A DETERMINISTIC FORCING SCHEME FOR DIRECT NUMERICAL SIMULATIONS OF TURBULENCE

Direct numerical simulations bf statistically-stationary homogeneous i sotropic turbulence require an artificial input of energy via a forcin g scheme: Previous forcing methods based on a stochastic addition of e nergy have resulted in a poor representation of the energy-containing range of the energy spectrum function and significant temporal fluctua tions of energy and other large-scale quantities. In this work a deter ministic forcing scheme for direct numerical simulation is developed w hich uses wave number-dependent linear amplification of the lower-wave number modes, relaxing them over time toward a model energy spectrum function,which accurately represents grid turbulence. The scheme is sh own to be robust and computationally efficient, resulting in velocity and scalar fields which quickly reach stationarity. It also has the si gnificant advantages over stochastic forcing methods of not introducin g additional statistical variability into the computations and allowin g more physically realistic large-scale motions. (C) 1998 Elsevier Sci ence Ltd. All rights reserved.