A temporally regularized buffer domain for flow-through simulations

• We demonstrate a new use for temporal regularization in fluid simulations.
• A new, efficient buffer-domain treatment is developed and demonstrated.
• Temporal regularization is effective in dampening all disturbances in a buffer domain.

For numerical simulations of inflow-outflow problems, the outflow condition is virtually always non-physical and often problematic. For such problems it is customary to append a “buffer domain” (“buffer zone” or “sponge layer”) to the computational domain. Within the buffer domain, the flow is modified in some non-physical way to minimize upstream influence. Here we propose a new type of buffer domain in which temporal regularization is exploited to rapidly attenuate traveling waves of all frequencies. Conditions appropriate for laminar flow can then be imposed at the outflow boundary. The method, whose computational overhead is minimal, may stand alone or potentially enhance other buffer-domain methodologies. The method is demonstrated both for the first-order wave equation and for two-dimensional free-shear flow.