The following velocity data include 5 cases for northbound trains and 6 cases for southbound trains. The velocities were measured using Debimo flow blades mounted on the principal center-lines of the eight compartments. Tabular data are provided for all 11 cases. Graphical illustrations are provided for one case in each train direction. Data can be found on the following pages: The installation of the blade flow sensors can be seen on the photographs page. |
 Blade Flow sensor |
1. Each flow compartment had two Debimo blade sensors:
2. Debimo blades are designed for measuring flow in one direction only, but they were exposed to flow in both directions in these tests. Their measurements must be disregarded when flow is in the reverse direction. To deduce the actual direction of flow, use the ultra-sonic flow measurements.
3. There were 16 Debimo blades, but only 8 recording transducers, etc. In the first few runs, only up-flow measurements were made. In later runs, only downflow measurements were made.
| Runs 35334-35338: | upflow measurements in all compartments |
| Runs 35339-35361: | upflow measurements in compartments 2-8 downflow measurements in compartment 1 (or W) |
| Run 35362 et seq: | downflow measurements in all compartments |
Compartment 1 was treated separately because its upflow Debimo blade was
found to be faulty.
4. The recording transducer for compartment 8 (or V) gave
an initial offset of approximately 3Pa. This causes stationary flow to be
reported as approximately 2m/s. It has much less influence at higher velocities.
For example, a true velocity of 20m/s would be reported as approximately 20.1m/s.
5. There is an unresolved question about the accuracy of the data from the Debimo blades. In particular, the average velocities in compartments 1-4 differ from those in compartments 5-8. This difference is not seen in the ultrasonic measurements. At the time of writing, the cause of the difference is under investigation. Until this question is resolved, it is recommended that the Debimo data are used only for qualitative purposes. The ultra-sonic sensors should be used for quantitative purposes.
| Equipment | Description |
|---|---|
| Up-flow measuring blade | Debimo 1750 (measuring blade length 1750mm) |
| Down-flow measuring blade | Debimo 1500 Measuring blade length 1500mm |
| Pressure to voltage converters | CP201-BO DP |
| Connecting tubes | Plastic tubes 1m in length connecting blades to voltage converter. |
Blade type flow measurement sensors and signal converters were supplied by Kimo. Accuracy of data is nominally better than 5% for wind speeds greater than 3m/s.
