In this paper, we present the results from Direct Numerical Simulations of turbulent, incompressible flow through a square duct, with an imposed temperature difference between two opposite walls, while the other two walls are supposed to be perfectly insulated. The mean flow is sustained by an imposed, mean pressure gradient. The most interesting feature, characterizing this geometry, consists in the presence of mean secondary motions in the cross-flow plane. These motions are relatively weak, in that their maximum intensity is about 2 ÷ 3% of the mean streamwise velocity, but they have a strong effect on both the flow and temperature field patterns. In this study, we focus on weak turbulence, in that the Reynolds number, based on the bulk velocity and the hydraulic diameter, is about 4400. Our results indicate that secondary motions do not affect significantly global parameters, like the friction factor and the Nusselt number, with respect to the plane-channel flow. It is conjectured that this circumstance could be due to a compensation effect, between the appearence of mean secondary motions, and the presence of the two boundary layers close to the vertical walls.

Direct Numerical Simulation of Turbulent Flow and Heat Transfer in a Square Duct at Low Reynolds Number

NOBILE, ENRICO;PILLER, MARZIO
2001

Abstract

In this paper, we present the results from Direct Numerical Simulations of turbulent, incompressible flow through a square duct, with an imposed temperature difference between two opposite walls, while the other two walls are supposed to be perfectly insulated. The mean flow is sustained by an imposed, mean pressure gradient. The most interesting feature, characterizing this geometry, consists in the presence of mean secondary motions in the cross-flow plane. These motions are relatively weak, in that their maximum intensity is about 2 ÷ 3% of the mean streamwise velocity, but they have a strong effect on both the flow and temperature field patterns. In this study, we focus on weak turbulence, in that the Reynolds number, based on the bulk velocity and the hydraulic diameter, is about 4400. Our results indicate that secondary motions do not affect significantly global parameters, like the friction factor and the Nusselt number, with respect to the plane-channel flow. It is conjectured that this circumstance could be due to a compensation effect, between the appearence of mean secondary motions, and the presence of the two boundary layers close to the vertical walls.
File in questo prodotto:
Non ci sono file associati a questo prodotto.

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: http://hdl.handle.net/11368/2568428
 Attenzione

Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo

Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus ND
  • ???jsp.display-item.citation.isi??? ND
social impact