Geoscience Reference
In-Depth Information
Fig. 6.5
Averagevaluesofbulkheattransfercoefficients
St
∗
versusmeansurfacefrictionReynolds
number Re
∗
for five different ice drift projects, MIZEX 1984 (Greenland Sea marginal ice zone,
summer), CEAREX 1988 (eastern Arctic Ocean, fall), CEAREX 1989 (north of Fram Strait, late
winter),ANZFLUX1994(Weddell Sea,winter),andSHEBA(1997-1998). Dot-dashcurveispre-
dictionaccording toYaglomandKader(1974) theoryforheat andmasstransfer overhydraulically
rough surfaces
isrequiredininterpretingthemeasurements.Neverthelessweareabletoexaminea
numberofdifferentstationswithsignificantlydifferentunderice
z
0
values.Averages
fromseveraldifferentexperimentsareshowninFig.6.5.Ofthefivestationaverages
shown, the most complete data set by far is from SHEBA (McPhee 2002; McPhee
et al. 2003), with an average value:
St
∗
=
0004.The average of all five
stations indicated by the dashed line is 0.0056.An obviousinferencefrom Fig. 6.5
isthat
St
∗
showsnodiscernibledependenceonReynoldsnumber,whenthelatteris
definedintermsofthefrictionvelocityandroughnesslength,inapparentcontradic-
tiontothelaboratoryresults.Itisperhapsworthnotingthatinthelaminar(Blasius)
solution leading to (6.7), both the Stanton and Reynolds numbers are based on the
“far-field”velocity,
V
,not
u
∗
0
orsomeotherturbulentscale velocity(Incroperaand
DeWitt 1985). Regardless, it appears that with our definition of bulk Stanton num-
ber (6.10) in terms of
u
∗
0
and
0
.
0057
±
0
.
T
, it remains relatively constant over a wide range
of conditions. This providesa critical constraint on values for the exchange coeffi-
cients
∆
α
h
(
S
)
∝
(
ν
/
ν
T
(
S
)
)
−
n
and
α
h
and
α
S
. IgnoringReynoldsnumberdependence,
n
.
R
=
α
h
/
α
S
≈
(
ν
T
/
ν
S
)
