A control volume can be defined as a region of interest where we want to describe the flow behavior and quantify the interactions between the flow and the body surfaces the flow comes into contact with. 

The control volume method consists in applying conservation laws, i.e. conservation of mass, balance of linear momentum and balance of energy, to the region of interest. By introducing suitable simplifying assumptions the differential equation system can be rewritten as a system of algebraic equations that can be solved for average quantities at the control volume boundaries: e.g. flow of mass, momentum and energy through the control volume boundaries, forces and mechanical power exerted at the control volume boundaries. The control volume method is not capable of providing quantitative information regarding the flow behavior within the control volume but is a valuable tool for supporting the setup of numerical simulations. Moreover it provides useful insight on widely employed Finite Volumes formulations.

Numerical simulations predict the flow behavior within the control volume by numerically solving a boundary value problem based on the Navier-Stokes equations, i.e. the system of conservation laws supplemented with suitable boundary and initial conditions. Accordingly, a sufficient amount of information regarding average quantities at the control volume boundary needs to be prescribed. The imposition boundary conditions is crucial for the well-posedness of the boundary value problem and for the success of the simulation

The concepts of convergence rate, mesh independence and computational cost will also be discussed in order to provide a complete overview of the field.