American Physical Society Division of Fluid Dynamics >
Fluid Dynamics Videos >
Please use this identifier to cite or link to this item:
|Title: ||Dynamics of Water Entry|
|Authors: ||Truscott, Tadd T.|
Aristoff, Jeffrey M.
Techet, Alexandra H.
|Issue Date: ||10-Oct-2008|
|Abstract: ||The hydrodynamics associated with water-entry of spheres can be highly
variable with respect to the material and kinematic properties of the sphere.
This series of five fluid dynamics videos illustrates several subtle but
interesting variations. The first series of videos contrasts the nature of
impact between a hydrophilic and hydrophobic sphere, and illustrates how
surface coating can affect whether or not an air cavity is formed. The second
video series illustrates how spin and surface treatments can alter the splash
and cavity formation following water entry. The spinning sphere causes a wedge
of fluid to be drawn into the cavity due to the no-slip condition and follows a
curved trajectory. The non-spinning sphere has two distinct surface treatments
on the left and right hemispheres: the left hemisphere is hydrophobic and the
right hemisphere is hydrophilic . Interestingly, the cavity formation for the
half-and-half sphere has many similarities to that of the spinning sphere
especially when viewed from above. The third video series compares two
millimetric nylon spheres impacting at slightly different impact speeds (Uo =
40 and 45 cm/s); the faster sphere fully penetrates the free surface, forming a
cavity, whereas the slower sphere does not. The fourth series shows the
instability of an elongated water-entry cavity formed by a millimetric steel
sphere with a hydrophobic coating impacting at Uo = 600 cm/s. The elongated
cavity forms multiple pinch-off points along its decent. Finally, a millimetric
steel sphere with a hydrophobic coating breaks the free surface with an impact
speed of Uo = 350 cm/s. The cavity pinches-off below the surface, generating a
Worthington jet that pinches into droplets owing to the Rayleigh-Plateau
|Appears in Collections:||Fluid Dynamics Videos|
Items in eCommons are protected by copyright, with all rights reserved, unless otherwise indicated.