# PorousFlowExponentialDecay

!syntax description /Kernels/PorousFlowExponentialDecay

## Description

The residual computed by PorousFlowExponentialDecay is (1) where is the variable, and and are AuxVariables (or real values). Combined with a TimeDerivative Kernel, this is useful for simulating exponential decay of . One example is simulating heat loss using the Lauwerier model.

!syntax parameters /Kernels/PorousFlowExponentialDecay

!syntax inputs /Kernels/PorousFlowExponentialDecay

!syntax children /Kernels/PorousFlowExponentialDecay