Murray S. Korman James E. Parker, III
Dept. of Phys., USNA, Annapolis, MD 21402
The nonlinear interaction of two, mutually perpendicular crossed
ultrasonic beams, overlapping in the presence of turbulence, generates a
scattered sum frequency component that radiates outside the interaction region.
In the absence of turbulence, virtually no scattered sum frequency component
exists (outside the interaction region). A theoretical investigation is
reported that relates the shape of the ensembled averaged scattered sum
frequency intensity spectrum, I[sub +] ((omega),(theta)[sub *]) (which exhibits
a Doppler shift, frequency broadening, skewness, and kurtosis), to the
scattering angle (theta)[sub *], incident and scattered wave vectors (where
K[sub +]=k[sub s]-[k[sub 1]+k[sub 2]]), and statistical properties of the
turbulent velocity field v. The n spectral moments <(K[sub +](centered
dot)v)[sup n]>(proportional to)(integral)I[sub +]((omega),(theta)[sub *])
((omega)-<(omega)>)[sup n] d(omega) (obtained from experiment) are used to
evaluate turbulent velocity correlations like