The wave drag coefficient is computed approximately for a nozzle containing a swirling flow as a function of R0−1, the inverse of the Rossby number. When R0−1 < λ1 and R0−1 = λn, where λn denotes the nth zero of the Bessel function J1, there is no wave in the flow and the wave drag is zero. The drag coefficient is found to be sub-divided into different regions between R0−1 = λn and λn+1, with n = 1,2,3,.… When each λn is exceeded, the drag coefficient jumps from zero to a value which is one order higher than its values in the previous region (except in the case n = 1), and then decreases to zero as R0−1 increases toward λn+1. Very high wave drag can be expected in flows of large swirl ratios.