Janus Spectra in Two-Dimensional Flows.
In large-scale atmospheric flows, soap-film flows, and other two-dimensional flows, the exponent of the turbulent energy spectra, α, may theoretically take either of two distinct values, 3 or 5/3, but measurements downstream of obstacles have invariably revealed α=3. Here we report experiments on soap-film flows where downstream of obstacles there exists a sizable interval in which α transitions from 3 to 5/3 for the streamwise fluctuations but remains equal to 3 for the transverse fluctuations, as if two mutually independent turbulent fields of disparate dynamics were concurrently active within the flow. This species of turbulent energy spectra, which we term the Janus spectra, has never been observed or predicted theoretically. Our results may open up new vistas in the study of turbulence and geophysical flows.
Fluid Mechanics Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan 904-0495.
Chien-Chia
CC
Liu
Fluid Mechanics Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan 904-0495.
Rory T
RT
Cerbus
Fluid Mechanics Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan 904-0495.
Pinaki
P
Chakraborty