Experiments were made in a 50 mm pipe system, with a vortex flowmeter situated downstream of double elbows out-of-plane. A Micro-Electro-Mechanical-System (MEMS) sensor was installed on the vortex shedder for sensing the flow motions associated with vortex shedding. Analysis of the MEMS sensor signals was carried out to obtain the quantitative information concerning the vortex shedding frequency, its uncertainty and the signal quality defined. As found, the lowest measurement uncertainty reduced was 0.319%, due to the case of the vortex shedder situated 18 D downstream of the double elbows for ReD = 6.25 × 104. On the other hand, the best signal quality in terms of the signal to noise ratio defined was 9.645, for the vortex shedder situated at 16 D downstream of the double elbows at ReD = 6.25 × 104. Further, under this flow condition, an X-type hotwire probe was positioned at 3 D and 1 D, respectively, downstream of the vortex shedder for surveying the velocity distributions in these cross-sectional planes. By applying a conditional sampling technique referring to the MEMS sensor signals obtained simultaneously, the hot-wire signals were analyzed and reduced for the ensemble-averaged flow structures in these two cross-sectional planes. The results indicate that the vortex shedding structures could be clearly identified at 1 D downstream of the vortex shedder, but had diffused greatly at 3 D downstream.
|Number of pages||11|
|Journal||Journal of the Chinese Society of Mechanical Engineers, Transactions of the Chinese Institute of Engineers, Series C/Chung-Kuo Chi Hsueh Kung Ch'eng Hsuebo Pao|
|Publication status||Published - 2008 Dec 1|
All Science Journal Classification (ASJC) codes
- Mechanical Engineering