Fourier Modes in Fluid Flow and Energy Cascade

The main challenge for wind engineers nowadays is the precise prediction of peak wind pressures on buildings, which are determined by the surrounding turbulent airflow. The computational fluid dynamics (CFD) is a powerful tool that helps to model turbulent flow reasonably accurately if the large eddy simulation (LES) approach is used with proper inflow turbulence. For the Random Fourier method, it was shown that due to the interaction of several Fourier modes, the energy provided at the inlet is lost while approaching the target location. In this work, the interaction of two and three modes with different combinations of wavelengths and amplitudes is studied to give more clarity on energy cascade phenomena. A detailed illustration of when an energy cascade happens in a long time and when it happens in a short time due to the modes interaction is reported. The future extension of this work will help develop more efficient inflow turbulence generators without much loss of energy and, hence, advance the CFD application for more accurate peak wind load prediction.