Papers & Presentations

• Share this page
  • Email
  • Facebook
  • Twitter
  • Delicious
  • Digg
  • Stumbleupon
  • More services...

Dual Solutions for Viscous Mixed Convection Flows in a Vertical Circular Duct: A Numerical Benchmark

Dual solutions exists for u_m < u_{m max}

S. Lazzari¹, A. Barletta¹ , E. Magyari^1,2, and F. Piccinini^3
1Dipartimento di Ingegneria Energetica, Nucleare e del Controllo Ambientale (DIENCA), University of Bologna, Bologna, Italy
²Institute of Building Technology, ETH - Zürich, Zürich, Switzerland
³Biomedical Engineering, Engineering School of Cesena, Cesena, Italy

Forced and free convection flow in a vertical isothermal circular duct is studied by taking into account the internal heating due to viscous dissipation.

The momentum and energy balance equations lead to a nonlinear boundary value problem that is solved numerically by means of the finite-element software COMSOL Multiphysics.

For any prescribed value of the average velocity smaller than a maximum, two solutions exist which have completely different thermal and mechanical characteristics (dual solutions).

It is shown how the software can be used to determine the velocity and temperature fields and the main interesting physical quantities for both the solutions.