Multiple boundary layers in simulations In recent years, aerodynamic simulations, such as airfoils, have become much more advanced. The invention of the computer has greatly increased aerodynamic simulation capabilities. Sub2D simulation software, used by Consulting Aviation Services, can create multi-body airfoil simulations, simulate viscous and inviscid flows, calculate the separation position of an airfoil, calculate lift, moment, and drag coefficients, and more again (Flansburg). Another aspect of the Sub2D software is its ability to measure the thickness and boundary layer characteristics of a viscous airfoil (Flansburg). This feature of Sub2D software is important for finding lift, drag, and moment coefficients, as well as separation coordinates, for viscous flow. To better understand the role of boundary layers in aerodynamic simulations and calculations, it is necessary to explain boundary layers, along with a few other concepts. Boundary Layers The book Boundary Layer Theory by H. Schlichting and K. Gersten is, to quote the back cover, "almost legendary". What can be deduced from this quote is that the book Boundary Layer Theory is authoritative in boundary layer science limit The book begins with a puzzle faced by 18th century scientists who studied fluid mechanics. These fluid mechanics based all their studies on an ideal fluid an ideal fluid, a body moving subsonically will not produce resistance (Schlichting & Gersten, 2000), known as the D'Alembert paradox, is the result of abandoning a key factor that distinguishes inviscid flow. from the viscous one.The key factor is tangential tension, or friction, and... the center of the paper... high-lift flow with separation control by periodic excitation informal, Hermann-Fottinger Institute for Fluid Mechanics, Technical University of Berlin, Berlin, Germany. Retrieved from http://www.cfd.tu-berlin.de/~schatz/PUBLICAZIONI/aiaa2001-0296.pdfSchlichting, H., & Gersten, K. (2000). Boundary layer theory. (8 ed.). Berlin: Springer.Stieger, R. (2002). The effects of wakes on boundary layer separation in low pressure turbines. (Unpublished doctoral dissertation, Cambridge University, Cambridge, UK) Retrieved from http://www-g.eng.cam.ac.uk/whittle/publications/rds/RStieger_PhD.pdf Tran, D. (2003). Comparison of the numerical simulation of the flow around an airfoil in high lift configuration with piv experimental results. Berlin: Springer. Retrieved from http://extras.springer.com/2004/978-3-540-21423-6/Proceedings/p043.pdf