Then

a - b·b - a´ a - a´

cos 2n[alpha] - cos 2n[theta] = 2------------ = ½ sin² 2n[alpha]------

a - a´·u - b u - b

[root](a - b.b - a´)[root](u - a·u - b´)

sin 2n[theta] = 2---------------------------------------- (20)

a - a´·u - b

[root](a - a·b - a´)

= sin 2n[alpha]--------------------;

u - b

2n c / b \ [root](a - b·b - a´)

----- ----- = ( 1 + ----- ) -------------------- (21)

[phi] [rho] \ u - b/ [root](u - a·u - a´)

a - a´ + (a + a´) cos 2n[alpha] - [a + a´ + (a - a´) cos 2n[alpha] cos 2n[theta]

= --------------------------------------------------------------------------------

(a - a´) sin² 2n[alpha]

cos 2n[alpha] - cos 2n[theta]

× -----------------------------

sin 2n[theta]

Along the wall AB, cos n[theta] = 0, sin n[theta] = 1,

a > u > b, (22)

/ Q \^n /b - a´ /a - u

ch n[Omega] = i sh log ( --- ) = i / ------ / ------ (23)

\ q / \/ a - a´ \/ u - b´

/ Q \^n /a - b /u - a´

sh n[Omega] = i ch log ( --- ) = i / ------ / ------ (24)

\ q / \/ a - a´ \/ u - b´

ds ds d[phi] m c Q

-- = ------ ------ = ------ = --- -- (25)

du d[phi] dt [pi]qu [pi] qu

_

AB / a Q du

[pi]-- = | --- --

c _/ b q u

_ _ _

/ | [root](a - b)[root](u - a´) + [root](b - a´)[root](a - u) |^1/n du

= | | --------------------------------------------------------- | --. (26)

_/ |_ [root](a - a´)[root](u - b´) _| u

Along the wall Bx, cos n[theta] = 1, sin n[theta] = 0,

b > u > 0 (27)

/ Q \^n /b - a´ /a - u

ch n[Omega] = ch log ( --- ) = / ------ / ------ (28)

\ q / \/ a - a´ \/ b - u´

/ Q \^n /a - b /u - a´

sh n[Omega] = sh log ( --- ) = / ------ / ------. (29)

\ q / \/ a - a´ \/ b - u

At x where [phi] = [oo], u = 0, and q = q0,

/ Q \^n /b - a´ / a /a - b / -a´

( --- ) = / ------ / --- + / ------ / ---. (30)

\ q0 / \/ a - a´ \/ b \/ a - a´ \/ q

In crossing to the line of flow x´A´P´J´, [psi] changes from 0 to m,

so that with q = Q across JJ´, while across xx´ the velocity is q0, so

that

m = q0.xx´ = Q.JJ´ (31)

_ _

JJ´ q0 | /b - a´ / a /a - b / -a´ |^1/n

-- = --- = | / ------ / --- - / ------ / --- | , (32)

xx´ Q |_ \/ a - a´ \/ b \/ a - a´ \/ q _|

giving the contraction of the jet compared with the initial breadth of

the stream.

Along the line of flow x´A´P´J´, [psi] = m, u = a´e^(-[pi][phi]/m),

and from x´ to A´, cos n[theta] = 1, sin n[theta] = 0,

/ Q \^n /b - a´ /a - u

ch n[Omega] = ch log ( --- ) = / ------ / ------, (33)

\ q / \/ a - a´ \/ b - u´

/ Q \^n /a - b /u - a´

sh n[Omega] = sh log ( --- ) = / ------ / ------. (34)

\ q / \/ a - a´ \/ b - u´

Encyclopaedia Britannica, 11th Edition, "Hydromechanics" to "Ichnography" Volume 14, Slice 2 · 第 54 / 120 题