Relationship between wall pressure and velocity-field sources

The objective of this investigation is to study the velocity-field sources for the fluctuating wall pressure, determine their locations in the boundary layer, and investigate their physics. The velocity-field sources and partial wall pressures were computed from a database generated by a direct numerical simulation of a low Reynolds number, fully developed, turbulent channel flow. Results show that the mean-shear (MS) and turbulence-turbulence (TT) partial pressures (${\pi }^{\mathrm{MS}}$ and ${\pi }^{\mathrm{TT}},$ respectively) are the same order of magnitude. The buffer region dominates most of the wave number range; the viscous shear layer is significant at the highest wavenumbers; the buffer and logarithmic regions are important at low wavenumbers. Over most of the wavenumber range, the contribution from the buffer region is the dominant TT component; in the low-wavenumber range, the viscous shear layer, buffer region, and logarithmic region are significant; in the medium and high wavenumbers the viscous shear layer and buffer region dominate. The most important TT partial pressures are ${\pi }_{23}^{\mathrm{TT}},$ ${\pi }_{13}^{\mathrm{TT}}$ and ${\pi }_{12}^{\mathrm{TT}}$ from the buffer region. It is conjectured that ${\pi }_{23}^{\mathrm{TT}}$ and ${\pi }_{13}^{\mathrm{TT}}$ may be generated by quasi-streamwise vortices. ${\pi }_{12}^{\mathrm{TT}}$ may be due to near-wall shear layers and spanwise vortices. ${\pi }_{23}^{\mathrm{TT}},$ ${\pi }_{22}^{\mathrm{TT}}$ and ${\pi }_{33}^{\mathrm{TT}}$ from the viscous shear layer are the dominant high-wavenumber partial pressures.