Fluid dynamics of liquids on Titan's surface

On the surface of Titan liquids can be present in three types of environmen ts: (i) oceans, (ii) seas and lakes, and (iii) fluvial channels. The liquid in these environments will be affected by several types of motion: progres sive (tidal) waves, wind-generated waves and unidirectional currents. The p hysical parameters of the liquid on Titan's surface can be reconstructed us ing the Peng-Robinson equation of state. The total energy of the waves, bot h tidal and wind, depends on the gravity and liquid density; both values ar e lower on Titan than on Earth. Thus, the same total energy will produce la rger waves on Titan. This is also valid also for the progressive waves, as it is confirmed by the physical relationship between horizontal velocity, w ave amplitude, and depth of the liquid. Wind-driven waves also will tend to be larger, because the viscosity of the liquid (which is lower on Titan) c ontrols the deformation of the liquid under shear stress, Wind-generated wa ves would be rather large, but the dimension of the liquid basin limits the size of the waves; in small lakes or seas the wave power cannot reach larg e values. Unidirectional currents are also affected by the liquid propertie s. Both the relations from driving and resting forces and the Reynolds numb er suggests that the flows exhibit a large erosional capacity and that, the oretically, a true fluvial network could be formed. However, caution should be exercised, because the cohesion of the sedimentary interface can armour bottom and induce laterally extensive, unchanelled sheet flows with small erosional capacity. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.