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5. Solution in I-DEAS

In this section you will evaluate the solution.

Once I-DEAS has finished with the calculations, check the status frame in the lower left corner of the screen. If no major errors occurred, the status should read No errors encountered in last run, and you can proceed to viewing the solution. It is very possible though that at least one warning appears. You can safely disregard it.

Switch to the task Post Processing. In this task, you will be able to view the different solutions.

Figure 1.80
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Click on the first icon, named Results. You will start with this step every time you would like to view a different solution.

Figure 1.81
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In the upcoming dialog, you will specify what solutions you would like to view. The main list box contains all available soltutions. In the case of this tutorial, we have solved for 3 different types: Velocity, Hydrostatic Pressure, and Coefficient of Pressure. In the dialog, you can now designate which of these solutions you would like to view. For now, accept the default settings and hit OK
Figure 1.82
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To view the solution, click on the icon featuring an arrow pointing to the right, as shown in Figure 1.83
Figure 1.83
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Next you will be selecting all components for which you would like to view the solution. Move your mouse cursor into the visualization frame and click on the right mouse button. Select All done from the available options.

Figure 1.84
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The results are now presented to you in the visualization frame. The differently colored regions denote different values of velocity (inverse pressure), where the green and blue regions experience less than yellow and red regions. The color bar near the right of the screen relates each color to a specific value of velocity. In this case, the colors range from 2.13 * 10-7 (blue) to 1.63 * 102 (red). The units under MKS (Meters Kilograms Seconds) are meters/second for velocity. Thus, the maximum velocity experienced is 163 meters/second (= 587 km/h = 365 mi/h).

Figure 1.85
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Zoom in so as to take a closer look at the motorcycle cross-section and visually evaluate its aerodynamic design. You will notice that the head of the rider as well as the "tail" of the bike experience the highest velocity (lowest pressure). This is very similar to the wing effect. However, most other regions near the top of the bike are rather uniformly colored, suggesting a smooth travel of wind over the surface. The bottom regions of the bike experience much lower velocity, mainly because the bike has been placed on a street. These lower velocities are in fact less than the incoming wind velocity of 50 m/s, which suggests that they indicate regions of drag. The main drag is experienced in front of the bike, where the wind stream lines find resistance and no escape, and right behind the bike, the wake.

Figure 1.86
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To test our numeric solution with respect to the force we have initially applied, we will now probe the incoming wind velocity. Pan to the left edge of the wind tunnel, and zoom in far enough to see the mesh elements, as shown in figure 1.87. Then, click on the third icon in the second row, as shown in figure 1.87.

Figure 1.87
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Move your mouse cursor over the mesh elements close to the left edge and select one or more elements by clicking the left mouse button. The values will be placed into the mesh, as well as into the status window in the left lower corner of the screen. You will notice that the values are approximately 50 (meters/second), which is the wind velocity we have entered in the Boundary Conditions as 400 Newtons. Remember that the wind tunnel is 8 meters in height, and that 400 Newtons as a Total Force divides into each unit meter (400 / 8 = 50). This suggests that we can more or less trust the numeric values in this wind tunnel.

Figure 1.88
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Pan the view to the motorcycle, and specifically to the rider's head. Probe the regions of high velocity to find out which is the highest. In the example, the velocity is as high as 163 m/s, which corresponds to 587 km/h. Note that this is rather high for a motorcycle travelling at 180 km/h. The motorcyclist's head would most likely blow off at this speed. In fact, the actual velocity is much less than the reported value.

Figure 1.89
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Potential Flow, as understood and computed by I-DEAS does not take into consideration that the stream lines do not actually wrap around the head in this example. Figure 1.90, top-most diagram, shows how I-DEAS computes Potential Flow. A realistic scenario is presented in the middle diagram, where the stream lines gradually taper off, and vortices form in the regions immediately behind the head. To remedy this misperception by the software, one might modify the cross-section to remove sudden breaks, as shown in the bottom-most diagram. However, for this introductory exercise, this is not required.

Figure 1.90
Figure 1.91 shows the Potential Flow for a cross-section of a Harley Davidson V-Rod.

Figure 1.91
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It appears to be less aerodynamic than the other example in this tutorial, as the color-graph shows much fewer regions of different velocities. In fact, most regions of the motorcycle are rather uniformly colored blue. The only concentration of high velocity is around the mirror regions.

Figure 1.92
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