facade, these events would certainly not lead to such a strong engulfment of the flow in the air space and the generation of these high speeds.

Thus, although the nodal code once again provides a good qualitative representation of the dynamics of pressure equilibration in the air gap in the presence of porosity, there are still some quantitative discrepancies. The biggest limitation in applying the model to this configuration is the choice of ξ<sub>permea</sub> which is difficult to choose a priori, as it seems to depend not only on the porosity of the facade, but also on the dynamics of the flow on the external facade.

### 5.3.5 Fully cut porous skin

We propose to test the model on a final configuration, which is that of a double skin that is fully cut and porous. The measurements carried out in this configuration, presented in §4.5.3 had shown that pressure balancing did not depend on either the porosity of the skin or the height of the building, but only on fluctuations in the pressure applied by the wind on the outside of the overlapped area.

The Figure 130 plots the calculated average and peak internal pressure profile and net differential and compares them with the measured values.

<figure><img src="image_134.png" /><figcaption>Figure 132 Profile of the average and peak pressure coefficient, interior on the left and net on the right, comparison of calculated and measured values, (configuration h_h_l_20_p_15_s_p)</figcaption></figure>

The figure shows that the average pressure profile inside the air gap balances out at a value comparable to that measured in the wind tunnel. In particular, the mean differential pressure $c_{pnet}$ changes sign between the top and bottom of the facade, again in line with what was measured in the wind tunnel. Note that the pressure value at the centre of the porous zone is slightly higher than that measured in the wind tunnel. The dynamics of the pressure signal also appear to be well represented, with calculated peak pressures close to those measured in the wind tunnel. In order to explore these dynamics in more detail, the Figure 133 plots the PDFs of the signals measured at 3 points on the facade.
<figure><img src="image_135.png" /><figcaption>Figure 133 - PDF of the pressure coefficient, interior, exterior and net, at three points of the double-skin facade, comparison of calculated and measured values (configuration h_p_I_20_p_15_s_p)</figcaption></figure>

Analysis of the figure shows that the nodal model is able to predict the shape of the internal pressure PDF $c_{p_{int}}$ but also the rather unusual change in shape of the pressure differential PDF $c_{p_{net}}$ between the top and bottom of the air gap. In addition to reproducing the shape of this PDF, the values are also quantitatively in very good agreement with what can be measured in the wind tunnel.

In this way, the nodal model appears to be perfectly capable of reproducing the instantaneous balancing of the pressure inside the air space of a porous double-skin facade that is completely intersected due to pressure fluctuations on the external face. It therefore allows a more accurate and controlled assessment of wind loads than the Eurocode could propose for this configuration, as shown Figure 99.
## 5.4 SUMMARY OF THE NODAL MODEL

As a reminder, the main advantage of using the nodal model is to be able to simulate the propagation of pressure fluctuations within the air gap, if this cannot be reproduced in the wind tunnel on models that are too small in scale. In this respect, the model's performance varies greatly depending on the geometric configurations investigated.

On geometric configurations where the flow dynamics inside the air gap are fairly low, the model seems to be capable of reproducing dynamic pressure balancing, with all its subtleties. The simulation of PDFs, both of the internal pressure signal and of the net pressure differential signal, shows fairly remarkable agreement with what has been measured in the wind tunnel. The tool is therefore of great interest for dimensioning configurations where the average loads are low, but the peak loads are non-negligible, and appear to respond to the dynamic balancing of pressure fluctuations at the various openings in the air gap.

However, the model appears to have serious limitations in certain flow configurations:

- first of all, it does a poor job of reproducing the loads induced by the inhomogeneities of the flow as it rushes through the air gap. The very nature of the nodal model makes it impossible to reproduce the accelerations generated by these inhomogeneities. Attempts to recreate these accelerations artificially, by reducing the thickness of the air space based on a priori knowledge of the flow, have been relatively unsuccessful, particularly with regard to the dynamic aspects of the pressure signal in the air space.

- it has difficulty in managing the strong flow dynamics within the air gap, particularly in the case of a 4-sided opening, where the air rushes in on the lower opening and is evacuated via the 3 other openings. The model's difficulty in predicting this configuration can be explained by a rather crude discretisation, in the form of a grid of ducts, of a 2D flow that is becoming too complex.

- Finally, the model has difficulty in reproducing air entrainment through the porosities of the double skin, because it does not take into account the competition between this entrainment through the porosities and the flow dynamics outside the facade.

This problem of reproducing the flow dynamics outside the double skin may also explain the differences in modelling mentioned in the previous points. In this sense, modelling tricks should certainly be used to improve the model's performance and thus increase its level of confidence.

In addition to its practical application, this work on the nodal model has also led to a better understanding of the mechanisms of pressure equalisation in the air gap, by exploring the limits of the model.
# 6 PRACTICAL APPLICATION TO THE WIND LOADS ASSESSEMENT OF DOUBLE-SKIN FACADES

The aim of this final part of the study is to return to the engineering problem of the wind load assessment of double-skin facades, and to develop strategies on the basis of the lessons learned from measurements on the reference experiment and the simulations carried out with the nodal model.

## 6.1 APPLICATION OF THE RESULTS OF THE STUDY TO THE ENGINEERING PROBLEM

Analysis of the measurements on the reference experiment showed that slight variations in the geometry of the building against which it was set, or in the geometry of the double-skin facade itself, could lead to very large variations in the wind loads on the double skin.

Given the infinite number of geometric combinations of buildings and double-skin facades that may exist in the existing or future building stock, it seems difficult to identify a generic rule that would cover all possible geometric configurations.

### 6.1.1 Conservative assessment

For a generic building, in the absence of any knowledge of how the pressure in the air space will balance out, a safe and dimensioning approach would be to consider the maximum possible load that could be applied to such a facade, in the worst possible configuration. In this sense, the analysis of loads obtained for all configurations taken together in section 4.7.1 has made it possible to draw up an initial outline of what such a major load case would be. It is shown schematically Figure 134.

<figure><img src="image_136.png" /><figcaption>Figure 134 - definition of a major load case for double-skin facades</figcaption></figure>

At the centre of the facade, a maximum peak compression of +2 and a peak pull-out of -1 are defined. They result from unfavourable configurations where the pressure in the air space has a sign opposite to that of the pressure on the external face of the double skin. Even if the Figure 103 showed a zone with lower loads in the centre of the facade, the analysis showed that it was difficult to define the contours of this zone, which depended heavily on the geometric configuration of the facade and the building against which it was leaning.

At the edge of the facade, a maximum peak compression of +3 and a peak pull-out of -1.5 are defined. The maximum compressions take into account the case of a feathered facade, which
can then be assimilated to an acroterion, but also the effects of the flow becoming entangled in the air space, which locally increase the loads. Peak pull-outs correspond to configurations where the wind flow is grazing, and very locally generates high pressure differentials pushing the double skin away from the building facade.

It then remains to define the distance noted *e* of the edge to which these loads apply. This will depend both on the wind flow at the scale of the facade, but also on the flow at the scale of the air space. The value of *e* will then result from a combination of the thickness of the air space and the Eurocode requirements for facade design. We therefore propose :

$$e = \max \left( 2a, \frac{b}{5} \right)$$

With *a* the thickness of the blade, and *b* the largest dimension (height, width) of the facade.

This increased load case would therefore be able to safely and conservatively cover all the double-skin facade configurations that could be installed on a building. It should be noted that this load case is more severe than the one proposed in the SNFA sheet [11].

### 6.1.2 Optimising the wind loads

However, analysis of the measurements has shown that pressure balancing can greatly reduce these wind loads. It may therefore be worth proposing an optimised assessment, taking these lower loads into account, in order to reduce the construction cost of the double-skin facade. However, this assessment must be carried out safely.

The best approach for assessing wind loads remains direct measurement of the pressure differential in an Atmospheric Boundary Layer wind tunnel, with synchronous measurement of the pressure on each side of the double-skin facade, as carried out on the reference experiment. Once again, this implies being able to instrument the model correctly for pressure measurement without disturbing the pressure balance of the air space. This restricts the investigation to small-scale buildings, making it possible to propose a scale model compatible with the dimensions of the Atmospheric Boundary Layer wind tunnel.

If the size of the model does not allow the air space to be represented at a sufficiently large size to be instrumented with pressure taps, pressure balancing can be simulated in a hybrid way, using a nodal model and the pressure signals measured at the boundaries of the air space. The net pressure differential is then calculated by subtracting the pressure signal measured on the outer face of the double skin from the virtual pressure signal calculated in the air gap by the nodal model. However, the work carried out in this study has shown that this approach gives satisfactory results in a limited range of geometric configurations of the double-skin facade. Configurations with high flow dynamics in the air space, or with a 4-sided opening, caused the nodal model to fail in its ability to accurately assess peak loads.

This study made very little mention of the use of CFD-type numerical simulations to assess the pressure balance of the air gap, even though numerous illustrations of the flow have been obtained in this report using this approach. CFD is proving to be a very interesting way of qualitatively assessing the pressure balance of the air gap. In this respect, it is even more effective than the nodal approach, since it can detect complex flow configurations where the air gap has many openings. That said, the RANS CFD industrial approach proposes quantitative evaluations of loads that are often far removed from those measured in atmospheric boundary layer wind tunnels. Above all, RANS CFD is unable to reproduce unsteady pressure equalisation in the air space. This is a very serious limitation for wind load assessment, since peak pressure differentials cannot be evaluated correctly. Once again, unsteady CFD simulation (LES, DES, etc.) could provide an answer to this question, but at calculation costs that would certainly be prohibitive for considering an industrial application of the approach. Does this mean that CFD should be eliminated from the process of assessing
loads on the double-skin facade? Quite the contrary. CFD offers a relevant visualisation of the flows, making it possible to anticipate how the pressure in the air gap will balance out, and thus propose an investigation method adapted to the wind tunnel measurement of peak loads, either by direct measurement on a model, or by a hybrid approach (wind tunnel measurement + nodal model).

It is therefore the combination of investigation methods that will make it possible to establish, on a case-by-case basis, the best wind dimensioning strategy for double-skin facades.

## 6.2 WIND DIMENSIONING STRATEGIES ACCORDING TO THE TYPE OF DOUBLE-SKIN FACADE

Once again, the best strategy for assessing wind loads on a double-skin facade remains direct wind tunnel assessment of the peak pressure differential, if the model allows pressure measurement of the air gap (scale of 1/100 or more).

If this is not the case, this paragraph sets out to establish a series of alternative wind loads assessment strategies, depending on the different types of double-skin facade.

### 6.2.1 Fully segmented double skin (watertight segmentation)

First, we consider the case of a fully segmented double skin, with perfectly watertight segmentation. A distinction is then made between the central part of the skin, which is closed at all 4 edges, and the part of the double skin that may be feathered at the edge of the facade.

<figure><img src="image_137.png" /><figcaption>Figure 135 Completely watertight double-cut skin</figcaption></figure>

There are two possible scenarios, depending on whether the skin is solid or porous:

#### 1) Case of a solid skin

*On the central section, which has been completely cut through:*

This case is similar to that of a normal building facade, and can be assessed using standard Eurocode evaluations. The pressure on the external face $p_{ext}$ is then assessed using either the regulatory approach (Eurocode §7.2.2 [8]), or by wind tunnel measurement, whereas the internal pressure is taken from the regulations (Eurocode §7.2.9 [8]) equal to $p_{int} = +0.2 \cdot p_{dyn}$ or $p_{int} = -0.3 \cdot p_{dyn}$, with $p_{dyn}$ the reference dynamic pressure at the facade height, so as to maximise the pressure differential $p_{net}$.

*On the feathered part of the border :*

This case is similar to that of an acroterion within the meaning of the Eurocode and can be dimensioned as such (Eurocode §7.4.1 [8])
## 2) Porous skin

→ On the central section, which has been completely cut through:

This case can be dealt with by calculating the pressure equilibrium of the cavity using a nodal model as described in §5.3.5. The pressures measured on the external face of the double skin are then used both as input data for the nodal model for pressure balancing in the air space and to calculate the peak pressure differential. This peak pressure differential can also be obtained using the regulatory approach (Eurocode §7.2.10 [8]), which proposes the following for this scenario $c_{p\_net} = \frac{2}{3}c_{p\_ext}$ for compression and $c_{p\_net} = -\frac{1}{3}c_{p\_ext}$ for pull-outs.

→ On the feathered part of the border :

This case is similar to that of an acroterion within the meaning of the Eurocode and can be dimensioned as such (Eurocode §7.4.1 [8])

## 6.2.2 Double-skinned channel type (horizontal / vertical)

We now consider a skin segmented to form a horizontal or vertical channel.

<figure><img src="image_138.png" /><figcaption>Figure 136 - Double-skinned, cut channel type</figcaption></figure>

Once again, there are two cases depending on whether the skin is solid or porous:

### 1) Case of a solid skin

→ On the central part of the channel:

This case can be dealt with by calculating the pressure equilibrium in the channel with a nodal model as carried out in §5.3.1. The pressures measured on the facade of the building, at the boundaries of the channel, are used as input data for the balancing model, which then produces a virtual pressure signal along the inside face of the double skin. The pressure measurements taken on the external face of the facade are then used to calculate the net pressure differentials.

In the case of high flow dynamics in the air gap (large pressure differential at the terminals, or high flow rates recorded in the nodal calculation), the study must be completed by an assessment of the effects of the flow becoming entangled in the air gap. This study can be carried out either by a complementary wind tunnel study, on a larger scale model of the air inlet, or by a CFD approach. This will enable an increase coefficient to be applied to the peak loads obtained using the nodal approach.
→On the feathered part of the border :

This case is similar to that of an acroterion within the meaning of the Eurocode and can be
dimensioned as such (Eurocode §7.4.1 [8])

2) Porous skin

This case is similar to the one tested §5.3.4 and is more problematic to study. In this case, the
nodal approach presented difficulties in reproducing the competition between the dynamics of
the flow outside the facade and that penetrating through the pores. The simulation results
showed a very strong dependence on the head loss coefficient ξpermea on the porosity of the
façade. This case must therefore be treated by including a sensitivity study on the coefficient
ξpermea coefficient, and using the most extreme case for the peak differential pressure p̂net then
calculated. More conservatively, these porous skins can also be considered as solid, and can
therefore be treated in the same way as the previous case.

6.2.3 Double skin open on 3 or 4 sides

We consider a skin open on 3 or 4 sides. This case is similar to the one studied in §5.3.2 and
§5.3.3.

<figure><img src="image_139.png" /><figcaption>Figure 137- Double skin open on 4 sides</figcaption></figure>

Two cases will be considered, depending on whether the flow dynamics in the air gap are low or high. This can be determined either by an initial nodal model, or by evaluating the flow using a CFD approach.

1) If dynamic is low

This case can be dealt with by calculating the pressure balance of the air gap using a nodal model, as described in §5.3.2 or §5.3.3. The study can then be completed by an assessment of the effects of flow entrapment in the air gap, as discussed for channel type double-skin façade.

2) If the dynamic is high

This is the most problematic case, and one for which the nodal approach has the greatest limitations. It is also the case most conducive to the generation of very high peak loads on the double skin, due to the very high flow dynamics. Therefore, if this case cannot be dealt with by wind tunnel measurements using a model of sufficient size to ensure a good representation of
the air gap, the only alternative will be to consider the conservative load case presented in §. **Erreur ! Source du renvoi introuvable.**

### 6.2.4 Summary

The Table 5 provides a visual summary of the different sizing strategies proposed in the previous paragraphs.

<table><thead><tr><th rowspan="2"></th><th rowspan="2">Facade type</th><th colspan="2">Strategy</th></tr><tr><th>Regulatory (Eurocode)</th><th>Hybrid (WT measurement + nodal)</th></tr></thead><tbody><tr><td rowspan="2">completely segmented</td><td>solid</td><td></td><td></td></tr><tr><td>porous</td><td></td><td></td></tr><tr><td rowspan="2">Channel segmentation (horizontal, vertical)</td><td>solid</td><td></td><td>with channel inlet increase</td></tr><tr><td>porous</td><td></td><td></td></tr><tr><td rowspan="2">Open on 3 or 4 sides</td><td>low dynamics</td><td></td><td></td></tr><tr><td>high dynamics</td><td></td><td></td></tr></tbody></table>

<table><caption>Table 5 - Summary of alternative strategies to direct wind tunnel measurement depending on the type of double-skin facade</caption><tr><td>level of confidence</td><td>very high</td><td>high</td><td>low</td><td>very low</td></tr></table>

This table shows that the alternative strategies proposed only cover a small proportion of the possible configurations of double-skin facades. The cases not covered by these alternatives are also representative of the complexity of the flows generated on these facade elements, which are difficult to model using simplified approaches.

## 6.3 CONSIDERATIONS FOR THE DESIGN OF DOUBLE-SKIN FACADES WITH REGARD TO WIND LOADS

In the final part of his thesis, Vaglio proposes [1] recommendations for the design of double-skin facades with regard to wind loads. These facades can have several functions, including providing a ventilation process to cool the building. The aim is to generate a flow in the air space at relatively low wind speeds. In the light of the measurements carried out in this study, it is clear that encouraging such a dynamic flow in the air space can lead to the generation of considerable wind loads during a storm. Optimising the ventilation function may therefore be to the detriment of the facade's wind resistance.

The results of this study allow us to draw up a few recommendations, from the point of view of wind loads, leaving aside for the moment the other functions of the facade.

In order to limit wind loads, it is advised to try to partition the air space as much as possible and create porosity in the double skin, in order to balance the pressure on either side of the facade. As well as limiting the wind loads on the double skin, this configuration is relatively well controlled from the point of view of wind loads assessment, and the loads can therefore be assessed with sufficient confidence. However, this arrangement of the double-skin facade will only create limited circulation in the air space.
In order to create a more substantial convection movement, it may be useful to use vertical segmentations to create channels, and create air circulation through the pressure difference between the bottom and the top of the facade. This principle has been illustrated in this study on the configurations of the level building and the low-rise building, equipped with vertical segmentations. These configurations will therefore lead to higher loads on the double-skin facade, but these can be measured fairly accurately using the modelling strategies proposed in the previous paragraph.

Finally, it might be preferable to avoid installing air space with too many openings, either because of the absence of segmentations, or because of the presence of porosities which lead to competition between the internal and external flow dynamics. These configurations are relatively poorly mastered from the point of view of wind loads assessment, and would lead to having to rely on a very conservative load case.

These design choices must, of course, be set against the facade's other functions. Significant wind loads can be compensated for by reinforcing the structure, but at the cost of the project. It is therefore necessary to assess, on a case-by-case basis, the benefits of refining the assessment of wind loads. The conservative load case proposed in **§Erreur! Source du renvoi introuvable.** may, for example, be compatible with a specification that does not require the structure to be lightened, and therefore does not require the assessment of loads to be refined.

Finally, there is the question of a double-skin facade with variable geometry, equipped with shutter systems that adjust according to wind conditions, either to ensure effective ventilation of the air space, or to reduce wind loads on the facade. So-called "bioclimatic" facades already exist, which can regulate the speed of the flow in the air space. However, such equipment raises the question of who bears responsibility in the event of a failure in the control system, which would prevent the facade from being placed in a safe position in the event of a gust of wind.
# 7 CONCLUSIONS AND OUTLOOK

The aim of this research is to study wind loads on double-skin facades.

The first part of the study presents a brief review of academic research on the subject and clearly sets out the associated engineering problem, i.e. the wind resistance of a double-skin facade to a 50-year storm. It highlights the need for a better understanding of the phenomenon of pressure balancing of the air space, which has a major impact on the wind loads of the double-skin facade. The engineering problem is essentially posed by the complexity of directly measuring the pressure differential on either side of the double-skin facade, on models that are too small to faithfully represent the flow in the air space.

The study is based on a reference experiment that enables the instantaneous pressure differential on either side of a large-scale double-skin facade to be measured in detail, against a cubic building. The model produced for the study has a number of modular features so that the effect of several geometric parameters on wind loads can be investigated. Measurements carried out in the Atmospheric Boundary Layer wind tunnel showed that small geometric variations could lead to large variations in wind loads on the double-skin facade. These effects, which are often counter-intuitive, have been explained using a detailed analysis of the measurements, supplemented by graphical representations of the flow resulting from numerical simulations.

The number of configurations investigated cannot claim to be an exhaustive representation of the installed base (or that to be built) of double-skin facades, as the combination of geometric parameters can be infinite. However, they are sufficiently numerous to illustrate the mechanisms responsible for pressure balancing of the air space, and their impact on the wind loads of the double-skin facade. Particular attention has been paid to the question of peak loads generated by atmospheric boundary layer turbulence. This aspect has been little studied in the literature, yet it lies at the heart of the engineering problem. These measurements could be supplemented if the geometric configurations representative of the installed base cannot be compared with the configurations dealt with during the study. The pressure measurements could also be supplemented by velocity measurements using laser velocimetry in the thickness of the air gap in order to confirm the flow structures described by the numerical simulation.

Analysis of the measurements showed that in most of the configurations tested, the pressure in the air space was directly related to the pressure fluctuations at its boundaries. This observation led the study to the use of a nodal model. This would enable the pressure signal in the air space to be virtually reconstructed from the pressure measurements taken at the terminals and on the external face of the double-skin facade. This model would then have a direct practical application for wind tunnel models where it is impossible to measure the pressure in the air gap.

Finally, modelling strategies for practical applications to industrial cases were proposed. These strategies have been deduced from analyses of measurements from the reference experiment, as well as from simulations carried out with the nodal model. Without claiming to cover all possible double-skin façade configurations, these strategies offer an initial practical approach to better understanding the wind dimensioning of these façades.
LIST OF REFERENCES

[1] J. C. Vaglio, "Aerophysics of double-skin. Sans cese preteondre pouvorie r eshausoitaoive a 'mensmebelde s conofingster cefacades: simulation-based determination of pressure coefficients for multi-story double-skin facades," 2015.

[2] H. J. Gerhardt and F. Janser, "Wind loads on wind permeable facades," *Journal of Wind Engineering & Industrial Aerodynamics*, vol. 53, pp. 37-48, 1995.

[3] F. Marques_da_Silva and M. Gloria_Gomes, "Gap inner pressures in multi-storey double skin facades," *Energy and Buildings*, vol. 40, p. 1553-1559, 2008.

[4] M. Jafari and A. Alipour, "Aerodynamic shape optimization of rectangular and elliptical double-skinfacades to mitigate wind-induced effects on tall buildings," *Journal of Wind Engineering & Industrial Aerodynamics*, vol. 213, 2021.

[5] G. Hu, S. Hassanli, K. C. S. Kwok and K. T. Tse, "Wind-induced responses of a tall building with a double-skin facade system," *Journal of Wind Engineering & Industrial Aerodynamics*, vol. 168, pp. 91-100, 2017.

[6] G. Hu, J. Song, S. Hassanli, R. Ong and K. C. S. Kwok, "The effects of a double-skin facade on the cladding pressure around a tall building," *Journal of Wind Engineering & Industrial Aerodynamics*, vol. 191, p. 239-251, 2019.

[7] F. H. Kemper and M. Feldmann, "Wind load assumptions for permeable cladding elements considering the installation context," *Journal of Wind Engineering & Industrial Aerodynamics*, vol. 184, p. 277-288, 2019.

[8] AFNOR, "Eurocode 1: Actions on structures. Part 1-4 General Actions - Wind Actions," 2005.

[9] G. Pomaranzi, N. Daniotti, P. Schito, L. Rosa and A. Zasso, "Experimental assessment of the effects of a porous double skin facadesystem on cladding loads," *Journal of Wind Engineering & Industrial Aerodynamics*, 2020.

[10] P. Skvorc and H. Kozmar, "The effect of wind characteristics on tall buildings with porous double-skin facades," *Journal of Building Engineering*, vol. 69, 2023.

[11] SNFA, "Fiche Technique n°45 Tableaux des Pressions de vent W50 applicables aux facades légères et déterminées selon l'Annexe Nationale NF EN 1991-1-4/NA," 2010.

[12] RAGE, "Façad multiple: Naturally ventilated double skin on the exterior," 2014.

[13] F. Demouge, "MATHIS: Technical Guide," 2019.

[14] G. Giovannelli and J. Guilhot, "Vitesse de ventilation naturelle dans la tranchée couverte Austerlitz-Tolbiac-Masséna," 2017.
[15] I. E. Idel'Cik, Memento des Pertes de Charges, Eyrolles, 1965.

[16] M. Rahiminejad and D. Khovalyg, "Review on ventilation rates in the ventilated air-spaces behind commonwall assemblies with external cladding," *Building and Environment*, vol. 190, 2021.

[17] V. Yellamraju, "Evaluation and design of double-skin facades for office buildings in hot climates," 2004.

[18] S. Matour, V. G. Hansen, R. Drogemuller and S. Omrani, *Adaptation of Double Skin Facade for warm climate from a wind harvesting perspective in tall buildings*.
ACKNOWLEDGEMENTS

This study was entirely financed by the CSTB Research & Development Department. The author would like to thank Hervé Charrue, Romain Mege and Nicolas Naville for their confidence in the allocation of the associated funding.

The author would also like to thank :

-Julien Rogé and Nicolas Pinoteau, for their trust and careful monitoring of this research work.

-Bruno Béliard and Patrice Metaireau, for producing the beautiful mockup of the reference experiment.

-Cyril Vachon, for his assistance during the wind tunnel tests.

-François Demouge, for his invaluable help in setting up the nodal model, and for his infinite wisdom in the delicate art of controlling head losses.

This report is dedicated to the memory of Gabriel Giovanelli, a great master of pressure balancing.
CSTB
le futur en construction

Entreprise publique au service de ses clients et de l'intérêt général, le Centre Scientifique et Technique du Bâtiment a pour ambition d'imaginer les bâtiments et la ville de demain, en accompagnant et sécurisant les projets de construction et de rénovation durable, pour améliorer la qualité de vie de leurs usagers en anticipant les effets du réchauffement climatique.

Il exerce pour cela cinq activités-clés : la recherche et expertise, l'évaluation, les essais, la certification et la diffusion des connaissances. Il répond ainsi à trois missions principales, au service des acteurs de la construction et de l'intérêt général : créer des connaissances et les partager, accompagner l'innovation, sécuriser et valoriser la performance.