The objective of the current innovation was to develop a simple but accurate method for predicting boundary layer transition that would include the growth characteristics of laminar boundary layer disturbances while requiring only the pressure distribution over an aerodynamic surface. Other existing methods either give only an estimate of the transition location [and only for surfaces where the TS (Tollmien–Schlichting) growth is the determiner of transition] with no disturbance growth characteristics, or require boundary layer information that must be extracted from a Navier-Stokes flow solver or obtained from a separate boundary layer solver.

The Modal Amplitude Tracking and Transition Computation (MATTC) method is a simple, efficient approach to predicting the growth of boundary layer instabilities for use in the analysis and design of aerodynamic surfaces having extensive regions of laminar flow. The method employs an empirical model developed using statistical analysis to determine the optimum coefficients in simple physics-based algorithms.

The key aspect of the MATTC approach is that it provides the details of the growth of both TS and CF (crossflow) disturbances without requiring boundary layer velocity or temperature profiles, or integrated quantities from these profiles. This makes the method much faster than existing methods. The MATTC approach also tends to be more robust than other methods, avoiding issues with boundary layer extraction or running a separate boundary layer solver that can have problems running if the velocity distributions are not smooth, or with early separation of the laminar boundary layer.

While the baseline MATTC method with the default coefficients for the TS and CF algorithms often gives results with sufficient accuracy, the accuracy for a given case can be improved by recalibrating the coefficients using results from a higher-fidelity boundary layer stability analysis. An auxiliary code for performing this recalibration is included in the MATTC software system.

This work was done by Richard Campbell of Langley Research Center and Matthew Campbell (independent consultant). NASA is seeking partners to further develop this technology through joint cooperative research and development. For more information about this technology and to explore opportunities, please contact This email address is being protected from spambots. You need JavaScript enabled to view it.. LAR-18096-1

NASA Tech Briefs Magazine

This article first appeared in the July, 2016 issue of NASA Tech Briefs Magazine.

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