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Today's class is in Computer lab ECJ 3.302

Today's class is in Computer lab ECJ 3.302. Lecture Objectives. Finish wall functions Velocity Temperature Concentration Introduce AIRPAK. A letter of intent . Surface boundaries wall functions. Wall surface. Introduce velocity temperature and concentration .

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Today's class is in Computer lab ECJ 3.302

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  1. Today's class is in Computer lab ECJ 3.302

  2. Lecture Objectives • Finish wall functions • Velocity • Temperature • Concentration • Introduce AIRPAK A letter of intent

  3. Surface boundarieswall functions Wall surface Introduce velocity temperature and concentration Use wall functions to model the micro-flow in the vicinity of surface Using relatively large mesh (cell) size.

  4. Surface boundarieswall functions Course mesh distribution in the vicinity of surface Y Wall surface Velocity in the first cell will depend on the distance y.

  5. Surface boundary conditions and log-wall functions E is the integration constant and y* is a length scale Friction velocity u+=V/Vt y*=(n/Vt) y+=y/y* 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. Surface cells Turbulent profile Laminar sub-layer

  6. K-e turbulence modelin boundary layer Wall shear stress Eddy viscosity V Wall function for e Wall function for k

  7. Modeling of Turbulent Viscosityin boundary layer forced convection natural convection

  8. Temperature and concentration gradient in boundary layer Depend on velocity field • Temperature q=h(Ts-Tair) • Concentration F=hc(Cs-Cair/m) m=Dair/Ds m- segregation coefficient h = f(V) = f(k,e) Tair Ts Into source term of energy equation hC = f(V, material prop.) Cair Cs

  9. Airpak Introduction(CFD software developed for in indoor airflow modeling)

  10. AIRPAK Software

  11. Example Modeling Problem Boundaries: • Office ventilation (tutorial 1 in handouts posted on the website) Geometry:

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