DeFrees Hydraulics Lab
The Joseph H. DeFrees Hydraulics Laboratory is the focal point of research and experimental studies in the environmental fluid mechanics and hydrology program. The lab is named after engineer and benefactor Joseph DeFrees ‘29 CE. Edwin “Todd” Cowen, Associate Professor, has been the Director of the laboratory since he joined the Cornell Faculty in 1998.
Hydraulics and hydrology deal primarily with the occurrence and movement of water and other fluids on the surface of the earth. It has been our challenge to make water do what civilization needs it to do like: open channel flow and deliver aqueducts with water, manage reservoirs, dissipate energy as water falls off a spillway. Faculty, students, and researchers are actively engaged in not only the traditional engineering applications that deal with river engineering, the hydrology of surface drainage and runoff, pipelines and conveyance systems, groundwater, flooding and its prevention, coastal processes and near shore oceanography, hydroelectric generation, water supply and distribution, irrigation, and fluid measurement. The movement and dispersion of water and pollutants in the unsaturated zone and in water supply aquifers is of great concern.
The state-of-the-art turbines and tilting water tanks reproduce some of nature’s hydrodynamic complexities in a variety of test conditions. Waves roll over a ripple bed. An artificial stream tumbles down the gentle slope of a flume. A turbulent, meandering current surges through a broad channel. Lasers flash as high-speed cameras record the scattered light from test particles in the tanks.
The DeFrees hydraulics lab is equipped with three main experimental facilities, a Wave Tank, a Wide Meandering Wave-Current Flume, and a Tilting Wind Water Tunnel. Companion data acquisition and analytical measurement equipment includes a selection of quantitative imaging systems that include digital cameras, light source (lasers) and associated optical components for illumination, computers for data acquisition, and image procession software. For detailed information about the quantitative imaging technology used in the Defrees Laboratory take a look at Quantitative Imaging Technology PDF file.
The Wave Tank is 32 meters long, .6 meters wide and one meter deep and is equipped with a hydraulic servo-system driven generator capable of producing both regular and irregular waves. The mid-section of the tank is equipped with a false bottom to allow structures to be mounted in the tank for structure/wave interaction experiments and for different bottom configurations to be studied such as flow over a rippled bed.
The Wide Meandering Wave-Current Flume is designed to model shallow coastal water for the study of meandering, wavy turbulent flows. This facility is unique because it is able to generate span-wise meanders in the flow field. The rear wall mounted piston-type wave maker is designed to generate monochromatic waves in the range from .3 Hz to 3 Hz. Funding for this facility is provided by the Office of Naval research and is part of the DARPE-ONR Chemical Plume Tracing Program. For detailed information about this facility please download and read the Wide Meandering Wave-Current Flume PDF file.
The third experimental facility is the Tilting Wind-Water Tunnel is suited for performing air-water interface experiments as well as modeling riverine systems. Its test section is 20.0m long, 1.000m wide, and 0.80 m deep. The maximum operating water depth of this closed recirculating loop water flume is 0.30 m. The slope of the facility can be set between -0.5% and 2.6% (-0.3° and 1.5°).
The facility is equipped with a variable speed, computer controllable, 25 HP pump capable of generating a maximum water flow rate of 0.25 m3/s. The air flow system is an open intake/outlet system with a variable speed, reversible, computer controllable, 12 HP fan capable of moving a maximum of 11.8 m3/s. This airflow rate is sufficient to generate strong wave action, wave breaking, and air entrainment. For more details, please refer to the PDF entitled Tilting Wind-Water Tunnel PDF file.