A proposed modification to Lundgren's physical space velocity forcing method for isotropic turbulence

As an alternative to spectral space velocity field forcing techniques commonly used in simulation studies of isotropic turbulence, Lundgren [Linearly forced isotropic turbulence," in Annual Research Briefs (Center for Turbulence Research, Stanford, 2003), pp. 461-473] proposed and Rosales and Meneveau ["Linear forcing in numerical simulations of isotropic turbulence: Physical space implementations and convergence properties," Phys. Fluids 17, 095106 (2005)] validated a physical space forcing method termed " linear forcing." Linear forcing has the advantages of being less memory intensive, less computationally expensive, and more easily extended to variable density simulations. However, this forcing method generates turbulent statistics that are highly oscillatory, requiring extended simulation run times to attain time-invariant properties. A slight modification of the forcing term is proposed, and it is shown to reduce this oscillatory nature without altering the turbulent physics. (C) 2013 AIP Publishing LLC.