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In this study, this paper presents the characteristics of pressure-related fluctuations in decaying turbulence generated by a multi-scale turbulence grid on the centerline. This study focuses on the turbulent kinetic energy related to dynamic pressure and the static pressure fluctuation RMS related to static pressure as the pressure fluctuation characteristics. As a multi-scale turbulence grid, a fractal turbulence grid used in previous studies is used. Two turbulence grids are used as the computational conditions. In the previous study, the velocity fluctuation of the multiscale grid turbulence was pointed out to follow an apparent exponential function on the centerline. In this study, the characteristics of the static pressure fluctuations on the central axis are mainly examined. The relative static pressure fluctuation intensity, which is often calculated in previous studies, is also discussed. In this study, the issue is approached by direct numerical analysis. The governing equations are discretized based on a high-order accuracy spatial discretization scheme, and the external force terms reproduce the no-slip conditions on the surface of the turbulent grid. In addition to the turbulent kinetic energy, the static pressure fluctuation RMS is shown in this study to follow an apparent exponential function on the central axis. [ABSTRACT FROM AUTHOR]

This study examines the accuracy of large-eddy simulation (LES) with the Smagorinsky model based on its dependence on the Reynolds number. The Smagorinsky model often uses a damping function at low Reynolds numbers. In contrast, the Vreman and coherent structure models, which do not require the use of this function, are analyzed as reference LESs. In this study, steady and unsteady isotropic turbulent flows are used. Unsteady turbulence is generated by varying the magnitude of the external forcing field based on a sinusoidal function using the linear forcing method. The values of the constants of the sub-grid scale models are optimized for steady-state turbulence. The results of the unsteady time series of turbulent kinetic energy obtained with the Smagorinsky model are in good agreement with those obtained with the Vreman model and the coherent structure model. This agreement was observed not only in the high Reynolds number condition but also in the low Reynolds number condition. Therefore, this study clarifies that the Smagorinsky model may not require a damping function for both steady and unsteady fields when turbulence is isotropic. [ABSTRACT FROM AUTHOR]

This study focuses on the effect of isotropic spatial resolution in the analysis of anisotropic turbulence fields by focusing on the discretization accuracy order of the viscous and convective terms. Large eddy simulations with the Smagorinsky model and the implicit model are used in this study. The effect of varying the computational Reynolds number by more than two orders of magnitude was examined by focusing on the Reynolds number dependence. The convection terms were discretized using second-and fourth-order central difference expressions. The viscous terms are discretized using second to eighth order central difference schemes. For turbulent kinetic energy, turbulent Reynolds number, and small-scale anisotropy, when the viscous term is discretized using second-order central difference accuracy, the dependence on Reynolds number is different from the results using other methods. On the other hand, the effect of the different accuracy orders of the convection term on these quantities was small. [ABSTRACT FROM AUTHOR]