Development of high-fidelity numerical methods for turbulent flows simulation

Energy-conserving discretizations are widely regarded as a fundamental requirement for high-fidelity simulations of turbulent flows. A well-known approach to obtain semi-discrete conservation of energy in the inviscid limit is to employ the skew-symmetric splitting of the non-linear term. However, this approach has the drawback of being roughly twice as expensive as the computation of the divergence or advective forms alone. A novel time-advancement strategy that retains the conservation properties of skew-symmetric-based schemes at a reduced computational cost has been developed. This method is based on properly constructed Runge-Kutta schemes in which a different form (advective or divergence) for the convective term is adopted at each stage. A general theoretical framework has been developed to derive new schemes with prescribed accuracy on both solution and energy conservation. The technique has been first developed and fine-tuned on the Burgers' equation, and then applied to the incompressible Navier-Stokes equations. Simulations of homogeneous isotropic turbulence performed at the Center for Turbulence Research (CTR) in Stanford have demonstrated that the novel procedure provides the same robustness of the skew-symmetric form while halving the computational cost for the non-linear term.