The authors suggest general methods for numerical studies in the field of fluid dynamics and heat and mass transfer. These methods are widely used in all branches of industry, especially in aerospace, automotive, energy, oil and gas. However, the application of these methods without special methodology can result in false results, which can be followed by very serious consequences. It can explain a very limited application of numerical methods, for example, in the nuclear industry and in the enterprises of the military-industrial complex. At the same time, the application of the mentioned methodology that has been tested for a wide range of applications, allows to obtain reliable results and define the required parameters of the object to study with the required accuracy and at reasonable time expenditure concurrently.