Boundary-layer transition-to-turbulence studies are conducted in the Arizona State University Unsteady Wind Tunnel on a 45-deg swept airfoil. The pressure gradient is designed so that the initial stability characteristics are purely crossflow dominated. Flow-visualization and hot-wire measurements show that the development of the crossflow vortices is influenced by roughness near the attachment line. Comparisons of transition location are made between a painted surface (distributed 9-/xm peaks and valleys on the surface), a machine-polished surface (0.5-/xm rms finish), and a hand-polished surface (0.25-/im rms finish). Then isolated 6-/im roughness elements are placed near the attachment line on the airfoil surface under conditions of the final polish (0.25-/zm rms). These elements create an enhanced packet of stationary crossflow waves, which results in localized early transition. The diameter, height, and location of these roughness elements are varied in a systematic manner. Spanwise hot-wire measurements are taken behind the roughness element to document the enhanced vortices. These scans are made at several different chord locations to examine vortex growth.

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In image-based measurements, quantitative image data must be mapped to threedimensional object space. Analytical photogrammetric methods, which may be used to accomplish this task, are discussed from the viewpoint of experimental fluid dynamicists. The Direct Linear Transformation (DLT) for camera calibration, used in pressure sensitive paint, is summarized. An optimization method for camera calibration is developed that can be used to determine the camera calibration parameters, including those describing lens distortion, from a single image. Combined with the DLT method, this method allows a rapid and comprehensive in-situ camera calibration and therefore is particularly useful for quantitative flow visualization and other measurements such as model attitude and deformation in production wind tunnels. The paper also includes a brief description of typical photogrammetric applications to temperature-and pressure-sensitive paint measurements and model deformation measurements in wind tunnels.