Aerodynamic interference of straight and tapered cylinder pairs near the first critical wind speed

The present investigation is concerned with the phenomenon of aerodynamic interference across three cases: between two circular cylinders; a pair of 1:50 tapered cylinders; and a pair of 1:40 tapered cylinders—all in staggered arrangement. Experiments were conducted in the 1.6 ​m × 1.6 ​m wind tunnel at IIT Delhi. Our focus is on the enhanced across-wind response of the downstream cylinder near the first critical wind speed (at which the vortex shedding frequency matches the natural frequency of the structure). It is shown that the magnification in the response (with respect to that of the isolated cylinder) is a strong function of both the pitch and the orientation. It is evident from the current investigation that the magnification factors recommended in IS 4998 (Part 1: 1992, see Fig. 1 therein/2015) and Eurocode 1 (Actions on structures- General actions- Part 1–4: Wind actions, see Equation E. 11 therein) need to be revised upwards. Further, the rule of thumb, used in the design of tall structures, that beyond 15/20 diameters interference is negligible is not tenable, especially for structures of identical geometry. •Aerodynamic interference of identical tall structures.•Staggered arrangement crucial at large separations in the vicinity of the critical speed.•Rule of thumb that “Beyond 20 diameters interference is negligible” not tenable.