Numerical treatment of the spike formation stage in marginally separated flows

The method of matched asymptotic expansions is used to describe the so‐called ’by‐pass' transition in marginally separated boundary layer flows. Such flows may typically be observed e.g. on the suction side of a slender airfoil if the angle of attack is raised above a critical value. As a consequence, transition to turbulent flow is triggered by the repeated bursting of a laminar separation bubble. For asymptotically large Reynolds numbers the bursting of a laminar separation bubble can be described by various consecutive stages. The present work addresses the numerical solution of the triple deck stage succeeding a finite‐time blow‐up of the marginal separation stage. Although the corresponding evolution equations of the triple deck stage have been studied extensively by Elliott and Smith, a reliable numerical solution has not yet been presented. Special emphasis is placed on the formulation of the matching condition to the terminal structure of the preceding marginal separation stage.