On the Impact of Spheres onto Liquid Pools and Ultra-viscous Films

  • Mohammad M. Mansoor

Student thesis: Doctoral Thesis


The free-surface impact of spheres is important to several applications in the military, industry and sports such as the water-entry of torpedoes, dip-coating procedures and slamming of boats. This two-part thesis attempts to explore this field by investigating cavity formation during the impact of spheres with deep liquid pools and cavitation in thin ultra-viscous films. Part I reports results from an experimental study on the formation of stable- streamlined and helical cavity wakes following the free-surface impact of heated Leidenfrost spheres. The Leidenfrost effect encapsulates the sphere by a vapor layer to prevent any physical contact with the surrounding liquid. This phenomenon is essential for the pacification of acoustic rippling along the cavity interface to result in a stable-streamlined cavity wake. Such a streamlined configuration experiences drag coefficients an order of magnitude lower than those acting on room temperature spheres. A striking observation is the formation of helical cavities which occur for impact Reynolds numbers
Date of AwardJun 2016
Original languageEnglish
Awarding Institution
  • Physical Science and Engineering
SupervisorSigurdur Thoroddsen (Supervisor)


  • Impact
  • Cavitation
  • Leidenfrost

Cite this