Zbornik radova Koridor 10 - Kirilo Savić

3rd International Scientific and Professional Conference
CORRIDOR 10 - a sustainable way of integrations
3. FLOW SIMULATIONS BY FLUENT
Flow simulations were made by use of ANSYS Fluent 12.1 software, for half-model train. Flow space
around the half-model was discredited by the tetrahedral mesh. Boundary conditions were defined
over the boundaries of the numerical flow model. In the near space all over the train body, the
appropriate mesh elements were placed in the zone of the boundary layer. Largeness of the boundary
layer mesh element was defined upon the condition of y + = 30 for the first mesh element row close to
the train body, with adequate 20% mesh element scale increment for every other mesh element row.
Number of mesh elements for the train was 5 millions. Numerical flow simulations were performed for
train velocities of 180 km/h. Boundary conditions at the flow space input and output, in which
simulations were done, were defined by pressures at those actual positions. All other boundary
conditions were defined by the flow symmetry.
Flow around the train was simulated as steady-state flow of the viscous incompressible fluid. The k – ε
Realizable model of turbulence was applied with standard wall functions. The average number of
iterations, needed for reaching of the result convergence was about 300 [10,11].
3.1. Results derived by numerical simulation
Figures 6 give the pressure distribution on the train half-model for velocity 50m/s (180km/h). The
maximum value of pressure is at the front of the train nose, near the stagnation point. Afterwards
stagnation point, the streamlines are accelerating and thus velocity appreciation caused pressure
drop. On the left side of the figure 6, on a scale is showing that maximum value of pressure is 1520
Pa.
Figure 6: Pressure distribution on the train half-model obtained using Fluent
for the speed v=50 m/s
Measurements in wind tunnel was obtained non-dimensional pressure coefficient Cp=0,55,
which corresponds to the pressure 1680 Pa. The figures show good agreement of the results.
4. CONCLUSIONS
Testing of train models in low speed wind tunnel are giving the pressure distribution on the train model
and the pressure distribution around the train model in the configuration of single drive on open track.
The diagrams of pressure distribution for the points of the front train section and top, in the train’s
plane of symmetry and slip angles of = -10 o , 0 o and 10 o , illustrate that the stagnation point in the
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