Compare TBL (Corcos) and Diffuse Acoustic Field correlation patterns
What is this tool? This visualizer helps you understand how pressure fluctuations on a surface are spatially correlated—that is, how pressure at one point relates to pressure at nearby points. This correlation is essential for predicting how structures respond to random pressure loading.
Corcos TBL Model (Turbulent Boundary Layer): When air flows over a surface at high speed, turbulent eddies create fluctuating pressures. These pressures are correlated over distances that depend on the eddy size and convection speed. The Corcos model captures this with exponential decay—correlation is stronger in the flow direction (Lx) than across it (Ly) because eddies are elongated by the flow.Reference: Corcos, G.M. (1964). J. Fluid Mech. 18(3), pp. 353-378.
Diffuse Acoustic Field (DAF): In a reverberant environment (like an acoustic test chamber), sound arrives from all directions equally. The resulting pressure correlation follows a sinc function—it oscillates and can even become negative, meaning pressures at certain separations fluctuate out of phase.Reference: Maidanik, G. (1962). J. Acoust. Soc. Am. 34(6), pp. 809-826.
λ = 135.00 in
Uc = 229.6 ft/s
Lx = 43.85 in
Ly = 6.26 in
Simply-supported beam with sinusoidal mode shapes φ_n(x) = sin(nπx/L)
km = 608.7 rad/in (modal wavenumber)
km = nπ/L defines the spatial frequency of the mode shape. Higher modes have shorter wavelengths (λm = 2L/n = 16.0 in).
Common aerospace aluminum alloy
Natural Frequency (Mode 3):
fn = 87.9 Hz
f_n = (n²π²/2L²) × √(EI/ρA) / 2π
First zero at r = 67.50 in
Understanding the Correlation Heatmap
Physical meaning: If Γ > 0, pressures at these two points tend to go up and down together. If Γ < 0, when one goes up, the other tends to go down. The center (0,0) is always Γ = 1 (a point is perfectly correlated with itself).
References: Corcos (1963, 1964), Fahy & Gardonio (2007), Blake (2017)