improving the piv method in vortex flow field velocimetry proposing a geometric air-core determination method

Piv method is one of the most widely used and modern techniques for velocimetry. measurement in air-core vortices involves some approximations due to the fluctuating nature of the vortex. to reduce measuring errors time averaging of recorded data can be carried out. however, since the velocity field in a vortex is plotted corresponding to its center, first the vortex center should be specified. in this regard, the present study proposes a geometrical method for determining the center of the vortex accurately. experimental measurements of the velocity field in air-core vortices were used to evaluate the performance of the proposed method. the results demonstrated that the vortex center fluctuations more in a lower strength vortex with a half air core than a vortex with a full air core. the comparison of the results with and without the present suggested method showed that this method increases the accuracy of the tangential velocity measurements.