Sunday, September 13, 2009

Boundary Layers

I walked outside yesterday and felt the wind blowing around me and I thought to myself "There's a boundary layer around me!" It was so exciting.

You see, a boundary layer is that layer of air right up close to some object that has fluid flowing over it. Suppose you were like me and you went and stood outside with the wind rushing past you. Because of friction, the air exactly next to your skin is not moving, it has a velocity of zero. And then as you get farther from your skin, the friction is less and the air begins to move slowly and so on, increasing in speed until it has reached the same speed as the rest of the flowing air around you. The section of air from right up exactly near skin to the point where is has increased in speed to the rest of the air is called the boundary layer because it is a layer all around you of air changing velocities. Now the reason you don't feel this is because it is so extremely small. But it becomes important when working with things like submarines or airplanes because the boundary layer is larger and affects the performance of the object more.
But they can be fun to learn about.

Tuesday, September 08, 2009

Dimensional Analysis and the Buckingham pi Theorem!!!

The Buckingham pie Theorem is used to help Dimensional Analysis of pies by using coefficients and coefficient connoisseurs to analyze the dimensions of the circularity of the pie and the parameters thereof including and not limited to the radius, the circumference, and the angular velocity.

The following definition is premeditatively and with the deliberate design to confuse categorically and without exception wrong and misleading. Pay no attention to it.

Dear me, what fun it is to use a Thesaurus. And truly the Buckingham pi Theorem has nothing whatever to do with pies or the analysis thereof. It is really instead a method of finding things out about fluid flows without having to use dimensions which is especially nice for comparing things particularly when you have some model of some prototype. For example, suppose I want to build a gigantic jet engine and I know that the power it uses is dependent on some certain variables (like how fast the engine is pushing air out). Well, to actually build it and then run and test it and then modify it, etc... would take a long time and a lot of money. So I build a little tiny model instead. And so I have to change a number of things to get results that will also be true for the big gigantic engine. And I can compare everything by using dimensionless units in the very neat method outlined by the Buckingham pi Theorem.

Thursday, September 03, 2009

mouses and micetraps

Heh heh, so yeah, I never did get around to posting more over the summer.
It was a great summer though.
I discovered Isaac Asimov's robot series with Elijah Baley.
And found that the Stewart's on my way home had tasty chocolate milk.
And we had many girls over for dinner every Monday night.
And lots of other little things went on.

And just this week the Semester started again.

And, horror of horrors! A mouse ran across my floor Sunday night. I was not happy. Mice should have no business running across my floor.
So my roommate's sister got us some mousetraps (not sticky roommate and I both agreed that we detested those). And together we set one on a paper plate in our kitchen Tuesday night. It sprung almost immediately after, but it turned out it just wasn't set firmly. So we reset it and then avoided it like the plague. Then, yesterday, I came home after TAing a class and saw around the corner that the trap had flipped over. So I peeked a little closer and sure enough: we had our mouse!
My roommate and I were both disgusted and contemplated calling someone up and bribing them with dinner if they took care of our mouse. But then we decided that we were independent young women so we could jolly well take care of our own mouse. And we did...using a shovel and a garbage bag.
We were so happy after that that we ended up calling people up for dinner anyway just to celebrate.