MassFLOW-3DTM as a simulation tool for turbidity currents: some preliminary results - From Depositional Systems to Sedimentary Successions on the Norwegian Continental Margin - page 587

Brazil. Accordingly, with exploration moving
ever further offshore, there is a growing need for
deeper understanding of turbidite successions
and their depositional processes. Early 3D numer-
ical analyses on Norwegian hydrocarbon fields
were undertaken using a previous version of the
software described herein (Heimsund, 2007). This
approach proved to be a useful tool for gaining a
better understanding of the geometry of these tur-
bidite reservoirs. Whilst the conceptual knowledge
developed from the analysis of seismic and outcrop
data has seen remarkable progress in recent years
(e.g. Duller et al ., 2010; Dykstra & Kneller, 2009;
Hadler-Jacobsen et al ., 2007; Mulder & Alexander,
2001; Schwab et al ., 2007), the fundamental sci-
ence of sediment transport and deposition based
on controlled experiments and direct observa-
tions of natural flows has been hampered by scal-
ing issues and practical problems in measuring
the most vital parameters (see Meiburg & Kneller,
2010). Currently, it seems that process-based
numerical simulations are the only way to bridge
the gap between laboratory experiments and large-
scale natural phenomena and, most importantly,
to concurrently calculate all flow parameters
(velocity, concentration, grain size, apparent vis-
cosity, turbulence intensity and bottom shear
stress) for the entire flow field during the whole
duration of the flow, which is impossible in phys-
ical experiments. However, simulating the flow
behaviour, erosion and deposition of turbidity cur-
rents in a realistic manner without rendering many
parameters negligible or constant has proven
highly challenging. More specifically, problems
arose in simulating sediment particle transport in
the inner region of turbidity current where the
concentrations are greatest and particle interac-
tions play an important role. In high-density tur-
bidity currents the boundary layer right above the
bed may even show transportation behaviour sim-
ilar to granular flows (Haughton et al ., 2009;
Postma et al ., 1988); in which case the previously
established bed-load models for turbid flows (e.g.
Huang et al ., 2005; Schmeeckle & Nelson, 2003)
cannot be applied. Further difficulties emerge
from the fact that most of the established physical
principals in fluid dynamics have been designed
originally for much larger particle sizes than those
which occur in turbidity currents. Numerical
models thus need to be improved and correlated
with physical experiments to account more realis-
tically for the interaction between the turbidity
current and the erodible substrate.

A CFD code that accounts for erosion, deposition
and the transport of sediment in high-density and
low-density turbidity currents has been imple-
mented recently in MassFLOW-3D TM (Basani &
Hansen, 2009), which is a customised version of
the commercial software Flow-3D TM . To test the
capabilities of this computational code, a compre-
hensive study has been undertaken with a focus
on flow dynamics and sedimentation in subma-
rine channels and terminal lobes. The main objec-
tive of the study is to carefully compare the
output of MassFLOW-3D TM with the results of
laboratory experiments and to define empirically
some of the theoretically-uncertain input param-
eters in the simulation model. The aim of the
paper is also to review the shortcomings of the
computational code and to discuss where it could
be improved in the near future. Once the physical-
numerical correlation was demonstrated to be
satisfactory, the aim has been to upscale the
simulation model to approximate natural phe-
nomena and determine the influence of individual
flow parameters on the properties of both the
flow and subsequent deposits. The results pre-
sented in this article are a preliminary outcome of
the comparative study and also address some
of the issues concerning the calibration of the
numerical model to laboratory experiments.
The first results also shed light on a number of
controversial issues regarding sediment transport
in high-density turbidity currents and flow
dynamics of turbidity currents in sinuous chan-
nels. The content of the paper is divided into an
introduction to MassFLOW-3D TM followed by
three sections each describing a separate case
study. The first two cases focus on velocity and
deposition in experimental high-density turbidity
currents by comparing physical experiments with
numerical simulations. In the last section, the
MassFLOW-3D TM numerical code is applied to a
natural-scale sinuous channel to explore flow
behaviour around channel bends.

NUMERICAL APPROACH

CFD is a tool for numerical solution of the physi-
cal equations describing fluid flow and sediment
transport. The method has been widely applied in
the engineering branches of fluid mechanics but
has thus far been little used in sedimentological
research and reservoir studies in a fully 3D numer-
ical scheme. The first CFD application to sediment