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Activity title

Non-Equilibrium Turbulent Boundary Layers in High Reynolds Number Flow at Incompressible Conditions

Activity Reference

AVT-349

Panel

Applied Vehicle Technology

Security Classification

NATO UNCLASSIFIED

Status

Proposed

Activity type

RTG

Start date

2019

End date

2023

Keywords

Pressure Gradient, Roughness, ThreeDimensionality, Turbulent Boundary Layer

Background

Ever improved fluid dynamics modelling and simulation tools are in constant demand in the naval sea and aviation communities, driven both by need and the advance of computer technology. Accurate prediction of boundary layers is a fundamental pre-requisite of successful vehicle design and operation in terms of drag, maneuvering and acoustics. Over the years the focus of incompressible boundary layer research has been, perhaps disproportionately, on low Reynolds numbers and idealized conditions. In the STO community there has been a heavy emphasis on compressible boundary layers and high-speed flow related non-equilibrium problems. Comparatively little attention has been paid to non-equilibrium boundary layers at conditions relevant to most naval vehicles and low-speed maneuvering air vehicles. The focus of this RTG will be on boundary layers at realistic conditions where the Reynolds number is large and the boundary layer grows on surfaces including roughness, curvature and three-dimensionality with regions of increasing and/or decreasing pressure.

Objectives

Advance the accuracy and range of prediction models for high Reynolds number non-equilibrium boundary layers at incompressible conditions. Specifically: • To establish a database of coordinated experiment data sets with well-defined uncertainties that systematically address the non-equilibrium conditions found in practical applications • To quantify the limitations of current LES and RANS models • To identify the conditions where higher fidelity models are required, and where they are not • To provide data, understanding and collaboration leading to the development of improved models

Topics

Experimental and computational fluid dynamics of high Reynolds number turbulent boundary layers under existing conditions. Efforts will first focus on experiments and computations of (a) two dimensional zero pressure gradient boundary layers over rough walls, and (b) two-dimensional boundary layers over smooth walls with pressure gradient. In a second phase the group will focus on systematically adding additional non-equilibrium effects to each of these. Specifically, the study of rough wall boundary layers will be extended to cases that consider either heterogenous roughness, pressure gradient or dynamic roughness. The study of boundary layers in pressure gradients will be extended to cases that consider either lateral curvature, complex curvature or roughness. Existing or planned experimental data sets have already been identified that address each of these non-uniformities. The computational methods to be employed will range from low-order models, through RANS to time resolving simulations including methods currently being used in defence-funded laboratories. Invited group members include those with existing computational methods that cover this range, as well as those with experience in employing these methods to military vehicles.

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