Ignoring this last effect may lead to erroneous conclusions on research on the origins of life on earth. This should not be interpreted as a blessing or condemnation for either side of the discussion on the important issue of climate change, but as a wake-up call to attention on what is modeled and how. When examined in detail all processes in nature are unsteady and all states are non-equilibrium states. Depending on the purpose of the model, several of these processes can be modeled as steady. Deciding when an unsteady model is necessary is based on examination of suitable non-dimensional parameters.
Theoretical models are attempts to emulate nature's response.
Numerical and analytic solutions of the theoretical model can only reproduce aspects of nature included in the model. Experimental models of the natural process provide data that can improve or validate the theoretical model. However, in all cases the final test is building and testing of a prototype. Steady models of inherently unsteady processes always lead to erroneous results. The individual research projects in the table of links above outline aspects of steady and unsteady modeling in piston engines, frequently referred to as internal combustion engines.