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发表于 2009-7-3 17:20:40
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关于这个问题, 我请教了DLR的一个哥们, 以下是他给我的回答.他说他只讲了几个简单的, 还有其他的原因, 不过这几个是关键的.
Key issues are these:
- the TSI system works only in water and not in air
The reason is that it is not sensitive enough to see the small aerosol particles which are used in air seeding. They use large glass spheres only and those reflect much more light. of course under such conditions our system can do the same.
-V3V do PTV and Tomo-PIV do PIV
The difference is that with particle tracking you can work on a very low seeding density only because each particle must be identified. This is PTV and comes for free with Tomo-PIV system anyway. But with Tomo-PIV the customer gets the patented algorithm for tomographic reconstruction and for tomographic PIV which gives a factor of 10 to 100 more vectors in the same volume. (typ. 200.000 to 400.000 for 2k x 2k cameras while for PTV it's 5.000 to 20.000)
- all apertures and focus are fixed in a V3V system, the customer has no flexibility to adjust anything according to the experiment (不过如果你不想进行任何调试就用, 缺点就是优点哈, 但是你的自由度就小了)
- the working distance is fixed in a V3V system, the customer has no flexibility to adjust anything according to the experiment
- the customer can not calibrate the V3V system if some change in focus or aperture happens the system must be sent in for factory calibration in the US
反正就我所知道的, V3V 在欧洲没有卖出去一套. 你们要想知道详情, 请参考papers from Lisbon and PIV07.
最近, Tomo-PIV的应用已经在JFM上发表了. 大家如有兴趣, 文章的简介如下,
J. Fluid Mech. (2009), vol. 622, pp. 33–62.
简介.
An experimental study is carried out to investigate the three-dimensional instantaneous
structure of an incident shock wave/turbulent boundary layer interaction at
Mach 2.1 using tomographic particle image velocimetry. Large-scale coherent motions
within the incoming boundary layer are observed, in the form of three-dimensional
streamwise-elongated regions of relatively low- and high-speed fluid, similar to what
has been reported in other supersonic boundary layers. Three-dimensional vortical
structures are found to be associated with the low-speed regions, in a way that
can be explained by the hairpin packet model. The instantaneous reflected shock
wave pattern is observed to conform to the low- and high-speed regions as they
enter the interaction, and its organization may be qualitatively decomposed into
streamwise translation and spanwise rippling patterns, in agreement with what has
been observed in direct numerical simulations. The results are used to construct
a conceptual model of the three-dimensional unsteady flow organization of the
interaction. |
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