Software for Analyzing Laminar-to-Turbulent Flow Transitions

Langley Stability and Transition Analysis Codes (LASTRAC) is a set of engineering software tools developed with the C++ language and modern software technologies for use in analyzing transition from laminar to turbulent flows. LASTRAC is a product of on-going NASA Langley research projects related to transition flow physics modeling and simulations. It is intended to be a set of easy-to-use engineering tools that can be applied to routine engineering design studies. At the current stage, LASTRAC is capable of performing transition calculations based on linear stability theory (LST) or linear and nonlinear parabolized stability equations (PSE) for a broad range of flow regimes and configurations of interest for the design of low-speed as well as supersonic and hypersonic vehicles. At present, LASTRAC is limited to two-dimensional, axisymmetric, or infinite swept-wing boundary layers. Options for general three-dimensional boundary layers are currently under development. The LST option makes it possible to perform traditional N-factor transition correlation. Linear and nonlinear PSE are used to track instability wave evolution from small-amplitude till early transition stage in a high-fidelity manner. It is planned to incorporate modules in LASTRAC that models the receptivity (the process by which perturbations are introduced into laminar boundary-layer flow) and late stage of the transition process. These software modules are intended to enable LASTRAC to perform computations for different stages of laminar-to-turbulent transition in an integrated fashion.