Experimental Resources

UNIVERSITY OF FLORIDA POWELL FAMILY STRUCTURES AND MATERIALS LABORATORY

The UF Powell Lab includes five wind hazard research instruments:


Boundary Layer Wind Tunnel (BLWT)

Equipment Resource: The BLWT is a 6 m wide, 3 m tall and 40 m long wind tunnel designed to simulate boundary layer flows to characterize the wind loading and structural behavior, including aeroelastic response of wind-sensitive structures (Figure 1). Unique aspects of this facility are its large size and automated continuously adjustable terrain roughness field (the “Terraformer”). Eight 1.5 m diameter, 75 HP motor driven Aerovent vaneaxial fans can generate speeds of up to 18 m/s while maintaining +/ 1 fan RPM. The Terraformer consists of a 6 m x 18 m field of 1,116 individually controlled 100 mm long x 50 mm wide cuboid elements which raise out of the tunnel floor up to 160 mm each, to form a heterogeneous or homogeneous terrain field. Reconfiguration of the terrain field takes approximately 2 minutes, allowing for rapid testing of multiple terrain configurations. Models are mounted on a 1-meter (current) or 4-meter (future upgrade) diameter turntable for 360° exposure to wind direction.

 

Experimental Protocol: The BLWT’s in-house instrumentation suite includes:

  • A 512 channel, 625 Hz Scanivalve ZOC33 pressure scanning system mounted under the turntable.
  • Four Turbulent Flow Instrumentation Cobra Probes that measure three components of velocity up to 2000 Hz, mounted on a traverse gantry to allow positioning anywhere within the tunnel cross-section.
  • Pitot tubes mounted at a reference height above the test section
  • Dwyer pressure sensors along tunnel walls
  • Two ATI Industries Nano25 6-Axis miniature load cells to quantify base forces and moments.

Because of its relatively large size and ability to generate a variety of approach terrains, the UF BLWT offers users tremendous flexibility. Using the standard relationship for similitude in bluff body aerodynamic testing, the parameters for model length scale, velocity scale and time scale can be adjusted to test a very wide range of possible test specimens and wind field conditions. The primary limitation is that the model does not block more than 5% of the tunnel cross section, or 0.9 m2, in order not to deviate from reference tunnel air flow characteristics.

The BLWT may be utilized to study rigid and/or aeroelastic scale models as well as other boundary-layer turbulence research topics (for example, UAVs). Typically, rigid models will utilize the Scanivalve system to quantify pressure distribution around the model envelope using built-in taps. Aeroelastic model response is quantified using a force balance and/or internal instrumentation.

Depending on the specific test protocol, data output may include the following:

  • Time-stamped Scanivalve pressure tap readings
  • Time-stamped Dwyer and Pitot pressures/atmospheric data
  • Time-stamped Cobra probe data
  • Boundary layer profile
  • Time-stamped force balance / load cell data
  • Fan motor data/system health data (RPMs, vibration, temperature)
  • Terraformer element position data

All data will be archived to the CI and will be immediately available to the user for interpretation and analysis.

Standard Operating Procedures

Scanivalve: cms_page_media/161/Scanivalve_SOP_v1.pdf

BLWT: cms_page_media/161/BLWT_SOP_v1a.pdf

Boundary Layer Wind Tunnel (BLWT)

Figure 1: Boundary Layer Wind Tunnel with test specimen and terraformer array


Multi-Axis Wind Load Simulator (MAWLS)

Equipment Resource: The MAWLS is a unique large-scale dynamic wind effects simulator that imposes dynamic air pressure in combination with static in-plane shear or uplift forces. The system is designed to accommodate walls, components, or cladding specimens up to 6 m tall by 8 m wide. This system supports the study of the interaction between static uplift or in-plane shear and time-varying pressure conditions to a level associated with an intense Saffir-Simpson hurricane wind scale category 5 hurricane or an EF5 tornado. Peak pressures in excess of 20 kPa while sustaining air flow in excess of 2,000 m3/min (to compensate for leakage around/through the test specimen) can be sustained, with a frequency response of 1 Hz. The system was designed to operate over a wide range of leakage conditions and changes in volume caused by specimens deflecting out-of-plane.

There are four principal components for the simulator: a fan, ducting, a control system, and the pressure chamber (Figure 2).

Figure 2: MAWLS Components

Five dampers (valves) comprise the control system: four butterfly dampers and a custom-built fast-acting opposed blade louver damper. The purpose of the four butterfly dampers is to change the flow configuration so that positive or negative pressure can be applied to the specimen, or alternatively bypass the chamber to drive air through a high-speed wind tunnel section. The louver damper modulates the system resistance, which changes the airflow in/out of the pressure chamber and thus causes a corresponding change in the pressure acting on the specimen (i.e., the operating point on the fan curve changes). Two differential transducers measure pressure inside the test chamber at a sampling rate of 120 Hz to drive the feedback mechanism for the louver damper. The control/feedback process is continuous; only analog feedback/control was implemented (no A/D or D/A is implemented). The control system allows the user to select a step-and-hold input (setting a pressure level to be maintained indefinitely), input from a function generator (for example a sine wave with defined mean, amplitude and frequency), or a trace (CSV input file containing the time history of a measured or simulated wind pressure signal).

The test specimen is mounted in the reaction frame that is clamped to the open side of the pressure chamber to close the pressure chamber for testing. The pressure chamber is 7.3 m wide x 5.5 m high x 1 m deep. The reaction frame system consists of primary and secondary reaction frames. The primary frame resists the catenary forces developed from the test specimen subjected to wind pressure loading and is fixed, while the secondary reaction frame can be removed and resized to accommodate the dimensions of the specimen (Figure 3).

The MAWLS operates in two modes:

  1. Pressure simulation where dynamic wind pressure is applied to large wall cladding and component systems, such as a commercial rolling door or a wall on a metal building. The instrument can apply static (steady) or time-varying positive or negative pressure conditions.
  2. Velocity simulation where turbulent airflow conditions over a roof deck are simulated to load discontinuous roof systems (e.g., tile and shingles), which is the Dynamic Flow Simulator (DFS, see below).

Experimental Protocol: The design of the MAWLS allows a wide variety of test setups and protocols. The size of the test chamber can be modified for component sizes in excess of 7 x 5 meters. The pressure box frame is designed to withstand large catenary forces generated by out-of-plane loading, and allows for significant out-of-plane displacements (see photos below). Users may choose from a library of test protocols, such as static, sinusoidal or realistic wind pressure trace for pressure tests, and acquire the test data for load and response via standard data acquisition interfaces. All test protocols and acquisition algorithms are customizable to ensure optimal experimental conditions. All data will be archived to the CI and will be immediately available to the user for interpretation and analysis.

Depending on the specific test protocol, data output will include the following:

  • Time-stamped target pressure
  • Time-stamped actual pressure
  • Time-stamped specimen-mounted instrumentation data as required (e.g. displacements, strains)
  • Time-stamped photographs of specimen performance as dictated by the user (e.g. Figure 4)

Standard Operating Procedure

2016-08-22 MAWLS-DFS SOP.pdf

Multi-Axis Wind Load Simulator (MAWLS)

Figure 3: Multi-Axis Wind Load Simulator with test specimen in place

 

Figure 4: Photographs of garage door (a) before testing; and (b) at failure


Dynamic Flow Simulator (DFS)

Equipment Resource: The DFS is used to determine ultimate wind uplift capacities of discontinuous roofing systems (such as tiles, asphalt- or metal-shingle systems), for which the uplift capacity is dependent on the geometric profile (high-profile versus near-flat profile) and effectiveness of air seals between rows of tiles. The unique features of the DFS include the maximum velocity at the test section – approximately 100 m/s – and the ability to replicate up to a 1 Hz waveforms. The DFS was designed to test full-scale roof specimens up to 2 m wide by 2.6 m long. The tile geometry affects the air leakage through the system and therefore the overall uplift loads generated. The wind field generated in a vertical plane above the shingle test specimen represents the variation of near-surface wind flowing above a roof.

Experimental Protocol: During velocity simulation mode, the MAWLS pressure chamber is shut off so that air is pulled through the blower from the exterior intake, then passes through the exterior exhaust, and travels into a high-speed wind tunnel section. The wind tunnel section starts with a setting chamber, which reduces the incoming turbulence and then accelerates the airflow through a contraction duct to the target velocity at the entrance to the test section (Figure 5). The cross-section area at the entrance to the test section is 213 cm wide x 38 cm tall. The bottom part of the test section is removable to accommodate roof samples, and it has a dimension of 243 cm long x 182 cm wide. All data will be archived to the CI and will be immediately available to the user for interpretation and analysis.

Depending on the specific test protocol, data output will include the following:

  • Time-stamped target velocity
  • Time-stamped actual velocity
  • Time-stamped specimen-mounted instrumentation data as required (e.g. displacements, load transducers)

Standard Operating Procedure

2016-08-22 MAWLS-DFS SOP.pdf

Dynamic Flow Simulator (DFS)

Figure 5: Dynamic Flow Simulator


High Airflow Pressure Loading Actuator (HAPLA)

Equipment Resource: The HAPLA simultaneously applies time-varying wind pressure and simulated wind-driven rain on a horizontal building façade (Figure 6). Ideal for rapidly evaluating large test matrices and trials leading up to testing on the MAWLS. The HAPLA consists of two 75 HP centrifugal fans configured to operate in series. Using two fans enables the HAPLA to maintain high air through-flow (leakage) rates (up to 51 m3/min). The ducting connects to a five-port air valve that controls chamber pressure by modulating the amount of air traveling from the test chamber to the exhaust port. The valve disk is connected to a rotary actuation system that provides positioning feedback. A variable intensity water spray system (VIWSS) simulates wind-driven rain effects on building envelope systems. The VIWSS is installed within the steel chamber and consists of two separate spray racks with 25 nozzles. A National Instruments PXI system controls the pressure in the chamber through a 50 Hz Proportional-Integral-Derivative (PID) controller that receives feedback from a pressure transducer in the test chamber, which can follow rapidly varying pressures traces with high fidelity. This design enables the HAPLA to test components under simultaneous fluctuating pressure and wind-driven rain conditions, up to a 3 Hz waveform at pressures up to 6 kPa.

Experimental Protocol: The design of the HAPLA allows a wide variety of test setups and protocols. The size of the test chamber can be modified for component sizes up to 2.4 x 2.4 meters. Users will be able to choose from a library of pre-configured test types, such as air permeability or pressure. The facility is set up to evaluate durability issues by testing newly built wall systems against weathered building components. Users can choose from a library of test protocols, such as static, sinusoidal or realistic wind pressure trace for pressure tests, and acquire the test data for load and response via standard data acquisition interfaces. All test protocols and acquisition algorithms are customizable to ensure optimal experimental conditions. Control of the test protocol and data acquisition are handled within a common LabVIEW interface so that a common trigger can initiate both testing and data acquisition, ensuring time compatibility of the load and response data. All data will be archived to the CI and will be immediately available to the user for interpretation and analysis. The output of the HAPLA is includes the following data:

  • Time-stamped target pressure
  • Time-stamped actual pressure
  • Time-stamped PLA valve position
  • PID control parameters (e.g., gain, derivative gain, integral gain, error)
  • DAQ Tasks output data (in engineering unit specified in NI Max)
  • Time-stamped water flow rate data (if applicable)
  • Time-stamped specimen-mounted instrumentation data as required (e.g. displacements, strains)

Standard Operating Procedure

2016-08-22 HAPLA SOP.pdf

High Airflow Pressure Loading Actuator (HAPLA)

Figure 6: High Airflow Pressure Loading Actuator


Spatiotemporal Pressure Loading Actuator (SPLA)

Equipment Resource: The Spatiotemporal Pressure Loading Actuator (SPLA) is a similar instrument to the MAWLS and HAPLA, but is an array of four independent Pressure Load Actuators (PLAs) which can be simultaneously controlled to apply independent pressure traces on separate regions of a single test specimen (Figure 7). The key features of the SPLA design is that it a) produces wind loads up to a Category 5 Hurricane (i.e. +5 kPa to -10 kPa range; b) can follow a pressure trace with high accuracy for a range of surface area; c) has a frequency response of up to of 4-6 Hz; and d) can operate with substantial air leakage (12 – 60 m3/min) through cracks in the building materials. The performance characteristics of the PLA depend on the size of the test chamber used. An independent servomotor controls the position of the rotating disc within each PLA which adjusts the chamber pressure. Each PLA is portable, and independently positioned depending on location of the sub-chambers for the experiment. A pressure transducer within each sub-chamber monitors the pressure and provides feedback to the each PLA. The four PLAs are networked together and controlled through a single PC-based control program.

Experimental Protocol: The user is able to choose from a library of test protocols, such as static, sinusoidal or realistic wind pressure trace for pressure tests, and acquire the test data for load and response via standard data acquisition interfaces. All test protocols and acquisition algorithms are customizable to ensure optimal experimental conditions. Control of the test protocol and data acquisition are handled within a common LabVIEW interface so that a common trigger can initiate both testing and data acquisition, ensuring time compatibility of the load and response data. All data will be archived to the CI and will be immediately available to the user for interpretation and analysis. The output of the SPLA is a single Hierarchical Data Format (HDF5) file that contains the following data for each PLA:

  • Time-stamped target pressure
  • Time-stamped actual pressure
  • Time-stamped PLA valve position
  • PID control parameters (e.g., gain, derivative gain, integral gain, error)
  • DAQ Tasks output data (in engineering unit specified in NI Max)
  • Time-stamped specimen-mounted instrumentation data as required (e.g. displacements, strains)

Standard Operating Procedure

SPLA_SOP_v1.00.pdf

Powell Laboratory Safety Manual

cms_page_media/161/CCE Safety Manual-Ver_1 0-rev.pdf

Spatiotemporal Pressure Loading Actuator (SPLA)

Figure 7: Spatiotemporal Pressure Loading Actuator