Effect of Operating Parameters on the Characteristics of Active-Grid-Generated Flows

Abstract

The characteristics of active-grid-generated flows are investigated. The streamwise flow velocities are measured using a hot-wire anemometry. The turbulence intensity, integral length scale, and power spectrum density are evaluated to understand the influence of active-grid-operating parameters such as the rotation rate of the grid's agitators and the duration of the agitator's constant-rate rotation. The effects of randomized rotation and the test-section type are also investigated. It is found that the randomization of the rotation rate improves the spectrum distribution of velocity fluctuation, while the statistical quantities of turbulence are not sensitive to the randomized rotation rate. The randomized duration does not affect the generated flow characteristics. The turbulence intensity and integral length scale can be correlated with a non-dimensional parameter expressed by the rotation rate, mesh size, and free-stream velocity. When the non-dimensional parameter is small, the test-section type shows no influence on the turbulence intensity and integral length scale.