The aim of the work is to perform numerical and experimental analyses of the wind flow around two structures with a circular cross-section placed side by side. These structures can have a smooth and a rough surface. In that case, the values of interference coefficient presented in Eurocode differ from those obtained from the author's numerical analyses, concerning very large Reynolds numbers Re. The aerodynamic drag force of the cylinder systems is determined on the basis of numerical Finite Volume Method analyses using the Computational Fluid Dynamics (CFD) module. Velocity and pressure fields are also presented. In order to verify the results, experimental tests were carried out in a wind tunnel. The results obtained at all stages (numerical models with a large number of Re; experimental studies of models with a lower Re number; numerical models with a lower Re number) were compared with each other. Each of the flow ranges (turbulent, transitional, laminar) is characterized by a different behavior and therefore, the aim of the work is also the correct creation of numerical models. Thus it is necessary to adjust the parameters of the numerical model. These analyses are used for testing the possibility of estimating wind load acting on a fragment of a structure of more complex, curved shape (e.g., water slide) using simplified models (e.g., helices, toruses, and cylinders). Eurocode EN 1991-1-4 does not cover complex structures based on circular cylinders.