Located in 200 Graf Hall
With the aid of the NSF support (0245206, 0324498),a new water tank was completed in 2006, and it is currently operational for precision experiments with optical instruments. The tank is 7.3 m long, 3.6 m wide, and 0.30 m deep. It is elevated so that the bottom is located 1.2 m above the laboratory floor; the bottom and sidewalls are made of glass. This design enables us to measure both wave and velocity fields from every angle using various optical techniques for flow visualization, as well as laser-Doppler anemometer (LDA) and particle-imagery velocimetry (PIV) systems. Prior to the assemblage, the surface of the entire 3.6m ´7.3m aluminum frame of the basin floor was planed in one piece to achieve a smooth flat surface, which – together with the height-adjustable columns – enables us to place glass plates precisely in the horizontal plane.
The wave basin is equipped with a 16-axis directional-wave maker system along the 3.6-m. long sidewall. Each paddle is pushed through hinge connections by two adjacent linear motion devices. The paddles are made of non-corrosive PVDF (Polyvinylidene fluoride) platesthat are moved horizontally in piston-like motions. The support system that contact water are made of stainless steel. Each paddle has a maximum horizontal stoke of 55cm – more than adequate to generate very long waves. The paddle array and linear motion devices are supported by a separate, structurally stiff, steel structure that spans one end of the wave basin and is bolted to the laboratory floor.
Each axis of linear-motor motion is produced by a complete factory-integrated unit (from Parker Daedal) that provides for sophisticated positioning of load. The use of a linear, rather than a traditional rotary, motor is the key to this sophistication; linear motors are inherently more accurate for producing linear positioning, since there is zero backlash with fast response and settling times and they obviate the need for the mechanical devices traditionally needed to change rotary motion into linear motion. The 8-pole motor units are capable of producing 50 lbs maximum force and 17 lbs of continuous force. A turbo PMAC digital controller (from Delta Tau, Inc.) provides the control for all axes of motion. This computer-based controller runs a dedicated real-time operating system for controlling motors; unlike other operating systems of this type, Delta Tau’s is open, giving us direct access to all memory locations, which can be monitored in real-time using background programs. Delta Tau’s software package provides an environment for accurate tuning of all motor/load axes of motion. In addition, the digital control algorithm provides “look ahead” capability, enabling the system to be controlled with no error. (Traditional servo systems require an error signal before they are controlled.) The look-ahead feature incorporates the known dynamical capabilities of the wavemaker system. This linear-motor wavemaker system, together with the precision wave basin, provides capability of generating precisely repeatable flow fields in the tank.
The water-wave tank: 7.3 m long, 3.6 m wide, and 0.30 m deep.
TSI Planar PIV system with 190mJ laser and the 4MP PIV camera.
AOS X-PRI 1.3 GB F2 high speed video camera: 500 fps @1280/1024 pixels with Image Studio Full software.
Spectra-Physics Centennia Thin-Disk Laser: 5-W diode-pumped solid-state (DPSS) continuous wave (CW) laser operating at 532 nm.
2 sets of optical-fibre links, and 3 sets of resonant scanners. Those can be used for aflow visualization technique called the laser induced fluorescent (LIF).
Chris Goldfinger (CEOAS)
Diane Henderson (Mathematics at Penn State)