Abstract
It was previously reported an input disturbance composed of some tens of frequencies can induce rapid development of homogeneous turbulence using a multi-fan type wind tunnel for which 99 small fans were driven to generate turbulence. Since this method includes many frequencies, little is known about requirements of frequencies. Here, we investigated streamwise development of homogeneous turbulence characteristics using input disturbances to which different pairs of frequencies contributed. First, disturbances composed of two selected frequencies, f_A = mf_0 and f_B = nf_0 were defined, and then two parameters, f_<mid> = (f_A + f_B)/2 and Δf = f_A - f_B, were introduced. It was found that integrated statistics such as intensity and scale were significantly dependent on fmid, but less dependent on Δf. Interestingly, however, in the case where m and n were coprime, more peaks emerged at frequencies af_A ± bf_B (a, b ; integers) in the downstream direction, but in the case where m and n were not coprime, regularly-spaced peaks sparsely appeared.
