MassFLOW-3DTM as a simulation tool for turbidity currents: some preliminary results - From Depositional Systems to Sedimentary Successions on the Norwegian Continental Margin - page 588

gravity flows was pioneered by Harbaugh (1970)
and, subsequently, by Tetzlaff & Harbaugh (1989).
After that, a number of 2D and depth averaged
3D software packages have been developed in the
last three decades, to calibrate numerical models
to physical models (Groenenberg et al ., 2009), nat-
ural events (Dan et al ., 2007; Pirmez & Imran,
2003; Salles et al ., 2008), geomorphic features
(Cartigny, 2012; Kostic, 2011) or outcrop observa-
tions (Groenenberg et al ., 2010). Only recently,
fully 3D codes capable of simulating sediment
transportation, deposition and erosion have been
developed and applied (Aas et al ., 2010a; Aas
et al ., 2010b). The deterministic process modelling
software, MassFLOW-3D™, has been developed and
used successfully to construct a three-dimensional
model for the simulation of turbidity currents.
All principal hydraulic properties of the flow
(velocity, density, sediment concentration, apparent
viscosity, turbulence intensity and bottom shear
stress) and its responses to topography can be
monitored continuously in three dimensions over
the whole duration of the turbidity current. The
present model has been calibrated and verified
against laboratory flows and can readily be up-
scaled to natural conditions (Aas et al ., 2010a; Aas
et al ., 2010b).
The fluid motion of a sediment gravity flow
in MassFLOW-3D™ is simulated by solving the
fully 3D transient Reynolds-averaged Navier-
Stokes equations (RANS) by a finite-volume-finite-
differences method in a fixed Eulerian rectangular
grid. The suspension of mono or poly-disperse,
non-cohesive sediment is treated as a continuous
phase and its variable spatial volumetric concen-
tration is calculated. The effects of flow turbulence
are simulated using the renormalisation-group
(RNG) model (Appendix I), in which the equation
constants are derived explicitly. This model is
thought to be superior to the commonly used k-
model in that it describes more accurately low
intensity turbulence in liquid flows. The drift
velocity (velocity needed to compute the trans-
port of sediments due to drift relative to the fluid
phase) of suspended particles is approximated by
a non-linear multi-phase model, allowing the dep-
osition of larger and faster drifting sediment to be
simulated more accurately. Particle interactions
in suspension (hindered settling, particle colli-
sions and interlocking of grains) are approximated
by the Richardson-Zaki correlation (Richardson &
Zaki, 1954). Erosion, settling and lifting of sedi-
ment particles are calculated in terms of tensors

superimposed on the sediment advection with
the turbulent fluid. Entrainment (re-suspension,
erosion) of sediment from the bed into the flow is
calculated with the Mastbergen & Van den Berg
model (Mastbergen & Van Den Berg, 2003), in
which the critical Shields parameter is predicted
using the Shield-Rouse equation (Guo, 2002). The
erosion model also accounts for particle armouring
by using the Egiazaroff formula (Kleinhans, 2002).
The rolling and saltating motion of larger sediment
near the packed bed interface (bed-load transport)
is predicted according to the Meyer-Peter & Müller
(1948) sediment transport equation. The governing
equations describing these separate modules can
be found in the MassFLOW-3D™ report (Basani &
Hansen, 2009) and in Appendix I of the present
paper.

FLOW DYNAMICS AND DEPOSITS
OF TURBIDITY CURRENTS: SELECTED
CASE STUDIES

Case study I: Flow structure of high-density
turbidity currents

In this section, a comparison is made between the
flow structures in our numerical modelling and
physical experiments on high-density turbidity
currents in a flume. The comparison is focused on
the behaviour of the head of a high-density turbid-
ity current (Case Study I-a, Table 1A) and its
steady state velocity profile in the body of the tur-
bidity current (Case Study I-b and c, Table 1B).

Laboratory set-up

The experiments were conducted in the flume
facilities of the Department of Earth Sciences at
Utrecht University. The set-up consisted of a
straight, 4 m long inclined channel connected to a
drainage basin. The width and depth of the chan-
nel was fixed to 0.07 m and 0.5 m, respectively
(Fig. 1). To prevent major water entrainment at the
inlet, an additional inlet piece was mounted
(Fig. 1). A more thorough description of the exper-
imental set-up can be found in Cartigny (2012). In
a first run (Case Study I-a), a mixture of fine sand
(d 50 =160 µm) and tap water, prepared in a 1.1 m 3
mixing tank, was pumped through an electromag-
netic discharge meter (Krohne Optiflux 2300) and
released into the flume. The inlet gate through
which the flow was released was 0.07 m high and