| In this paper, the characteristics of velocity and concentration fields of surface-cross jets are studied in detail for different temperatures(0℃,9℃& 18℃) and different scales(1,2,3& 4). The factors of instantaneous concentration fields and the diffusion trend are acquired, in the mean time, the characteristics of concentration field of stationary-free jets are studied in different Reynolds numberAccording to different optics-reverberation character of water and tracking particle, this paper put forward a method of PIV to identify concentration uniting the threshold segmentation method. The result shows that the value of jet flow is reliable and can reflect the real status.Based on the model test, the instantaneous concentration and velocity images in different temperatures and scales are put forwarded. And the range, shape and trend of diffusion are acquired. Also the variety of diffusion shape is concluded in different outlet Reynolds numbers. The formula of relation between concentration at axis and concentration at outlet and the critical Reynolds number at outlet are presented.The content in this paper is preparatory attempt which combines image technique and jet flow field measurement technology. This research make strong base for the further application of image technique in jet flow and has significant learning and practicable value.
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