Examples of the application of constrained multivariate optimisation techniques to the design of aerofoil sections. Design point: single, geometry var: LE and TE flaps, initial aerofoil: combat aircraft section, CFD: BVGK (inviscid), Euler code.
Abstract:ESDU 00023 presents examples of the application of constrained multivariate optimisation techniques in inviscid flow. The constrained multivariate optimisation technique for the design of aerofoil sections, CODAS, has two inviscid CFD options - an Euler code, only available for inviscid flow, and BVGK in its inviscid mode. The Euler code can be used for both subsonic and supersonic freestream conditions whilst, for subsonic freestream conditions, BVGK (inviscid) can be useful in situations where BVGK (viscous) has difficulties. ESDU 00023 compares the behaviour of BVGK (inviscid) with the Euler code in identical transonic CODAS studies. The particular case being used in these examples is that of deflection of simple leading- and trailing-edge flaps on the combat aircraft aerofoil used in ESDU 00022. The optimisation objective is to minimise the drag coefficient at a single design point - Mach number 0.79, lift coefficient 0.75. The basic section was designed originally to meet various design points applicable to a modern combat aircraft by deflection of plain leading- and trailing-edge flaps. The thickness distribution of the section (5.821 per cent thickness/chord at 42.39 per cent chord, 0.2552 per cent leading-edge radius/chord ratio, trailing-edge thickness 0.7335 per cent chord) was designed to ensure a good supersonic capability. The section is highly cambered to provide a very high manoeuvre performance at a Mach number of 0.79. Reduction of the drag of this aerofoil section at the selected flight condition is to be sought by the changes in effective camber available from the deflection of leading- and trailing-edge plain flaps, hinged (in this case) at 15 per cent and 75 per cent of chord, respectively. ESDU 00023 is one of a series illustrating the process of using such optimisation techniques, indicating their advantages and revealing the kinds of problems that can arise. To facilitate this, it is in narrative form. An introduction to the application of constrained multivariate optimisation techniques to the design of aerofoil section shapes is given in ESDU 99019.
- Euler Code
- Garabedian and Korn Method
- Leading-Edge Devices (sealed)
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