L-shape
An L-Shape or L-Shaped Domain is an area or an area that is often used in the numerics of partial differential equations to test a problem (so-called benchmark problem ). The area is characterized by the fact that it has six corners and is reminiscent of the letter L (possibly rotated or mirrored) . In addition, the L-shape is not a convex set . Some partial differential equations have a singularity at the origin where the re-entrant corner is , which is an additional problem in solving these equations.