The paper discusses recent work in the Theoretical Division at the Aircraft Research Association Limited (ARA) on the modelling of complex configurations, rotors, propulsion and viscous flows. The general features of the ARA multiblock system, which provides a grid generation and Euler flow solution capability for complex configurations, are discussed. Although very successful, the system has various limitations, in particular the tendency for the grid quality to depend on configuration complexity and type. A new multiblock system is being developed which allows regions of unstructured grid to be included, giving increased flexibility in dealing with complex geometries and other improvements. Work on rotors has included the development of a new Euler code for propellers, as a replacement for the code in current use. Improvements in flow solution offered by the new code are illustrated. In the propulsion field, the extension of a viscous-coupled Euler code for afterbody flows to a complete cowl unit is described briefly. The code is particularly relevant to the new generation of large civil turbofans. Work on Navier-Stokes methods for afterbody/nozzle flows is also discussed. Other work on viscous flows includes a 2-D investigation into viscous modelling with hybrid grids, and the further development of an established transonic flow aerofoil code.

Free vibration analysis of laminated composite beams, plates and stiffened plates using the finite element method has been presented. To give due importance to the shear deformation in composite materials, a high-order element which considers the quadratic variation of shear strain along the thickness of the element has been developed. The element has been developed using the quadratic isoparametric shape functions. Therefore, it can accommodate curved boundaries. Moreover, the stiffener element can have an arbitrary planform and it need not pass through any nodal point. The stiffener element has been developed in such a fashion to make the mesh division free from the location of the stiffener. This is extremely advantageous for optimisation of the path of the stiffener in a stiffened plated structure, while it is not necessary to modify the mesh division whenever the stiffener path is modified. Two different shape functions — the eight-node Serendipity and the nine-node Lagrangian — have been employed and a comparison between their performances has been presented. Two schemes for the generation of mass matrix, namely the lumped mass scheme and the consistent mass scheme, have been developed. The elements have been implemented in the ASKA element library and they can be used along with any standard ASKA element.

This is a summary of work detailed in a more comprehensive paper which contains a major re-examination of, and challenge to, the assumptions of aerodynamics theory as applied to infinite flow fields at the speed of sound and their consequent relevance to the reality of free flight.

In steady-state flow fields generally, fore-bodies are embedded in the flow by a process based on the contraction of the streamline cross-sections. In subsonic flow this is achieved by velocity increase whereas in supersonic flow it is by velocity decrease. A primary reason for the challenge to accepted theory lies in the fact that, in a steady-state sonic field streamlines can only increase from their undisturbed area (Fig. 1) and this leads to fundamental difficulties in the construction of the forward flow field which in turn lead to the various theoretical anomalies.