Two approaches to the calculation of approximate symmetry exemplified using a system of advection-diffusion equations

摘要: Two algorithms used to evaluate the approximate symmetries of nonlinear systems are compared from a theoretical view point. The two quite distinct cast into form where one method can clearly be seen more general than second. circumstances for equivalence methods presented and these cases it is shown how found by may easily calculated These ideas exemplified calculating new symmetry reductions advection-diffusion equations that describe simultaneous transport heat, moisture solute in porous media which contain unknown shape functions.