A computational study is presented, which examines theperformance of variants of second-moment closure andnon-linear eddy-viscosity models when used topredict attached and separated flows over a highlift aerofoil for a range of incidence angles. Thecapabilities of both model types, especially inrespect of resolving the onset of suction-sideseparation at high incidence, are contrasted withthose of a low-Re k-ε model basedon the linear Boussinesq stress-strain relationship.The second-moment model contains a conventionallinear approximation of the pressure strainingprocess; a cubic (realisable) variant has beeninvestigated in an earlier study and found to offerno advantages. The quadratic eddy-viscosity modelfeatures coefficients which are sensitised to thestrain and vorticity invariants. While both models,in the form originally proposed, are superior to thelinear eddy-viscosity variant, neither performs wellin respect of resolving separation, unless modifiedso as to return the requisite low level of shearstress in the boundary layer approaching separation.Once separation is resolved with sufficient realism,the near wake aft of the trailing edge is also wellrepresented. All models return poor representationsof the far wake which is characterised by low levelsof turbulence production to dissipation ratio.

The design of control systems for helicopters in hoverand at low speed is a basic requirement for theextension of mission profiles and new missiondemands. A special task for various applications isthe position hold under wind and gust conditionsabove a ground fixed or moving target, like ashipboard reference, or a small vessel or lifeboatin rescue missions. For the solution of this problema controller concept was developed and thefeasibility was proven and successfully demonstratedin flight tests.

The in-flight helicopter simulator ATTHeS of the DLRhas been equipped by the Institute of FlightMechanics with an innovative measurement system forthe hover position above a target. A video camera incombination with a highly parallel computer systemfor processing the optical information was used asan integra ted sensor system for the measurement ofthe relative position of the aircraft to a target.Based on the existing well-proven flight controllaws of ATTHeS for the forward flight condition,which are implemented for handling qualitiesinvestigations, these control laws were modified andadapted to fulfil the special requirements of theposition hold task, including altitude hold andheading hold capabilities. The integrated system ofoptical position sensor and control computer enablesthe helicopter to hover automatically above adefined target in constant altitude and withconstant heading. Flight tests above a moving carunder wind and gust conditions underline the futurepotential of the overall system to be used underoperational conditions.

A three-dimensional moving mesh method for solving theEuler equations describing the compressible flowabout a wing undergoing arbitrary motions anddeformations is described. A finite-volumeformulation is chosen where the volumes distort asthe wing moves or deforms. By using transfiniteinterpolation, a technique for generating therequired sequence of grids has been developed.Furthermore, as the speeds of the grid at thevertices of the finite volumes are required by theflow solver, transfinite interpolation is also usedto obtain these by interpolation of the boundaryspeeds. A two-dimensional version of the method hasalso been developed and results for both two- andthree-dimensional transonic flows are presented andcompared with experimental data where available.

This note reports tests in a shock tunnel in which afully integrated scramjet configuration produced netthrust. The experiments not only showed that impulsefacilities can be used for assessing thrustperformance, but also were a demonstration of theapplication of a new technique(1) to themeasurement of thrust on scramjet configurations inshock tunnels. These two developments are ofsignificance because scramjets are expected tooperate at speeds well in excess of 2 km/s, andshock tunnels offer a means of generating high Machnumber flows at such speeds.