fuckyeahfluiddynamics: Surface properties can have surprising effects on fluid behavior. This image shows the evaporation of several droplets over time. All of the initial droplets are of the same volume, but they are placed on a surface which is a) superhydrophobic, b) hydrophobic, or c) hydrophilic. The more hydrophobic the surface, the larger the initial contact angle between the droplet and surface and the smaller the wetted area of the surface. Yet despite this seemingly large surface area exposure to air, the droplet on the superhydrophobic surface is the slowest to evaporate. (Photo credit: C. Choi)

fuckyeahfluiddynamics:

Surface properties can have surprising effects on fluid behavior. This image shows the evaporation of several droplets over time. All of the initial droplets are of the same volume, but they are placed on a surface which is a) superhydrophobic, b) hydrophobic, or c) hydrophilic. The more hydrophobic the surface, the larger the initial contact angle between the droplet and surface and the smaller the wetted area of the surface. Yet despite this seemingly large surface area exposure to air, the droplet on the superhydrophobic surface is the slowest to evaporate. (Photo credit: C. Choi)

fuckyeahfluiddynamics: If you have any leftover hard-boiled eggs, you can recreate this bit of fluid dynamical fun. Spin the egg through a puddle of milk, and you’ll find that the egg draws liquid up from the puddle and flights it out in a series of jets. As the egg spins, it drags the milk it touches with it. Points closer to the egg’s equator have a higher velocity because they travel a larger distance with each rotation. This variation in velocities creates a favorable pressure gradient that draws milk up the sides of the egg as it spins, creating a simple pump. To see the effect in action check out this Science Friday video or the BYU Splash Lab’s Easter-themed video. (Photo credit: BYU Splash Lab)

fuckyeahfluiddynamics:

If you have any leftover hard-boiled eggs, you can recreate this bit of fluid dynamical fun. Spin the egg through a puddle of milk, and you’ll find that the egg draws liquid up from the puddle and flights it out in a series of jets. As the egg spins, it drags the milk it touches with it. Points closer to the egg’s equator have a higher velocity because they travel a larger distance with each rotation. This variation in velocities creates a favorable pressure gradient that draws milk up the sides of the egg as it spins, creating a simple pump. To see the effect in action check out this Science Friday video or the BYU Splash Lab’s Easter-themed video. (Photo credit: BYU Splash Lab)

clearscience: fuckyeahfluiddynamics: Any time there is relative motion between a solid and a fluid, a small region near the surface will see a large change in velocity. This region, shown with smoke in the image above, is called the boundary layer. Here air flows from right to left over a spinning spheroid. At first, the boundary layer is laminar, its flow smooth and orderly. But tiny disturbances get into the boundary layer and one of them begins to grow. This disturbance ultimately causes the evenly spaced vortices we see wrapping around the mid-section of the model. These vortices themselves become unstable a short distance later, growing wavy before breaking down into complete turbulence. (Photo credit: Y. Kohama) When a fluid flows next to a solid, the fluid right next to the solid is always stuck to its surface. This means it has zero velocity with respect to the solid. This is called the no-slip boundary condition, and it’s why boundary layers exist. The picture above is a special situation meant to make a beautiful and illustrative image. However, boundary layers exist everywhere: the wind blowing across your face, the water right next to you when you’re swimming, the air right next to your car when it’s driving. Since air is hard to see, in the picture they use smoke so you can see it. As boundary layers continue across objects, they always go through a transition from well-behaved and layer-like to disordered and gnarly-looking. The word for layer-like is “laminar.” The word for disordered and gnarly is “turbulent.” In the picture you can see the laminar-to-turbulent transition very well.

clearscience:

fuckyeahfluiddynamics:

Any time there is relative motion between a solid and a fluid, a small region near the surface will see a large change in velocity. This region, shown with smoke in the image above, is called the boundary layer. Here air flows from right to left over a spinning spheroid. At first, the boundary layer is laminar, its flow smooth and orderly. But tiny disturbances get into the boundary layer and one of them begins to grow. This disturbance ultimately causes the evenly spaced vortices we see wrapping around the mid-section of the model. These vortices themselves become unstable a short distance later, growing wavy before breaking down into complete turbulence. (Photo credit: Y. Kohama)

When a fluid flows next to a solid, the fluid right next to the solid is always stuck to its surface. This means it has zero velocity with respect to the solid. This is called the no-slip boundary condition, and it’s why boundary layers exist.

The picture above is a special situation meant to make a beautiful and illustrative image. However, boundary layers exist everywhere: the wind blowing across your face, the water right next to you when you’re swimming, the air right next to your car when it’s driving. Since air is hard to see, in the picture they use smoke so you can see it.

As boundary layers continue across objects, they always go through a transition from well-behaved and layer-like to disordered and gnarly-looking. The word for layer-like is “laminar.” The word for disordered and gnarly is “turbulent.” In the picture you can see the laminar-to-turbulent transition very well.

fuckyeahfluiddynamics:

When liquids hit a surface much hotter than their boiling point, a thin layer of gas can form between the drop and surface, allowing the drop to glide along. This Leidenfrost effect is what makes drops of water skitter across a hot pan. But what happens when the pan isn’t flat? The video above shows a Leidenfrost drop on a ratchet-like surface. Instead of gliding or skittering randomly, the drop self-propels toward the steepest section of the ratchet  This behavior allows researchers to design surfaces that guide the drops on an intended path. (Video credit: G. Lagubeau and D. Quéré)

(Source: annualreviews.org)

fuckyeahfluiddynamics:

Hydraulic jumps occur when a fast-moving fluid enters a region of slow-moving fluid and transfers its kinetic energy into potential energy by increasing its elevation.  For a steady falling jet, this usually causes the formation of a circular hydraulic jump—that distinctive ring you see in the bottom of your kitchen sink. But circles aren’t the only shape a hydraulic jump can take, particularly in more viscous fluids than water. In these fluids, surface tension instabilities can break the symmetry of the hydraulic jump, leading to an array of polygonal and clover-like shapes. (Photo credits: J. W. M. Bush et al.)

This is so awesome.

I think I'm friendly. You should say hi.

Some of my interests:

Myself
Science!
Space!
Music
Movies
Chemistry
Biology
Sci Fi
Ukulele
Hip Hop
Latin
Hayao Miyazaki

And some other stuff.