Automatic Transition Predictions Using Simplified Methods

Abstract

Laminar-turbulent transition remains a critical issue in a number of cases, including drag reduction, performance prediction of high-lift systems, improved accuracy in general computational fluid dynamics, and reduction of computation cycles for development of optimization tools. Transition delay remains one of the most promising technologies for reducing air transport energy consumption, through natural or hybrid laminar flow control. The use of linear stability theory, either local or nonlocal, remains rather demanding in terms of knowledge and user interaction. Hence, a demand exists for simplified, robust, and accurate transition prediction tools to be inserted into general flow solvers, of boundary-layer or Reynolds-averaged Navier-Stokes types. The problem can be solved by developing transition criteria or database methods. In this last case, characteristics of an actual flow are derived from known solutions of model flows. ONERA, the French Aerospace Laboratory, has long been involved in the development of such methods, and the present paper aims at providing a comprehensive view of the tools developed in the second category, applicable from low-speed two-dimensional to transonic three-dimensional flows, and even to three-dimensional supersonic flows.

Natural laminar flow wing for supersonic conditions: Wind tunnel experiments, flight test and stability computations

“…Nonetheless, this method can be time consuming since it requires solving an eigenvalue problem at each station of disturbance path for each frequency and spanwise wave-number. In this context, a simplified stability method, called Database, has been developed at Onera [15,50]. The principle of such a method consists in computing an analytical growth rate as a function of local parameters and mean flow properties.…”

“…3). As demonstrated by the linear stability results, CF instability is dominated by the properties of this inflection point [15,16] (altitude and velocity gradient). These properties are still valid for supersonic flows but there are extended to the generalized inflexion point (GIP) defined as the value of z where the quantity micron-sized roughness elements (i.e.…”

Development and Application of Transition Prediction Techniques in an Unstructured CFD Code (Invited)

“…For the application of the LST-based e N method within a large CFD system it is possible to either apply an automated linear stability code [22] or database methods of different approximation levels [27][28][29][30][31][32][33] so that an automatic and autonomous execution of transition prediction can be carried out during the ongoing run of a CFD simulation. At the same time, information and data about the stability behavior of the laminar boundary layer from the point of neutral stability (critical point) up to the point where the critical N-factor is reached (point of transition onset) are calculated and can be made available to the user.…”

Complementary Numerical and Experimental Data Analysis of the ETW Telfona Pathfinder Wing Transition Tests

“…3-5. In this work a second step was performed, stability analysis was performed using numerical pressure distributions in addition to experimental pressure distributions. The stability analysis was based on linear stability theory using the LILO 10 code (with exact stability code and database methods) and the CASTET code 11 (exact stability methods) and the ONERA database method 12,13 . Stability analysis for pressure distributions obtained with the DLR-TAU and the CFD++ RANS solutions was performed using LILO.…”