Wind Turbine
Wind Turbine
Wind Turbine
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aerospace<br />
domain of length 60m, width<br />
20m, and height 15m. A volumetric<br />
mesh of tetrahedral and prismatic<br />
cells was used. The profiles along the<br />
sides and on top of the train generated<br />
by the other partners in the<br />
project were used as inlet boundary<br />
conditions. The ground under<br />
the train was given a uniform speed<br />
equal to that of the moving train.<br />
A steady-state simulation using<br />
the k-ε turbulence model was initially<br />
performed on multiple processors.<br />
The symmetric solution showed<br />
low pressure on the shoulder areas<br />
of the end car and a high pressure<br />
region on the back face that results<br />
from the onset of separation. A transient<br />
calculation was then initiated<br />
using the steady solution as a starting<br />
point. Using time steps of up to<br />
0.01s, unsteady flow developed with<br />
a period of oscillation on the order<br />
of 1 Hz. This frequency was found<br />
to be in good agreement with measurements<br />
reported by a Japanese railway<br />
company 1 . Further runs were<br />
done using smaller time steps and<br />
a higher order turbulence model<br />
(RSM), yielding identical oscillations<br />
in the flow. Based on the CFD results,<br />
the aerodynamic coefficients were<br />
calculated. These forces and moments<br />
served as an input for Multi Body<br />
Systems (MBS) calculations performed<br />
by Bombardier Transportation, and<br />
the running comfort was evaluated.<br />
Luckily, the oscillations were found<br />
to be far too weak to cause vehicle<br />
movements, so they would not cause<br />
any passenger discomfort. ■<br />
references<br />
1 Kohama, Y., Koshikawa, T. and<br />
Okude, Wake Characteristics of a High<br />
Speed Train in Relation to Tail Coach<br />
Oscillations, Vehicle Aerodynamics<br />
Conference, Loughbuough Univ.,<br />
UK, 1994. steady unsteady<br />
Comparison of surface pressure for the steady and unsteady cases<br />
High Speed Train<br />
Path lines and planes showing velocity magnitude contours behind the train<br />
Fluent NEWS spring 2002 15