Ludwig Prandtl's contributions to fluid mechanics include his development of lifting line theory (to describe the lift and drag of wings of finite span), his work in turbulence, and his experimental and theoretical studies of gasdynamics. Prandtl was trained as a solid mechanist and continued to contribute to solid mechanics throughout most of his career. However, his discovery of the boundary layer is regarded as one of the most important breakthroughs in fluid mechanics of all time and has earned Prandtl the title of Father of Modern Fluid Mechanics.