This work covers basic techniques for DNS and LES that can be applied to practical problems of flow, turbulence, and combustion. It presents numerical methods for compressible and incompressible three-dimensional flows, such as high-order discretization schemes, high-fidelity boundary conditions, and coupling aspects. The book gives sample numerical simulation results that exemplify the practical application of the methods. It also discusses advanced topics and current challenges, including detached eddy simulation, SGS modeling, and multiscale flow simulations. The appendix contains sample FORTRAN programs to illustrate the implementation of finite difference numerical schemes.