**How to model trees?**

On this page, a short advice for the numerical modeling of trees is given.

The easiest way of the numerical tree modeling is to assign a **pressure loss coefficient
** *
λ**
*[Pa (Pa m)^{-1}] to vegetation containing grid cells.

Assume a
permeable obstacle of streamwise depth *d* which fills the entire cross
section of a duct (forced convection condition).
The
**pressure
loss coefficient ** **
λ**
gives
the difference in static pressure

with

*
u*
mean velocity component in streamwise direction

*d* obstacle's streamwise depth

*p _{luv}*
static pressure windward of the obstacle

*p _{lee}*
static pressure leeward of the obstacle

*ρ* density of fluid

The
**pressure
loss coefficient ****
λ**
is a parameter depending on the
internal
structure of the
obstacle
and describes
integrally
the
permeability.