Geoscience Reference
In-Depth Information
Fig. 10 CDF of
V
x
and
V
y
kurtosis for
Q ¼
10 dm
3
s
1
and
DH ¼
0,
DH ¼
10, and
DH ¼
30 cm
Figure
9a-f
shows that the values of the
V
x
and
V
y
kurtoses are spreader with the
presence of seepage; hence the density functions are flatter. Figure
10
confirms this
fact (looking at the kurtoses
cumulative density function
, CDF). The last three
histograms of Fig.
9g-i
show that the values of the
V
x
skewness (grouped in 10
data classes without seepage and in 13 with seepage) are spreader when seepage
flows through the bed. Therefore, the density functions of the flow measurements
are skewer when seepage exists. Hence, the histograms depicted in Fig
8
are typical
cases of the behavior of the turbulent fluctuations.
3 Conclusions and Final Remarks
The previous analysis demonstrates that the presence of upward seepage mainly
influences the velocity fluctuations of the open channel turbulent flow. Figures
8
-
10
show that the velocity field of the channel flows is more irregular when flow
through the hyporheic zone exists. Additionally, the TKE and the Reynolds stresses
are affected by the presence of this seepage. The modification in the behavior of the
turbulent stresses can be one of the reasons why seepage is smoothing the bed
evolution and bed forms above all in places where secondary flows arise and entrain
the material from the bed (Herrera-Granados
2008b
).
A future step of this research is to perform the numerical analysis of this phe-
nomenon: (1) treating the seepage flow as a new boundary condition in a turbulent
model or (2) integrating the interaction of both processes; it means that there is a
necessity to analyze together seepage (using a laminar flow model) and open-
channel (using a turbulent flow model) flows in the same numerical approach.
References
Czernuszenko W, Holley E (2007) Open-channel turbulence measurement with a three-component
acoustic Doppler velocimeter. In: Transport phenomena in hydraulics. Polish Academy of
Science, Warsaw, pp 49-79
