RANS vs. viscous panel methods for airfoil shape optimization (ICAS 2022)

See the paper here: www.researchga...
Presented by Eytan Adler at the 33rd Congress of the International Council of the Aeronautical Sciences in Stockholm, Sweden.
As the computational resources available to aerodynamicists increase, so does the number of tools with which they can analyze their designs. The key skill of a good engineer is understanding when each tool produces realistic results. Even if no available tool can capture all relevant physical phenomena, this knowledge allows engineers to alter their designs to account for the missing physics. However, with the increasing use of numerical optimization for aerodynamic shape design, the opportunity for this intuition to shape the design is reduced as the optimizer makes design decisions based purely on numerical results. This makes the choice of analysis method critical. Previous studies have compared panel-based aerodynamic tools and RANS CFD to predict and analyze the key aerodynamic phenomena in different flight conditions. But few, if any, have compared the impact of proper tool selection on the optimal aerodynamic shapes. In this work we show the effect of aerodynamic analysis method selection on the optimal aerodynamic shape and the consequences of choosing one that does not capture the relevant flow physics. In particular, we show that modeling boundary layer transition can produce significantly lower drag designs across almost the entire range of Reynolds numbers at which airfoils are used in practice. Additionally, we find that the simple compressibility correction used in XFOIL is sufficient to produce well performing airfoils for flight Mach numbers up to 0.65, after which point the ability for the flow solver to model shock formation is critical. Our results will provide aerodynamicists with the data and intuition to make informed decisions when selecting analysis methods for optimization.

[@vishnusankar5335]

Quite interesting research work, thanks Eytan Adler! Wanted to let you guys know that your efforts to present your work on a public forum are helping undergrad students, like me from India, to appreciate what we are learning in the classroom.

[@jichaoli]

Really nice studies and impressive slides!

[@markoj3512]

yep the problem with XFOIL, there is no subroutine implemented to stop if the local Machnumber exceed 1, or if the local pressure coefficient is lower than the critical pressure coefficient.