GRGR (20) Part 3, Episode 13: Notes, Part 1 of 2

[Michael Perez]

450.6  “log cabin + c = houseboat”  That is, a log (as opposed
to “logarithm of”) cabin plus “sea” is a houseboat.  [A-her,
a-her, a-her.]

453.21  “Péclet”  from: 
http://www.me.utexas.edu/~heatran/bios/peclet.html  “A
French physicist, born February 10, 1793, at Besancon, France,
Jean Claude Eugene Peclet became one of the first scholars of
the Ecole Normale at Paris (Gay-Lussac and Dulong being his
teachers). He was elected professor at the College de Marseille
in 1816, teaching physical sciences there until 1827. He
returned to Paris when he was nominated Maitre de
Conferences at the Ecole Normale and was elected Professor at
the important Ecole Centrale des Arts et Manufactures. 
  “Peclet's publications were famous for their clarity of
style, sharp-minded views and well performed experiments.
His most famous book _Traité de la Chaleur et de Ses
Applications aux Arts et Aux Manufactures_ (Paris 1829) was
distributed world-wide and translated into German. 
  “He retired in 1852 to devote himself exclusively to
teaching and continued lecturing until his death on December
6, 1857 in Paris.”

  And from:
http://astrosun.tn.cornell.edu/students/rathbun/lpsc29/time4.html  
  “Recall that the Peclet Number is the ratio of the thermal
diffusion timescale to the dynamical timescale. When
expressed in terms of physical quantities, it is a function of the
surface gravity, the initial radius of the blob, the density of the
blob, the temperatures of the diapir and of the surrounding
medium, the viscosity fo the medium and the thermal
diffusivity of the medium.
  “The viscosity and the termal diffusivity of ice can be
written as functions on only the temperatre of the medium, so
the Peclet Number is only a function of the temperature of the
medium and the initial radius of the blob. 
  “If we combine this with the maximum initial depth as a
function of the initial Peclet Number, then we have the
maximum initial depth as a function of only th initial radius of
the blob and the temperature of the surrounding medium.”

454.27  “The Rocket creating it own great wind . . . no wind
without both, Rocket and atmosphere”  This is of some
conceptual importance.  Growing up during the space age as I
did, some fundamentals of propulsion go unquestioned.  While
the rocket within the atmosphere is “pushing” against air
molecules for some of its lift, but fighting against full gravity
and the weight of the atmosphere that is also being pulled by
gravity.  Fahringer may also be trying to say that outside the
atmosphere, there are no air molecules against which to push,
but also less effects of gravity and no air to swim through.  The
rocket must rely on its own “wind” - the gases produced by the
combustion within it - to propel itself.  The speed of the gases
expelled by this reaction - the rocket’s wind - remains constant,
but the relative airspeed changes as it is frees itself from the
effects of gravity.  Note also the capitalization of Rocket in the
quoted passages.

454.28  “venturi”  from WWWebster Dictionary at 
http://www.m-w.com/cgi-bin/dictionary
“Main Entry: ven·tu·ri
Function: noun
Etymology: G. B. Venturi died 1822 Italian physicist
Date: 1887
: a short tube with a tapering constriction in the middle that
causes an increase in the velocity of flow of a fluid and a
corresponding decrease in fluid pressure and that is used
especially in measuring fluid flow or for creating a suction (as
for driving aircraft instruments or drawing fuel into the flow
stream of a carburetor)”




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