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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.

Abstract. The article briefly shows how to estimate the safety of recreational water slides by numerical analysis of motion of the users. There are presented: mathematical description of a typical water slides geometry, simplified model of a sliding person, model of contact between the user and the inner surface of the slide, equations of motion written for a rigid body with 6 degrees of freedom and finally some sample results compared to the limitations set by current European Standard.

A group of six pre-graduated students of Civil Engineering, Mathematics and Mechatronics studied problems of dynamics of structures within a project called Vibration Busters implemented in a formula of Project Based Learning. They worked under supervision of professors from the above mentioned faculties. Students, according to their competencies, implemented a procedure of numerical analysis of the problem within Mathematica system, built a physical model of a frame and loaded it with vibrating electrical motors and measured behaviour of the structure. The aim of the project was to develop methods of passive and active controlling of vibrations of building structures. A technology of 3D printing was implemented to build a structure. Thanks to the project students had an opportunity to share their skills and knowledge and acquire several new hard and soft skills. It was also a unique experience for supervisors and a great opportunity to extend fields of interdisciplinary cooperation. The aim of the presentation is to share results and experience gained thanks to this extraordinary and successful educational project.