One of the most important stages of designing the framework of high-rise stacks is the calculation of loads on the stack and on the mechanical core of the gas outlet pipes located inside the stack. In current normative documents there is no data on the aerodynamics of the mechanical core. At the same time the aerodynamic coefficients of pipes in the core differ from the aerodynamic coefficients of single cylinders. When dealing with gas dynamics problems, program complexes in which control

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... e method is applied are getting widespread use. When problems are solved in such complexes, the speed of wind current and the size of the structure are selected, and the required Reynolds numbers similarity is achieved. This paper presents the results of the research which deals with the flow-over of the mechanical core of four pipes in the gas-dynamic complex STAR-CD, the work of which is based on control volume method. In the research two options of the mechanical core model are considered, depending on the cylinders' relative position. The first option is the ratio of the distance between the cylinders' centers 1.5d, the second option is the ratio 2. For each design option the flow-over by the wind current at three angles of attack 0 0 , 30 0 and 45 0 is simulated.