# Leading edge or trailing edge stall?

As I wrote last week, I'm doing a Benedek 10355 airfoil performance report. At this point of the work I am analyzing the stall of the profile at a fixed Reynolds number. The Benedek 10355 airfoil has a thickness of 10.1%. Figure 1 shows the polar calculated with Xfoil at Reynolds number = 500,000.

Analyzing this curve, and comparing it with this answer, it seems to me that we are in the presence of a trailing edge stall. In fact, after the stall angle ($$\alpha_{stall} = 11.0°$$), the decrease in the lift coefficient is gradual ... Then, however, at about $$\alpha = 21°$$ there is a sudden change in lift, as if a laminar bubble had "burst". Figure 2 shows the separated zone for $$\alpha = \alpha_{stall} = 11.0°$$.

Looking at the pressure coefficient, there appears to be a laminar bubble very close to the leading edge (Figure 3). As the incidence increases, this bubble moves more and more towards the leading edge and, when $$\alpha = 22°$$, it "disappears". This makes me think that maybe at low incidences there is a trailing edge stall and then, going further, a leading edge stall ... Maybe I'm missing something? Thanks.

• So what you're asking is where flow separation's happening? Commented Nov 21, 2020 at 18:15
• @CamilleGoudeseune, yes I am asking where the laminar flow separation is happening and if we can talk about a combined leading edge-trailing edge stall. Commented Nov 21, 2020 at 18:19

• thank you for helping me this time too. What do you suggest is best for my report? Stop at 12-13° or show this "anomalous" Xfoil behavior? I have to do a post-stall study, that's why I'm interested in going beyond $\alpha_{stall}$. Thanks again Commented Nov 22, 2020 at 10:54