Test Room for Validation of Airflow Patterns estimated by Computational Fluid Dynamics
✍ Scribed by G. Zhang; S. Morsing; B. Bjerg; K. Svidt; J.S. Strøm
- Book ID
- 102575261
- Publisher
- Elsevier Science
- Year
- 2000
- Tongue
- English
- Weight
- 322 KB
- Volume
- 76
- Category
- Article
- ISSN
- 0021-8634
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✦ Synopsis
Symmetrical room geometry is not a su$cient condition for the design of a ventilated room where twodimensional air#ows are to be generated. Three-dimensional e!ects were observed in a symmetrically designed 3 m high by 5 m wide by 8)5 m long test room having a 0)019 m high slot inlet opening under the ceiling.
The attached jet velocity pro"le measured at the ceiling in the symmetrical centre plane agreed well with the theoretical calculations based on two-dimensional #ow, but large di!erences were found away from the symmetrical centre plane. The velocities in the jet 4)5 m downstream from the inlet wall were up to twice as high on one side compared to the other side. During the measurement period the side with high velocities occasionally changed without any obvious disturbance in the room. Smoke tests showed that the jet for some periods turned towards the right downstream corner, and then changed and turned to the left, thus showing a semi-stable #ow behaviour. The measured velocities in the symmetrical centre plane were only slightly a!ected by the switch-over and remained at the same level throughout the experiment. In both semi-stable conditions, the return air direction diverged 303 from the symmetrical plane.
Modi"cation of the room with four 0)5 m high vertical guiding plates attached to the ceiling resulted in an acceptably uniform two-dimensional #ow. The guiding plates changed the ceiling jet pro"le so it did not agree with the theoretical jet pro"le for an attached, two-dimensional #ow. The maximum velocity became lower. At #oor level, the direction of the return air was parallel to the symmetrical centre plane, without changes in the mean velocity.
Systematic validation of #ow behaviour is thus necessary before the assumption of two-dimensional #ow could be accepted and a study is carried out in the symmetrical plane only.