Stiring, Mixing, and Everyting in Between

Hot, cold, salty, fresh, sheared, stratified, convective, and awesome!

[build-a-diy]

8-foot giant squid pillow.

You’ll need:

2 yards of felt

1 yard of patterned fabric (I suggest a polka dot-type pattern so it looks like suction cups)

1 medium piece of black felt, 1 medium piece of white felt (for the eyes)

white thread, black thread and thread of the same color as the felt you’re using

pins

about 5 lbs. of stuffing

a couple big sheets of paper to draw your pattern

You can find many of these things down at the many places on Fabric Row, on 4th Street between Bainbridge and Catherine. Pearl, at 417 South Street, sometimes has stuffing if you can’t find any.

First, you need to draw out your patterns. Here’s a basic template to get you started, although most of the measurements are reasonably fudgeable. If in the likely event you don’t have any four-foot-long pieces of paper lying around, just tape a few pieces together.

Once you’ve drawn out your eight patterns, it’s time to cut the fabric. Pin the pattern to the fabric, laid flat, and cut out the following, leaving a half an inch or so of extra fabric around the edge of the pattern:

FOR THE ARMS: 8 felt and 8 fabric cutouts of piece 1

FOR THE, UH, LONGER ARMS: 2 felt and 2 fabric cutouts of piece 2

FOR THE BODY: 2 felt cutouts of piece 3

FOR THE FIN: 4 felt cutouts of piece 4

FOR THE HEAD: 1 felt cutouts of piece 6

FOR THE EYES: 2 white felt cutouts of piece 7 and 2 black felt cutouts of piece 8

So now you’ve got all your pieces ready, it’s time to start sewing them together. I did mine by hand because my sewing machine is busted and I get a kind of Zen buzz from sewing by hand, but if you have a non-busted one I recommend that you use it as it will be MUCH EASIER. You’re going to be sewing everything with the nice side of the fabric facing in, then turning it inside out to stuff it.

THE ARMS: (To make a quilted pattern that looks like suckers, see this other post). Pin together one patterned fabric piece 1 and one felt piece 1 (with the nice sides facing the inside). Sew down around the U-shape and back up, leaving the top open. Then turn the arm inside out, stuff it (it’s easiest to do both of these things if you sort of scrunch it up like you’re trying to put on a pair of tights, excuse the non-dude-friendly reference) and sew the top closed. Do the same for the other seven arms and rejoice in the fact that this is the most tedious part. Same deal with the two long arms, they’re just harder to stuff.

THE FINS: Pin together two of your piece 4s and sew together the curvy outer edge. Turn the piece inside out, so the seam you just sewed is on the inside, and start sewing up the other side, stuffing gradually as you go along. You should end up with a triangle-ish puffy thing. Repeat for the other two piece 4s.

THE BODY: Put down one piece 3, then place the two fins you have down with the point up and the curvy side pointing in, then make a sandwich by putting the other piece 3 down on top. Pin it all together and sew around the edges with the two fins still inside, as shown. Turn it inside out and move on to…

THE HEAD: So take piece 6 and the ten arms you’ve already done. Lay the arms, fabric side facing you, out with the arms’ top seams in a line half an inch from the top of piece 6. The order should be arm arm arm arm BIG ARM arm arm arm arm BIG ARM. The legs should be almost entirely covering piece 6. Pin them in place and sew a straight line through the individual legs seams to attach the legs to piece 6.

When you pick up the other side of piece 6, you now have something resembling a really weird untied hula skirt. Sew together the two 9-inch ends of piece 6 with the fabric side of the arms on the outside, and keep it inside out for the moment.

PUTTING IT ALL TOGETHER: Fit the open end of the body through the arms (still fabric side facing out) and pull the edge all the way through the felt cylinder so it’s even with the edge that DOESN’T have arms attached to it. Sew around the diameters of the head cylinder and the body cylinder to attach them, then pull the legs down over the head and you’re almost done!

Stuff the body, then seal it off by sewing piece 5 over the open end (even if you do have a functional sewing machine, you’ll probably have to do this part by hand).

THE EYES: Sew the black circles on the white circles and whipstitch the eyes onto the head. You do this last because you can’t tell where they’re going to end up on the end product if you put them on before stuffing the body.

[mhoecker]

I imagine the offices of @deepseanews are covered in these.  Please no one tell me otherwise.

[fuckyeahfluiddynamics]

When a fluid is stratified into layers, it’s possible to have waves generated and transmitted along the interface between layers. Because these waves remain inside the bulk fluid, they are called internal waves. They often occur in the atmosphere or the ocean as fluids with different properties move past changing terrain. The Strait of Gibraltar is an excellent source of internal waves. The tidal exchange of waters between the Mediterranean Sea and Atlantic Ocean takes place through a narrow corridor interrupted by the peak of Camarinal Sill. The internal waves generated by the constriction are large enough that their effect on the surface flow is visible to satellites. The video above visualizations data from a numerical simulation of flow through the Strait, showing the obstacles, flow, and wave structures generated. (Video credit: J.C. Sanchez Garrido et al.)

[mhoecker]

Map of the strongest stratification found in the water column.  Vertical mixing is easiest in regions where stratification is weak.  The dependence on season is strongest in polar regions, especially regions associated with deep convection in the North Atlantic and the Southern Ocean.

Companion to the previous post

[mhoecker]

Depth of the pycnocline extracted from the MIMOC http://www.pmel.noaa.gov/mimoc/ data set.  You can see the seasonal oscillation between deep convection and shallow stratification in the polar regions.  Also visible is the persistent pool of warm water in the West Pacific in contrast to the shallow stratification near the strong upwelling off the west coast of South America.

[mhoecker]

I like symmetry yes I do!

I like symmetry how about you?

[mhoecker]

Normally I like my oceanography more fluid but the Ross Sea is so nifty https://www.youtube.com/watch?v=VENwb1UfodI via @NASAGoddard

[fuckyeahfluiddynamics]

Rotation can cause non-intuitive effects in fluid dynamical systems. UCLA Spinlab’s newest video tackles the problem using four demonstrations. The first two deal with droplets released in air, first in a non-rotating environment and then in a rotating one. As one would expect, in a non-rotating environment, droplets fall through the tank in a straight line. When rotating, though, the droplets follow a deflected, straight-line path due to centrifugal effects. This is the same as the way passengers in a car feel like they’re being thrown to the outside of a turn on a curvy road. When the experiment is repeated with a tank of water instead of air, the results are different. The densities of the creamer and water are much closer to one another, so the droplet falls much slower than before. The tank now rotates faster than time it takes the drop to fall. This smaller timescale means that the droplet experiences more acceleration from Coriolis forces than centrifugal forces in the rotating tank of water. Thus, instead of being thrown outward, the drop now forms a column aligned with the axis of rotation. (Video credit: UCLA Spinlab; submitted by Jon B.)

[mhoecker]

Getting accurate rain rates for ocean models is difficult. Adjacent rain gauges on a ship can measure wildly different values.  This is important because a downpour can be a stronger influence on surface buoyancy than evaporative cooling or solar heating. (For scale mid-day equatorial sun is like laying down under four full strength bathroom heat lamp bulbs, 250W each)  Thankfully the good people at NASA Goddard http://www.nasa.gov/centers/goddard/home and others are hard at work trying to get a smoother product for those of us who keep our oceans inside a lattice of silicon and copper.

[mhoecker]

I love the Pacific Marine Environmental Laboratory http://www.pmel.noaa.gov/ they have wonderful toys and they like to share (their data)

[mhoecker]

Often doing science comes down to counting things, @vihartvihart muses over what it means to count things in a way that is both interesting and entertaining.

[fuckyeahfluiddynamics]

Like many sports, the gameplay in football can be strongly affected by the ball’s spin. Corner kicks and free kicks can curve in non-intuitive ways, making the job of the goalie much harder. These seemingly impossible changes in trajectory are due to airflow around the spinning ball and what’s known as the Magnus effect. In the animation above, flow is moving from right to left around a football. As the ball starts spinning, the symmetry of the flow around the ball is broken. On top, the ball is spinning toward the incoming flow, and the green dye pulls away from the surface. This is flow separation and creates a high-pressure, low-velocity area along the top of the ball. In contrast, the bottom edge of the ball pulls dye along with it, keeping flow attached to the ball for longer and creating low pressure. Just as a wing has lift due to the pressure difference on either side of the wing, the pressure imbalance on the football creates a force acting from high-to-low pressure. In this case, that is a downward force relative to the ball’s rightward motion. In a freely moving football, this force would curve its trajectory to the side. (GIF credit: SkunkBear/NPR; original video: NASA Ames; via skunkbear)

[fuckyeahfluiddynamics]

The Kelvin-Helmholtz instability looks like a series of overturning ocean waves and occurs between layers of fluids undergoing shear. This video has a great lab demo of the phenomenon, including the set-up prior to execution. When the tank is tilted, the denser dyed salt water flows left while the fresh water flows to the right. These opposing flow directions shear the interface between the two fluids, which, once a certain velocity is surpassed, generates an instability in the interface. Initially, this disturbance is much too small to be seen, but it grows at an exponential rate. This is why nothing appears to happen for many seconds after the tilt before the interface suddenly deforms, overturns, and mixes. In actuality, the unstable perturbation is present almost immediately after the tilt, but it takes time for the tiny disturbance to grow. The Kelvin-Helmholtz instability is often seen in clouds, both on Earth and on other planets, and it is also responsible for the shape of ocean waves. (Video credit: M. Hallworth and G. Worster)

[mhoecker]

Propeller Whirl Demonstration

Couple a gyroscope to an elastic beam and you get the whirl mode via @NASA_Langley

[mhoecker]

An impressive example from NASA of a minimal observation array to measure derivatives in three dimensions. Observation arrays all share the same problems, be they at in a lab, at sea or in space. The number of observation platforms limits the information you have about your field.

One gives you the value.

Two or more in a line give you a mean value and a one dimensional derivatives.  More sensors in the line allow higher order 1-D derivatives. Time series can be used to estimate one component of the signals propagation speed.

Three or more in a planar array measure the mean and two dimensional derivatives. More sensors in the arrays give higher order 2-D derivatives.  Time series can be used to estimate two components of the signals propagation speed.

Four in a volume filling array yield a mean and derivatives in all three dimensions.  More sensors in the array give higher order 3-D derivatives. Time series can be used to estimate all three components of the signals propagation speed.

[mhoecker]

Basics of surface gravity waves. Top image is exaggerated to show amplitude. Lower image has typical ocean waves slope (A*k~0.1) and shows velocity dependence on depth.

[mhoecker]

Idealized internal gravity wave packet showing how group velocity is perpendicular to phase velocity.

Reposted from my YouTube

http://youtu.be/xf8Y6YYxvew

[mhoecker]

Comparing running average weights generated from window functions which ensure continuous derivatives of ever increasing order.  For samples over an interval T (t in the range 0,T) the window is sin(π t/T)k and has a roll off proportional to f-2-2*k in the power spectra and in the filter transfer function so go forth and design your own windows/running average filters with a prescribed roll off.

P.S.

The first zero crossing of the transfer function is around f~(1+.5*k)/T but that's approximate

P.P.S.

The generating script which is meant as a filter https://github.com/mhoecker/Process-DynaMO-LES/blob/desktop/harmfill.m