A lot of modeling domains, as gas c

A lot of modeling domains, as gas channel and gas diffusion layer, may be large as opposed to the others. This can create unreasonably large computational problems, which may not be able to be solved. Scaling the equations and dimensions of the geometry can create a more reasonable model size. Dimensional analysis is a method for reducing the number and complexity of experimental parameters that affect the physical phenomena occurring in the cell. In this situation, we can introduce a characteristic length, L, and a characteristic velocity, Vin. For flow in a rectangular form, L is the cell height. Vin, Pin, Tin, and Ci,in, are the input velocity, pressure, temperature and species concentration respectively. In this case, novel dimensionless variables are defined as follows