HP 50G, User Manual, Page: 228 / 887

Page 6-22
The combined equation has primitive variables: h
f
, Q, L, g, D,
ε
, and Nu .
Launch the numerical solver
(
‚Ï
@@OK@@ )
to see the primitive variables listed
in the SOLVE EQUATION input form:
Suppose that we use the values hf = 2 m,
ε
= 0.00001 m, Q = 0.05 m
3
/s, Nu
= 0.000001 m
2
/s, L = 20 m, and g = 9.806 m/s
2
, find the diameter D. Enter
the input values, and solve for D, The solution is: 0.12, i.e., D = 0.12 m.
If the equation is dimensionally consistent, you can add units to the input
values, as shown in the figure below. However, you must add those units to the
initial guess in the solution. Thus, in the example below we place 0_m in the D:
field before solving the problem. The solution is shown in the screen to the right:
Press
`
to return to normal calculator display. The solution for D will be listed
in the stack.
⎟
⎟
⎟
⎟
⎠
⎞
⎜
⎜
⎜
⎜
⎝
⎛
⋅ =
Nu
D
QD
D
DARCY
gD
L Q
h
f
4 /
,
8
2
5 2
2
π
ε
π