Two input parameters - initial porosity and initial medium permeability - are required to use Kozeny-Carman porosity-permeability relationship (see OGS: [case] KozenyCarman for detailed usage documentation). The
ConTracer test case you mentioned has demonstrated how to use the Kozeny-Carman equation. In this test case, the required input parameters both are given under the subtree
<parameters>. Please scroll down the project file to take a look.
For the time-series output of permeability change, you can do that with a slight change in the member function
ProcessLib/ComponentTransport/ComponentTransportProcess.cpp · master · ogs / ogs · GitLab).