Home > Research & Engineering > Inlet and Nozzle Technology Development

Physics Modeling and Validation

Improvements in physical modeling and validation of those methods are critical to advancing numerical simulation capability.

Boundary Layer Bleed Modeling

Flow domain and Mach number contours for an oblique shock interacting with a bleed region on a flat plate. — Oblique shock interaction with bleed model boundary condition. Credit: Slater

The modeling of porous bleed boundary conditions was improved by scaling of sonic flow coefficient data for 90-degree bleed holes. This bleed model demonstrated good agreement with experimental data and three-dimensional computational fluid dynamics (CFD) simulations of bleed holes.

Slater, J.W., “Improvements in Modeling 90 degree Bleed Holes for Supersonic Inlets,” NASA TM 2009-215597, Jun 2009. Also AIAA-2009-710.
Slater, J.W., and Saunders, J.D., “Modeling of Fixed-Exit Porous Bleed Systems,” NASA TM 2008-215178, May 2008. Also AIAA-2008-0094.

Vortex Generator Modeling

Comparison of Mach number contours on an axial slice downstream of gridded and modeled vortex generators. The contours indicate the counter-rotating vortex pair shed by the device.] — Mach number contours for gridded and modeled vortex generator. Credit: Dudek

Including small-scale geometry details like vortex generators in a numerical simulation can be quite tedious and computationally expensive. Replacing those physical features with a modeled source term significantly aids preliminary design studies.

Dudek, J.C., “Modeling Vortex Generators in a Navier-Stokes Code,” AIAA Journal, Vol. 40, No. 4, Apr 2011.
Dudek, J.C., “Modeling Vortex Generators in the Wind-US Code,” NASA TM 2010-216744, Jul 2010. Also AIAA-2010-32.

Large Eddy Simulation (LES)

Scale resolving simulations are increasingly being used to improve the understanding and prediction of complex flow physics.

LES of a Hot Subsonic Jet

LES prediction of turbulent heat flux in a hot subsonic axisymmetric jet. Credit: DeBonis

One example demonstrating how LES can be used to inform turbulence models is in the prediction of hot jets. In this work, the WRLES solution was validated against the individual velocity (v) and temperature (T) data. The LES was then used to compute the turbulent heat flux correlation (vT) since simultaneous measurement of both velocity and temperature at a single point is not practical. These results showed the inadequacy of the thermal gradient diffusion approximation used by most RANS turbulence models.

DeBonis, J.R., “Prediction of Turbulent Temperature Fluctuations in Hot Jets,” NASA/TM-2017-219531, Jul 2017. Also AIAA-2017-3610.

LES of a Shock-Wave Boundary-Layer Interaction (SWBLI)

Three-dimensional view of LES of a shock-wave boundary-layer interaction in a rectangular duct. Half of the duct shows the smooth time-averaged mean solution. The other half shows the instantaneous turbulent structures. — LES of a shock-wave boundary-layer interaction in a rectangular duct. Credit: Vyas

Another example demonstrating the complex flow physics being studied is the sidewall effects on an impinging shock-wave boundary-layer interaction. Statistics from this simulation with the FDL3DI solver will be used to inform turbulence models better.

Vyas, M.A., et al., “Sidewall Effects on Exact Reynolds-Stress Budgets in an Impinging Shock Wave/Boundary Layer Interaction,” NASA/TM-2019-220143, Mar 2019. Also AIAA-2019-1890.

LES of a THX3 Single Cooling Hole Experiment

Mean temperature contours on axial slices downstream of a single cooling hole. Comparison of experimental data, FDL3DI LES, GFR LES, and FUN3D Reynolds stress model RANS. — LES of a THX Phase III single cooling hole experiment. Credit: NASA/Borghi

A third example is the FDL3DI and GFR simulations of the THX Phase III single cooling hole experiment described above. Again, in this case, velocity and temperature predictions were compared with the experiment. LES values of turbulent heat flux (vT) were then used to assess turbulence models.