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Alfredo José Rodríguez Alarcón Advisors: Dr. Francesc Giralt Dr. Joan Herrero

Turbulent Thermal Convection inside Enclosures by Direct Numerical Simulation and Nonlinear Analysis. Alfredo José Rodríguez Alarcón Advisors: Dr. Francesc Giralt Dr. Joan Herrero. Scheme. Why study thermal convection inside enclosures? Objectives Natural (free) convection

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Alfredo José Rodríguez Alarcón Advisors: Dr. Francesc Giralt Dr. Joan Herrero

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  1. Turbulent Thermal Convection inside Enclosures by Direct Numerical Simulationand Nonlinear Analysis Alfredo José Rodríguez Alarcón Advisors: Dr. Francesc Giralt Dr. Joan Herrero

  2. Scheme • Why study thermal convection inside enclosures? • Objectives • Natural (free) convection • Two dimensional convective heat transfer inside enclosures • Remarks • Project emphasis and summary Turb. Thermal Convec. In. Enclsrs. by DNS & Nonlin. Anal.

  3. T2 T1>T2 g Fluid T1 Thermal convection insideenclosures Problemconfiguration Turb. Thermal Convec. In. Enclsrs. by DNS & Nonlin. Anal.

  4. Why study thermal convection inside enclosures? Compact Vacuum Furnace • This configuration is often employed for the reduction of energy loss, e.g. • Thermal insulation of furnaces and similar systems. • Solar energy collectors. Sketch of a flat-plate collector Turb. Thermal Convec. In. Enclsrs. by DNS & Nonlin. Anal.

  5. Why study thermal convection inside enclosures? • In manufacturing systems, flow regimes determination is important because product quality can be affected by the flow patterns, e. g. • Crystal growing facilities • Melting furnaces • Plastic molding systems Vertical velocity contours in the horizontal midplane z=0 for different flow patterns (Puigjaner et al. 2004) Turb. Thermal Convec. In. Enclsrs. by DNS & Nonlin. Anal.

  6. Why study free convection insideenclosures heated from below? • Theoretical developments and understanding of the convective heat transfer phenomena. “Convection is a major feature of the dynamics of the oceans, the atmosphere, and the interior of stars and planets.” (Bodenschatz et al. 2000) Temperature isosurface for the nondimensional value of T=0.6 Pr=100. (Breuer et al. 2004) Turb. Thermal Convec. In. Enclsrs. by DNS & Nonlin. Anal.

  7. Objectives Overall • To carry out a primary study on turbulent thermal convection inside cubical enclosures by direct numerical simulation and nonlinear analysis. Secondary • To develop an adequate computational code for the study of turbulent thermal convection inside cubical enclosures. Turb. Thermal Convec. In. Enclsrs. by DNS & Nonlin. Anal.

  8. Natural (thermal) convection • The two basic Heat Transfer processes are conduction and radiation. • Conduction is due to the motion of microscopic particles that comprise a material. • Convection occurs when conductive heat transfer is coupled with the motion of the fluid. • In general, in the natural convection fluid movement is due to density differences in presence of a body field (i.e. gravitational acceleration). Turb. Thermal Convec. In. Enclsrs. by DNS & Nonlin. Anal.

  9. Quiescent, thermally stratified fluid T1>T2 T2 H g g T1 RaH < 1708 NuH = 1 Two dimensional convective heat transfer inside enclosures Cellular flow pattern T1>T2 T2 H T1 RaH > 1708 NuH > 1 Turb. Thermal Convec. In. Enclsrs. by DNS & Nonlin. Anal.

  10. Two dimensional convective heat transfer inside enclosures • Rayleigh number (RaH), Nusselt number (NuH) as well as Prandlt number (Pr) appear in scale analysis and dimensionless equations. • When governing equations are written in dimensionless disturbance variables, the RaH determines the emerging of flow instabilities. Turb. Thermal Convec. In. Enclsrs. by DNS & Nonlin. Anal.

  11. Remarks • The initial flow is laminar and with increasing Ra, it undergoes transition to turbulence. • NuH, is function of RaH, Pr, geometry, thermal boundary conditions, flow structures. Turb. Thermal Convec. In. Enclsrs. by DNS & Nonlin. Anal.

  12. Remarks • Currently, turbulent thermal convection has been better studied through experiments, hence there are not enough 3D numerical simulations. • Transition to turbulence and turbulence itself need further understanding due to the difficulty of characterizing both numerically as well as experimentally chaotic fluid movement. Turb. Thermal Convec. In. Enclsrs. by DNS & Nonlin. Anal.

  13. Project emphasis • To understand the physics of thermal convection inside enclosures. • To be aware of the advantages and limitations of current numerical methods available for the problem of study. • Select the appropriate numerical scheme to develop computational code in FORTRAM. • Test code developed with known problems and previous analysis. Turb. Thermal Convec. In. Enclsrs. by DNS & Nonlin. Anal.

  14. Questions, comments? Thank you Turb. Thermal Convec. In. Enclsrs. by DNS & Nonlin. Anal.

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