Boundary layer wind-tunnel

The boundary layer wind-tunnel is especially designed for investigations of buildings when the simulation of atmospheric boundary layers is necessary. The general form as well as the construction principle are the same as described above for the aerodynamic tunnel, but the boundary layer wind-tunnel has only two return parts. Equal axial fans are used. The dimensions of the nozzle exit are 2m x 1m and the complete test section is closed with an adjustable roof plate. A maximum speed of about 40 m/s (uniform velocity) may be achieved at the nozzle exit. Due to space restrictions, the test section could only be 8,6 m long. This section is too small for the natural growth of thick boundary layers usually necessary for simulations at reasonable model scales and therefore, artificial stimulation of suitable velocity profiles may be achieved via a grid of rods with variable spacing at the nozzle exit. The test section floor may be covered with roughness elements of various size and spacing (Lego bricks). Thus, the commonly accepted exponential wind profiles may be simulated over most of the test section height by using proper combinations of stimulated velocity profiles and roughness. Furthermore, a turntable allows rotation of the tested area in the downstream part of the test section in order to investigate the effects of varying wind directions.