The APDE seminar on Monday, 11/7, will be given by Sameer Iyer (UC Davis) in-person in **Evans 740,** and will also be broadcasted online via Zoom from **4:10pm to 5:00pm PST**. To participate, email Sung-Jin Oh ().

**Title**: Reversal in the stationary Prandtl equations

**Abstract**: We discuss a recent result in which we investigate reversal and recirculation for the stationary Prandtl equations. Reversal describes the solution after the Goldstein singularity, and is characterized by spatio-temporal regions in which $u>0$ and $u<0$. The classical point of view of regarding the Prandtl equations as an evolution completely breaks down. Instead, we view the problem as a quasilinear, mixed-type, free-boundary problem. Joint work with Nader Masmoudi.