The MIIS Eprints Archive: No conditions. Results ordered -Date Deposited. 2021-08-05T15:47:52ZEPrintshttp://miis.maths.ox.ac.uk/images/sitelogo.gifhttp://miis.maths.ox.ac.uk/miis/2009-10-21T08:01:10Z2015-05-29T19:51:47Zhttp://miis.maths.ox.ac.uk/miis/id/eprint/250This item is in the repository with the URL: http://miis.maths.ox.ac.uk/miis/id/eprint/2502009-10-21T08:01:10ZAn interpolation tool for aircraft surface pressure dataAirbus UK are concerned with designing efficient wings for aircraft. In the design process, the aerodynamic load on the wing is calculated for various configurations including different Mach numbers and angles of attack. The aerodynamic load is calculated from the pressure profile around the wing. Airbus use a number of different methods to calculate the pressure, primarily CFD calculations and wind tunnel experiments. However, experiments and calculations cannot be performed for all configurations.

Airbus asked the Study Group to investigate interpolation methods which incorporate wind tunnel and CFD data to calculate the aerodynamic load for many different configurations.Mahbubul AlamDarryl AlmondChris BuddAndrew HillHartmut Schwetlick2007-06-19Z2015-05-29T19:47:22Zhttp://miis.maths.ox.ac.uk/miis/id/eprint/102This item is in the repository with the URL: http://miis.maths.ox.ac.uk/miis/id/eprint/1022007-06-19ZHeight-volume characteristics of a fuel tankA key feature of any aircraft is its fuel system. Fuel is stored in large tanks (typically within the wing of the aircraft) which are approximately rectangular, but have detailed internal structure. A typical tank is illustrated in Figure 1, in which we can see the internal stringers and other small details.

Figure 1: An example of a typical fuel tank showing the internal structures including corners and stringers.

A key aspect of aircraft safety is an accurate measurement of the amount of fuel in the tank. To determine this, the height h of the fuel at certain points within the tank is measured and the fuel volume V is determined from this. However the relationship between height and volume depends crucially on the pitch angle, α, and roll angle, β, of the tank. (This is clear to all of us when we drive a car and see that the indicated fuel level in the tank depends upon whether we are going up or down hill at the time.) At present Airbus uses lookup tables to link height to volume for a set of pitch and roll angles. As the fuel tanks become more and more intricate, the huge amount of data required becomes an issue. The problem posed to the Study Group was whether the lookup tables can be replaced by suitable functions. (Note that we only considered the static problem, which assumed that the fuel was in equilibrium. The much harder problem of determining the volume of a sloshing fuel was not considered, but might make a very interesting problem for a future Study Group.)

To solve this problem we require a combination of numerical analysis and geometry. Numerical methods are needed to determine suitable approximations to the h-V function. However, generating such approximations turns out to be very subtle, because of the way that the fuel interacts with the tank geometry. This leads to h-V curves which are nonsmooth and have to be approximated very carefully. An understanding of the way that this nonsmoothness arises and how the resulting curves can be approximated forms the basis of this Study Group report.Chris Budd2007-06-19Z2015-05-29T19:47:29Zhttp://miis.maths.ox.ac.uk/miis/id/eprint/108This item is in the repository with the URL: http://miis.maths.ox.ac.uk/miis/id/eprint/1082007-06-19ZShimmy in aircraft landing gearShimmy is an oscillation in aircraft landing gear that can occur both on landing and take-off, typically in a band of velocities. It causes excessive wear on components and can cause accidents. The nose wheel is roughly like a caster on a shopping trolley: the horizontal axle of the wheel is mounted in an assembly that is free to rotate about a vertical axis. Shimmy is (or at least includes) oscillation of the wheel assembly about this vertical axis. The current engineering approach has little understanding of the physical mechanisms causing shimmy, but relies on the use of shimmy dampers, and on systematic maintenance and replacement of landing gear components. Simulations are carried out with finite element models and multi-body systems, and there are theoretical models due to Stépán and Somieski. In fact shimmy can also involve lateral oscillation of the landing gear (as well as torsional) and can be coupled to and caused by flutter of the airframe. The phenomenon is multi-scale in nature, as it can be linked to normal mechanical wear of key components at one scale, and gross flexibility effects at the vehicle scale. Airbus wish to identify it earlier in order to address passenger comfort, pilot comfort, manage mechanical wear and avoid overfatiguing the system elements. Specifically, Airbus wish to identify key system elements that may cause shimmy, when given a particular configuration of an aircraft. At early stages of development the configuration may involve the shape and size of the fuselage and design of the landing gear, whilst at the other end of the development process, the configuration may also consist of detailed system elements such as actuators, etc. Airbus relies on systematic maintenance and replacement of landing gear components, thereby avoiding the occurrences of the abovementioned phenomena.David BartonDavid Wood