Appendixes



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An Assessment of Naval Hydromechanics Science and Technology Appendixes

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An Assessment of Naval Hydromechanics Science and Technology This page in the original is blank.

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An Assessment of Naval Hydromechanics Science and Technology A Research Facilities and Equipment for Naval Hydromechanics Technology NATIONAL ASSET HYDROMECHANICS TEST FACILITIES Naval Surface Warfare Center, Carderock Division Facility Summary Two parallel towing tanks are located at the Naval Surface Warfare Center, Carderock Division (NSWCCD), in Carderock, Maryland. One tank is subdivided by a bulkhead to provide two independent basins with separate carriages. The first basin includes a deep section 6.7 m deep, 271 m long, and 15.5 m wide, and a shallow section 3 m deep, 92.4 m long, and 15.5 m wide. The carriage has a maximum speed of 9.3 m/s. The adjoining second basin is 6.7 m deep, 575 m long, and 15.5 m wide, with a pneumatic wave maker at one end and a wave-absorbing beach at the other. The carriage in this basin has a maximum speed of 10.3 m/s. The other towing tank, known as the high-speed basin, is 904 m long with a deep section 4.9 m deep, 514 m long, and 6.4 m wide and a contiguous shallow section 3 m deep, 356 m long, and 6.4 m wide. A pneumatic wave maker is at the deep end and an absorbing beach is at the shallow end. Two carriages are located in the high-speed basin, with maximum speeds of 16.5 m/s and 25.7 m/s. The maneuvering and seakeeping basin is 110 m long by 73 m wide with a depth of 6.1 m except for a 10.7 m deep by 15.2 m wide trench parallel to the long side of the basin. Two banks of pneumatic wave makers are located along the length and width of the basin. The wave makers can generate waves up to 0.6 m in height and from 0.9 to 12.2 m in length. Both regular and irregular waves can be generated. The basin is spanned lengthwise by a bridge supported on a rail system that permits the bridge to traverse one-half the width of the basin and rotate 45 degrees from the longitudinal centerline of the basin. The carriage, supported under the bridge, has a maximum speed of 7.7 m/s. The rotating arm basin is 79.2 m in diameter and 6.1 m deep. The bridgelike arm has an undercarriage that can be set to a specific test radius. Steady-state speeds of 15.4 m/s can be obtained in one-half

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An Assessment of Naval Hydromechanics Science and Technology revolution at the 36.6 m radius. Speeds up to 25.7 m/s can be obtained at the same radius in two revolutions. The circulating water channel is a free surface, closed-circuit channel. The test section is 2.7 m deep, 18.3 m long, and 6.7 m wide. The maximum speed is 5.1 m/s. The 36 in. variable-pressure water tunnel has a recirculating, closed circuit with a resorber and two interchangeable circular test sections, an open jet, and a closed jet. The maximum speed is 25.7 m/s and the pressure range is 414 kPa to 14 kPa. Propeller dynamometers are located on the upstream and downstream shafts, along with a right-angle drive dynamometer and an inclined-shaft dynamometer. Lake Pend Oreille is in northern Idaho. Its main physical attributes are as follows: depths of 1,150±5 ft over approximately 26 mi²; ambient noise 10 to 15 dB below sea state zero, with 25 percent probability (night); isothermal at 39.5 °F below the surface layer; 0.02 knot current below 100 ft; standard deviation of transmission loss fluctuations 0.3 dB at 10 kHz and 1 kyd; volume reverberation of −39 dB dropping to −53 dB in 0.3 s; and active sonar pulses reflected from models received before reflections from lake boundaries. Major test facilities include large-scale models of submarines as well as small, laboratory-size objects for fundamental research. Powered or buoyantly propelled large-scale models provide data at Reynolds, Froude, and Helmholtz numbers that closely approximate full-scale values. Although mechanical damping cannot be scaled, data acquired over many decades on several classes of submarines provide guidance for model design. The Large Scale Vehicle (LSV) is a ¼-scale powered model of the SSN 21 submarine. This unmanned vehicle travels at commanded depths and speeds over an instrumented range where its radiated noise is measured. The output of 2,000 on-board sensors is simultaneously recorded. A second vehicle, LSV II, a ¼-scale model of the Virginia class, is scheduled for delivery in 2000. The intermediate-scale measurement system, installed in 1995, is designed to obtain precision measurements of the low- and mid-frequency active and passive acoustic signature characteristics of large submarine models. The system includes transmit and bistatic receive arrays capable of synthesizing farfield plane waves. The onboard data acquisition system contains over 1,000 channels as well as a 34-channel hull excitation system. Experiments can be remotely controlled and data can be processed in real time. Secure data links to Carderock allow scientists access to data, thereby creating a virtual laboratory. The Large Cavitation Channel is located in Memphis, Tennessee. It is a closed-circuit, closed-jet test section 3 m wide, 3 m deep, and 13 m long, with a very low acoustic background level. The working maximum velocity is 18 m/s, with an absolute pressure range of 3.5 to 414 kPa. Naval Undersea Warfare Center Facility Summary The Naval Undersea Warfare Center (NUWC) acoustic wind tunnel, suitable for both internal and external studies, is a low-noise (−40 dB at 100 Hz) facility for hydroacoustic, boundary layer turbulence, and wake studies. The 48-in. diameter, 108-in. long test section of the anechoic (100 Hz to 40 kHz) closed jet has a speed range of 0 to 200 ft/s, with turbulence intensity less than 0.3 percent and exit flow uniformity greater than 99.5 percent. Its 78-in. diameter, 500 hp, 14-in. diameter blower is mounted on 160-ton concrete for vibration isolation. It has instruments for flow visualization, high-speed photography, and acoustic measurements, and is supported by rapid model prototyping using stereolithography. The Langley seawater tow tank (2,880 ft long, 24 ft wide, and 12 ft deep), which is owned by NASA and operated by NUWC, enables testing in both fresh- and saltwater (14 to 18 parts per thousand) environments. With a speed range of 0 to 68 ft/s, it is capable of full-scale, six-component load testing. A retractable gate allows the first 50 ft of the tank to serve as a drydock during model installation and

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An Assessment of Naval Hydromechanics Science and Technology maintenance. The tow tank is also used for unmanned underwater vehicle launch, maneuvering, and recovering, and supercavitating vehicle studies. The NUWC research tow tank (90 ft long, 4 ft wide, and 3 ft deep), which can employ either fresh-or saltwater as its medium, has a speed range of 2 to 10 ft/s. A retractable gate allows the first 15 ft to be used as a drydock during model installation and maintenance. The last 60 ft of the tank provide visual access. The NUWC research water tunnel (1 ft × 1 ft, 10-ft test section) employs either fresh- or saltwater and is used for medium-scale studies in fully developed duct flow, boundary layer (drag control, separation, reattachment), and cavitation. The tunnel operates at a speed of up to 30 ft/s with a turbulence level less than 0.5 percent. The NUWC quiet water tunnel (acoustically quiet above 30 Hz) is well suited for the measurement of pseudosound and flow-induced noise and allows three different configurations of the test section: circular (1.75 in. and 3.5 in. diameter), square (1.1 in. × 1.1 in. and 2.2 in. × 2.2 in.), and rectangular (12 in. × 4.4 in.). Up to the maximum centerline speed of 55 ft/s, the facility enables wall pressure (piezoelectric) and velocity vector (hot film and laser Doppler anemometer) measurements with 48 channel data acquisition at 5 kHz. ACTIVE ACADEMIC TEST FACILITIES Applied Research Laboratory/Pennsylvania State University Facility Summary The Garfield Thomas water tunnel (closed-loop, closed-jet; 48 in. diameter, 9.27 m long) can operate at a speed of up to 18 m/s at a turbulence level of 0.1 percent, and its air content can be controlled to below 1 ppm. This tunnel is used for steady and time-dependent force and torque measurements on powered models with a diameter of up to 63.5 cm and for measures of their cavitation performance. The cavitation tunnel (closed-loop, closed-jet) operates in two configurations: circular (12 in. diameter, 30 in. long) and rectangular (20 in. × 4.5 in., 30 in. long) with speeds up to 24.38 m/s. It is used for steady and time-dependent pressure, force, and cavitation noise measurements on unpowered models (up to 2 in. diameter). The 6 in. cavitation tunnel (closed-loop, closed-jet) operates at a speed of up to 21.34 m/s and is used for studies of cavitation phenomena and axial-flow pump performance. The ultrahigh-speed cavitation tunnel (closed-loop, closed-jet) uses water, freon 113, or alcohol at a speed of up to 83.8 m/s and is used for incipient and desinent cavitation studies. The subsonic wind tunnel (closed-loop) has a 1.219 m × 4.88 in. test section and can operate at speeds up to 45.72 m/s with a turbulence level less than 0.2 percent. It is used for studies of boundary layers, wakes, and wall-wake interactions. The cascade facility (35.5 cm × 3.5 cm) can operate at a speed of up to 36.6 m/s with a turbulence level of less than 0.2 percent and is used for basic research in turbomachinery blading. The boundary layer research tunnel (30.2 cm diameter, 7.6 in. long) operates at a speed of up to 9 m/s. The working medium is glycerine, allowing detailed measurements in turbulent boundary layers over a wide Reynolds number range as well as in a viscous sublayer structure. The axial flow research fan (open-circuit or in conjunction with a flow-through anechoic chamber) is used for studies of turbomachinery noise and vibration and can operate at flow-through velocities up to 34.14 m/s and relative velocities up to 91.44 m/s.

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An Assessment of Naval Hydromechanics Science and Technology The flow-through anechoic chamber (9.3 m high × 5.5 m wide × 6.8 m deep working volume) has a cutoff frequency of 70 Hz and is used for basic research in turbomachinery, active and reactive acoustics for air moving and cooling systems, and scale model testing of proposed auditoriums. The quiet wall jet facility (open-circuit, open-jet, with or without flat plate) operates at a speed of up to 35 m/s. Its blower is located in a sound and vibration isolation box and is provided with a muffler at intake. It is used for radiated sound studies of boundary layers and separated flows. The high Reynolds number pump facility (five-row, axial flow) is used within the test section of the Garfield Thomas water tunnel for blade-to-blade flow-field and cavitation studies in blade tip/end wall regions. It operates at speeds of up to 15.5 m/s and blade Reynolds numbers of up to 6 × 106. The centrifugal pump test facility (closed-circuit, quiet, noncavitating control valve) has an inlet casing of 12 in. diameter and an exit casing of 29 in. diameter. It is used for pump performance studies, including acoustic and vibration measurements. University of Michigan The University of Michigan towing tank is located in Ann Arbor, Michigan. It is a 6.7 m wide, 3.05 m deep, and 109.7 m long basin with a plunger wave maker at one end and a wave-absorbing beach at the other. The carriage has a maximum speed of 6.1 m/s. The wave maker can generate waves 0.25 m high and up to 8 m in length. University of New Orleans The University of New Orleans towing tank is located in New Orleans, Louisiana. The tank is 4.6 m wide, 2 m deep, and 38.3 m long with a flap-type wave maker at one end and a wave-absorbing beach at the other. The carriage has a maximum speed of 3.66 m/s. The wave maker can generate regular, transient, and irregular waves with a maximum height of 0.5 m and wavelengths of 0.3 to 22 m. U.S. Naval Academy The U.S. Naval Academy towing tank is in Annapolis, Maryland. The tank is 7.92 m wide, 4.87 m deep, and 117.5 m long with an articulated-flap wave maker at one end and a wave-absorbing beach at the other. The low-speed carriage has a maximum speed of 7.6 m/s and the high-speed carriage has a maximum speed of 14 m/s. The wave maker can generate regular, irregular, and transient waves up to 1 m high and 1 to 30 m long. Texas A&M, University of Texas The Offshore Technology Research Center is a National Science Foundation engineering research center jointly operated by Texas A&M University and the University of Texas. The basin is in College Station, Texas, and is 45.7 m long, 30.5 m wide, and 5.8 m deep. An adjustable-depth pit is located in the basin, which is 9.1 m long, 4.6 m wide, and 5.8 to 16.8 m deep. The wave maker consists of 48 articulated flaps capable of producing regular, irregular, focused, and short-crested waves. Waves up to 0.9 m in height with a period of 0.5 to 4.0 s can be produced. A current of up to 0.6 m/s can be generated.

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An Assessment of Naval Hydromechanics Science and Technology University of Minnesota The Saint Anthony Falls Laboratory (SAFL) of the University of Minnesota in Minneapolis is equipped with three water tunnels. The 6-in. water tunnel was originally designed to model the NSWCCD 36-in. water tunnel. The tunnel is currently modified to have a 190 mm × 190 mm test section and a maximum flow speed of about 8 m/s. The 10-in. free jet water tunnel was specially designed to perform studies of supercavitating flow at very low cavitation number, of the order of 0.01. The maximum attainable velocity is about 15 m/s. This tunnel has a unique design. A free jet of about 250 mm (10 in.) in diameter and 1,000 mm long is created in a test section approximately 600 mm in overall diameter. This water tunnel has a nonrecirculating flow that aspirates the test section in passing through it, thus providing a convenient means of obtaining reduced test section pressures. The 1,270 mm long high-speed water tunnel is a recirculating flow facility with a 190 mm × 190 mm test section. It can be operated in either a free surface mode or a closed jet mode at a maximum speed of 30 m/s with a turbulence level of less than about 0.3 percent. The maximum test section pressure is 4 bars. The tunnel has several unique features, including a special gas removal system that can remove as much as 4 percent by volume of injected air. This allows the gas content in the tunnel to increase from 2 to 15 ppm in about four hours. In its present operating mode, the test section also has a separate acoustic tank containing an array of hydrophones for acoustic studies. The tunnel is equipped with a special vortex nozzle to measure the tensile strength of the water, a phase Doppler anemometer for bubble size measurements, a laser Doppler anemometer system, and a force balance. It is driven by a 150 hp motor and has a specially designed and built axial flow pump that is extremely quiet and highly resistant to cavitation. The SAFL also has a multipurpose main test channel. This is the highest capacity open channel facility in the laboratory (76 m long × 2.7 m wide × 1.8 m deep). It has its own intake structure that is capable of inflows up to 8.5 m³. The channel can be used either as an open channel with flow depth controlled by a downstream tailgate, as a towing tank, or as a wave tank. This facility has a towing carriage that operates at a constant velocity up to 6.1 m/s. The wave maker can make waves up to 1 m (peak to trough). Boundary layer research with zero background noise can be conducted in the SAFL rising body facility, consisting of a vertical standpipe 24 m high and about 1 m in diameter. A wire-guided buoyant body can be released at the bottom and captured at the top. California Institute of Technology The facilities at the California Institute of Technology in Pasadena, California, include three water tunnels. The high-speed water tunnel has two working sections—0.3 m diameter circular and rectangular with walls adjustable up to 0.15 m wide × 0.76 m high. Maximum velocities in these sections are about 27 m/s and 18 m/s, respectively. Pressure can be varied over the range from vapor pressure to 2 atm. The free surface tunnel has a square section 0.5 m × 0.5 m and a maximum velocity of about 7 m/s. The low-turbulence tunnel has a test section 0.3 m × 0.3 m, a maximum velocity of 8.5 m/s, and pressure variable from 0.1 to 1.3 atm. This tunnel has a right-angle drive for propeller observations. Massachusetts Institute of Technology The Massachusetts Institute of Technology marine hydrodynamics water tunnel, in Cambridge, Massachusetts, has a closed-jet test section 0.5 m × 0.5 m × 1.5 m long with large viewing windows. The maximum velocity is 10 m/s and the minimum pressure is 0.1 atm. The tunnel can be operated with

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An Assessment of Naval Hydromechanics Science and Technology a free surface or fully flooded. Instrumentation includes an updated LDV system for in-depth flow field measurement and correlation with theory for both propellers and foil sections. The latest addition is a special test section for waterjet pump performance analysis. University of Iowa The Iowa Institute of Hydraulics Research at the University of Iowa in Iowa City, Iowa, has a towing tank 3 m wide, 3 m deep, and 100 m long. The drive carriage and model trailer are cable-driven, with a speed range of 0 to 3 m/s. The drive carriage houses equipment for conventional analog-digital data acquisition such as dynamometers, wave gauges, and multihole pitot probes. There is also instrumentation on board for particle image velocimetry (PIV) data acquisition including a PIV vector processor and hardware for automated movement of traverses for equipment (sensor) positioning. The instrumentation includes a four-channel dynamometer; linear potentiometers for model attitude measurement; capacitance, acoustic, and servo-mechanism probes for wave elevation measurements; differential pressure transducers and multihole pitot probes for flow-field velocity and pressure measurements; and a towed PIV system. The wave maker is capable of generating regular and irregular waves, with wavelengths of 0.25 to 6 m and amplitudes of 0 to 15 cm.