16 Uncertainty Treatment Applications: High-Enthalpy Flow Ground Testing
535
study as seen in Sect. 16.2. According to this, each aspect of the problem has to be
validated separately on ground testing facilities with occasional access to full flight
data if the budget allows, but even in this situation the data is quite sparse to be
validated against.
A question remains unanswered: how to identify and treat the uncertainties concerning the coupling involved in real flight when each model for each phenomenon
has been validated separately in dedicated facilities?
Uncertainty quantification studies could help understand the intricacies of the
different models and how this reflects on real-scale cases when put it all together in
an extrapolation framework as seen in Sect. 16.4.1.
The interplay between the physical phenomena studied in the two types of
facilities has to be assessed when referring to three different parameters to be
reproduced on ground and in flight in such a way that the uncertainty of taking
into account the correlated effects is far lower than otherwise. By doing so, we can
approach the design problem with confidence intervals in the domain of the flight
conditions as desired by the engineers as our final objective.
16.5 Conclusions and Remarks
Numerical simulations and experiments of atmospheric entry flows pose a challenge
full of complexities.
Ground testing of entry vehicles cannot be achieved in a single facility and
different aspects of the atmospheric entry flight have to be tested in dedicated
facilities allowing different types of flow and testing times.
The mathematical description of the system, the physico-chemical models,
reveals traces of non-linearities, coupling phenomena, and complex mechanisms
whose knowledge still rests upon experimental correlation. High-speed and high
temperature effects turn an otherwise well-characterized system, into a choice of
models and descriptions. It is this lack of knowledge that leads to urge the community to undertake uncertainty quantification analyses for design and safety purposes.
The numerical methods depicted here clear their way through the complexities
and stiffness of the equations to find approximate solutions. Uncertainty quantification must deal with the different aspects that make these flows so complex:
• Intricate multi-physics and non-linearities of the system when coupling flow,
radiation and ablation in the same problem.
• High dimensionality of stochastic space when chemical reactions have to be
taken into account. Each reaction is characterized through reaction constants and
additional parameters to account for the production/deletion of species.
• The computational cost of these CFD solutions is high. The computational
domain with refined mesh close to the boundaries together with possible nonequilibrium states where equations for the different species must be additionally
solved are some of the issues slowing down the convergence.
535
study as seen in Sect. 16.2. According to this, each aspect of the problem has to be
validated separately on ground testing facilities with occasional access to full flight
data if the budget allows, but even in this situation the data is quite sparse to be
validated against.
A question remains unanswered: how to identify and treat the uncertainties concerning the coupling involved in real flight when each model for each phenomenon
has been validated separately in dedicated facilities?
Uncertainty quantification studies could help understand the intricacies of the
different models and how this reflects on real-scale cases when put it all together in
an extrapolation framework as seen in Sect. 16.4.1.
The interplay between the physical phenomena studied in the two types of
facilities has to be assessed when referring to three different parameters to be
reproduced on ground and in flight in such a way that the uncertainty of taking
into account the correlated effects is far lower than otherwise. By doing so, we can
approach the design problem with confidence intervals in the domain of the flight
conditions as desired by the engineers as our final objective.
16.5 Conclusions and Remarks
Numerical simulations and experiments of atmospheric entry flows pose a challenge
full of complexities.
Ground testing of entry vehicles cannot be achieved in a single facility and
different aspects of the atmospheric entry flight have to be tested in dedicated
facilities allowing different types of flow and testing times.
The mathematical description of the system, the physico-chemical models,
reveals traces of non-linearities, coupling phenomena, and complex mechanisms
whose knowledge still rests upon experimental correlation. High-speed and high
temperature effects turn an otherwise well-characterized system, into a choice of
models and descriptions. It is this lack of knowledge that leads to urge the community to undertake uncertainty quantification analyses for design and safety purposes.
The numerical methods depicted here clear their way through the complexities
and stiffness of the equations to find approximate solutions. Uncertainty quantification must deal with the different aspects that make these flows so complex:
• Intricate multi-physics and non-linearities of the system when coupling flow,
radiation and ablation in the same problem.
• High dimensionality of stochastic space when chemical reactions have to be
taken into account. Each reaction is characterized through reaction constants and
additional parameters to account for the production/deletion of species.
• The computational cost of these CFD solutions is high. The computational
domain with refined mesh close to the boundaries together with possible nonequilibrium states where equations for the different species must be additionally
solved are some of the issues slowing down the convergence.