|Advanced Wind Tunnel Boundary Simulation II|
|Applied Vehicle Technology|
Boundary Interference, CFD, CFD Validation, Correction, Support Interference, Uncertainty Quantification, Validation Experiment, Wall Interference, Wind Tunnel
The discipline of adjusting wind tunnel data for wall boundaries has been in practice almost as long as wind tunnels have been in existence. Demand for more accurate data has continued to push the development of correction methodologies and boundary representation. Additionally, more emphasis has been placed on the validation of computational tools for use in vehicle design and analysis, with the intent to significantly reduce the number of ground tests required to verify a concept. Better correction methods used in ground testing would lead to improved accuracy in the prediction of aerodynamic behavior of future aircraft systems designed for military operations. For example, transport aircraft tend to have large blunt tails that have a tendency to separate easily and advancement in propulsion systems have moved installed systems away from conventional axially directed thrust.
In 1995, the AGARD Fluid Dynamics Panel planned what became AGARDograph 336 which was published in 1998 as a sequel to 1966 publication of AGARDograph 109. Although both of the documents still contain valid information, the requirements placed on the field of wall interference are increasingly stringent in alignment with computational prediction and validation requirements. Correction is still appropriate for certain kinds of production tests, but understanding the interference itself is more appropriate for computational fluid dynamics (CFD) validation activities. The move to more CFD based design has reduced the demand for testing, and as a result, support of specialists in experimental aerodynamics have diminished.
In 2018, NATO STO sponsored the AVT-284 Research Workshop on Advanced Wind Tunnel Boundary Simulation focused on evaluation of high-fidelity CFD simulation of wind tunnel boundaries including test section walls, upstream and downstream flowpaths and support hardware along with comparison to established results; development of recommendations for the use of high fidelity simulation of wall boundaries and model support hardware; and identification of key areas requiring further research and development. The AVT-284 Workshop attracted a unique blend of experimental and computational fluid dynamicists focused on high fidelity simulations of experimental facilities for both improved interference corrections and validation experiments for computational prediction. The attendees participated in extensive discussions during the workshop and advocated for a follow-on workshop two years from AVT-284 to evaluate further developments and continue development of high fidelity simulations and corrections. The majority of the presenters at the AVT-284 workshop considered their papers to be a status report of work in progress. Some papers had only just managed to complete a few cases and were unable to answer many of the questions that were to be addressed in the workshop. It is expected that by spring of 2020 many of these works in progress will be able to address these questions.
The proposed workshop will evaluate developments in high-fidelity CFD (Euler, Reynolds Averaged Navier-Stokes, Detached Eddy Simulation, Large Eddy Simulation, Lattice Boltzmann, etc.) simulation of wind tunnel wall boundaries and other installation effects including support hardware and compare with established results. The workshop will develop recommendations for the use of high fidelity simulation of wall boundaries and model support hardware, and identify key areas requiring further research and development.
• Use of high fidelity computational methods in simulation of wind tunnel tests
• The method of determination of the reference quantities (Mach number, angle of attack, etc.).
• A comparison of the applied methods to experimental data or other reference work.
• Variations in the modelling assumptions, with their corresponding effects.
• Identification and appropriate justifications of improvements over established methods permitted by the high fidelity modelling.
• A discussion of the “cost” and “risk” of the high fidelity modelling compared with the benefit it provides.