Analysis of a Goldschmied Propulsor Using Computational Fluid Dynamics Referencing California Polytechnic’s Goldschmied Propulsor Testing

Abstract

The Goldschmied Propulsor is a concept that was introduced in mid 1950's by Fabio Goldschmied. The concept combines boundary layer suction and boundary layer ingestion technologies to reduce drag and increase propulsor efficiency. The most recent testing, done in 1982, left questions concerning the validity of the results. To answer these questions a 38.5in Goldschmied Propulsor was constructed and tested in Cal Poly's 3x4ft wind tunnel. The focus of their wind tunnel investigation was to replicate Goldschmied's original testing and increase the knowledge base on the subject. The goal of this research was to create a computational fluid dynamics (CFD) model to help visualize the flow phenomenon and see how well CFD was able to replicate Cal Poly's wind tunnel results. CFD cases were run to get a comparison of the computational model and the wind tunnel results. For the straight tunnel geometry for the 0.385" slot and cusp A we found a body, pressure and friction drag, fan off C D of 0.0526 and a fan on at 500 Pascals with a C D of 0.0545. This is similar to the wind tunnel results but because of large errors in measuring overall drag we are not able to directly compare to the wind tunnel results. Overall we see that the trends match, mainly that the fan does not decrease the total pressure drag. This was a result of poor geometry and high fan speeds needed for attachment. The tested geometry is less than ideal and has a long way to go before it is of a shape that would have the potential to reduce the pressure drag as much as Goldschmied claimed. Future efforts should be put forth optimizing the aft body to reduce the low pressure in front of the slot and improving aft entrance of the slot to allow for a smoother flow.v ACKNOWLEDGMENTS

Numerical analysis of Goldschmied geometry with boundary-layer suction

“…Validation of the present numerical work is presented through Fig. 5, which compares the results of the present work with that of [7] and [8] in terms of the coefficient of static pressure for two different cases. The results show parity within satisfactory level.…”

“…Many years later, Birkenstock [6] pointed out the utility of this aerodynamic pressure thrust phenomenon in the design of fuel-efficient high speed aircraft. Later Peraudo et al [7] and Saubert [8] used CFD to computationally verity the phenomenon as applicable to the modern day scenario.…”