Emeritus ( /ɨˈmɛrɨtəs/; plural emeriti; abbreviation emer.) is a post-positive adjective used to designate a retired professor, bishop, or other professional. The female equivalent, emerita (/ɨˈmɛrɨtə/), is also sometimes used, but phrases such as professor emerita are not in proper usage according to Latin grammar rules.

In many cases the term is conferred automatically upon all persons who retire at a given rank. This is the usual case for retired professors. In other cases, it is used when a person of importance in a given profession retires or hands over the position so that his former rank can still be used in his title.

In the United States, the word is used either as a postpositional adjective (e.g., "professor emeritus"), or as a preposition adjective (e.g., "emeritus professor"). There is a third usage, although not employed as often, in which the word follows a full title (e.g., professor of medicine, emeritus.)

It is also commonly used in business and non-profit organizations to denote perpetual status of the founder of an organization or individuals who moved the organization to new heights as a former key member on the Board of Directors (i.e. Chairman Emeritus; Director Emeritus; President of the Board Emeritus.)

Bram van Leer is the Arthur B. Modine Professor of aerospace engineering at the University of Michigan, in Ann Arbor. He specialises in Computational fluid dynamics (CFD), fluid dynamics, and numerical analysis where he has made substantial contributions.

Professor van Leer developed MUSCL scheme, which stands for Monotone Upstream-centered Schemes for Conservation Laws, and the term was introduced by him in a seminal paper (van Leer, 1979). In this paper he constructed the first high-order, total variation diminishing (TVD) scheme where he obtained second order spatial and temporal accuracy. It is a finite volume method that provides high accuracy numerical solutions to partial differential equations which can involve solutions that exhibit shocks, discontinuities, or steep gradients. In 1982 he published another important paper that introduced a computationally efficient alternative, based on flux-vector splitting, to the exact Riemann solver in Godunov algorithm (van Leer, 1982).

The idea is to replace the piecewise constant approximation of Godunov's scheme by reconstructed states, derived from cell-averaged states obtained from the previous time-step. For each cell, slope limited, reconstructed left and right states are obtained and used to calculate fluxes at the cell boundaries (edges). These fluxes are, in turn, used as input to the (approximate) Riemann solver. The Riemann solver solutions are averaged and used to advance the solution in time.