1. September 2015
MSc Computational Fluid Dynamics
School of Aerospace, Transport and
Manufacturing
Impact of curvature correction on wingtip vortex flow
Introduction
Carla Vidal Martinez-Illescas Approach to Problem
The curvature correction implementation in OpenFOAM® was
initially verified with the 2D Bump-in-channel NASA test case.
The purpose of verification is to determine that the turbulence
model has been correctly implemented rather than assessing
how close to the experiments are the turbulence model
predictions.
Conclusions
Summary of Results
Vortex decay was improved close to 30% when using
curvature correction in the commercial code.
Even though most of the variables of the curvature correction
function rely on velocity gradients, gradient scheme was not
found to be decisive in obtaining vortex decay improvement
given a high quality mesh.
OpenFOAM® solver is apparently more dissipative than the
commercial one and this may be the reason of the more
modest improvement. However, further investigations are
needed to understand the specific reasons behind this
observation before any conclusions can be drawn.
Any hypothesis cannot be disregarded concerning axial
velocity overshoot but wall treatment would the first thing to
examine.
Supervisor – Dr. Panagiotis Tsoutsanis
A common approach in turbulence modelling is to use the
Boussinesq hypothesis:
However, it is unable to account for stress-strain misalignment.
This is particularly important for rotating flows, such as wingtip
vortex flows.
Figure 3. Axial velocity in vortex core without curvature
correction (top) and with curvature correction (bottom) in
commercial code.
Figure 2.Turbulent variables in boundary layer in 2D Bump-in-
channel NASA test case.
Figure 1.Wingtip vortex flow.
The curvature correction was applied afterwards to the wingtip
vortex flow. The set up in Chow, Zilliac and Bradshaw
experiment “Mean and Turbulence Measurements in the Near
Field of a Wingtip Vortex” was simulated in the commercial
code and in OpenFOAM®.
A grid convergence study was performed before stepping into
results analysis.
The benefits of sensitising turbulence models to curvature and
rotation have been extensively reported in the literature.
Applied to wingtip vortex, early decay is prevented.
The aim of this work is twofold: to reproduce the results
already observed by other authors using a commercial code
and to implement a curvature correction for k-ω SST
turbulence model in OpenFOAM® and assess its impact on
wingtip vortex flow.
In OpenFOAM® an improvement close to 20% in vortex
decay was observed. However, already in the case without
curvature correction OpenFOAM® presented an axial velocity
overshoot compared to the commercial code. As a
consequence, maximum axial velocity did not match the
experiments when curvature correction was applied.
Also, TotalSim customised turbulence model was found to be
incompatible with curvature correction.