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Appraisal of the Suitability of Turbulence Models in Flow Calculations

The need for reasonably accurate turbulence models
is becoming more and more pressing due to the prog-
ress made with the development of efficient solu-
tion procedures for the Reynolds-averaged Navier-
Stokes equations. Though turbulent flow research is
being done at many places for quite some time now,
progress has been slow. The field of research is
wide and comprises very different flow types, e.g.
turbulent boundary layers along airplanes or ships,
atmospheric boundary layers, open water flows,
internal flows, flows with chemical reactions, etc.
A summary of the research work going on presently
in Belgium and the Netherlands will be given here.
The main aim of the paper, however, is to review
concisely the state of the art in general and to
discuss the prospects for accurate turbulence
models.

After the summary of local work in section 2, the
state of the art in turbulence modelling will be
exemplified for a few simple flows in section 3. 0n
the basis of the results of the brief analysis some
conclusions will be drawn. Finally in section 4 the
author’s view on the status and prospects of tur-
bulence modelling will be expressed.

At NLR in the Netherlands the activities in 3D
turbulent boundary layer research have been taken
up again in an extensive measurement program of
mean flow and turbulence properties in the shear
layers of a swept wing (Fig. 1). This is a European
collaborative project with companion measurements
in the French F2 wind tunnel (Van den Berg, 1988).
Further work at NLR concerns 2D turbulent shear
layers, namely turbulence measurements in wakes at
strong adverse pressure gradients, as occur on
wings with flaps.

Fig. 1 Garteur swept wing model for 3D turbulent
shear layer measurements in the NLR 3x2 m2
wind tunnel

At Delft University three research groups are ac-
tive in turbulence research. At the Faculty of
Aerospace Engineering an experimental investigation
of the flow in the vicinity of an airfoil trailing
edge is near completion (Absil & Passchier, 1990).
Pitot, Laser-Doppler and hot-wire measurements are
carried out on a fine measurement grid to resolve
the sudden local changes in the flow near the trai-
ling edge (Fig. 2). At the same Faculty recently
measurements have been initiated to obtain tur-
bulence data downstream of a laminar separation
bubble, as well as in turbulent wakes at large
adverse pressure gradients to supplement the NIR
data.