Principle And Practice Of Hotwire Constant Temperature ...

11 th Israeli Symposium on
Jet Engines and Gas
Turbines, October 2012
Technion, Israel
Sensitivity Analysis
Logarithmic differentiation of Nu gives:
Re f ( , U , T 0
) M f( U , T 0
)
(Re, M, )
1 logNu 1 log
S
2logRe logRe
1 logNu 1 log
Su
S
+
2
logM logM
K 1 1
S K1n mS S S
T0
t t u
Aw
2 2
11log
logNu
S
2
K logRw
logTw
A logR logI
w
e' ρ' u'
= S
ρ
+ S
u
+ S '
E ρ U
w
nt logk logT0
m log
logT
t 0
e'
1 ρ'
E
1 S1 Sρ1
Su1 ρ
- '=
e' S
S
2
ρ2
S
u2
u'
E
2
U
∆ [S ρ /S u ] with ∆ is limited to 8 % [ ] ill-conditioned
∆ [S ρ /S u ] with ∆d wire = 5μm to 9 μm up to 20 %
Instantaneous Density AND Velocity Fluctuations can be Computed