1 / 16

Lecture Objectives

Lecture Objectives. Review wall functions Discuss: Project 1, HW2, and HW3 Project topics. Surface boundary conditions and log-wall functions. E is the integration constant and y * is a length scale. Friction velocity. Correction. y *=( n / V t ). k - von Karman's constant.

zora
Télécharger la présentation

Lecture Objectives

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Lecture Objectives • Review wall functions • Discuss: Project 1, HW2, and HW3 • Project topics

  2. Surface boundary conditions and log-wall functions E is the integration constant and y* is a length scale Friction velocity Correction y*=(n/Vt) k- von Karman's constant The assumption of ‘constant shear stress’ is used here. Constants k = 0.41 and E = 8.43 fit well to a range of boundary layer flows.

  3. K-e turbulence model in boundary layer Wall shear stress V Eddy viscosity Wall function for e Wall function for k

  4. HW2 • Problem 1 • Problem 2 • K- RNG vs. LES vs. DNS

  5. DNS • Example from the previous project class Boundary conditions !

  6. LES vs. RANS • Examples form the ongoing project

  7. Cough simulation

  8. What do you see with RANS

  9. What do you see with LES Velocity Vorticity

  10. Calculation time cost • Modeling of unsteady cough and particle dispersion • - period of 1 minute • mesh size: 500,000; particle #: 600,000; time step: 0.001s • Computers: 4 core 3.4 MHz 1) RANS Cough + particle injection (1s) Steady state calculation of background flow Particle dispersion (60 s) Conversion to unsteady 6-12 hours 3-6 hours 24-48 hours Calculation Time (2-5 day) 2) LES RANS to get Steady state background flow LES calculation to get fully developed turbulent flow (calculation of 1500 seconds) LES+part. inject (1s) LES+part. dispersion (60 s) 3-6 hours 2-3 weeks 1~2 weeks Calculation Time (2-4 weeks) 10

  11. Comparison: Velocity LES RANS Measurements

  12. Comparison: Peak Velocity and Turbulence

  13. Comparison: Cumulative Exposure 7 micron particles

  14. HW3 • Questions?

  15. Project 1 Airpak; How to : • Define occupancy zone • Zero diffusion • Refine mesh • Define isosurface • ….

  16. Final project topics • You will define the project topic • Examples from previous years • Single side natural ventilation • Atrium ventilation - design problem • Rain water collection • Ventilation effectiveness – parametric study • Surface convection • Surface mass transfer

More Related