Depth vs speed

Depth vs speed

Post by Brett Dani » Tue, 16 Mar 1993 11:26:51


I swim in a 55 yard pool that varies in depth from each end to the middle.
The pool is only 3' at each end and drops to 5' 8" in the middle.  The shape
is a little too difficult to draw, but the floor of the pool drops from about
3' 6" to 5' 8" over the middle third of the pool.  

My question is that my speed seems to drop over the middle third of the pool.
Is this an illusion caused by the floor being further from the eye? or am I
actually accelerating over the shallow ends of the pool?

--

Brett Daniel
School of Computing Science
Curtin University of Technology
Western Australia.

 
 
 

Depth vs speed

Post by atwood8.. » Tue, 16 Mar 1993 13:24:01

Quote:

> I swim in a 55 yard pool that varies in depth from each end to the middle.
> The pool is only 3' at each end and drops to 5' 8" in the middle.  The shape
> is a little too difficult to draw, but the floor of the pool drops from about
> 3' 6" to 5' 8" over the middle third of the pool.  

> My question is that my speed seems to drop over the middle third of the pool.
> Is this an illusion caused by the floor being further from the eye? or am I
> actually accelerating over the shallow ends of the pool?

> --

> Brett Daniel
> School of Computing Science
> Curtin University of Technology
> Western Australia.


I am a competitive swimmer at the University of Northern Iowa and I have had
similar experiences throughout my years of swimming.
It feels like you are swimming slower in a deep water pool due to the distance
between you and the bottom.  It is similar to flying in a plane and watching
the ground pass below, it doesn't feel like you are going really fast.  Some
people say that deep water pools actually are "faster" than more shallow pools.
It still doesn't feel like you are moving, but your times are actually nearly
the same.

|8-)

Jay "Drift" Atwood
University of Northern Iowa
Cedar Falls  IA  USA

 
 
 

Depth vs speed

Post by earhartgr.. » Tue, 16 Mar 1993 10:41:51

Quote:

> My question is that my speed seems to drop over the middle third of the pool.
> Is this an illusion caused by the floor being further from the eye? or am I
> actually accelerating over the shallow ends of the pool?
> Brett Daniel

From what I have read/heard, a deeper pool is faster, and although I am not
a physicist (Political Scientist and Historian) here is why.  As you swim,
or make any motion in water, you create not only horizontal waves (wakes),
but also vertical and diagonal ones.  Swimming in a shallow pool, it is
easier for these waves to refract off the bottom and move back and
interfere with you.  As such, the more depth you have, the more area you
have in which to absorb the shock of these diagonal and vertical waves.

For another, more visible, manifestation of this, look at world class
pools.  They will be, for the most part, 1.5 meters deep.  If they do it,
it must be fast.  Sidelight/Personal Interest Story: I swam in Munich's
olympic pool during January.  There (as well as a couple other European pools)
the depth was adjustible.  As I was warming down one day doing backstroke,
they dropped the depth for club practice.  As I went to place my feet on my
ground, what to my suprise did I find?  Water, and no floor!  Ok, my cute
little story's over, but I hope I helped to answer your question (or at
least fuel debate.)

Greg Earhart                                    Boy's Play Basketball
Buena Vista College                             Men Wrestle
Corfield, Iowa, USA                             Only ANIMALS Swim!

   "I'll argue anything for an hour, maybe two if I believe in it."

 
 
 

Depth vs speed

Post by Andrew Moo » Wed, 17 Mar 1993 07:57:25

Quote:

>it must be fast.  Sidelight/Personal Interest Story: I swam in Munich's
>olympic pool during January.  There (as well as a couple other European pools)
>the depth was adjustible.  As I was warming down one day doing backstroke,
>they dropped the depth for club practice.  As I went to place my feet on my
>ground, what to my suprise did I find?  Water, and no floor!  Ok, my cute

Okay, I'll bite, I had read these pools were "floor adjustable" and
although this probably quickly heads towards alt.trivia.pools but...
considering the quantity/mass of water, how do they adjust the depth ?

Andrew.

--
    Andrew Moore      |    Department of Robotics and Digital Technology
Ph:  +61 3 565 3218   |   Clayton Campus, Monash Uni, VIC 3168, Australia

 Be interested in the future, you will be spending the rest of your life there.

 
 
 

Depth vs speed

Post by Pete Moo » Wed, 17 Mar 1993 11:30:51

Quote:


>>Sidelight/Personal Interest Story: I swam in Munich's
>>olympic pool during January.  There (as well as a couple other European pools)
>>the depth was adjustible.  As I was warming down one day doing backstroke,
>>they dropped the depth for club practice.  As I went to place my feet on my
>>ground, what to my suprise did I find?  Water, and no floor!
>Okay, I'll bite, I had read these pools were "floor adjustable" and
>although this probably quickly heads towards alt.trivia.pools but...
>considering the quantity/mass of water, how do they adjust the depth ?

Most modern pools (or at least, those that I have seen) are constantly
overflowing, usually at the sides, while heated and filtered water is being
pumped in, usually through small jets in the bottom of the pool. The
overflow is collected, filtered, and pumped back in. Changing the depth of
the pool by raising or lowering the floor would presumably not affect this
arrangement, provided it was not done too quickly. Perhaps a mechanism
would be required to increase the inflow (when lowering the floor) or
discard some of the overflow (when rasing it).
--

 | The effort to understand the universe is one of the very few things |
 | that lifts human life above the level of farce, and gives it some   |  
 | of the grace of tragedy   -  Steven Weinberg                        |
 +---------------------------------------------------------------------+
 
 
 

Depth vs speed

Post by Benjamin John Keye » Wed, 17 Mar 1993 12:43:02

Though the idea of moving enormous volumes of water in and out of a pool
is an interesting engineering problem, i'm no longer an engineer and
would have to guess that the water volume is constant and the pool
bottom is merely moved up and down.   There must be some type of spill
over though when the pool depth is decreased.   Though used for
different purposes here there are some adjustable bottom pools in the
states.  (They are used for handicapped access and for serious
rehabilitation of accident victims.  drive whhel chair on to platform,
lower patient into pool.  simple and effective.)
 
 
 

Depth vs speed

Post by Larry Hua » Thu, 18 Mar 1993 00:38:56

Swimmers!  I think you all missed the point regarding adjustable
pool bottoms.  Think of it this way:  a pool is just a big
rectangular hole in the ground, and you can add a mechanical
movable floor layer to it (movable in the vertical direction).
This floor layer is full of small holes so that when it's moved
up or down it will not affect the volume of water in the pool.
Those of you who have swum in 50 M pools with a bulkhead dividing
it into two 25M halves will know what I mean.  The adjustable
pool bottom uses the same idea, only in the vertical direction.

 
 
 

Depth vs speed

Post by Doug.Gilli » Thu, 18 Mar 1993 00:53:08

Quote:


>> I swim in a 55 yard pool that varies in depth from each end to the middle.
>> The pool is only 3' at each end and drops to 5' 8" in the middle.  The shape
>> is a little too difficult to draw, but the floor of the pool drops from about
>> 3' 6" to 5' 8" over the middle third of the pool.  

>> My question is that my speed seems to drop over the middle third of the pool.
>> Is this an illusion caused by the floor being further from the eye? or am I
>> actually accelerating over the shallow ends of the pool?

>> --

>> Brett Daniel
>> School of Computing Science
>> Curtin University of Technology
>> Western Australia.

>I am a competitive swimmer at the University of Northern Iowa and I have had
>similar experiences throughout my years of swimming.
>It feels like you are swimming slower in a deep water pool due to the distance
>between you and the bottom.  It is similar to flying in a plane and watching
>the ground pass below, it doesn't feel like you are going really fast.  Some
>people say that deep water pools actually are "faster" than more shallow pools.

I don't understand all of the variables but I can say that everything I
have heard since my children began competitive swimming about a year ago
is that the deeper the pool the faster the times.  I think it has to do
with the amount of turbulance that is generated by the swimmers in the
water therefore it must be faster to swim in water with less turbulance.
This seems to hold true with one of the other factors that I have heard
which effects pool speed which is the type of lane lines and whether
there is an empty lane on each side of the pool.  Evidently large lane
lines deaden the waves generated by swimmers which effectively calms
the water.  Also, if there is a good bit of distance (an empty lane for
example) between the outside swimmer and the side wall of the pool, the
wave dies out and isn't deflected back as strongly.  To me, all of these
factors seem to be related to the smoothness/roughness of the water.
I'm sure there are other reasons but these are the ones I have heard of.

Based on what I have said above, you should actually be going faster over
the deeper part of the pool.

Just my .02 worth.  I would like to hear any other reasons why a deeper
pool is supposed to be faster.  Everyone I have talked with has said
that all other factors being even, the deeper the pool the faster.  Does
anyone disagree with this?

Doug Gilliam

Quote:
>It still doesn't feel like you are moving, but your times are actually nearly
>the same.

>|8-)

>Jay "Drift" Atwood
>University of Northern Iowa
>Cedar Falls  IA  USA

** Doug Gilliam (Fed. Systems)  803-739-6184
** NCR - MCPD Columbia          FAX 739-7318
** 3325 Platt Springs Rd.       VoicePlus 632

 
 
 

Depth vs speed

Post by Dick Ki » Thu, 18 Mar 1993 06:15:01

Quote:


>>it must be fast.  Sidelight/Personal Interest Story: I swam in Munich's
>>olympic pool during January.  There (as well as a couple other European pools)
>>the depth was adjustible.  As I was warming down one day doing backstroke,
>>they dropped the depth for club practice.  As I went to place my feet on my
>>ground, what to my suprise did I find?  Water, and no floor!  Ok, my cute

>Okay, I'll bite, I had read these pools were "floor adjustable" and
>although this probably quickly heads towards alt.trivia.pools but...
>considering the quantity/mass of water, how do they adjust the depth ?

Don't know for sure, but i would suspect that there is a real floor below the
adjustable false floor.

There's probably water in between the two.

There would need to be holes or grates in the false floor.

-dk

 
 
 

Depth vs speed

Post by Kevin Henders » Thu, 18 Mar 1993 15:34:06

Quote:
> My question is that my speed seems to drop over the middle third of the  
pool.
> Is this an illusion caused by the floor being further from the eye? or  
am I
> actually accelerating over the shallow ends of the pool?

There is physical evidence that shows the deeper the cannal/pool relative  
to the bow (sp.) size the faster the vessel will travel because of less  
resistance.  Waves, apparantly hit the bottom and bonce back and cause  
some extra resistance.

I have been told, that relative to the size of humans (around 6'), that  
appropriate depth for a pool to be without any added resistance is 8 feet  
or more.  Most good pools are this depth.

Incidently, Ben Franklin did, I believe, the first study on resistance in  
relation to the vessels length in some cannals in France, when they were  
trying to develop a faster way to haul produce/trade.

Hope this helps.

Kevin C. Henderson

Go Stanford Card!  Stanford Men's Swimming No. 1