A large number of physical phenomena are modeled by nonlinear partialdifferential equations, subject to appropriate initial/ boundary conditions; theseequations, in general, do not admit exact solution. The present monograph givesconstructive mathematical techniques which bring out large time behavior ofsolutions of these model equations. These approaches, in conjunction with moderncomputational methods, help solve physical problems in a satisfactory manner. Theasymptotic methods dealt with here include self-similarity, balancing argument,and matched asymptotic expansions. The physical models discussed in some detailhere relate to porous media equation, heat equation with absorption, generalizedFisher's equation, Burgers equation and its generalizations. A chapter each isdevoted to nonlinear diffusion and fluid mechanics. The present book will be founduseful by applied mathematicians, physicists, engineers and biologists, and wouldconsiderably help understand diverse natural phenomena.