Polymer and surface roughness effects on the drag crisis for falling spheres

Abstract : We make time resolved velocity measurements of steel spheres in free fall through liquid using a continuous ultrasound technique. We explore two different ways to induce large changes in drag on the spheres: 1) a small quantity of viscoelastic polymer added to water and 2) altering the surface of the sphere. Low concentration polymer solutions and/or a pattern of grooves in the sphere surface induce an early drag crisis, which may reduce drag by more than 50 percent compared to smooth spheres in pure water. On the other hand, random surface roughness and/or high concentration polymer solutions reduce drag progressively and suppress the drag crisis. We also present a qualititative argument which ties the drag reduction observed in low concentration polymer solutions to the Weissenberg number and normal stress difference.
Document type :
Preprints, Working Papers, ...
Complete list of metadatas

Cited literature [21 references]  Display  Hide  Download

https://hal-ens-lyon.archives-ouvertes.fr/ensl-00168943
Contributor : Jean-François Pinton <>
Submitted on : Thursday, August 30, 2007 - 6:17:26 PM
Last modification on : Thursday, April 19, 2018 - 2:54:03 PM
Long-term archiving on : Thursday, April 8, 2010 - 9:33:25 PM

Files

dragred_submit.pdf
Files produced by the author(s)

Identifiers

  • HAL Id : ensl-00168943, version 1
  • ARXIV : 0708.4291

Collections

Citation

Nicolas Lyotard, Woodrow Shew, Lydéric Bocquet, Jean-François Pinton. Polymer and surface roughness effects on the drag crisis for falling spheres. 2007. ⟨ensl-00168943⟩

Share

Metrics

Record views

188

Files downloads

319