the cs_user_head_losses function is used to compute the values of the head loss term, and is called at each time step for each previously defined head loss volume zone.

(cs_user_zones.c and cs_user_head_losses.c)

Volume zones may be defined using the GUI, or through the cs_user_zones (in cs_user_zones.c).

cku is the local head loss term.

It appears on the momentum as follows:

$\rho \der{\vect{u}}{t} = - \grad p + \vect{headloss} \: (+\: \text{other terms})$

with

$\vect{headloss} = - \rho \tens{cku}\cdot \vect{u} \,\: (\text{in } kg\cdot m^{-2} \cdot s^{-1})$

For a distributed head loss, let ${ \tens{\xi_l} = \dfrac{\tens{dh_l}}{(0.5 \rho u^2)}}$ given by the litterature ( $\tens{dh_l}$ is the head loss per unit length)

the source term tspdc is equal to $\tens{dh_l} = - \tens{\xi_l}(0.5\rho\vect{u}^2)$

we have $\tens{cku} = 0.5\tens{\xi_l}|\vect{U}|$

For a singular head loss, let $\tens{\xi_l} = \dfrac{\tens{dh_s}}{0.5\rho\vect{u}^2}$ given by the litterature ( $\tens{dh_s}$ is the singular head loss)

the source term tspdc is equal to

$\frac{\tens{dh_s}}{L} = - \frac{\tens{\xi_l}}{L} (0.5 \rho\vect{u}^2)$

. We have

$\tens{cku} = 0.5\frac{\tens{\xi_s}}{L}|\vect{u}|$

where $ L $ is the length over which we have chosen to represent the singular head loss.

Head loss setting examples

Here is the list of examples:

Basic examples