An evaluation of data compression algorithms

Non-specialist users of data compression often encounter difficulties with the selection of an algorithm, suited for their application. This report tries to facilitate this task by providing the necessary information about the algorithms. Four established, at the National Aerospace Laboratory available algorithms were selected for this study: -...

Implementation aspects of a decompressor for compressed METEOSAT data on a VME/68000 system

This report describes the results of a feasibility study into some aspects of a proposed METEOSAT image data compression unit. The study was performed to support the preparation of a proposal for ESOC. For the considered algorithms (ESTEC 1 & MEANDER 1) an estimate of the needed processing power based on the 68000 instruction set was made. This...

Data compression in computational fluid dynamics

Computations in numerical fluid dynamics create large sets of data. Transmission of these datasets requires a high speed communication link or, alternatively, the use of data compression techniques. This report describes the results of a study to the applicability of data compression techniques. An algorithm is designed that yields favourable...

Image data reduction with splines and segmentation with emphasis on earth observation

This report describes the results of a feasibility study on image data compression using spline approximation and image segmentation, with emphasis on earth observation applications. The main subjects dealt with, are: the data compression method, implementation aspects, the test software and test results. It appears that a reduction factor of 5...

Impact/fatigue performance of a (±45₂, O₄)s type carbon/epoxy laminate

In this report the results of an impact damage and fatigue investigation are discussed. Comparative impact tests have been carried out on a solid (± 45₂,O ₄)s carbon/epoxy base laminate and the same type of laminate covered with outer layers of glass, aramid or carbon fabric. In addition an Aramid Reinforced Aluminium Laminate (ARALL) was...

A CAD-system for the design of stiffened panels in wing box structures

In this paper the CAD system DESTIP is described. DESTIP is developed at the NLR for designing compression panels in wing box structures. Application of the system yields optimal panels in the sense that they meet all the requirements imposed by the designer and have minimum weight per unit width. Weight reductions ranging from 0 to 10% have...

Boundary-layer calculations on the leeward surface of a slender delta wing at incidence

The three dimensional flow field around delta wings with leading-edge vortex flow can be computed with panel methods. However, secondary flow separation may occur on the leeward surface of the wing. The associated free vortex sheet can be modeled in the potential flow calculation method, if the location of the secondary separation is provided by...

Compressibility and fugacity of gaseous hydrogen

The concept of fugacity is explained. Application of compressibility and fugacity data in hydrogen embrittlement calculations is discussed. Equations of state are reviewed. Compressibility factors and fugacity coefficients are calculated. A best estimate is proposed.

A quasi-simultaneous calculation method for strongly interacting viscous flow around an infinite swept wing

An outline is presented of a new code, called VISIAN, for the analysis of aerodynamic flows with strong viscous-inviscid interaction. The code is based on the recently developed quasi-simultsuieous method for the calculation of strongly interacting boundary layers. The feasibility of this method has already been demonstrated liy means of a...

Fracture toughness and corrosion properties of the aluminium plate alloys 7010-T651 and 7150-T6E189

A comparative experimental investigation was done on the advanced plate alloys 7010-T651 from ALCAN and 7150-T6E189 from ALCOA. The mechanical properties, fracture toughness and corrosion properties were determined. The most notable finding was the excellent fracture toughness of alloy 7150-T6E189 combined with a high tensile strength. The...

The influence of bending-torsional coupling on the buckling load of general orthotropic, midplane symmetric and elastic plates

The influence of bending-torsional coupling on the buckling load of general orthotropic, midplane symmetric and elastic plates has been studied. First this effect has been analysed for the case of infinitely long plate strips, resulting in approximate analytical solutions, which can be presented graphically for the entire range of the elastic...

The use of panel methods with a view to problems in aircraft dynamics

A survey is given of the basic principles of the panel methods. The most frequently used methods, steady as well as unsteady, are described in some detail. Recent developments aiming at improvönent and extension of the range of applicability are reviewed. The use of panel methods for the determination of stability derivatives is discussed....

Aerodynamic data and off-design characteristics of the modified quasi-elliptical airfoil section NLR 7101

A program for the computation of a compressible turbulent boundary layer under infinite swept wing conditions.

A method is presented to compute the 3D compressible turbulent boundary layer on an adiabatic wall under infinite swept wing conditions. The mathematical model of turbulence is based on a generalisation of Bradshaw's 2D shear stress equation. This results in a system of 5 equations valid along 5 distinct characteristics. A brief discussion is...

Two dimensional MHD duct flow: Numerical analysis and measurements

Finite element calculation of axisymmetric subcritical compressible flow

An iterative finite element calculation is presented of the subcritical CGmpressible flow about a thin parabolic arc of revolution and inside an axisymmetric air intake. The calculations were performed in tenns of the stream function as well as in terms of the velocity potential Both results for the parabolic arc of revolution are compared with...

Computations with the Garabedian and Korn program for two-dimensional transonic flows with embedded shocks

The report describes experiences with the Garabedian and Korn program for the computation of compressible potential flows, with or without shocks, both supercritical shockless flows and flows with shock waves. Computations for a number of quasi-elliptical aerofoils indicated that the conformal mapping procedure should be handled with care....

Experimental results around the design condition of a quasi-elliptical aerofoil modified for rear loading