PSI - Issue 6

A.M. Belostotsky et al. / Procedia Structural Integrity 6 (2017) 322–329 Author name / Structural Integrity Procedia 00 (2017) 000 – 000

329

8

Based on the results of the calculations in the coupled formulation for different flow velocities, the vertical displacement of point 1 (see Fig.1) and the angle of rotation of the section ϑ , ° of time t were obtained. The loss of stability was determined by an unlimitedly increasing displacement or angle of rotation. Table 5 presents the values of the critical velocity in comparison with [1], in which the authors give both the value obtained in the course of their numerical calculation and the experimental value.

Table 5 Comparison of the results of the numerical simulation of the FSI problem with ref. [1] V CR , m/s

Experiment [1]

11.5

FSI [1]

8 - 10

FSI

12 - 15

Comparing the results, it can be noted that the value of the critical velocity was overestimated in contrast to the results presented in [1]. This is partly due to the fact that the k- ω SST model used can underestimate the pulsation components of the aerodynamic loads and also dilute the frequency spectrum, which in turn has not shown an aerodynamics instability for a velocity of 12 m/s. The exact critical velocity can be determined by performing additional calculations for intermediate velocities. The results of coupled calculations showed that for supercritical wind velocities a classical flutter with two degrees of freedom is observed. A sharp increase in the amplitude of the oscillations occurs when the slope of the cross section reaches 5°. In this case, the cross section begins to rap idly move downward and the process can be characterized as galloping. This is well correlated with the engineering estimate, which showed that the smallest angle at which galloping is possible is 5°. The critical velocity for this position is 14.37 m/s, wh ich also correlates with the results of the related calculations. The critical velocity for the vortex shedding excitation is an exception and equal 2.44 m/s. Such a big difference can be explained by the fact that the engineering estimates do not take into account the change in the frequency characteristics of the wind flow in the flow around the oscillating structure. This indicates the imperfection of standards, and the need of their improvement and development.

Acknowledgements

The Reported study was funded by Government Program of the Russian Federation "Development of science and technology” (2013 -2020) within Program of Fundamental Researches of Ministry of Construction, Housing and Utilities of the Russian Federation and Russian Academy of Architecture and Construction Sciences, the Research Project 7.1.2” and Ministry of Education and Science of the Russian Federation (RF President Grant, agreement №14.Z56.16.8493 -MK).

References

[1] Zhan H, Fang T. Flutter stability studies of Great Belt East Bridge and Tacoma Narrows Bridge by CFD numerical simulation, the7th International Colloquium on Bluff Body Aerodynamics and Applications (BBAA7), Shanghai, China, 2012. [2] Eurocode 1: Basis design and action on structures. Part 2- 4: «Wind action». ENV 1991 – 2 – 4, – CEN, 1994. [3] Afanasyeva I.N., Adaptive technique of numerical simulation of three-dimensional dynamic problems of civil aerohydroelasticity.// PhD thesis, Moscow State University of Civil