The stability of the laminar flow established after the sudden closure of a channel is investigated by numerical simulations of the Navier-Stokes and continuity equations. The basic flow computed by the present approach agrees satisfactorily with the one obtained by other authors using a Pohlhausen technique. A stability analysis performed computing the time development of 2-D perturbations of small amplitude shows that the flow is more unstable than predicted by a quasi-steady approach. The large amplitude perturbations detected in previous experimental visualizations of decelerating channel and pipe flows are qualitatively reproduced. The results of the simulations show that the amplification of the perturbation is accompanied by the formation of vortices which survive for long time. Finally, the spatial longitudinal energy spectrum is examined and the existence of a wavenumber range in which the slope of the spectrum ranges from -3 to -4 is observed. The numerical simulations in the nonlinear regime allow to have a deeper insight into the physical mechanism leading to the appearance of turbulence.

Two-dimensional perturbations in a suddenly blocked channel flow

SCANDURA, Pietro
2003-01-01

Abstract

The stability of the laminar flow established after the sudden closure of a channel is investigated by numerical simulations of the Navier-Stokes and continuity equations. The basic flow computed by the present approach agrees satisfactorily with the one obtained by other authors using a Pohlhausen technique. A stability analysis performed computing the time development of 2-D perturbations of small amplitude shows that the flow is more unstable than predicted by a quasi-steady approach. The large amplitude perturbations detected in previous experimental visualizations of decelerating channel and pipe flows are qualitatively reproduced. The results of the simulations show that the amplification of the perturbation is accompanied by the formation of vortices which survive for long time. Finally, the spatial longitudinal energy spectrum is examined and the existence of a wavenumber range in which the slope of the spectrum ranges from -3 to -4 is observed. The numerical simulations in the nonlinear regime allow to have a deeper insight into the physical mechanism leading to the appearance of turbulence.
2003
Flow blockage; Stability; Vorticity
File in questo prodotto:
File Dimensione Formato  
blocked_channel.pdf

solo gestori archivio

Tipologia: Versione Editoriale (PDF)
Licenza: NON PUBBLICO - Accesso privato/ristretto
Dimensione 411.78 kB
Formato Adobe PDF
411.78 kB Adobe PDF   Visualizza/Apri

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.11769/1889
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 2
  • ???jsp.display-item.citation.isi??? 1
social impact