# Lecture Objectives LES Multizone modeling Examples of LES: Lecture Objectives LES Multizone modeling Examples of LES:

https://www.youtube.com/watch?v=hz7UjN_vYuw Vorticity formula: LES vs RANS RANS: LES: Low pass filter resolve large scale eddies Model effect of small scale eddies

Cut-off scale (space grid), cut of time scale LES Similar to RANS we are using effective viscosity for LES: Gradient of velocity tensor: is the rate-of-strain tensor for the resolved scale Finally:

So no additional transport equation! This is SubGrid Scale (SGS) model Smagorinsky model (1963) eddy viscosity is model There are Many more: Algebraic Dynamic model Dynamic Global-Coefficient model

Localized Dynamic model LES Time Step Depends on the length scale and velocity CourantFriedrichsLewy (CFL) number condition for convergence while solving hyperbolic differential equations Multizone modeling

CONTAM and COMIS http://www.bfrl.nist.gov/IAQanalysis/ NO momentum equation Just pressure, temperature, and continuity Depends heavily on boundary condition and orifice coefficients that define flow between zones Good for buoyancy driven flow Boundary condition for

multizone modeling Exterior pressure (wind) Temperature distribution (requires some assumption or energy modeling) Wind pressure around building Very complex and unsteady For multizone we are introducing many simplifications:

. Multizone vs. Moltizonla Multizonal is like CFD (detailed grid with no orifice between i- between zones) but no momentum equation