Paper 3: Volume 4 No.4 March 2006 Edition
Wind Driven Flow Through Openings - Analysis of the
Stream Tube
Tomohiro
Kobayashi1,3, Kazunobu Sagara2, Toshio Yamanaka2,
Hisashi Kotani2 and Mats Sandberg3
1Dept.
of Architectural Engineering,
Osaka
University
,
Osaka
,
Japan
2Dept. of Global Architecture,
Osaka
University
,
Osaka
,
Japan
3University of Gävle,
KTH
Research
School
, 801 76 Gävle,
Sweden
Abstract
Wind
approaching a building provided with openings on the windward and leeward
sides has a choice, either it flows through the openings or flows around
and above the building. This choice gives rise to a dominant stream tube
containing the fluid flowing through the openings. In this paper the
stream tube is analysed based on wind tunnel measurements and CFD
simulation. A house model with dimensions 120 mm (Width)×120 mm (Height)×180
mm (Length) was provided with rectangular openings of equal size located
opposite each other. The end walls were thin giving rise to a sharp edged
opening. The size of the openings expressed as the porosity (opening area
divided by the façade area) was 1.3 %, 5.2 %, 11.6 %, 20.7 % and 46.5 %.
In the wind tunnel, velocity including velocity fluctuations and pressure
were measured along the centre line through the openings. In the CFD
prediction it was possible to visualize the stream tube by the method of
"flying particles". This made it possible to explore the change
in shape of the stream tube and to calculate the cross-sections of the
stream tube at different positions and to know the total pressure
distribution within the stream tube cross section. Finally, the discharge
coefficient based on stream tube analysis was compared to that from a
conventional chamber method.
Key
words: cross-ventilation,
large opening, stream tube, discharge coefficient, wind tunnel models, CFD.
References
Furukawa J, Yamanaka T,
Kotani H: (2000) “Cross-ventilation rate of building with windows
arranged in series (Part3)” Summary
of Technical Papers of the Annual Meeting of the Architectural Institute
of Japan, Environmental Engineering, pp.553-554. (In Japanese).
Murakami S, Shinsuke K,
Akabayashi S, Mizutani K: (1991) “Wind tunnel tests on velocity-pressure
field on cross-ventilation with open windows” ASHRAE
Transactions : Symposia, pp525-538.
Sandberg M: (2002)
“Airflow through large openings - A catchment problem?”, Proceeding of ROOMVENT 2002,
Denmark
, pp541-544.
Sandberg M: (2004) “An alternative view on the
theory of cross-ventilation”, The International Journal of
Ventilation, 2, (4), pp409-418.
True JJ, Sandberg M,
Heiselberg P, Nielsen PV: (2003) “Wind driven cross-flow analysed as a
catchment problem and as a pressure driven flow” The
International Journal of Ventilation, HybVent-Hybrid Ventilation Special
Edition, 1,
February, pp89-101.
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IJV Volume 4 No 4
Contents
Paper
1: Interacting Plumes
Paper
2: Outlet C-Values
Paper
3: Wind Driven Flow
Paper
4: CFD & Full-Scale
Paper
5: Tomography
Paper
6: Time Varying
Paper
7: Pre - Cooling
Paper
8: Wind Catcher
|
