The flow field of a laboratory-simulated tornado was studied by means of 2-D Particle Image Velocimetry or PIV technique with the purpose of investigating the effects of roughness on the near-ground tornado-like vortex structure and its velocity distribution. The results show the flow regime transition from multi-celled vortices over the smooth surface at a higher swirl ratio to singleor dual-celled vortices with roughness. Significant difference in velocities and turbulence characteristics is observed as a result of increasing ground roughness. This work is part of a project that seeks better understanding of the near-ground flow field and resulting wind-induced loads on structures in a tornado. 德國(guó)LaVision PIV/PLIF粒子成像測(cè)速場(chǎng)儀