user's manual for corhyd: an internal diffuser hydraulics model - IfH

Gradual contraction (Idelchik 1986)
4
3
2
( − .0125⋅
n + 0.0224⋅
n − 0.00723⋅
n + 0.0044⋅
n − 0.00745)
3 2
ζ
c
= 0
0
0
0
0
⋅ ( β − 2πβ
−10β)
with A0
and β in rad
n = 1.0 A
0
≤
1
For β > 50°, the formulation for gradual expansion leads to a greater loss coefficient than the one
for a sudden expansion. Therefore Idelchiks formulas was adopted so that for β > 50° losses are
equal the loss for β = 50°.
Code (see files: CommonFeederPipe.m, feederpipes.m, DiffuserLosses.m,
Losses_common_feeder.m).
Bending
(reference
velocity =
velocity after
bending
Bend (Kalide 1980)
3.5
⎡
⎛ D ⎞ ⎤ δ
ζ0
= ⎢0.131+
0.159⎜
⎟ ⎥ ⋅
⎢⎣
⎝ R ⎠ ⎥⎦
180°
where D is the pipe diameter and R the radius of the bend. Often applied as R = 3D. Delta is the
angle of the bend (e.g. 90° for rectangular bends).
Code (see files: CommonFeederPipe.m, feederpipes.m, DiffuserLosses.m,
Losses_common_feeder.m)
Division
flow
of
Friction due to bend (Idelchik 1986)
L
ζ
fr
= λ with
L δ R
= π
D D 180°
D
(Idelchik 1986)
∆p
ζ
s
c,
s
ζ
s
= =
2
ρV
/ 2 ( / ) 2
s
Vs
Vc
∆p
ζ
st
c,st
ζ
st
= =
2
ρV
( ) 2
st
/ 2 Vst
/ Vc
ζ
c,s
from Diagram 7.15, ζ
c, st
from Diagram 7.17 (Idelchik, 1986 or Annex chapter 10). Curves
fitted by the following code:
Determination of zeta' (in the following zeta double underline) c,s
vRatio = (q(i)/Ar(i)) / ((sum_q(i-1)+q(i))/Ad(i));
if Dr(i)/Dd(i)