"ESDU 84004 gives a correlation of experimental data drawn from a large number of sources that enables spillage drag to be estimated for a wide range of configurations at incidences up to 20 degrees and for mass flow ratios from zero to unity. The method is well suited to aircraft project studies and one particular application is providing spillage drag at low values of intake mass flow ratio (below 0.4@ say) for use with the ""bare-engine"" windmilling drag and airflow data of ESDU 81009. That combined use of those two ESDU methods to estimate the drag of an inoperative turbo-jet or turbo-fan engine is described in ESDU 84005. Two comprehensive practical worked examples illustrate the use of the correlation."
ESDU 84004 A-1984 history
1984ESDU 84004 A-1984 Estimation of spillage drag for a wide range of axisymmetric intakes at M less than 1.