This paper describes a comparative evaluation of twodata smoothing algorithms for use in a two stepestimation-beforemodelling procedure for aircraftparameter identification. A simple fixed lagsmoother is compared with the usual, and morecomplex, modified-Bryson-Frazier smoother in thefirst, state estimation, step of the aircraftparameter identification procedure. The comparisonis illustrated by application to the analysis of theDutch Roll motion of the Embraer EMB-312 Tucano.Both algorithms were found to give results ofcomparable accuracy although the fixed lag smootheris computationally more efficient. It was concludedthat the fixed lag smoother algorithm is anacceptable alternative to themodified-Bryson-Frazier algorithm in aircraftparameter identification applications.

Progress in aeroelasticity of fixed and rotary wingaircraft is compared by means of a selective review.Discussion of the role of concurrent engineeringleads into modelling and validation, these beingdealt with under the headings of aerodynamics,structural and integrated models. Formulation andsolution of equations of motion are considered,which relate mainly to rotorcraft, and thenaeroelastic performance improvement is covered. Thisincludes optimisation, aeroservoelasticity andpassive devices. Basic insight providing models arereviewed and the paper concludes with, furthercomments on insight, and also future progress inaeroelasticity.

The forces due to normal pressure have been measured inthe region of the junction between a rear-loadedwing swept forward at 28°, and a flat plate on whicha turbulent boundary layer had developed. TheReynolds number was 1·03 × 106, based onthe streamwise wing-chord of 500 mm. At lowincidences, 0° < α ≤ 6°, thelocal pressure drag coefficients were found to benegativeaway from the junction,and the interaction with the junction was found tobe favourable;that is the pressuredrag coefficient became more negative as thejunction was approached. At α = −3° the pressuredrag coefficient changed from a positive value awayfrom the junction to a negative value close to theplate. These results contrast with those for aswept-back wing-plate interaction, which has beenreported as being unfavourable so far as thepressure drag was concerned. At 6° incidence, theinteraction remained favourable but there wasevidence of root stall beginning. At an incidence of9°, root stall was much more marked and the positivepressure drag coefficient increased as the junctionwas approached.

Asymmetric vibration of multilayered conical shell withcore layers of viscoelastic material areinvestigated in this paper. The analysis presentedherein considers bending, extension in plane shearand transverse shear deformations in each of thelayers, and also includes rotary, longitudinaltranslatory and transverse inertias. Appropriatetrigonometric series are used as solution functionsin the Galerkin method to reduce the governingequations to a set of matrix equations. Thecorresponding principle of linear viscoelasticityfor harmonic motion is used for evaluating thedamping effectiveness of shells with elastic andviscoelastic layers. A computer program has beendeveloped for determining the resonance frequenciesand associated system loss factors for various modesof families of asymmetric vibration of a generalmultilayered conical shell consisting of anarbitrary number of specially orthotropic materiallayers. Variation of resonance frequencies and theassociated system loss factors with total thicknessparameter and circumferential modal number forthree, five and seven layered conical shells, withthree sets of classical end conditions: simplysupported at both ends, clamped-clamped andfree-free, which can be of some use to designers,are been reported.

Non circular jets are emerging as a new class ofpassive control mechanism of jet flow. Jets issuingfrom non circular nozzles, rectangular, square,triangular, elliptic etc, are found to entrainseveral times more ambient fluid than equivalentaxisymmetric nozzles. Non circular jets aregenerally referred to as non axisymmetric orthree-dimensional jets. The increased entrainment ofthese asymmetric jets, particularly that of ellipticjets, has attracted the attention of manyresearchers. As asymmetric jets, multiple jets ofdifferent geometric configurations have also beenproved to be effective in passive control of the jetflowfield. Multiple asymmetric jets may be expectedto emerge as an effective method of passivelycontrolling the jets. Many researchers have studiedthe flow field of single three dimensional jets andmultiple circular or plane jets. But studies onmultiple threedimensional jets are very limited.Pani and Dash studied the flowfield ofthree-dimensional single and multiple free jets.Their observed mean velocity distribution resultswere in agreement with the theoretical profiles.

The multidisciplinary problem of tail buffeting issolved using three sets of equations. The first setis the unsteady, compressible, full Navier-Stokesequations which are used for obtaining the flowfieldvector and the aerodynamic loads. The second set isthe coupled aeroelastic equations which are used forobtaining the bending and torsional deflections ofthe tail. The third set is the grid-displacementequations which are used for updating the gridcoordinates due to the tail deflections. For thecomputational applications, a sharp-edged delta wingof aspect ratio one and a rectangular vertical tailof aspect ratio one placed in the plane of geometricsymmetry behind the wing are considered. Theconfiguration is pitched at a critical angle ofattack (α = 38°) which produces asymmetric,vortex-breakdown flow from the delta wing primaryvortices. The results show the effects of coupledand uncoupled bending-torsional responses and theeffects of Reynolds number.

This paper proposes a correlation which attempts torelate an aerofoil's low speed dynamic stall onsetincidence to particular parameters describing itsstall behaviour in steady conditions. Theseparameters, which can be derived from experiment orpredictive algorithm, are the incidence of steadystall and a term related to trailing-edge separationcharacteristics. The correlation is based on a largeamount of data obtained from a number of aerofoilsbroadly classified into two families: the NACA fourdigit series of symmetrical sections and a family offour profiles with the NACA 23012 as the genericshape.

The correlation has been extended to low pitch ratesoutside the “deep” dynamic stall range and, whilstit pertains to stalling under ramp motions, a linkhas been established with oscillatory motions. Thepotential of the correlation is demonstrated by itsapplication to the design of a symmetric aerofoilfor use on wind turbines.