Dissipation of kinetic energy in two-dimensional bounded flows.

The role of no-slip boundaries as an enstrophy source in two-dimensional (2D) flows has been investigated for high Reynolds numbers. Numerical simulations of normal and oblique dipole-wall collisions are performed to investigate the dissipation of the kinetic energy E(t), and the evolution of the enstrophy Omega(t) and the palinstrophy P(t). It is shown for large Reynolds numbers that dE(t)/dt=-2Omega(t)/Re proportional, variant 1/sqrt[Re] instead of the familiar relation dE(t)/dt proportional, variant 1/Re as found for 2D unbounded flows.