NASA Air-Sea Interaction Research Facility
Located at Wallops Flight Facility, Wallops Island, VA
- Main Research Tank: 60 ft. Length x 4 ft. Height x 3 ft. Width
- Air Flow: Top 1.5 ft., 18 m/s max., computer controlled, temperature and humidity control (cooling)
- Water Flow: Bottom 2.5 ft., Reversible, 30 cm/s max. without false bottom, computer controlled, temperature control (heating)
- Wave Height Data: Capacitance Probes
- Wave Slope Data: Height Difference and Video Imaging Optical Techniques
- Air Flow Data: Pitot Tubes and Pitot Arrays, 2 Ch. Hot Film Anemometer
- Water Flow Data: 2 Ch. Laser Doppler Anemometer, Profiling
- Low Frequency Waves: Hydraulic Wave Generators, Each End, Random Signal to 10 Hz
- Data Collection and Analysis: PC Control and Switching of Experiments, Automated Experiments, A/D Conversion and D/A Drive Signals, MatLab, IDL, LabView, DASYLab, Igor Pro Software Environments, Image Processing and Analysis, HHT/EMD processing, Support for All Major Programming Languages, Internet connections
History and capability
Marking its 30th year of operation, the NASA Air-Sea Interaction Research Facility has recently completed major modifications to both expand its capability, and modernize its operation. Located at the Wallops Flight Facility in Code 614.2, the Ocean Sciences Branch within the Sciences and Exploration Directorate of NASA Goddard Spece Flight Center, the main wave research tank of the facility now has water flow smoothing chambers, a larger air flow smoothing chamber, a centralized/symmetric water pumping station, and computer control of the wind and water current speeds. New coils have been added in the air flow ducts to allow cooling and humidity control of the air flow. Four commercial spa heaters provide heating and temperature control of the water when needed. Because of the full computer control of conditions generating the phenomena under study, as well as control over timing and repeatability that is now possible, transient phenomena as well as steady state problems can be studied with experiments conducted automatically around the clock until the desired amount of data is available. With full internet connectivity, researchers can receive data and results at their home institutions if travel capability tot he Facility is limited.
Impact of the facility
The primary objectives of the facility is to test theoretical results and to collect empirical data for the development of remote sensing techniques, in support of microwave remote sensor development and algorithms for air-sea interaction studies. Early in its history, the facility produced theory and measurements demonstrating that the ocean surface was not a Gaussian distribution, but had a skewness that should be accounted for. The EM bias correction is now addressed to correct for this skewness. Additional early work showed that an overshoot in wave spectral levels as waves developed under increasing winds would affect radar measurements of winds, which has now been observed and acknowledged. Over its 22 year history, the facility has produced over 50 refereed research articles, a half dozen book chapters, graduate students from the Johns Hopkins University, Harvard University, the University of Heidelberg, and Scripps Institution of Oceanography in their thesis research, as well as researchers from other universities, other government agencies, and researchers from other countries in joint experiments. Recent results have helped explain the directional distribution of waves and energy in response to increasing winds and fetch, as well as the development of high frequency surface wave structures that respond quickly to wind changes, and that are in the wave length bands observed by remote sensors in operation and under development.
Unique features of the facility include:
- identical flow settling chambers for water flow that provides identical flow conditions with or against the waves, with great uniformity and repeatability at all flow speeds
- dual hydraulic wave generators that can provide identical wave profiles, packets, and packet groups with or against the wind direction, with precise repeatability
- precise control of winds, including starting times, rate of increase in changing winds, maximum speed, and duration
- real time data processing during experiment phase to allow the final results to be seen and conditions altered to pin down the process with the best data set possible
- computer control of all aspects of the experiment for fully automated experiments, producing data around the clock from normal 8 hour work shifts, including control of wind speed, current and wave conditions, measurements of wind and current speeds, wave elevations and slopes at various fetches, and wave image analysis with video techniques
- internet connections to the facility to allow visiting scientists to participate in software development, experiments, data processing, and journal article preparation without having to travel to be physically located at the facility
- temperature control of heated water, temperature and humidity control of cooled air flow
After completing the most recent modifications, the facility went immediately back into operation by hosting the FEDS.04 joint experiment with the University of Alberta, the University of Washington/APL group, as well as Columbia University/Lamont-Doherty Earth Observatory and WFF personnel. Already in progress is a study of wave interaction with water turbulence conducted with the Johns Hopkins University, as well as a study of the influence of waves and wave growth on the wind profile.
Support for the facility has come both from NASA HQ’s RTOP and several reimbursable sources. Its complete description is in NASA Reference Publication 1277, of June, 1992, the updated version available from Dr. Steven R. Long, Code 614.2, NASA GSFC/WFF, Wallops Island, VA 23337, USA.