Internal wave families in stratified flow past a bluff body

The wave field of a horizontally moving circular disk in a stratified fluid is studied using large eddy simulations. Linear as well as nonlinearly stratified backgrounds are investigated. The diameter based Reynolds number is 5000 and the minimum background Froude number is 1 for all cases. In linear stratification, steady lee waves and unsteady wake generated waves are found as in previous work. In the case of nonlinear stratification, an additional third family, namely, steady Kelvin wake waves, which resemble the Kelvin ship wave pattern, is also found. The qualitative difference between the steady lee wave and the steady Kelvin wake wave is shown by visualization on horizontal planes. Linear theory provides insight into the amplitude and structure of these two different types of steady waves. The wavenumber-frequency properties of the family of unsteady wake generated waves are obtained. Trapping of these unsteady waves while traversing a background with nonlinear stratification is also discussed.