# Coupled multi-physics calculations

From Serpent Wiki

## External coupling

## Iteration

## Power relaxation

Serpent relaxes the power distribution calculated in the iterations using the stochastic approximation based method, where the power distribution at iteration is calculated by

where is the unrelaxed power distribution tallied on iteration , is the relaxed power distribution after the previous iteration, is the active neutron population simulated on iteration and is an underrelaxation factor that can be defined by the set relfactor option.