New Approach to Surface Oil-Flow Visualization

New approach to surface oil-flow visualization is suggested. This method can be called as Particle Image Surface Flow Visualization. The idea of new method is to mark an oil film applied on the model surface with contrast hard particles and to measure particles displacements. At least two images of particles distribution on the model surface with some time interval are acquired for each investigated regime. The pairs of images are processed with cross-correlation analysis similarly to analysis used in Particle Image Velocimetry method to obtain the parameters of particle movement. Direction of particles shift is coincident with the direction of surface streamline and allows to restore surface streamlines pattern. Magnitude of particles shift is proportional shear stress value and can visualize separation zones, shock waves and boundary layer transitions on investigated surface. Since only small shift of oil film is analyzed the multiple tests with different airflow parameters can be made using one model preparation. The results of method application for airfoil tests at low Reynolds numbers are presented.