296
14 Prospects and Challenges for Aerodynamics
very innovative technologies which will be implemented during optimisation and
operated at cruise conditions, for instance laminar flow wings.
The rapid progress in CFD is quite often misinterpreted as a way forward for rendering wind tunnels obsolete. Indeed, if the processing power of computers continue
to progress at the same rate as that over the last several decades, by a factor greater
than 100 every 10 years, it is probable that the aerodynamicists starting their career
will be able, to conduct a full Navier-Stokes simulation (DNS) on a complete aircraft
configuration in a few hours. However, due to the stringent safety requirements in
aviation and the lessons still to be learnt from the development of unconventional configurations, where different boundary conditions might emerge, it will be very risky
to run a design campaign entirely on simulations. The coupled numerical modelling
and experimentation is a complementary approach which increases the confidence
level in the result. The wind tunnels are thus not intended to disappear but in fact to
evolve.
In the short run, the industrial wind tunnel tests will be more focussed on productivity, by improving the capability to obtain an increasingly large amount of data
and a variety of measurements for the same duration of test. Therefore, it implies the
following:
– Integration of more sensors in the models and simultaneous optical flow diagnostic
techniques on the model surface, using time-resolved PSP, TSP, and other laseroptical techniques such as LDV and PIV to mention a few.
– Motorisation of certain movable parts of the models, such as control surfaces, to
limit the change-over of configurations, which result in down time of the wind
tunnel; this will require further development in the control systems.
In the medium term, the innovative aircraft architectures will certainly include
more integrated propulsion systems so the traditional split between drag and thrust
will not be relevant. It will be then necessary to represent the flow through the
propulsion systems in wind tunnel tests; this is already achieved by with TPS (see
Sect. 4.3.2), but will become essential for almost all wind tunnel testing of full
configurations. The models will be increasingly complex, therefore more expensive.
Progress in manufacturing techniques, additive layer manufacturing in particular,
should allow important advances in this field to allow for further miniaturisation
of parts. Reduction of the production cycles of the models is also a challenge for
productivity.
The rapid growth in aviation will probably lead to an increase in the number of airports and possibly night flights in the vicinity of urban areas. Due to the already stringent noise regulations imposed by the certification body further research in aeroacoustics will be favoured for the identification of the aerodynamic noise sources and
to control it to acceptable certification levels. This will necessitate further progress
in the means and techniques of acoustic signal capturing and treatment that could be
implemented in the main wind tunnels facilities.
A generalisation of the techniques of real time adaptation of the test section walls
(shape and/or permeability) to recreate unconfined conditions in flight would be
particularly useful for transonic tests and could allow the testing of larger models
(see Sect. 4.2.2).
14 Prospects and Challenges for Aerodynamics
very innovative technologies which will be implemented during optimisation and
operated at cruise conditions, for instance laminar flow wings.
The rapid progress in CFD is quite often misinterpreted as a way forward for rendering wind tunnels obsolete. Indeed, if the processing power of computers continue
to progress at the same rate as that over the last several decades, by a factor greater
than 100 every 10 years, it is probable that the aerodynamicists starting their career
will be able, to conduct a full Navier-Stokes simulation (DNS) on a complete aircraft
configuration in a few hours. However, due to the stringent safety requirements in
aviation and the lessons still to be learnt from the development of unconventional configurations, where different boundary conditions might emerge, it will be very risky
to run a design campaign entirely on simulations. The coupled numerical modelling
and experimentation is a complementary approach which increases the confidence
level in the result. The wind tunnels are thus not intended to disappear but in fact to
evolve.
In the short run, the industrial wind tunnel tests will be more focussed on productivity, by improving the capability to obtain an increasingly large amount of data
and a variety of measurements for the same duration of test. Therefore, it implies the
following:
– Integration of more sensors in the models and simultaneous optical flow diagnostic
techniques on the model surface, using time-resolved PSP, TSP, and other laseroptical techniques such as LDV and PIV to mention a few.
– Motorisation of certain movable parts of the models, such as control surfaces, to
limit the change-over of configurations, which result in down time of the wind
tunnel; this will require further development in the control systems.
In the medium term, the innovative aircraft architectures will certainly include
more integrated propulsion systems so the traditional split between drag and thrust
will not be relevant. It will be then necessary to represent the flow through the
propulsion systems in wind tunnel tests; this is already achieved by with TPS (see
Sect. 4.3.2), but will become essential for almost all wind tunnel testing of full
configurations. The models will be increasingly complex, therefore more expensive.
Progress in manufacturing techniques, additive layer manufacturing in particular,
should allow important advances in this field to allow for further miniaturisation
of parts. Reduction of the production cycles of the models is also a challenge for
productivity.
The rapid growth in aviation will probably lead to an increase in the number of airports and possibly night flights in the vicinity of urban areas. Due to the already stringent noise regulations imposed by the certification body further research in aeroacoustics will be favoured for the identification of the aerodynamic noise sources and
to control it to acceptable certification levels. This will necessitate further progress
in the means and techniques of acoustic signal capturing and treatment that could be
implemented in the main wind tunnels facilities.
A generalisation of the techniques of real time adaptation of the test section walls
(shape and/or permeability) to recreate unconfined conditions in flight would be
particularly useful for transonic tests and could allow the testing of larger models
(see Sect. 4.2.2).