California Institute of Technology


Field Testing

The Caltech Field Laboratory for Optimized Wind Energy (FLOWE) was established in 2010 to demonstrate and test new wind energy technologies at full-scale and under natural wind conditions. Located in northern Los Angeles Country, FLOWE includes a research wind farm comprised of 42 1.2-kW vertical-axis wind turbines. The turbine array is reconfigurable to study the effect of various spatial arrangements on wind farm performance. In addition, point-wise, two-dimensional and volumetric measurements of airflow around and within the turbine array are conducted using laser velocimetry techniques. Research at FLOWE aims to optimize arrangements of vertical-axis wind turbines in order to avoid destructive aerodynamic interference among the turbines and, potentially, to achieve constructive interference between adjacent turbines. The net result is significantly higher power extraction from a given wind farm footprint.

Wind Tunnel Testing

The Lucas Adaptive Wall Wind Tunnel is an aerodynamic test facility on the Caltech campus. Commissioned in 2002, it was built as a replacement for the historical Ten Foot Tunnel. The Lucas wind tunnel uses adaptive wall technology in the test section to reduce and even eliminate the need for data corrections required in straight-wall tunnel tests. While the tunnel is operating, pressure measurements are taken along the floor and ceiling of the test section; combined with the current displacement profiles, a one-step predictive algorithm determines the required wall contour for the current model configuration and adapts the walls to match. The system effectively "tricks" the air into thinking it is in an infinite flowfield, rather than confined by the walls of the tunnel. The test section of the wind tunnel is 1.5 x 1.8 x 7.6 m with a maximum wind speed of 70 m/s. Force measurements and laser velocimetry enable full dynamic characterization of test objects in the facility.

Water Tunnel Testing

The 40-meter tilting free-surface water channel at Caltech was originally constructed in 1967, and a full renovation of mechanical and electrical components was completed in February 2007. Flow in the water channel is driven by two independent pumps (8 and 25 HP, respectively) to allow for efficient operation at a wide range of flow speeds and water depths. In a non-tilted configuration, the pumps can achieve sustained flow speeds over 1 m/s (at 50 percent water level), and generate intermittent flow at further increased speeds. The length of the channel ensures that fully-developed flow exists throughout the majority of the facility. A series of computer-controlled screw jacks operate to tilt the water channel up to a maximum slope of two percent. In a tilted configuration, the upstream end of the facility is raised, while the downstream end is lowered. Flow speeds can be substantially augmented when the channel is operated in a tilted configuration. A motorized traverse can tow up to 200 lbs. along the channel and is enabled with a captive trajectory control system. Controlled wave generation is facilitated by an oil-pressurized piston mechanism (Hydraulic Control, Inc.) mounted at the downstream end of the channel. Depending on the impulse delivered by the wave generator and the tilt angle of the channel, both breaking and non-breaking surface waves can be created.

Materials Testing

In-situ mechanical testing is performed in the "SEMentor," an in-situ mechanical testing instrument developed by Prof. Julia Greer in 2008. The individual components comprising this piece of equipment are a FEI Quanta 200 Field Emission SEM and a MTS (now Agilent) Nanoindenter Dynamic Contact Stiffness (DCM) module. Nanoindenter tips are purchased directly from the vendors and subsequently modified to the desired geometries (grips, tines, wedges, etc.) via FIB. The Greer laboratory is also equipped with the G200 Nanoindenter (Agilent Corp.), which is also used for (ex-situ) compression, fatigue, and bending testing to enhance and validate the data obtained in the SEMentor. This instrument has the necessary functionality for nano-scale compression and standard nanoindentation testing.

Materials Fabrication

The fabrication and post-mortem analysis of tested small-scale structures relies heavily on the use of Caltech's Kavli Nanoscience Institute (KNI) facilities. Sample fabrication involves standard micro-fabrication equipment, all of which is available in KNI: multi-target sputtering thin film deposition system, Leica (E-beam) and Heidelberg (optical) lithography systems, Oxford ion mill, Tylan low-stress silicon nitride deposition furnace, and wet chemistry benches. In addition, a suite of FEI instruments is available for in-line sample characterization and microstructural analysis: Quanta 200 and Sirion FEG SEMs, 2 FIBs (Nova 200 and Nova 600), Omniprobe micromanipulator, and TEM (TF20). High-resolution TEM (FEI TF30) is also available.

Computational Flow Physics Laboratory

Tim Colonius (flow control + biomedical)

Our computational facility includes a PSSC Labs PowerWulf cluster with over100 CPUs for algorithm development and medium-scale computations. Large scale simulations are being carried out at external facilities including the NSF Teragrid and several DoD computing sites. The laboratory also includes large-scale storage and workstations for visualization and post-processing of simulation data.

McKeon Group

Beverley J. McKeon (flow control)

Experimental work in the McKeon group is performed in recirculating wind and water facilities (Merrill, Lucas Adaptive Wall and NOAH tunnels) in the Graduate Aerospace Laboratories. Their respective capabilities and size are as follows:

Merrill: 0.6 x 0.6 x 2.4 m, Rex = 3.3 x 106/m
Lucas: 1.5 x 1.8 x 7.6m, Rex = 4.4 x 106/m
NOAH (water): 0.6 x 0.6 x 2.4 m, Rex = 3.0 x 105/m

Our primary diagnostics include high frame-rate, stereo Particle Image Velocimetry (LaVision), constant temperature anemometry (AA Labs) and distributed pressure scanning/transducer systems (Scanivalve, Baratron), along with laser displacement measurement sensors (Keyence) for bench and in-situ characterization of the behavior of morphing surfaces. The Millikan cluster is available for supporting computations.