2
+
= 0
The other condition follows
Prandtl's equation. Its advective terms must vary with the downstream distance
in a manner that is identical to the variation of the diffusion term. Considering how some of the expressions vary - there is, for example
,
and it is also evident that

we get for variations of the first advective term:

.. while for the diffusion term
the variation with downstream distance is

Comparing the exponents in these approximations for the two terms leads to the other condition:
2
- 1 =
- 2 
The solutions satisfying the two contitions are:
= - 1/3,
= 2/3.
A similar derivation may be done for the axisymmetric jet (issuing from a round hole nozzle), where the momentum condition is
so that the corresponding condition for the exponents is
and the resultant values of the exponents are:
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This is page Nr. I04 from textbook
Vaclav TESAR : "BASIC FLUID MECHANICS"
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