Chapter 1 Introduction 1.1 The main models 1.2 Notations and some preliminary lemmasChapter 2 The Navier-Stokes Equations with Damping 2.1 Introduction 2.2 Existence of weak solutions 2.3 Existence and uniqueness of strongsolutionsChapter 3 Decay of Navier-Stokes Equations withDamping 3.1 Introduction 3.2 A priori estimates on upper bound of decay 3.3 A priori estimates on lower bound of decay 3.4 The decay of the weak solutionsChapter 4 Stokes Approximation of Non-homogeneousNavier-Stokes Equations 4.1 Introduction 4.2 Existence of weak solutions 4.3 Existence and uniqueness of strongsolutionsChapter 5 Large Solutions to Non-homogeneous Navier-StokesEquations 5.1 Introduction 5.2 The global existence of solutions 5.3 The global stability of solutionsChapter 6 Some Remarks on Planar Boussinesq Equations. 6.1 Introduction and the main results 6.2 The case of smooth initial dataReferences