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 the ESDU 'Toolbox Apps'. These provide user friendly webbased interfaces to some ESDU programs. Some Toolbox Apps are only available to subscribers, others are freely available to subscribers and nonsubscribers alike.
Subscriber Toolbox Apps

ESDU 74036: Drag due to a circular cavity in a plate with a turbulent boundary layer at subsonic, transonic and supersonic speeds
From Data Item ESDU 74036.
This app implements ESDUpac A7436, which, in turn, is based correlations of experimental results obtained on a plate at zero incidence, for predicting the increment in drag for Mach numbers less than 3. The methods apply to a cavity with sharp edges, walls normal to the plate, flat bottom and no throughflow; no information is available on rounding or chamfering of the corners, but such edge modifications should not be assumed to be beneficial. The depth/diameter ratio varied from 0.04 to 1.5 but a method of dealing with a cavity in which the ratio is less than 0.04 and based on the method of ESDU 75031 is utilised. The data apply strictly in zero pressure gradient flows, but guidance on their use where there is a pressure gradient is given in the Data Item.
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ESDU 75028: Drag due to grooves in a flat plate with turbulent boundary layer, at subsonic and supersonic speeds
From Data Item ESDU 75028.
ESDU 75028 is derived from a correlation of experimental data that enable the drag increment to be predicted due to a groove of planform aspect ratio greater than 8 normal to the flow. For grooves inclined at angles to the flow exceeding 60 degrees the data for the grooves normal to the flow apply, while for grooves inclined between 0 degrees (parallel to the flow) and 60 degrees a method for obtaining the maximum increment is suggested based on the use of ESDU 75031 to predict the increments due to the forward and rearwardfacing steps together with an appropriate skin friction allowance.
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ESDU 75031: Drag of twodimensional steps and ridges immersed in a turbulent boundary layer for Mach numbers up to 3
From Data Item ESDU 75031.
ESDU 75031 gives an empirical method for the prediction of the drag increment due to a variety of twodimensional excrescences, each mounted normal to the flow direction on a flat plate, and immersed in a turbulent boundary layer for Mach numbers up to 3. The excrescence types are (1) a forwardfacing step, ramp (chamfered step), or a radiused step, (2) a rearwardfacing step, ramp (chamfered step), or a radiused step, and (3) a square section ridge or a rectangular section ridge (of height/length ratio 2), with or without radii to the top corners.
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Free Toolbox Apps

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 V_{TAS}, V_{EASM}, 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 liftcurve slope app from ESDU TM 169
This app employs a modified version of the HelmboldDiederich equation (described in ESDU TM 169) to estimate the liftcurve 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 PrantlGlauert factor. The original HelmboldDiederich equation was often used before there was general access to more soundly based methods such as the liftingsurface 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 windtunnel 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 semiempirical 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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Inelastic stressstrain curves from ESDU 89052
This app provides a method of estimating the stressstrain 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 stressstrain 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 stressstrain form used by the app is detailed in ESDU 89052, 'Construction of inelastic stressstrain curves from minimal materials data', and ESDU 76016, 'Generalisation of smooth continuous stressstrain curves for metallic materials'.
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ESDU Series:
 Aerodynamics
 Aircraft Noise
 Composites
 Dynamics
 Fatigue  Endurance Data
 Fatigue  Fracture Mechanics
 Fluid Mechanics, Internal Flow
 Fluid Mechanics, Internal Flow (Aerospace)
 Heat Transfer
 Mechanisms
 Performance
 Physical Data, Chemical Engineering
 Stress and Strength
 Structures
 Transonic Aerodynamics
 Tribology
 Vibration and Acoustic Fatigue
 Wind Engineering
ESDU Packages:
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