An experimental setup for three-degree-of-freedom large-amplitude free vibration in wind tunnel test. The setup includes a rigid test model, rigid circular rods, rigid lifting arms, arc blocks with grooves, lightweight high-strength thin strings, linear tensile springs, fixed pulleys, and bearings. Large-amplitude three-degree-of-freedom free vibrations of test models can be adapted by the vertical deformation of the springs without any tilt. The possible nonlinear mechanical stiffness due to vertical spring tilt and lateral spring deflection in the traditional setup are excluded. It is convenient to install the test model and adjust the initial angle of attack in the new experimental setup. The linear stiffness property and hence constant vibration frequency can be ensured for very large-amplitude vibrations due to the eliminations of spring deflection and tilt.

Disclosed herein is a technique of configuring flexible photovoltaic tracker systems with high damping and low angle stow positions. Under dynamic environmental loads implementing a high amount of damping (e.g., greater than 25% of critical damping, greater than 50% of critical damping) or a very high amount of damping (e.g., 100% or greater of critical damping, infinite damping) enables the flexible tracker system to prevent problematic aeroelastic behaviors while positioned in a low stow angle. The disclosed technique is further applied to a prototyping process during wind tunnel testing.

A transducer body includes a support comprising a pair of clevis halves; a sensor body coupled to each of the clevis halves, wherein the sensor body is disposed between the clevis halves and includes a generally rigid peripheral member disposed about a spaced-apart central hub, the central hub being joined to each of the clevis halves with the peripheral member spaced apart from each clevis half, wherein at least three flexure components couple the peripheral member to the central hub, and wherein the flexure components are spaced-apart from each other at generally equal angle intervals about the central hub; and a lockup assembly configured to selectively inhibit movement of the sensor body relative to the clevis halves.

A test fixture for measuring the skin friction of anisotropic surface finish on a material is described. The test fixture can be utilized in a wind tunnel. The test fixture can include a plate having a cavity configured to receive a circular specimen disk. A motor can be coupled to the plate to rotate the circular specimen disk. During a test, a fluid can flow over the plate in a particular direction and the motor can rotate the circular specimen disk to determine the effect of the flow angle on the average skin friction coefficient of a surface finish of a material. The circular specimen disk can easily be attached and detached from the test fixture to allow circular specimen disks with different surface finishes to be tested.

Rotary actuator assemblies and associated methods are disclosed. The rotary actuator assemblies include a rotary actuator, a rotary element, and a magnetic element. The rotary actuator is configured to generate a torque. The rotary element is coupled to the rotary actuator and is configured to rotate responsive to receipt of the torque. The magnetic element is configured to bias the rotary element in a rotary direction. The methods include rotating a rotary element responsive to receipt of a torque from a rotary actuator and applying a supplemental torque to the rotary element with a magnetic element.

A wake generator for placement in a wind tunnel between a wind source and a test object includes a first frame member having a first track formed thereon, where the first track has a shape including a first side that is substantially rounded and a second side that is substantially flat. The wake generator may include a mounting plate disposed within a perimeter of the first track, where the mounting plate is rotatable relative to the first frame member about a first axis. The wake generator may also include a plurality of bars slidably engaged to the mounting plate and structurally configured to traverse along the first track when the mounting plate is rotated about the first axis, where each of the plurality of bars includes a pivotal connection allowing each of the plurality of bars to pivot about the pivotal connection when traversing along the first track.

Rotary actuator assemblies, wind tunnels including the same, and associated methods are disclosed. A rotary actuator assembly includes a rotary element and a rotary actuator with a shape memory alloy element. The rotary actuator is configured to generate a first torque and a second torque in opposing rotary directions to rotate the rotary element. A rotary actuator assembly further includes an assist magnetic element and a receiver magnetic element configured to generate a magnetic force therebetween. Wind tunnels include an aerodynamic model with a rotary actuator assembly to rotate a portion of the aerodynamic model with respect to an airstream in a chamber. A method of rotating a rotary element includes modulating a temperature of a shape memory alloy element and applying a supplemental torque to the rotary element with an assist magnetic element and a receiver magnetic element.

The invention provides a large-amplitude vertical-torsional coupled free vibration device, which belongs to the technical field of vertical-torsional coupled free vibration device for wind tunnel test. The gear blocks are consolidated at both ends of the beam. The screws, beam, and the gear blocks are fixed on the model, and they can fulfil the vertical-torsional coupled free vibration. The toothed plate is attached to the sliding block that iteratively moving along the vertical guide rail which is fixed to the ground. The vertical springs attached to the sliding blocks provide both vertical and torsional linear stiffness for the suspension vibration system. The springs only have vertical linear tensile deformations without any lateral tilt, which ensures the linear vertical and torsional stiffness of the model, and the lateral freedom is effectively restrained. This device can achieve the large-amplitude vertical-torsional coupled free vibration of the model, and the deficiency of the traditional device where springs are apparently tilted and the inefficacy of linear stiffness can be avoided. The lateral vibration is restrained, and it is applicable to large-amplitude vertical-torsional coupled free vibrations.

A test bench, in particular a convertible wind channel balance, including a lifting frame for lifting at least one wheel belt unit, wherein the wheel belt unit has at least one belt which is looped around at least two rollers, a weighing platform, which is mounted so as to be relatively movable in relation to a test bench frame, at least one force sensing member arranged between the weighing platform and the test bench frame in order to sense forces between the weighing platform and the test bench frame, wherein at least one self-centering docking member is provided between an auxiliary frame and the weighing platform.

This present disclosure is about a wind tunnel balance axial section. A wind tunnel balance is a sensor that measures six force/moment components from a test model in a wind tunnel. An axial section, one of the six measurement sections in the balance, is the hardest section to design because it is often required to measure an axial force which is much smaller than other force components. Therefore, there is a specific design requirement for the axial section to selectively amplify the axial force response and suppress the non-axial responses. This disclosure presents a sensor mechanism composed of elastic linkages to achieve this design requirements for the axial section.