STO-Activities: (no title)
Activity title:
Common Research Wind Tunnels for CFD Verification and Validation
Activity Reference:
AVT-387
Panel:
AVT
Security Classification:
NATO UNCLASSIFIED
Status:
Active
Activity type:
RTG
Start date:
2024-01-01T00:00:00Z
Actual End date:
2026-12-31T00:00:00Z
Keywords:
boundary conditions, Computational Fluid Dynamics, validation, Verification, wind tunnel
Background:
Experimental fluid dynamics (EFD) has been used for decades within the design and analysis process of aerospace and naval vehicles. Typically, flow facilities such as wind tunnels are employed to reproduce a specific flow field within a well-controlled physical experiment in order to investigate the aerodynamics of a vehicle. Using the similitude principle, the results obtained from the experiment can be extrapolated to identify the aerodynamic characteristics of flight conditions. Computational fluid dynamics (CFD) is often used as a complement of EFD in order to reproduce the experiment numerically. The CFD solution obtains the entire volumetric flow field over the investigated vehicle, which is far more detailed than during the experiment, often based on measurements within 2D sections or on discrete measurement points. Although considered reliable and useful for many conditions, CFD methods applicable for industrial applications such as Reynolds averaged simulations often demonstrate strong limitations and inaccuracy to predict separated and unsteady flows. Well-documented experimental campaigns are still required to evaluate and improve CFD models. Today, CFD calculations are no longer limited to the prediction of the aerodynamic flowfield around a vehicle in freestream conditions. The computations are also used to reproduce the flow conditions within the wind tunnel experiment in order to improve the comparison between numerical and experimental results. Furthermore, these calculations including the wind tunnel facility are used to identify the impact of the wind tunnel environment over the measurements compared with free flight conditions.
Unfortunately, precise details such as shape, reference flow determination, and boundary conditions in such facilities are often not known to the level of accuracy required by CFD. As a result, there is always a question whether disagreements between CFD predictions and experimental measurements are caused by the CFD models or by some inconsistency in flow setup or boundary conditions. One of the outcomes of the 2021 NATO AVT 338 Workshop was the idea of identifying one or more Common Research Wind Tunnels (CRWTs). Just as common research models for airplane configurations have enabled rigorous comparison and assessment of computational models in terms of their ability to predict vehicle flows, the CRWTs would provide test cases for the computational modeling and experimental documentation of wind tunnel facilities. The goal would be to address many of the technical challenges identified at the conclusion of AVT 338, such as developing best practices for uncertainty quantification, facility instrumentation and documentation, reference conditions, gridding and turbulence modeling, and modeling of complex boundary conditions.
Objectives:
To advance the validation of CFD modeling using wind tunnel tests. Specifically:
? Selection of a small number (three or four) “common research wind tunnels” (CRWTs). This selection will be made based on the requirement that they be fully open/available for the purposes of this effort. “Open” means that all geometry, boundary conditions, and in-house measurement methodologies of the CRWTs are provided without restriction to all partners. Multiple CRWTs are needed to properly represent different speed ranges and associated facility types. Three strong candidates have already been identified.
? Determination of a series of empty wind tunnel test cases for the CRWTs. These may include both tests that have already been completed, with data already available, and new tests. They will be measured and computed with the goal of improving CFD methodology. The ultimate goal is to improve both accuracy (comparison with wind tunnel data) and consistency (comparison between codes/methods) of the CFD predictions.
? Development of a series of test cases that include aerodynamic bodies in the wind tunnels will also be required to assess CFD capabilities. These aerodynamic bodies may be “standard shapes” typically used by each facility as part of their in-house calibration procedure, or they may be defined by the team to be some other well-defined, unrestricted test article that is available for testing. These test cases may include both center-mounted (full-span) models as well as wall-mounted (semi-span) models. These will also include blind test cases and rigorous experimental uncertainty estimation.
? Comparative assessments of CFD modeling of the CRWTs for the above empty and model test cases, thereby defining a series of best practices for key elements of wind tunnel test modeling.
Topics:
The major scientific topic areas of the activity include:
? Experimental and computational fluid dynamics of the flow in the selected wind tunnels
? Best practices for CFD in wind tunnels
? Parametric studies for uncertainty quantification of wind tunnel flows
Contact:
Open2Partners:
Title:
Created at 18/10/2022 17:00 by System Account
Last modified at 16/05/2024 22:00 by System Account
Go back to list
Home(NATO STO)