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Activity title

Separated Flow: Prediction, Measurement and Assessment for Air and Sea Vehicles

Activity Reference

AVT-307

Panel

Applied Vehicle Technology

Security Classification

NATO UNCLASSIFIED

Status

Active

Activity type

RSY

Start date

2017

End date

2019

Keywords

Aerodynamics, Computation, Experiment, Hydrodynamics, Laminar, Separated Flow, Subsonic, Supersonic, Transonic, Turbulent, Unit Problems, Vehicle Performance

Background

Separated flows are a critical issue to the aerodynamic and hydrodynamic performance of aircraft and ships. Although air and sea vehicles are traditionally designed to develop attached flow at cruise conditions, they also routinely develop separated flows within the broader operating envelope, such as at maneuver conditions, and occasionally even at cruise. Separated flow effects cause cruise performance penalties, and can often restrict vehicle operating conditions due to such matters as stability and control and/or buffet. Separated flows and their effects are often unsteady. Separated flows occur in many ways for air or sea vehicles. Some examples of separated flows, along with associated vehicle components and operations, include (i) juncture flow separation (wing-body, wing-pylon), (ii) shock/boundary-layer separation (transonic wings, supersonic inlets), (iii) leading-edge vortex separation (wings/keels for maneuvering aircraft/ships), (iv) lifting-surface stall separation (wings in high-lift conditions), (v) wing wake separation (wing effects on tail performance), and (vi) aft-body wake/vortex separation (aircraft cargo deployment, ship controls). Many of these separated flows occur on smooth surfaces, and exhibit significant Reynolds number scaling effects. A symposium was held by AGARD in 1975 to benchmark needs and capabilities for separated flow issues of interest to NATO. Since that time, much has changed in vehicle technology, numerical simulation capability, and experimental methods. However, separated flows remain a critical issue for vehicle performance and development technology (experiments, numerics) of air and sea concepts. For example, the European Flightpath 2050 Vision for Aviation identifies aerodynamics as one of the high-leverage discipline for future vehicle development, and the NASA CFD Vision 2030 identifies unreliable predictions of turbulent separated flows, with current methods, as a major inhibitor to the expansion of CFD to predict a broader portion of the aerodynamic design space. The purpose for this activity is to establish a new baseline on separated flow issues and research capabilities, with a focus on NATO interests, through an STO symposium. Basic symposium objectives are enumerated in the following section. Leverages of expertise from recent AVT activities will be sought (e.g., AVT-147, AVT-161, AVT-183, AVT-191, AVT-246).

Objectives

The objectives for the proposed symposium are: - To establish the baseline for current and anticipated air and sea vehicle issues regarding separated flow effects. - To establish the baseline of current capability to predict separated flow effects and to measure separated flow phenomena that are relevant to air- and sea-vehicle needs. - To identify key areas requiring further research and development. To this end, a program committee will be formed to address all planning and execution requirements of this symposium. It is anticipated that the symposium could be large, on the order of 50 scientific/plenary papers, and the committee will balance the solicitation response with the resources available from the host nation. The program committee will pursue the following objectives: - Identify the state of the practice for separated flow research and analysis. - Identify the communities that are conducting separated flow research relevant to NATO air and sea vehicles. - Allow for contributions that address configuration (systems level) and fundamental (unit problem) interests. - Develop a call that meets the symposium objectives. - Organize the symposium to foster participant interactions. - Organize the sessions in accordance with the meeting goals and the accepted papers. - Complete the work in 4 years (e.g., January 2017 to December 2020). - Deliver the results in a formal scientific document (STO Meeting Proceedings)

Topics

Separated flow aerodynamics and hydrodynamics. Current and anticipated air and sea vehicle issues regarding separated flow effects. Current capabilities in experimental and numerical investigations of separated flows.

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