Most heavy goods vehicles in service today are fitted with add-on aerodynamic devices. The most common of which is the cab-mounted roof deflector. Such devices provide appreciable drag savings, however, they are often not optimised for the trailer. When a wind yaw angle is present, their savings also diminish as the yaw angle increases. The work conducted within this thesis investigated the possibility of using an adjustable deflector for active flow control. The optimum deflector height for a given trailer height was initially investigated using wind tunnel testing. The variation of this optimum with yaw angle and container separation was then investigated. From the results a 3D look-up table was generated. A control scheme was proposed that used the 3D look-up table requiring only three measurable inputs. The three inputs required were: the wind yaw angle, the container height and the container separation. A pressure differential located on the deflector was found to linearly relate to the wind yaw angle. This relationship allowed on-road measurement of the wind yaw angle and therefore enabled the development of a prototype controller. Extensive on-road testing and unsteady computational simulation were conducted. The results obtained indicated a mean yaw angle magnitude of around 5 perturbed by four fundamental low frequencies. These frequencies were identified in the runs conducted over the test period and an average frequency established. Higher frequency disturbances were attributed to the wakes of leading heavy goods vehicles and were filtered by a suitably chosen numerical filter. Finally, an estimation of the efficiency of the active device was made using a combination of simulation and full scale testing. From the results obtained, an optimised deflector generated an average drag reduction of 7.4%. An estimated additional drag reduction of 1.9% over the optimised deflector was predicted through use of an active system.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:655966 |
| Date | January 2013 |
| Creators | Barden, Jason |
| Contributors | Garry, Kevin P.; Whidborne, James F. |
| Publisher | Cranfield University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://dspace.lib.cranfield.ac.uk/handle/1826/9293 |
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