ESDU Toolbox

IHS ESDU provides essential design methods and software for the aerospace, defence, transportation, energy and related industries. These methods and software are produced and rigorously validated in concert with the collective knowledge of hundreds of engineers from around the world.

Listed below are some lightweight 'apps' that perform various engineering calculations. These apps are freely available to subscribers and non-subscribers alike.

Flight Sciences

  • International Standard Atmosphere app

    This app determines, at a specified pressure altitude in the International Standard Atmosphere (ISA), absolute and relative values of pressure, temperature and density together with the absolute values of the speed of sound, kinematic and dynamic viscosity and thermal conductivity. It also determines VTAS, VEASM, kinetic pressure and unit Reynolds number for a specified Mach number at the given pressure altitude. Calculations are limited to the troposphere and stratosphere.

    Section 4, of the ESDU Aerodynamics Series contains additional information on Atmospheres. In particular, for calculations at greater altitudes and for further details of the ISA consult ESDU 77021. A range of 'design' atmospheres that differ from the ISA is given in ESDU 78008.

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  • Wing lift-curve slope app from ESDU TM 169

    This app employs a modified version of the Helmbold-Diederich equation (described in ESDU TM 169) to estimate the lift-curve slope of a wing of trapezoidal planform. In order for the method to be applicable the wing must be thin and employ only moderate camber and twist, and the flow must remain both attached and wholly subcritical. Compressibility effects are catered for by means of the classic Prantl-Glauert factor. The original Helmbold-Diederich equation was often used before there was general access to more soundly based methods such as the lifting-surface theory (which is the basis of ESDU 70011). However, the improved and modified version of the equation used in this app provides estimates accurate to within a few per cent of those obtained by ESDU 70011, which itself has been assessed as providing estimates to within around 5% of wind-tunnel test data. The limits of applicability in terms of flow and geometric parameters for which the app produces results have been restricted to those cited for the method from ESDU 70011.

    The full background to this method, and that of ESDU 70011, is given in ESDU TM 169 in the ESDU Aerodynamics Series.

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  • Skin friction coefficient on a flat plate

    This App uses the semi-empirical method of Spalding and Chi to obtain the local and mean skin friction coefficients for a turbulent boundary layer on a smooth flat plate with zero pressure gradient and zero heat transfer.

    The data are applicable to flows with Reynolds numbers based on streamwise distance over the range 100 thousand to 1000 million and for Mach numbers up to 5.

    The equations used are taken from Appendix A of ESDU 78019, which itself is based on the method described in ESDU 68020. Both of these Items are to be found in the Aerodynamics Series.

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Aerospace Structures

  • Inelastic stress-strain curves from ESDU 89052

    This app provides a method of estimating the stress-strain behaviour of a metallic material within the assumptions that this behaviour may be represented by a smooth continuous generalised curve. The method is valid for both tensile and compressive stress-strain data.

    The curve is derived using the Young's modulus and two data points in the inelastic region (the tensile strength is used solely to limit the extent of the curve). The curve follows the modulus in the elastic region and in the inelastic region the greatest accuracy is in the region of the two data points used to derive the curve.

    The two data points in the inelastic region may be given as either (a) two proof stresses and the corresponding permanent strains, or (b) two stresses and the corresponding total strains.

    The theoretical basis for the generalised stress-strain form used by the app is detailed in ESDU 89052, 'Construction of inelastic stress-strain curves from minimal materials data', and ESDU 76016, 'Generalisation of smooth continuous stress-strain curves for metallic materials'.

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