## Completed Projects

## Current Projects

## DNS of a spatially developing incompressible mixing layer

** Collaborators: ** Dr. S. M. Murman (NASA Ames), Dr. Y. Peet (Arizona State University)

** Student: ** Juan Diego Colmenares Fernandez

In direct numerical simulations (DNS), a mixing layer develops from interaction of two co-flowing laminar boundary layers; no artificial perturbations are seeded into the flow to trigger the flow transition to turbulence. The flow conditions used in simulations closely match those in experiments by Bell & Mehta (1990). DNS are conducted using the spectral-element code Nek5000.

Current results:The research team would like to acknowledge the computational time allocation on Pleiades supercomputer at NASA’s High-End Computing Capability, where the simulations were conducted, as well as the UNM Center for Advanced Research Computing , where a part of the simulations and post-processing was conducted.

## Uncertainty quantification in DNS data with RANS-DNS simulations

** Collaborators: ** Dr. S. M. Murman (NASA Ames)

** Student: ** Juan Diego Colmenares Fernandez

Statistical data obtained from DNS are often used as reference data for validating turbulence models. Thus, accuracy of the DNS data itself is of particular importance for understanding the potential error in Reynolds-averaged Navier-Stokes (RANS) simulations. Our recent studies demonstrate that when the DNS data is used to represent budget terms in the RANS equations, simulations of wall-bounded turbulent flows conducted with such equations (herein referred to as RANS-DNS simulations) produce unphysical results. We investigate the contribution of various uncertainty sources in DNS on the RANS-DNS simulation results.

Current results:*Physics of Fluids*, 2016, 28(11). DOI: 10.1063/1.4966639 manuscript.

## Fourth-Order RANS-based turbulence closure

** Collaborators: ** Dr. S. M. Murman (NASA Ames), Dr. A. Jemcov (University of Notre Dame)

** Students: ** Juan Diego Colmenares Fernandez, Bryan Kaiser

The results are reported in AIAA2015-3067, AIAA2014-2207 and

S. V. Poroseva, S. M. Murman, “ Sensitivity of a New Velocity/Pressure-Gradient Model to Reynolds Number,”
*Proc. TSHP-10*, Chicago, IL, July 6-July 9, 2017.

S. V. Poroseva, B. E. Kaiser, J. A. Sillero, S. M. Murman, “Validation of a Closing Procedure for Fourth-Order RANS
Turbulence Models with DNS Data in an Incompressible Zero-Pressure-Gradient Turbulent Boundary Layer,”
* Int. J. Heat Fluid Flow*, 2015.

S. V. Poroseva, S. M. Murman, “ Reynolds-Stress Simulations of Wall-Bounded Flows Using a New Velocity/Pressure-Gradient Model,”
*Proc. TSHP-9*, Melbourne, Australia, June 30-July 3, 2015.

S. V. Poroseva, S. M. Murman, “
On Modelling Velocity/Pressure-Gradient Correlations in Higher-Order RANS Statistical Closures,”
*Proc. the 19th Australasian Fluid Mechanics Conference*, Melbourne, Australia, December 8-11, 2014.

The research team would like to acknowledge a partial support for this project from NASA under award NNX12AJ61A. A part of simulations were conducted using the high-performance facilities of the UNM Center for Advanced Research Computing .

## Completed Projects

## RANS simulations of two-dimentional turbulent flows with OpenFoam

** Graduated students: ** Robert Habbit, Andrew Porteous, Sebastian Gomez, Benjamin Graves

OpenFOAM is an attractive Computational Fluid Dynamics solver for evaluating new turbulence models due to the open-source nature and
the suite of existing standard model implementations. Before interpreting results obtained with new turbulence models, a baseline for
performance of the OpenFOAM solver and existing models is required. In our study, we assessed the accuracy of simulation results
obtained with standard models for the Reynolds-averaged Navier-Stokes equations implemented in the OpenFOAM incompressible solver.
Planar (two-dimensional mean flow) benchmark cases generated by the AIAA Turbulence
Model Benchmarking Working Group (TMBWG) were considered:

2D ZPG boundary layer over a flat plate,

2D bump-in-channel flow, and

2D NACA 4412 airfoil in addition to

the case of a 2D circular cylinder.

Simulations were conducted with Spalart-Allmaras one-equation, Wilcox’s 2006 version of the two-equation k-ω, and SST 1994 turbulence models (as formulated at the TMBWG website for each case). Simulations are also conducted with Reynolds Stress Transport models. OpenFOAM results were compared with those obtained with NASA CFL3D and FUN3D codes (available at the TMBWG website) and with DNS, LES, and experimental data when available. Results are reported in AIAA2015-2609, AIAA2015-0519 , and AIAA2014-2087.

The OpenFOAM source files with the standard formulation as specified at the TMBWG website can be uploaded here as a single zip file. Changes to the original OpenFOAM files are documented here . When using the files, a reference to our paper will be appreciated.

The project was supported in part by NASA under award NNX12AJ61A. A part of simulations were conducted using the high-performance facilities of the UNM Center for Advanced Research Computing .

## Sensitivity study of turbulent flow simulations over a rotating disk

** Graduated student: ** Michael A. Snider

With increasing the demand for renewable energy, there is a need for accurate and reliable simulations of a flow around a wind turbine.
To be of use as an engineering design and planning tool, such simulations should be conducted in a timely manner.
This can be achieved if a flow is modeled with Reynolds-Averaged Navier-Stokes turbulence models.To reduce uncertainties in results of simulations, one has to ensure the convergence of a numerical solution with respect to various simulation
parameters. In this study, the effects of the size of computational domain, boundary proximity, grid stretching, and initial grid wall spacing
were analyzed. Due to the complex geometry of wind turbines, a flow over an infinite rotating disk was considered as the first step.
Such flow represents a rotating wind turbine with an infinite number of blades. Simulations were conducted with five turbulence models using
structured meshes in Star-CCM+ (AIAA2012-3146).

The research team would like to acknowledge the UNM Center for Advanced Research Computing for providing consulting support and parallel computational resources, and also, CD-adapco for providing Star-CCM+ to the University of New Mexico for academic purposes.