Three Dimensional Mixed Convection in Plane Symmetric-Sudden Expansion: Symmetric Flow Regime


Three-dimensional simulations of laminar buoyancy assisting mixed convection in a vertical duct with a plane symmetric sudden expansion are presented to illustrate the effects of the buoyancy assisting force and the duct's aspect ratio on the flow and heat transfer. This geometry and flow conditions appear in many engineering applications, but 3-D heat transfer results have not appeared in the literature. This study focuses on the regime where the flow and thermal fields are symmetric in this geometry. The buoyancy force is varied by changing the heat flux on the stepped walls that are downstream from the sudden expansion, and the duct's aspect ratio is varied by changing the width of the duct while keeping the expansion ratio constant. Results are presented for duct's aspect ratio of 4, 8, 12, 16, and ∞ (2-D flow), and for wall heat fluxes between 5-35 W/m2. The Reynolds number and the range of wall heat flux are selected to insure that the flow remains laminar and symmetric in this geometry and reverse flow does not develop at the exit section of the duct. Results for the velocity, temperature, and the Nusselt number distributions are presented, and the effects of the buoyancy force and the duct's aspect ratio on these results are discussed.


Mining Engineering

Second Department

Mechanical and Aerospace Engineering


National Science Foundation (U.S.)
United States. Department of Energy

Keywords and Phrases

3-D Numerical Simulation; Heat Transfer; Internal Flow; Laminar Mixed Convection; Separated Flow

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version


File Type





© 2009 Elsevier, All rights reserved.

Publication Date

01 Jan 2009