Wind tunnel experiments for simulating turbulent motions in a real atmospheric boundary layer

A wind tunnel experiment was conducted to simulate large-scale turbulent motions in an atmospheric boundary layer (ABL). The large-scale turbulent motions originating from outer-layer disturbance were generated using an active grid installed at the front of the test section and the winglets of the active grid were randomly rotated. The large-scale horizontal motions in the ABL were generated in the wind tunnel using the active grid when appropriate values of the angle and rotation speed were chosen. The validity of the present method using the active grid was confirmed by comparing the integral scale and energy spectra obtained by the experiments with empirical formulas inferred from field observations. This indicates that the present method of using the active grid accurately simulates the turbulent motions in a nearly neutral ABL.