# 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^{[1]}, 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.