We report research experience in applying an Unsteady Reynolds-Averaged Navier-Stokes (URANS) solver for the prediction of time-dependent flows in the presence of an active flow control device. The configuration under consideration is a synthetic jet created by a single diaphragm piezoelectric actuator in quiescent air. Time-averaged and instantaneous data for this case were obtained at Langley...

A fast Newton–Krylov algorithm is presented that solves the turbulent Navier–Stokes equations on unstructured 2-D grids. Themodel of Spalart andAllmaras provides the turbulent viscosity and is loosely coupled to themean-flow equations. It is often assumed that the turbulence model must be fully coupled to obtain the full benefit of an inexact Newton algorithm. We demonstrate that a loosely coup...

The separation of a turbulent boundary layer, which is encountered in devices such as airfoils, diffusers and turbomachinery, is one of the most challenging research topics in fluid mechanics. Its understanding and its prediction with turbulence models are however still not satisfactory. The reason may be partly due to a shortage of reliable data from numerical simulations, which account for Re...

An unstructured grid method is presented to compute three-dimensional compressible turbulent flows for complex geometries. The Navier-Stokes equations along with the one equation turbulence model of Spalart-Allmaras are solved using a parallel, matrix-free implicit method on unstructured tetrahedral grids. The developed method has been used to predict drags in the transonic regime for both DLRF...

We combine data assimilation and machine learning to correct the RANS Spalart-Allmaras turbulence model. The final neural-network contribution is a Boussinesq-correction, rather than turbulent eddy-viscosity adjustment. Flows over periodic hills at distinct Reynolds numbers geometries were selected demonstrate potential gain of learning-augmented models.

Abstract The new term belongs in the “basic,” free-shear-flow part of Spalart–Allmaras (SA) model, and extends an idea Secundov team, incorporated ν t -92 model. It detects transverse curvature distribution eddy viscosity $$ \tilde{\nu } ν ~ , so that it is passive tw...

The efficiency of a turbine increases in general with an increase of the temperature of the working gas. In modern turbines this gas temperature may well exceed the melting temperature of the metal walls (Harasgama, 1995). Locally high heat transfer can lead to an excessive temperature and high thermal stresses in the walls, causing an early fatigue of the high pressure turbine components. Thus...

Reynolds-Averaged Navier-Stokes (RANS) methods have become an important design tool in aerospace industry. Turbulence models, which are required for closure of the RANS equations, are a substantial component in these methods. Several flow regimes exist where the accuracy of flow predictions depends strongly on the turbulence model used. Turbulence has a major influence on the growth rate of bou...