### Direct Numerical Simulation of Secondary Flows in Ducts Forced by a Non-Uniform Pressure Gradient

#### Abstract

Turbulent ﬂow in ducts of rectangular section presents secondary ﬂows due to the presence of turbulence. In this work we study this kind of turbulent ﬂow driven by a non-uniform force in the vertical direction. This kind of forcing is used to model the stratiﬁcation effect over the driving force of the ﬂow. Of particular interest to this work are gravity currents, which are stratiﬁed ﬂows generated by the gravity action over relatively small differences in density between two ﬂuids. The fact that the ﬂow is forced by the action of gravity on the density proﬁles causes the stratiﬁcation effects to appear on two very different scales. On the microscopic scale stratiﬁcation modulates turbulence and on the macroscopic scale stratiﬁcation modulates the driving force of the ﬂow. The objective of this work is to analyze separately the macroscopic effect of stratiﬁcation inhibiting completely the microscopic effect of stratiﬁcation. In this work, variations produced on secondary ﬂow of the second kind when the ﬂow is driven by forces that vary linearly and exponentially in the vertical direction are analyzed. These results are compared with the case of ﬂow driven by an uniform force in the vertical direction. To this aim fully resolved direct numeric simulations are performed with a pseudo-spectral code.

#### Full Text:

PDF

Güemes 3450

S3000GLN Santa Fe, Argentina

Phone: 54-342-4511594 / 4511595 Int. 1006

Fax: 54-342-4511169

E-mail: amca(at)santafe-conicet.gov.ar

**Asociación Argentina de Mecánica Computacional**Güemes 3450

S3000GLN Santa Fe, Argentina

Phone: 54-342-4511594 / 4511595 Int. 1006

Fax: 54-342-4511169

E-mail: amca(at)santafe-conicet.gov.ar

**ISSN 2591-3522**