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Aerodynamic forces are the result of various complex viscous flow phenomena such as three-dimensional turbulent boundary layer on the body surfaces, longitudinal vortices induced by three-dimensional boundary layer separation, and high turbulence caused by flow separations. Understanding the flow characteristics and, especially, how the aerodynamic forces are influenced by the changes in the vehicle body shape, are very important in order to improve vehicle aerodynamics (particularly for low drag shapes). The present study was an attempt to provide insights for better understanding of the complex three-dimensional flow field around a vehicle by observing the limiting surface streamlines and the surface pressure gradients in the stream-wise and the transverse directions. The main objective of this work is to provide a comprehensive diagnostic analysis of the basic flow features in order to learn more about the flow separations in three-dimensions.

Weld Joints are widely used in automotive and aerospace industry. The main issue in the weld joints is the quality inspection to detect the disconnection in the welded area. In this paper, Shearographic technique with dynamic excitation is introduced to test the weld joints. In the experiments, the coupons are of 4 very thin layers of metal sheets welded together. The goal is to find out if there are any disconnections between the layers. They are clamped and then excited by a PZT actuator from behind. A real time digital Shearographic system with a self-refreshed reference image technology has been developed to display the measuring result, i.e. shearogram. A big range of driving frequencies is scanned to find the proper frequency and amplitude that can help to identify the disconnections. The results show that when the driving frequency reaches the resonance frequency, there will be big amplitude and thus a fringe pattern becomes visible on the coupon surface.