Introduction to hydrodymanics?

[Misr]

Hello World
I can't introduce the concepts of hydrodynamics into my mind,such as the streamline.
I can't imagine what is a streamline?
What makes us say that the flow is turblant or the flow is steady?
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"the direction of the tangent drawn at any point on the streamline represents the direction of tangential velocity" so what is tangential velocity?
[PLAIN]http://img265.imageshack.us/img265/9021/unled11e.jpg
I imagine that,this means ,if the fluid particle was to leave the streamline,it will move in the direction and with this tangential velocity.Is that true?
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"the rate of flow is constant along the path of the flow,since fluids are incompressible"
I don't understand.What is the rate of flow?
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why is the blood flow in aorta faster than the other arteries?
I know how to explain this biologically,it is because aorta is the nearest to the heart
but if we look at this in a physical point of view,We will find that the cross sectional area of aorta is bigger,so the speed of blood flow in the aorta should be smaller.then how could we explain this physically?may be because the speed of blood flow in Aorta is distributed among those arteries so the speed becomes less in smaller arteries.
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I can't imagine at all,what is viscosity?
[PLAIN]http://img36.imageshack.us/img36/4862/unled123j.png
If we imagine a liquid between two plates ,plate A is moving while plate B is not moving
Why does the speed of the fluid decreases as we go down from A to B?

what is the force of viscosity?and why is this force inversely proportional to the vertical distance between the the moving layer and the layer that is not moving?

After answering my questions,could you recommend some good websites about fluids?
my favourite website "the physicsclassrooms" usually uses a very simple language
I used this website to understand many concepts about waves but misfortunately,there's no tutorials about fluids in this website.

P.S I'm really serious in learning and understanding new ideas in the correct way,so please don't let me down..
another P.S my physical knowledge is very basic

Thanks in advance..

 

[Curl]

How good is your maths?

 

[Misr]

Not good.I study biology this year instead of maths

 

[NascentOxygen]

I can't imagine what is a streamline?

In non-turbulent flow, it is the path traced out by a particle in the flow.

What makes us say that the flow is turblant or the flow is steady?

If flow becomes turbulent, streamlines get scrambled up and destroyed.

so what is tangential velocity?

The instantaneous velocity of a particle in the stream.

"the rate of flow is constant along the path of the flow,since fluids are incompressible"
I don't understand.What is the rate of flow?

measured in litres per minute.

I can't imagine at all,what is viscosity?

Compare honey with water.

 

[Misr]

In non-turbulent flow, it is the path traced out by a particle in the flow.

Only one particle?or particles of a certain layer in the fluid?

The instantaneous velocity of a particle in the stream.

Yeah,that's good but why does the direction of the instanoeus velocity different from the actual direction of the particle?
could you read this?:

I imagine that,this means ,if the fluid particle was to leave the streamline,it will move in the direction and with this tangential velocity.Is that true?

tell me if I'm thinking of this in the right way or not

measured in litres per minute.

Great got it now

Compare honey with water.

Yeah I can imagine this but I need some detail:

If we imagine a liquid between two plates ,plate A is moving while plate B is not moving
Why does the speed of the fluid decreases as we go down from A to B?

what is the force of viscosity?and why is this force inversely proportional to the vertical distance between the the moving layer and the layer that is not moving?

when we say that the viscosity of honey is more than that of water , we probably mean that the friction forces between the layers of the honey is greater than that of water
right?
thanks

 

[NascentOxygen]

Only one particle?or particles of a certain layer in the fluid?

Not layers. Streamlines are lines; pencil-thin channels of tiny dimension. Picture millions of parallel transparent pipes each channelling a stream of molecules. Strings of molecules.

Yeah,that's good but why does the direction of the instanoeus velocity different from the actual direction of the particle?

It doesn't. Because what you understand by the direction of the particle is in fact its instantaneous velocity.

Yeah I can imagine this but I need some detail:

Well, you are going to have to research some of your assignment yourself. I'm just giving you a start.

when we say that the viscosity of honey is more than that of water , we probably mean that the friction forces between the layers of the honey is greater than that of water
right?

Viscous friction, yes.

 

[Misr]

Not layers. Streamlines are lines; pencil-thin channels of tiny dimension. Picture millions of parallel transparent pipes each channelling a stream of molecules. Strings of molecules.

So streamlines are strings of molecules moving together on a line?

It doesn't. Because what you understand by the direction of the particle is in fact its instantaneous velocity.

I don't understand what you mean
The particle is moving in the direction of streamline right?
and the instanoeus velocity is tangent to the streamline
so the actual path of the particle is different from the direction of tangential velocity
how could you explain this??
Another point is that I don't know wheather this idea is correct or not:

I imagine that,this means ,if the fluid particle was to leave the streamline,it will move in the direction and with this tangential velocity.Is that true?

Well, you are going to have to research some of your assignment yourself. I'm just giving you a start.

and that's what I'm doing now.I'm already researching on the topic and there are some unanswered questions about viscosity in this thread
Actually,I don't understand what kind of research do you mean

Thanks

 

[boneh3ad]

So streamlines are strings of molecules moving together on a line?

Not, streamlines are not actually a physical thing, but more of a mathematical construct along which certain properties are constant. There is no line of particles, though if there was, they would all share the same time history of their properties.

The particle is moving in the direction of streamline right?
and the instanoeus velocity is tangent to the streamline
so the actual path of the particle is different from the direction of tangential velocity
how could you explain this??

No. The tangent vector of any line is the direction of the line at that point. If you froze time, a particle at that point would have a velocity vector pointing tangent to its associated streamline.

Another point is that I don't know wheather this idea is correct or not:

If fluid particles were attached to streamlines then yes, that would make sense. As it is, it is an acceptable way to visualize the situation.

 

[NascentOxygen]

So streamlines are strings of molecules moving together on a line?

That's how you can picture them. Though of course they are not bonded together; conditions they experience just happen to be identical so they follow the same path as the particles before and after them. Like a multi-line highway of well-behaved cars all headed for the same destination, and threading their way along the arterial freeways of a city.

The particle is moving in the direction of streamline right?
and the instanoeus velocity is tangent to the streamline

So that if you consider a sufficiently short length of the streamline, then it is its own tangent. So the velocity vector lies along the path.

so the actual path of the particle is different from the direction of tangential velocity

No. The tangent changes as the path changes, so that the tangent is always along the path (provided you consider a sufficiently short piece of the path).

Actually,I don't understand what kind of research do you mean

Library or search engine research.