MassFLOW-3DTM as a simulation tool for turbidity currents: some preliminary results - From Depositional Systems to Sedimentary Successions on the Norwegian Continental Margin - page 595

(A) (B)

Simulated Average Velocity Profile in the Body
of the Current Two Grain Sizes

Non-dimensional Average Velocity Profiles
in the Body of the Current Two Grain Sizes

0.12 2

1. 6

0.08

1. 2

0.8

0.04

0.4

0

0

0 0.4 0.8

Velocity (ms -1 )

1. 2 0 0.2 0.4 0.6 0.8 1

Non-dimensional Velocity

UVP 50-50 Velocity Profile
DefaultParametersTlen0.002
DefaultParametersTlen0.0015

DefaultParametersTlen0.001
DefaultParametersHigherRoughnessTlen0.001

Fig. 7. (A) Velocity profiles for the body of a two-grain-size turbidity current, averaged on a 53 second period for the differ-
ent numerical runs of Table 1C. (B) Non-dimensional velocity profiles for the body of a two-grain-size turbidity current,
averaged on a 53 second period for the different numerical runs of Table 1C.

Once again, it is apparent that the simulated val-
ues match the measured values, considering the
affect that changing some numerical parameters
slightly changes the shape of the velocity profile
in the CFD results. As a general observation, the
flow thickness and velocity in the simulations are
slightly exaggerated with respect to the physical
measurements. In this case the average difference
between simulated and measured velocity values
is c. 13%. Apparently, dimensionalisation of the
multi-species simulation is less well constrained
relative to the mono-species simulation (Fig. 6).
This could be due to the fact that when adding a
second species to the system, there are more vari-
ables and therefore the experimental inaccuracies,
or numerical issues, such as simulating a natural
bi-modal grain size distribution quite crudely with
only two grain diameters, expand. Again, when
the shape of the velocity profile only is compared
(Fig. 7B), the fit is near-exact; just as in the mono-
species simulation (Fig. 6B).

Table 2. Flow parameters for Run 2 and Run 4 of the Baas
et al . (2004) experiments.

Run 2 Run 4

Mean grain size (mm) 0.235 0.235

Initial sediments concentration (%) 27 14

Turbidity current volume (l.) 158.9 135.8

Channel slope angle (deg) 8.6 8.6

Case study II: Deposition of laterally-expanding
high-density turbidity currents

Baas et al . (2004) showed that the geometry and
internal composition of submarine lobes, as mod-
elled in laboratory, depends mainly on the sedi-
ment grain size and suspended concentration of
turbidity currents. To test the depositional capabili-
ties of the MassFLOW-3D TM numerical code, two of
his experimental runs were replicated (Run 2 and
Run 4; Table 2), to compare the geometry of the