Publications
3-D, bluff body drag estimation using a Green's function/Gram-Charlier series approach
In this study, we describe the extension of the 2-d preliminary design bluff body drag estimation tool developed by De Chant1 to apply for 3-d flows. As with the 2-d method, the 3-d extension uses a combined approximate Green's function/Gram-Charlier series approach to retain the body geometry information. Whereas, the 2-d methodology relied solely upon the use of small disturbance theory for the inviscid flow field associated with the body of interest to estimate the near-field initial conditions, e.g. velocity defect, the 3-d methodology uses both analytical (where available) and numerical inviscid solutions. The defect solution is then used as an initial condition in an approximate 3-d Green's function solution. Finally, the Green's function solution is matched to the 3-d analog of the classical 2-d Gram-Charlier series and then integrated to yield the net form drag on the bluff body. Preliminary results indicate that drag estimates computed are of accuracy equivalent to the 2-d method for flows with large separation, i.e. less than 20% relative error. As was the lower dimensional method, the 3-d concept is intended to be a supplement to turbulent Navier-Stokes and experimental solution for estimating drag coefficients over blunt bodies.