Across-wind aerodynamic parameters of tall chimneys with circular cross section—a new empirical model

The prediction of across-wind response of circular cylinders remains a challenging task, despite extensive research efforts. An attempt has been made to correlate the rms lift coefficient due only to vortex shedding, C′L,VS both in wind tunnel and full-scale conditions by separating the local rms lift coefficient, C′L, into two components, one due to the lateral turbulence and the other due to the vortex shedding. Based on the literature, and also using test results measured by the authors, it is found that the final value of C′L,V, as discussed in the paper, show a mean value of 0.089 with a coefficient of variation of 18%, independent of Reynolds number regime. The above value plus 1.66 times the standard deviation gives a value of 0.115 which is in excellent agreement with the value of C′L,VS=0.12 recommended for design of chimneys under open terrain conditions, as per the Indian Standard Code of Practice: IS: 4998 Part-2, 1992. Further it is shown that the Griffin universal Strouhal number, G attains a mean value of 0.065 with a coefficient of variation (cov) of 8%, independent of sub-critical and trans-critical Reynolds number regime.