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| Titel |
Dynamical modelling of fluvial deposition processes on Titan |
| VerfasserIn |
Piotr Witek, Leszek Czechowski |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250091913
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| Publikation (Nr.) |
 EGU/EGU2014-6229.pdf |
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| Zusammenfassung |
| Observations of the Cassini-Huygens mission have revealed the complex environment
on the surface of Titan, with rivers and lakes of liquid hydrocarbons and mobile
sediments in form of dunes and rounded blocks of ice observed at the Huygens landing
site. The presence of river valleys and identification of depositional landforms is a
strong indication that Earth-like processes of sediment transport and deposition
are operating on the surface of this moon. Our aim is to simulate these processes
using numerical model to identify the similarities and differences between these
processes on both bodies. Special attention is given to the processes at the river/lake
interface which results are identifiable in satellite images, such as depositional
landforms. The model is based on the Navier-Stokes equations for depth-integrated two
dimensional, turbulent flow. Additional equations are used to describe transport of
sediments.
We have considered the problem of von Karman parameter known as von Karman
constant. In fact its value could vary in the range of 0.25 to 0.6 (see eg. Gaudio, Miglio, Dey,
J. Hydraulic Res., 48: 658-663, 2010). However, it does not depend of the fluid parameters
but on the properties of the bed sediments. This fact allows the use of model developed for
terrestrial rivers.
The flow equations consist of the depth-integrated 2D momentum equations for turbulent
flows and the depth-integrated continuity equation:
( )
-u- -u- -u- -Z- 1- --(hÏxx) -(hÏxy) Ïbx-
-t + u-x + v-y = - g-x + h -x + -y - hÏ
(1)
( )
-v- -v- -v- -Z- 1- --(hÏyx) -(hÏyy) Ïby-
-t + u-x + v-y = - g-y + h -x + -y - hÏ
(2)
-Z-+ -(uh)-+ -(vh)-= 0
-t -x -y
(3)
where u and v are depth-integrated velocity components in directions x and y,t is the time, h
is the local depth, g is the gravitational acceleration, Z is the water surface, Ïij are depth
integrated Reynolds stresses, and Ïbi are the shear stresses on the bed and flow
interface.
We explore the flow properties and the deposition of material as a function of several
parameters. We observe sedimentation at the mouth of the river creating river delta in
conditions corresponding to surfaces of Titan and Earth. Deltas forming in Titan’s conditions
are found to evolve faster, accumulation of sediments forms the mouth bar and diverges the
flow in a shorter period of time than in terrestrial conditions. Our results are compared with
observations of the Cassini probe.
We are also planning the experimental work on this subject to compare with results of
numerical modelling.
Acknowledgements: this work was partially supported by the National Science Centre
(grant 2011/01/B/ST10/06653). |
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