OBJECTIVES:
Provision of access to the following infrastructure(s):
TU/e ABLWT

Name of the infrastructure and its installations:
TU/e Atmospheric Boundary Layer Wind Tunnel (ABLWT)

Location (town, country) of the infrastructure:

Horsten 80, 5612 AZ Eindhoven, Netherlands

Web site address:
https://www.tue.nl/en/research/research-labs/wind-tunnel/
https://www.tue.nl/en/our-university/about-the-university/support-services/equipment-and-prototype-center/

Reference contact for potential TA user groups
Stefanie Gillmeier – s.g.gillmeier@tue.nl

Bert Blocken – b.j.e.blocken@tue.nl

DESCRIPTION OF THE INFRASTRUCTURE:

The wind tunnel is a closed-loop circuit atmospheric boundary layer wind tunnel (ABLWT) with a total length of 46 m and a test section length of 27 m. The test section is 3 m wide and 2 m high (Figure 1). The turbulence level at the exit of the contraction is about 0.3%. Low-turbulence measurements are performed in the front part of the test section (near the contraction), while high-turbulence (atmospheric) measurements are performed towards the rear part of the test section. The test section consists of nine modules, each of which 3 m in length and width. The first three modules can be taken out and replaced by a hydraulically operated horizontal platform for open section testing of larger obstacles. Wind catchers can be installed for the open section tests. The wind tunnel is instrumented with two high-accuracy turning tables of 2 m in diameter at the 2^nd module for low-turbulence measurements and at the 8^th module for atmospheric measurements.

Each module has a glass side wall and a partially glass ceiling to provide visual and laser access. A glass floor is available at the rear turntable location. The glass side wall of every module can slide upwards to create physical access to the inside of this module. The roof has partial openings to reduce longitudinal pressure gradients. Eight Pitot-static tubes are mounted on the side of every module to monitor the pressure along the whole test section (27 m).

The unique character of this facility is its exceptionally long test section (27 m) together with its flexibility to be operational in closed as well as open sections for low and high turbulence flows. In the closed section, the long test section of this facility allows it to reproduce neutral ABL winds for different terrain categories in accordance with the International Standard Codes in civil engineering. For this purpose, L-shaped metal squared elements of different sizes (0.02 m – 0.08 m) and vortex generators (i.e., spires) are combined in order to generate ABL flow at different geometric scales.

Another unique feature is the large degree of visual access to the test section with large side and ceiling windows along the test section. A camera system records all measurements from a side and top view.

The measurement equipment is partially equipment that was purchased at commercial companies and equipment that was designed and fabricated in-house in collaboration between the wind tunnel team and the university’s Equipment Prototype Center (EPC). The commercially purchased measurement equipment is composed of a programmable Laser-Doppler Anemometer (LDA) that can be translated along the entire test section length of 27 m, and can be placed on top, besides or below the test section. The LDA provides a non-intrusive way to obtain time-series of point velocity measurements in complex flow fields. In addition, a qualitative flow visualization can be carried out by means of smoke machines and visualization lasers that can be placed at any position, when operating in open and closed test sections. A three-axis traverse system with a Cobra j-probe mount can translate along the entire length of the wind tunnel’s test section and allows the positioning of the measurement equipment at any location inside the wind tunnel to measure the three-components of the wind speed. Pitot-static tubes are installed to monitor the approaching reference wind flow. Eight Pitot-static tubes are mounted on the side of every module to monitor the pressure along the whole test section (27 m). A Scanivalve pressure measurement system with 256 pressure transducers that can measure the pressure at 256 locations simultaneously with a frequency of up to 800 Hz is used to estimate wind loads on a large variety of scaled models (as buildings, solar panels, etc.). Pollutant dispersion measurements are carried out with a Fast – Flame Ionization Detector (Fast – FID) from Cambustion.

The in-house designed equipment consists of a range of high-precision force sensors (accuracy of about 0.001%) designed and manufactured by the EPC. The range of force sensors stretches from 20 N to 100 N and can capture forces in one and two directions, respectively. In addition, four commercial 3-axis-force sensors are available with a horizontal range of 0.5 kN and a vertical range of 2.5 kN for tests on large and heavy objects.

A unique feature resulting from the collaboration between wind tunnel and EPC is that, depending on the user’s requirements, new measurement equipment or specific models with integrated sensors can be designed and developed internally by EPC.

Figure 1. Illustration of the atmospheric boundary layer wind tunnel of TU/e.

Services currently offered by the infrastructure:
The infrastructure comes with the commitment of a team of three highly skilled technical staff members, a wind tunnel operational manager and one to three scientists. The experiments themselves are performed by either the wind-tunnel operation manager or one of the scientists, both of which have a PhD in engineering/fluid mechanics to ensure high-quality tests and efficient on-site continuous evaluation of test results. For every test, detailed preparation is made by multiple online or on-site planning meetings with the prospective user. Preliminary tests are always carried out to check the performance of every single detail related to the facility, equipment, and models to be tested.

The infrastructure has been operational since 2017 and since then has been used for several pioneering research and practical projects in the wide field of wind engineering and aerodynamics. For brevity only a few examples (Figure 2):

1. Wind tunnel measurements of wind pressure distribution on the façades of a large educational building (by van Hooff T., Gillmeier, S., Blocken B.);
2. Wind loads on lightweight solar panels (project: Reliable Accelerated Power generation for Industrial Deployment – RAPID). (by Blocken B., Gillmeier S., Ricci A., van Druenen T., Zheng X.);
3. Scaling effects on experimentally obtained external pressure measurements – implication on a mechanical ventilation system for asbestos removal. (by Jayakumari A.K.R., Gillmeier S., Ricci A., Blocken B.);
4. Assessing the ventilation potential of differently designed buildings by means of indoor velocity measurements. (by Mutmainnah Sudirman, Gillmeier, S., van Hooff T., Blocken B.);
5. COVID-19 aerosol dispersion in and around buildings and persons. (by Blocken B., Ricci A., Gillmeier S., Xia L., Qin P., van Druenen T., Kang L., Alanis Ruiz C., Zheng X., Diepens J.F.L., Maas G.A.).

Figure 2. Overview of projects carried out by the TU/e team in cooperation with international partners.

DESCRIPTION OF WORK:
Modality of access under this proposal:
Transnational Access to a number of selected user-groups will be granted for the use of the ABLWT at the TU/e (The Netherlands). Travel and subsistence costs for the users will be covered both for the preliminary meeting and for the testing phase. The staff of the TU/e ABLWT will be able to assist all users for the logistics. A typical TA project will use approximately 12 access days, including 1 day for video-call meetings before and after the tests, 3 days for the preparation of the experimental setup inside the wind tunnel, 5 days for the actual tests and 3 days for post-processing of data and writing technical reports. Depending on the complexity of the project, different scaled-model configurations can be tested in this time frame, for several reference wind directions. The operating mode (i.e., open and closed test section) of the ABLWT, the scale of the model to be tested (e.g., 1:40, 1:500, etc.), the equipment to be used for measuring (e.g., velocity, pressure, forces) as well as the measurement locations (e.g., in and around the structure) will be defined in cooperation with the user-groups during meetings prior to the official tests. The above-mentioned number of access may also slightly increase if required by the high complexity of the project. The TU/e ABLWT staff is willing to host the user-groups at the Ventur building (hosting the facility) before, during and after the experimental tests.
Access to TU/e ABLWT will be given to projects mainly focusing on wind forces, wind comfort and safety assessment on isolated buildings, groups of buildings, urban areas, complex hilly terrains, individual or groups of solar panels, etc. The dispersion of pollutants highly risky for humans can also be an object of investigation. Idealized and more realistic street canyons, as well as complex urban environments (e.g., cities, port areas, semi-indoor spaces, etc.) can be tested at various scales. When operating in a closed test section, the long test section of this facility will allow it to reproduce neutral ABL winds for different terrain categories representative of different wind speed, turbulence intensity and length scale profiles approaching the buildings/structures. When operating in open test section mode, the real full-scale object or simpler a model of the object of interest can be tested with an approaching uniform wind at different turbulence levels and speeds.

Support offered under this proposal:
After the proposal acceptance, the TU/e ABLWT staff will start the communication with the TA users for the administrative, technical, and scientific aspects of the projects.
The TA and TU/e ABLWT staff will work closely for the whole duration of the project in order to successfully achieve the final goal. The TU/e ABLWT staff will provide support to properly define the scale of the model (if operating in closed section mode), the material to be used and the measurement equipment to be used for measuring. Models can also be designed and constructed by the EPC of TU/e.
Each single user will be provided with raw data results, high-resolution photos, and videos of the performed tests. The scientific staff of TU/e ABLWT will be happy to provide the TA with technical and scientific support for the interpretation of the experimental results as well as for the post-processing of data. Video-call meetings can always be scheduled after the wind-tunnel tests for a further discussion of the results.

Outreach to new users:
The TU/e ABLWT staff will disseminate through the social media channels and websites associated with TU/e and the ABLWT staff members (as LinkedIn and Twitter). The calls will be also shared with the whole International Association for Wind Engineering (IAWE, www.iawe.org), the Italian Association for Wind Engineering (ANIV, www.aniv-iawe.org) and the youth section of this (ANIV-G), the German-Austrian-Swiss Wind Engineering Society (Windtechnologische Gesellschaft D-A-CH, www.wtg-dach.org), the Dutch-Flemish Wind Engineering Association and with researchers, practitioners, universities, public/private institutions working on similar fields and directly reachable by email.
In order to encourage prospective university BSc/MSc and PhD students, the TU/e ABLWT usually takes part in “Open day” events organized by TU/e. During these days, a brief introduction about the facility and short practical demonstrations are provided to the guests highlighting potential applications in Wind Engineering and Urban Physics. In addition, courses spreading state-of-the-art knowledge regarding many different aspects of Wind Engineering and Urban Physics are officially included in BSc, MSc and PhD courses.
Although still in its early days, the TU/e ABLWT has established strong collaborations with national and international private/public companies and other institutions in the last 4 years by developing a significant number of industrial and research projects. Nevertheless, an EU funded TA activity will help to reach new users and novel scientific goals often unattainable due to the lack of funds.

Review procedure under this proposal:
For details on the TA evaluation process, please refer to Task 1.2 of WP1 and the process followed by the TA-SEP in particular.