Abstract
We discuss the fundamental characteristics of pressure fluctuation in fractal-generated turbulence, generated by a square-type fractal grid, along the center line. Several experiments in recent years have indicated an unconventional nature of fractal-generated turbulence, in contrast to conventional grid turbulence and homogeneous isotropic turbulence, although all fall into the general category of grid turbulence. Although numerical analyses such as direct numerical simulations can investigate quantities that are difficult to measure, such as fluctuation in static pressure and derivatives of velocity fluctuations, there have been few numerical investigations on fractal-generated turbulence. Therefore, in this research we attempt to simulate such quantities of fractalgenerated turbulence along the center line, where previous experiments focused on turbulence characteristics. The Reynolds number based on the effective mesh size is 2500. The computational domain size in the streamwise direction is larger than one hundred times the effective mesh size. The numerical technique of our direct numerical simulation is based on the higher order Runge-Kutta method and the finite-difference method basically consisting of the Morinishi scheme. The results show that the ratio between the rms fluctuating static pressure and the intensity of the velocity fluctuation, which would be constant according to theories of homogeneous isotropic turbulence, increases along the streamwise direction.
