  A major drawback of Boussinesq-type subgrid-scale stress models used in
large-eddy simulations is the inherent assumption of alignment between
large-scale strain rates and filtered subgrid-stresses. A priori analyses using
direct numerical simulation (DNS) data has shown that this assumption is
invalid locally as subgrid-scale stresses are poorly correlated with the
large-scale strain rates [Bardina et al., AIAA 1980; Meneveau and Liu, Ann.
Rev. Fluid Mech. 2002]. In the present work, a new, non-Boussinesq
subgrid-scale model is presented where the model coefficients are computed
dynamically. Some previous non-Boussinesq models have observed issues in
providing adequate dissipation of turbulent kinetic energy [e.g.: Bardina et
al., AIAA 1980; Clark et al. J. Fluid Mech., 1979; Stolz and Adams, Phys. of
Fluids, 1999]; however, the present model is shown to provide sufficient
dissipation using dynamic coefficients. Modeled subgrid-scale Reynolds stresses
satisfy the consistency requirements of the governing equations for LES, vanish
in laminar flow and at solid boundaries, and have the correct asymptotic
behavior in the near-wall region of a turbulent boundary layer.
  The new model, referred to as the dynamic tensor-coefficient Smagorinsky
model (DTCSM), has been tested in simulations of canonical flows: decaying and
forced homogeneous isotropic turbulence (HIT), and wall-modeled turbulent
channel flow at high Reynolds numbers; the results show favorable agreement
with DNS data. In order to assess the performance of DTCSM in more complex
flows, wall-modeled simulations of high Reynolds number flow over a Gaussian
bump exhibiting smooth-body flow separation are performed. Predictions of
surface pressure and skin friction, compared against DNS and experimental data,
show improved accuracy from DTCSM in comparison to the existing static
coefficient (Vreman) and dynamic Smagorinsky model.
