Re: PV Dirigible Prop Alternative To Super Pressure

From	jimp@specsol.spam.sux.com
Newsgroups	sci.physics
Subject	Re: PV Dirigible Prop Alternative To Super Pressure
Date	2016-06-11 17:38 +0000
Organization	A noiseless patient Spider
Message-ID	<utut2d-9o9.ln1@mail.specsol.com> (permalink)
References	(5 earlier) <07e56ba3-9ceb-4b0a-b65f-7586249be835@googlegroups.com> <3mnr2d-hd2.ln1@mail.specsol.com> <5b47f95b-50b8-420e-b53b-63ef9afdecfe@googlegroups.com> <qgis2d-315.ln1@mail.specsol.com> <ec05fe4b-f839-4b5b-993a-82517617a93f@googlegroups.com>

Show all headers | View raw

Bret Cahill <bretcahill@aol.com> wrote:
>> >> >> >> For the third time, why is the Reynolds number of any sphere, of any size,
>> >> >> >> and of any material always the same number?
>> >> >> > 
>> >> >> > If the diameter or "characteristic dimension" is larger or smaller, you get a larger or smaller Nre.
>> >> >> > 
>> >> >> > If the velocity in inversely proportional to diameter then the Nre is the same for all sizes of that shape in that fluid, i.e. a golf ball going 300 km/hr has the same Nre as a cyclist helmet going 30 km/hr and the air holes in the helmet actually _reduce_ drag like the dimples on the golf ball reduce drag.
>> >> >> > 
>> >> >> > Maybe you meant the Reynolds number can be applied to any size object.
>> >> >>  
>> >> >> The Reynolds number is directly proportional to the diameter of the
>> >> >> cross section, so the comment about size is incorrect.
>> >> >> 
>> >> >> Equal sized spheres, no matter the material, be they soap bubbles or lead,
>> >> >> have the same Reynolds number.
>> >> > 
>> >> > The speeds would need to be the same as well, a rare coincidence because
>> >> > soap bubbles always move slowly w/ respect to wind speed.
>> >> 
>> >> As the Reynolds number is directly proportional to velocity, 
>> > 
>> > then different speeds => different Nre.
>> > 
>> >> comparing
>> >> Reynolds numbers at differing speeds 
>> > 
>> > A golf ball going 300 km/hr has the same Nre as a cyclist helmet going
>> > 30 km/hr because the helmet ix 10X bigger than the ball.
>> > 
>> > The air holes in the helmet actually _reduce_ drag like the dimples on
>> > the golf ball reduce drag.
>> > 
>> > The reason is the speeds and diameters are different but the Nre are
>> > the same, 50K - 100K where dimpling works.
>>  
>> As Reynolds number is dependant on speed as you have realized,
> 
> Speed as well as diameter.
> 
> A small high speed object can have the same Nre as a large low speed object.

Therefor talking about Reynolds number without speed is pointless.


-- 
Jim Pennino

Thread

PV Dirigible Prop Alternative To Super Pressure Bret Cahill <bretcahill@aol.com> - 2016-06-04 12:47 -0700
  Re: PV Dirigible Prop Alternative To Super Pressure jimp@specsol.spam.sux.com - 2016-06-05 02:11 +0000
    Re: PV Dirigible Prop Alternative To Super Pressure Bret Cahill <bretcahill@aol.com> - 2016-06-04 22:22 -0700
      Re: PV Dirigible Prop Alternative To Super Pressure jimp@specsol.spam.sux.com - 2016-06-05 17:36 +0000
        Re: PV Dirigible Prop Alternative To Super Pressure Bret Cahill <bretcahill@aol.com> - 2016-06-05 13:52 -0700
          Re: PV Dirigible Prop Alternative To Super Pressure jimp@specsol.spam.sux.com - 2016-06-05 22:56 +0000
            Re: PV Dirigible Prop Alternative To Super Pressure Bret Cahill <bretcahill@aol.com> - 2016-06-08 00:57 -0700
              Re: PV Dirigible Prop Alternative To Super Pressure jimp@specsol.spam.sux.com - 2016-06-08 19:27 +0000
                Re: PV Dirigible Prop Alternative To Super Pressure Mahipal <mahipal7638@gmail.com> - 2016-06-08 19:16 -0700
                Re: PV Dirigible Prop Alternative To Super Pressure jimp@specsol.spam.sux.com - 2016-06-09 02:52 +0000
                Re: PV Dirigible Prop Alternative To Super Pressure Mahipal <mahipal7638@gmail.com> - 2016-06-09 06:55 -0700
                Re: PV Dirigible Prop Alternative To Super Pressure jimp@specsol.spam.sux.com - 2016-06-09 16:22 +0000
                Re: PV Dirigible Prop Alternative To Super Pressure Mahipal <mahipal7638@gmail.com> - 2016-06-09 13:23 -0700
                Re: PV Dirigible Prop Alternative To Super Pressure jimp@specsol.spam.sux.com - 2016-06-09 21:14 +0000
                Re: PV Dirigible Prop Alternative To Super Pressure Mahipal <mahipal7638@gmail.com> - 2016-06-09 14:49 -0700
                Re: PV Dirigible Prop Alternative To Super Pressure Bret Cahill <bretcahill@aol.com> - 2016-06-09 19:46 -0700
                Re: PV Dirigible Prop Alternative To Super Pressure jimp@specsol.spam.sux.com - 2016-06-10 05:53 +0000
                Re: PV Dirigible Prop Alternative To Super Pressure Bret Cahill <bretcahill@aol.com> - 2016-06-10 10:07 -0700
                Re: PV Dirigible Prop Alternative To Super Pressure jimp@specsol.spam.sux.com - 2016-06-10 17:49 +0000
                Re: PV Dirigible Prop Alternative To Super Pressure jimp@specsol.spam.sux.com - 2016-06-10 21:22 +0000
                Re: PV Dirigible Prop Alternative To Super Pressure Bret Cahill <bretcahill@aol.com> - 2016-06-10 19:40 -0700
                Re: PV Dirigible Prop Alternative To Super Pressure jimp@specsol.spam.sux.com - 2016-06-11 05:00 +0000
                Re: PV Dirigible Prop Alternative To Super Pressure Bret Cahill <bretcahill@aol.com> - 2016-06-11 01:13 -0700
                Re: PV Dirigible Prop Alternative To Super Pressure jimp@specsol.spam.sux.com - 2016-06-11 17:38 +0000
  Re: PV Dirigible Prop Alternative To Super Pressure Bret Cahill <bretcahill@aol.com> - 2016-06-08 00:58 -0700
    Re: PV Dirigible Prop Alternative To Super Pressure noTthaTguY <abu.kuanysh05@gmail.com> - 2016-06-08 07:23 -0700
    Re: PV Dirigible Prop Alternative To Super Pressure Bret Cahill <bretcahill@aol.com> - 2016-06-08 14:18 -0700
      Re: PV Dirigible Prop Alternative To Super Pressure Sergio <invalid@invalid.com> - 2016-06-08 16:26 -0500
      Re: PV Dirigible Prop Alternative To Super Pressure jimp@specsol.spam.sux.com - 2016-06-08 21:41 +0000
        Re: PV Dirigible Prop Alternative To Super Pressure benj <nobodyxx@gmail> - 2016-06-08 20:23 -0400
          Re: PV Dirigible Prop Alternative To Super Pressure jimp@specsol.spam.sux.com - 2016-06-09 00:34 +0000
            Re: PV Dirigible Prop Alternative To Super Pressure benj <nobodyxx@gmail> - 2016-06-08 21:07 -0400
              Re: PV Dirigible Prop Alternative To Super Pressure "hanson" <hanson@quick.net> - 2016-06-08 19:22 -0700
              Re: PV Dirigible Prop Alternative To Super Pressure jimp@specsol.spam.sux.com - 2016-06-09 02:36 +0000
  Re: PV Dirigible Prop Alternative To Super Pressure Bret Cahill <bretcahill@aol.com> - 2016-06-08 14:42 -0700
    Re: PV Dirigible Prop Alternative To Super Pressure Bret Cahill <bretcahill@aol.com> - 2016-06-09 20:20 -0700
      Re: PV Dirigible Prop Alternative To Super Pressure Bret Cahill <bretcahill@aol.com> - 2016-06-10 10:10 -0700
        Re: PV Dirigible Prop Alternative To Super Pressure Bret Cahill <bretcahill@aol.com> - 2016-06-11 11:02 -0700
      Re: PV Dirigible Prop Alternative To Super Pressure Bret Cahill <bretcahill@aol.com> - 2016-06-10 20:11 -0700

csiph-web