to mass and momentum, which makes modeling fire very difficult. Combustion plays a major role in internal flows like those in car, jet, and rocket engines. (Photo credit: master.blitzy)

  • Featured Video Play Icon

    Bursting Bubbles

    Sometimes bursting one bubble just leads to more bubbles. This high-speed video shows how popping a bubble sitting on a fluid surface can lead to a ring of daughter bubbles. When the surface of the bubble is ruptured, filaments of the liquid that made up the surface are drawn back toward the pool by surface tension, trapping small pockets of the air that had been inside the bubble. A dimple forms on the surface and rebounds as a jet that lacks the kinetic energy to eject droplets. Watch as the jet returns to the interface, and you will notice the tiny bubbles around it. At 56 ms, one of the daughter bubbles on the left bursts. See Nature for more. (Video credit: J. Bird et al)

  • Featured Video Play Icon

    Vibrating Oil

    This high-speed video shows the behavior of oil on a vibrating surface. As the amplitude of the vibration is altered various behaviors can be observed. Initially small waves appear on the surface of the oil, then the surface erupts into a mass of jets and ejected droplets, reminiscent of a vibrated interfaces within a prism or vibration-induced atomization. When the amplitude is reduced after about half a minute, we see Faraday waves across the surface, as well as tiny droplets that bounce and skitter across the surface. They are kept from coalescing by a thin layer of air trapped between the droplet and the oil pool below. Because of the vibration, the air layer is continuously refreshed, keeping the droplet aloft until its kinetic energy is large enough that it impacts the surface of the oil and gets swallowed up.

  • Featured Video Play Icon

    Frozen Fluid Illusion

    This video creates the illusion of a jet of water frozen in mid-air. The effect is achieved by vibrating the water at the frequency of the speaker, then filming at a frame rate identical to the vibrational frequency. Thus the water pulses at the exact rate that the camera captures images, making the water appear stationary even though it is moving. (submitted by Simon H)

  • Featured Video Play Icon

    Granular Eruptions

    Granular flows, which are made up of loose particles like sand, often display remarkably fluid-like behavior. Here researchers explore the behavior of granular flows when a solid impacts them at high speed. The sand, unlike a fluid, does not have surface tension, yet we still observe many of the same behaviors. Like a fluid, the sand splashes and creates cavities and jets as it deforms around the fallen object. The sand even “erupts” as submerged pockets of air make their way back to the surface.

  • Drops Through Drops

    Drops Through Drops

    The splashes from droplets impacting jets create truly mesmerizing liquid sculptures. Corrie White is one of the masters of this type of high-speed macro photography. Her work captures the instantaneous battles between viscosity, surface tension, and inertia. The fantastic structure seen here through the falling droplets is created by a series of drops timed so that the later ones strike the Worthington jet produced by the initial drop’s impact. (Photo credit: Corrie White)

  • Flying Squid

    Flying Squid

    Ever seen a squid fly? Not many have, but the behavior may be more common than you think. Thanks to a set of photos from an amateur photographer, scientists have managed to estimate the velocity and acceleration of squid as they propel themselves out of the water by squirting a jet behind them. Researchers found that their speeds in air are roughly five times that in water, thanks to decreased drag. Previously it was thought that the flying behavior might be linked to escaping predators, but some now suggest that it enables migration over long distances by saving energy.

More posts