The efficiency, productivity and environmental friendliness of a piston internal combustion engine are determined by the perfection of intra-cylinder processes. Therefore, the study of the gas-dynamic structure of the flow during the process of filling the cylinder through the valve remains an important and relevant task in the field of applied gas dynamics and engine engineering. In this study, the results of modeling of velocity fields in a cylinder were compared with experimental data based on optical methods (TIM (thermal imaging method) and PIV (particle image velocimetry) method). The article describes the features of the object of study, the mathematical model, laboratory stands, measuring devices, boundary conditions and the algorithm for conducting experiments. The calculated velocity fields, thermograms of the flow structure and experimental velocity fields in the cylinder are obtained. A comparison of the obtained data showed that the quantitative differences between the flow velocity fields in the cylinder for numerical modeling and laboratory experiments do not exceed 4.8% for an initial air velocity in the intake manifold of no more than 20 m/s. An increase in the initial air flow velocity causes a discrepancy between the results of modeling and experiments, so further adjustment of the mathematical model is necessary (in particular, clarification of the properties of the working environment) to improve the accuracy and reliability of the forecast. The developed mathematical model can be applied to improve the quality of calculation of gas exchange processes and design of intake systems in piston engines.