Profile drag of axisymmetric bodies at zero incidence for subcritical Mach numbers
ESDU 78019 gives a correlation of computed results using a method that allows iteratively for the displacement effects of the boundary layer and wake. It is found that by plotting the profile drag of the body as a fraction (the form factor) of the skin friction on a flat plate with the same transition position at the same Reynolds and Mach numbers, the data can be correlated and shown graphically simply as a function of body geometry parameters for a datum condition of transition at the nose, zero Mach number and fixed Reynolds number. Correction factors, also given graphically, correct the data for different transition positions and Mach numbers from datum. To assist in obtaining the value of profile drag, additional graphs give the flat plate mean skin friction for an appropriate range of transition positions, Reynolds numbers and Mach numbers. The method of correlating the data has been found to be accurate within 1 per cent for a range of body geometry and flow conditions. The computational method itself was found to agree within 5 per cent with a limited number of reliable experimental data available in the literature. A worked example illustrates the use of the data. ESDU 77028 gives, for a range of forebody and afterbody shapes, the geometry parameters required for the use of the correlation.
Although the method is relatively simple to apply, it is fairly time consuming to evaluate by hand due to the need to determine some second-order effects of body geometry. Analytic equations were therefore developed using the original database, producing a simplified method given in Addendum A. The equations are easily programmed and give a correlation only marginally worse than the graphical method and, moreover, they extend the method to cover a greater range of transition positions. Tentative provision is also made for bodies of smooth non-circular cross section. A computer program of the simplified method is provided as ESDUpac A7819.
|Data Item ESDU 78019|
|Toolbox CFM Run||
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|Figure 1||Body geometry effect|
|Figure 2||Index within correlating parameter combination for body shape|
|Figure 3||Correction to correlating parameter combination for forebody shape and length|
|Figure 4||Transition effect|
|Figure 5||Mach number effect|
|Figure 6||Indices within correlating parameter combination for Mach number|
|Figure 7a||Flat plate mean skin friction coefficient; fully-turbulent boundary-layer|
|Figure 7b||Flat plate mean skin friction coefficient; fully-turbulent boundary-layer|
|Figure 8||Flat plate compressibility factors; fully-turbulent boundary-layer|
|Figure 9||Effect of transition on flat plate mean skin friction coefficient|