Third International Conference on Applications of Mathematics to Nonlinear Sciences. Electron. J. Diff. Eqns., conf. 27 (2024), pp. 27-47. Title: Nonlinear non-autonomous Boussinesq equations Authors: Andrei Ludu (Embry-Riddle Aeronautical Univ., Daytona Beach, FL, USA) Harihar Khanal (Embry-Riddle Aeronautical Univ., Daytona Beach, FL, USA) Adrian Stefan Carstea (National Institute of Physics and Nuclear Eng., Romania) Abstract: We study solitary wave solutions for a nonlinear and non-autonomous Boussinesq system with initial conditions. Since the variable coefficients introduce distortions and modulations of the solution amplitudes, we implement a multiple-scale approach combining various modes in order to capture the coupling between the nonlinear evolution and the effect of the variable coefficient. The differential system is mapped into a solvable system of nonlinear and non-autonomous ODE which is integrable by recursion procedures. We show that even in the limiting autonomous case, the multiple-scale approach gives a new possibly integrable dispersionless coupled envelope system, which deserves further study. We validate our theoretical results with numerical simulations, and we study their stability. Published August 20, 2024. Math Subject Classifications: 35Q51, 35Q53, 35G50, 34E13, 93C70. Key Words: Boussinesq; non-autonomou; nonlinear; multiple-scale; soliton.