Measurement example archives.

■ Camera
We used high resolution high sensitivity double shutter type pco.4000-PIV.The specification of this camera is resolution 4008 × 2672 pixels, gradation 14bit monochrome, cooling is ⊿ - 45 degrees.

■ Analysis algorithm
Image deformation correlation, multi grid correlation, central difference method, double correlation we are used together.With multigrid correlation, high resolution can be achieved by reducing the interrogation window while keeping the amount of movement of particles between the two time adequate.It is possible to improve S / N ratio by double correlation and improve secondary accuracy by the central difference method.Furthermore, by applying image deformation (image deformation of subpixel), highly accurate analysis without peak locking becomes possible.

■ Seeding
It is the most important technique in large scale PIV in large wind tunnel.The seeding generator used PivPart45.This generator can atomize DEHS (or DOS) oil with Rasukin nozzle and generate a large amount of particles of about 2 μm in particle size.DEHS is harmless, but if the particle size is 1 μm or less, it will reach the back of the lung when inspired.On the other hand, it is said that if it is 2 μm or more, it comes into contact with the wall near the bronchial tube and does not reach deeply.Considering the impact on the human body, I think that the size of about 2 μm is good.

■ Diffusion of seeding　Seeding lake
As is common in PIV, how to spread seeding particles evenly is an important point.Global seeding (Scatter it throughout the wind path) is the best way to diffuse uniformly.If the seeding is continued to be sprayed from the downstream position of the measurement section of the wind tunnel, the whole wind path will be filled with seeding.For PivPart45 it will be ready for measurement in a few minutes even in a large wind tunnel.In this method, however, it is better to avoid as much as possible considering the impact on the wind tunnel because it will cause a large amount of seeding particles to flow back into the wind path for a long time.So we use seeding spray porous nozzle called seeding lake.Seeding Lake is a collection of multiple tubules with pores opened.It is possible to achieve uniform seeding without influencing the flow by installing and spraying immediately after the rectification cavern, and it can do with the minimum amount of seeding necessary.

Measurement area size

Final search window size