Direct numerical simulation of superfluid turbulence
by Morris, Karla, Ph.D., CITY UNIVERSITY OF NEW YORK, 2008, 93 pages; 3330496

Abstract:

At low temperatures, as quantum effects become increasingly apparent, helium (He4) transforms into a superfluid. The motion of superfluid helium (He II) can be decomposed into two interpenetrating components: (1) an inviscid (superfluid) liquid containing line vortices with quantized circulation and (2) a (normal fluid) gas of elementary thermal excitations. At sufficiently high driving velocities, the motion of He II becomes unstable and transitions to turbulence, commonly termed superfluid turbulence or quantum turbulence. A growing body of empirical evidence suggests that the macroscopic statistical behavior of quantum turbulence closely matches that of classical turbulence despite considerable differences in the physics at the mesoscopic scale of the inter-vortex spacing and the microscopic scale of the vortex core diameters [47,50]. Although a commonly used phenomenology involving quantum-vortex/normal-vortex locking has achieved some success in explaining the macroscopic similarities, current laboratory measurements lack sufficient spatial resolution to verify vortex locking. The work presented here investigates the detailed mechanisms underlying quantum turbulence via direct numerical simulations (DNS) of superfluid vortex interactions with interpenetrating normal fluid turbulence. The driving fluid is the normal component which behaves as a statistically homogeneous isotropic turbulent flow, and both forced and decaying cases are simulated. The data obtained from the simulation is analyzed using wavelet transforms and velocity correlations. The normal fluid calculation employs a Navier-Stokes (NS) solver developed by Rouson and Xu [31] in a manner that facilitates rapid integration of new physics by expressing dynamical equations in forms very closely mirroring their analytical expression. The superfluid calculation employs a vortex filament method originated by Schwarz [39,40,41]. The Navier-Stokes and vortex filament equations are marched in time using a software module developed by Rouson, Morris and Xu [33] which facilitates rapid implementation of time advancement algorithms for coupled multi-physics problems.

 
AdvisersJoel Koplik; Damian Rouson
SchoolCITY UNIVERSITY OF NEW YORK
SourceDAI/B 69-09, p. , Dec 2008
Source TypeDissertation
SubjectsMechanical engineering; Condensed matter physics; Plasma physics
Publication Number3330496
Adobe PDF Access the complete dissertation:
 

» Find an electronic copy at your library.
  Use the link below to access a full citation record of this graduate work:
  http://gateway.proquest.com/openurl%3furl_ver=Z39.88-2004%26res_dat=xri:pqdiss%26rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation%26rft_dat=xri:pqdiss:3330496
  If your library subscribes to the ProQuest Dissertations & Theses (PQDT) database, you may be entitled to a free electronic version of this graduate work. If not, you will have the option to purchase one, and access a 24 page preview for free (if available).

About ProQuest Dissertations & Theses
With over 2.3 million records, the ProQuest Dissertations & Theses (PQDT) database is the most comprehensive collection of dissertations and theses in the world. It is the database of record for graduate research.

The database includes citations of graduate works ranging from the first U.S. dissertation, accepted in 1861, to those accepted as recently as last semester. Of the 2.3 million graduate works included in the database, ProQuest offers more than 1.9 million in full text formats. Of those, over 860,000 are available in PDF format. More than 60,000 dissertations and theses are added to the database each year.

If you have questions, please feel free to visit the ProQuest Web site - http://www.proquest.com - or call ProQuest Hotline Customer Support at 1-800-521-3042.