A simplified approach to simulate prescribed boundary layer flow conditions in a multiple controlled fan wind tunnel

Abstract

The development of a method to simulate desired approach flow characteristics in a multiple controlled fan boundary layer wind tunnel (MCFWT) is described. A MCFWT uses flow control techniques to impart the desired turbulence characteristics in lieu of using a roughness grid upwind of the test section to generate a boundary layer. In contrast to other MCWFT techniques, the proposed approach (a) relies on the direct simulation of scaled wind speed and direction records and (b) implements a closed-loop proportional-integral-derivative controller to modulate the wind speed and control the turbulence characteristics. A case study is presented using a 1:10 scale model of the Full-Scale Test Facility at the Insurance Institute for Business & Home Safety Research Center. Simulation of marine, open and suburban approach boundary layer flow yields good agreement between the model and measured values, including mean velocity and turbulence intensity profiles, integral length scales and power spectra. Control of longitudinal and lateral fluctuations is considered herein; Good agreement between the target and measured vertical turbulence intensity profiles was also achieved after the longitudinal and lateral turbulence profiles were matched.