Field Research Facility Research Articles

FRF Spectrum: TMA with Kitaigorodskii's f-4 Scaling

This paper describes the development of a mathematical function which represents the spectrum of wind-generated gravity waves in water of arbitrary depth. The derivation parallels that of the TAM spectrum. The primary difference is that Philips' (1958) model for saturation at high frequencies is replaced by Kitaigorodskii's (1983) model. This spectrum incorporates wind speed directly into the formulation and is consistent with an fE-4 power law scaling for deep water. In its raw form the new model requires four internal constraints (gravity, depth, wind speed and peak frequency), and has four model coefficients. Values for the coefficients are determined for 1,022 observations of wave spectra made at the Corps of Engineers Field Research Facility (FRF) in depths of 19, 8.5 and 6m. The coefficients are then correlated with dimensionless combinations of the physical parameters associated with the spectrum to see if the number of coefficients can be reduced. If three of the coefficients are held constant at their mean values, a direct relationship to wave steepness is obtained for the forth coefficient that is related to the peakedness of the spectrum.

Downhole seismic source

A prototype model of a downhole controlled seismic source has been built and field tested. This instrument is a swept‐frequency, penumatically powered seismic source that operates in the 10 to 100 Hz range. This particular version is a vertical‐dipole source and generates vertically polarized shear waves. The instrument is an improved version of a downhole monofrequency source first tested in the crust of Kilauea Lava Lake, Hawaii, in 1981. The present prototype source was field tested recently at the Chevron Oil Field Research facility in La Habra, California. Data from this test, combined with calculations for a full‐scale instrument, indicate that considerable amounts of energy can be coupled into the ground with this type of downhole source. Signals from these prototype sources are easily detectable at distances of 150 m or more. A larger version of the source is currently being designed and fabricated for use in 0.20 m diameter holes, and it will theoretically have a range 30 times greater than the current prototype model. This new seismic source has applications in scientific studies related to the Continental Scientific Drilling Program. The source also has applications in locating magma bodies for the Magma Energy Program and in evaluating oil reservoirs.

Observations of local wind effects on longshore currents

Two sets of nearshore current data are available from measurements made at the Coastal Engineering Research Center's (CERC) Field Research Facility (FRF). These data are examined to characterize the nearshore currents at the FRF site and to identify the processes which contribute to the total current vector. The data indicate that local winds and atmospheric pressure fields can be important factors contributing to nearshore currents. Quantitative evidence is presented which shows a direct relationship between the mean longshore current and mean longshore wind speed. For coastal engineering studies which require estimates of nearshore currents, it is recommended that meteorological factors be included in the estimation techniques.

Field Data on Seaward Limit of Profile Change

Many coastal engineering problems require an estimate of the seaward limit of sediment transport, defined as the minimum depth at which no measurable change in water depth occurs. A procedure to estimate this limit depth was evaluated using measurements collected at the Coastal Engineering Research Center's Field Research Facility located on the Atlantic Ocean. The data consisted of measured wave characteristics and accurate repetitive nearshore surveys which extended out to a depth of 30 ft (9 m). Ten unique data points were used in the evaluation with measured limit depths ranging from 18 to 21 (3.9 to 6.4 m). These depths were overpredicted by an average of 4.6 ft (1.4 m). This difference could be reduced to 1.3 ft (0.4 m) by adjusting the coefficients in the equation. A reasonable correlation was also obtained using a simple multiple of wave height.

High Wave Grouping in Shallow Water

Characteristics of groups of high ocean waves are studied in varying water depths using field measurements and laboratory simulations. Field data were collected from a shore‐perpendicular line of gages at the Coastal Engineering Research Center Field Research Facility during one storm with onshore winds. Laboratory data were obtained over a plane 1:30 slope by generating the energy spectrum measured offshore in the field. Parameters indicative of wave grouping are observed to vary little outside the surf zone, but decrease greatly after wave breaking occurs. Field and laboratory parameters are generally consistent although some laboratory parameters sensitive to details in the record appear to be distorted by standing wave oscillations in the flume. In particular, the modulation period or time lag between successive groups and the length of the group containing the highest wave in the record are distorted in the laboratory.

DUCK82 - A COASTAL STORM PROCESSES EXPERIMENT

In recent years, several field experiments have been conducted to define nearshore processes and sediment transport patterns under "normal" wave and wind conditions. Large arrays of wave and current measuring sensors, combined with bathymetric surveys, have provided preliminary evidence of complex relationships between forcing processes and sediment response. To date, however, lack of both rugged instrumentation and a means to survey nearshore areas during high wave conditions have precluded measurements of storm-related nearshore processes. To document the response of a typical East Coast site to extratropical storms (northeasters), a cooperative experiment known as DUCK- 82, was conducted in October, 1982 at the Field Research Facility (FRF) of the U. S. Army Engineer Waterways Experiment Station, Coastal Engineering Research Center, Vicksburg, Miss. Participating in the experiment were investigators from the FRF, the 0. S. Geological Survey, Oregon State University, and the University of Washington. Newly developed sensors and equipment were deployed which, for the first time, allowed a comprehensive analysis of the processes affecting the magnitude and time scale of short-term nearshore response.

LONGSHORE VARIABILITY OF WAVE RUN-UP ON NATURAL BEACHES

The longshore variability of wave run-up from a natural beach is examined using data from a large field experiment at the Field Research Facility in Duck, North Carolina, in October, 1982. Two particular runs were selected for intensive analysis. These were chosen to represent a dissipative and a reflective surf zone condition, so have I ribarren numbers 0.97 and 1.81 respectively. The dissipative data run showed much more uniform statistics in the longshore than did the reflective run. Also, the dissipative run was dominated by the infragravity band energy while the reflective run was dominated by the incident band. Selection of several important frequency bands for frequency-domain EOF analysis showed that the lower frequency peaks appeared to be associated with leaky modes (very long longshore wavelengths) and the pier had little influence. On the other hand, higher frequencies were clearly influenced by the pier in both amplitude and phase. An interesting subharmonic peak from the reflective run appeared to be a low (but not zero) mode standing edge wave. A new technique,time exposure photography, is introduced. It allows the quick determination of longshore variability such as would be produced by a dominant standing edge wave. It can also be used to image offshore bathymetry and sand bar systems.

TIME SCALES OF NEARSHORE PROFILE CHANGES

Time scales of nearshore profile change are examined using a unique set of highly accurate surveys collected over a 3% year period at CERC's Field Research Facility. The data are analyzed in terms of the formation and movement of the nearshore bars and with empirical eigenfunctions. The largest and most rapid changes in the profiles occurred during storms. The inner bar (depth of -0.6 to 1.5 m, 1.6 to 4.5 ft) moved offshore during even minor storms and recovered relatively quickly. The outer bar (depth of 3 to 4 m, 9 to 13 ft) formed during the largest storms and recovery was considerably slower, requiring six months or longer. The eigenvector analysis confirmed the importance of storms but identified a seasonal shift of material from the beach and inner bar to the offshore.

WAVE MEASUREMENT WITH DIFFERENTIAL PRESSURE GAUGES

The potential error of estimating the small pressure gradient under a directional wave field through the subtraction or comparison of relatively large total-head signals from adjacent pressure transducers in an array is avoided through the use of differential pressure transducers which measure directly the pressure gradients. A device which utilizes four differential pressure tranducers placed orthogonally about one absolute pressure transducer, (the "DPG"), was developed and field-tested at the U.S. Army Corps of Engineers Coastal Engineering Research Center Field Research Facility, Duck, North Carolina. The first five directional Fourier coefficients of the directional ocean spectra were developed from the DPG data, and although no other in_ situ directional wave monitors were available for comparison, the directional peak determined from the DPG agreed well with simultaneous High Frequency (HF) radar data. The DPG instrument is about one-half the size and less than one-sixth the weight of conventional pressure sensor arrays. The field establishment of the orientation of directional-measuring instruments is also discussed.

Field intercomparison of nearshore directional wave sensors

Five measurement strategies (four in situ, one remote) for estimating directional wave spectra were intercompared in a 1980 experiment at the Coastal Engineering Research Center's Field Research Facility in Duck, NC. The systems included two pressure sensor/biaxial current meter combinations (different manufacturers), a triaxial acoustic current meter, an SXY gauge (square array of four pressure sensors), and a shore-based imaging radar. A detailed error analysis suggests sources for differences in estimated wave spectra from the different instruments; in general, they intercompare favorably. The major deviation among in situ gauges was associated with the triaxial acoustic current meter. Reliance on a vertical velocity measurement (instead of a direct pressure or sea-surface elevation measurement) can contribute additional uncertainty in directional spectral estimates. The imaging radar was successful in distinguishing multiple wave trains at the same frequency, which was not possible with the simple spectral estimation analysis applied to in situ data. However, the radar is not useful in providing accurate estimates of spectral density, nor in distinguishing multiple wave trains of different frequencies coming from the same direction. Selection of a measurement strategy for a particular need depends on the precise data requirements for that application. Although the five tested intercompared well, in practice not all are equally suitable for every application.

NEARSHORE SUSPENDED SEDIMENT LOAD DURING STORM AND POSXTSTORM CONDITIONS

As part of the DUCK-X experiment at the CERC field research facility at Duck, North Carolina in September, 1978, suspended sediment measurements were made along the CERC pier. In situ bulk water samples were collected during a moderate northeast storm and two days later during post-storm wave conditions. Concentrations varied from approximately 0.01 g/1 to over 10.0 g/1. Vertical arrays of suspended sediment samples indicated that concentration decreases rapidly up to two meters above the bed, then remains relatively constant, reflecting the nature of the suspension; intermittent suspension of sand near the bed, and continuous washload higher in the water column. Concentrations were at a maximum during storm conditions when measured values were 3 to 5 times higher than during non-storm conditions. The total load of sediment in a pier cross section during sampling periods in storm and post^storm conditions was calculated from arrays of 49 samples each. With H1/3 exceeding 2.3 HI and the surf zone width over 300 m during the storm, the total load of sediment in suspension was approximately 10 times higher than during poststorm conditions (Hi 73 - 1.2 m and surf zone width approximately 100 m) . Estimates of the longshore flux of suspended sediment indicate that as much as 60 times more sediment was transported during storm than during post-storm conditions. Longshore transport of sediment measured from 5 cm above the bed to the surface reached the equivalent of 22,330 m^/day. This value corresponds very closely to longshore transport predicted from wave energy flux. During post-storm conditions, on the other hand, transport of suspended sediment accounts for less than one-third of the transport predicted from wave energy flux.

The Icefield Ranges Research Project, 1975 And 1976

During 1975 and 1976, research staff and students occupied the base camp of the Icefield Ranges Research Project (IRRP) at Kluane Lake (61 N, 138 30 W) from early April to mid-October. Altogether 126 individuals representing universities and institutes in Canada and the United States made use of the field research facilities during these two years. A decrease from 3,200 mandays of accommodation and subsistence in 1975 to 2,799 in 1976 reflected increasing difficulties in obtaining funds for field research in the North. Adverse weather in the St. Elias Mountains in 1975 caused several projects to be severely restricted. Poor radio conditions and aircraft operational problems provided further difficulties. At one time both of AINA's ski-equiped Helio-Courier aircraft were out of commission. ... In 1976, however, generally good weather conditions prevailed, radio communications were vastly improved, the aircraft remained airborne and the projects prospered. Several improvements were made to the base camp itself. ... In cooperation with Parks Canada and Environment Canada, a year-round meteorological programme was carried out during 1975 and 1976 at the base camp by the camp Manager, A. Williams. ... [The following research programs are described: High Altitude Physiology Studies (HAPS), Glacier inventory of St. Elias Mountains, Glacier geophysics projects, Environmental controls on geomorphic processes, and Study of small mammals.]

Casing Strain Tests of 13 3/8-in., N-80 Buttress Connections

Introduction In typical oilfield casing design work, engineers specify the force that a casing must withstand. For example, it is generally necessary for each section of a casing string to support the weight of all the pipe that is suspended below. The force and stress are known quantities, and the resulting pipe deformation, called strain, can be calculated using the physical properties of the casing steel. However, there are situations where the casing loading is of a displacement type, for which the deformation is specified. In this case, the stress is unknown. An example is surface casing subjected to soil subsidence. In soil subsidence, the compacting soils will tend to strain the adjacent casing, and the amount of resulting pipe strain can be essentially independent of the casing properties. As a part of the Prudhoe Bay permafrost-thaw subsidence studies, Exxon Co., U.S.A., and Atlantic Richfield Co. conducted a testing program to determine the amount of casing strain that would cause failure. The casing tested, 13 3/8-in., N-80, 72-lb/ft buttress, is used as surface casing in many Prudhoe wells. Testing Procedure Three tension tests and three compression tests were made with strain gauges installed as shown in Fig. 1. The compression specimens were of relatively short length (2 1/2 ft) to prevent Euler buckling. (Actual surface casing will not column buckle if it is laterally supported by cement and the formation.) The tension specimens used welded end fixtures to provide a means of attachment to the test machine. The casing tested was 13 3/8-in.-OD, controlled yield N-80 (normalized), 72-lb/ft buttress, selected from mill runs for Prudhoe Bay. Both mill- and field-end connections were constructed by the torque-turn method, which specifies both minimum turns and minimum torque required for a satisfactory connection. Mill ends were made at the mill with an epoxy thread-lock compound, while the field ends used a teflon thread compound. Based on metallurgical test coupons, the API yield strength (0.5-percent strain) of this casing ranged from 83 to 92 ksi. The ultimate strengths ranged from 110 to 122 ksi and occurred at strains of 12 to 16 percent. Elongation (maximum strain) was 25 to 35 percent, indicating good ductility. The post-yield behavior was uniform, with plastic moduli of 550,000 to 850,000 psi. Wall plastic moduli of 550,000 to 850,000 psi. Wall thicknesses were uniform, and averaged 0.495 in. (API minimum/nominal is 0.450/0.512 in.2) The samples were tested at the U. of California Field Research Facility at Richmond. Load increments of 50,000 to 200,000 lb were spaced 5 to 30 minutes apart. Tension Test Results Fig. 2 shows the tension axial-strain readings for the D locations, which are located on the pipe 7 in. from the buttress collar. There were three tests, and the mill-end and the field-end gauges provided six sets of data. Test 1 was terminated without failing the casing at a load of 2,250,000 lb and with pipe strains of 3.6 percent (mill end) and 3.7 percent (field end). Tests 2 and 3 experienced fractures near the last perfect thread of the mill end at loads of 2,350,000 and 2,250,000 lb, respectively. The mill-end strains were 3.6 to 4.2 percent. Fig. 3 shows a comparison of strain data taken at various locations on the casing. JPT P. 1301

Fecundity and Egg Survival of the Central Johnny Darter (Etheostoma nigrum nigrum) in Southern Michigan

WAITE, E. R. 1911. Antarctic fishes. British Antarct. Exped., 1907-09. Repts. Sci. Invest. Biol. 2 (2) :11-16. WOHLSCHLAG, D. E. 1960. Metabolism of an Antarctic fish and the phenomenon of cold adaptation. Ecology 41(2) :287-292. . 1961a. Growth of an Antarctic fish at freezing temperatures. Copeia 1961 (1) :11-18. 1961b. General ecology and physiology of Antarctic fishes. In Science in Antarctica, Part 1, The Life Sciences in Antarctica. U. S. Natl. Acad. Sci. Publ. 839:113-114. 1962. Antarctic fish growth and metabolic differences related to sex. Ecology 43 (4): 589-597. . 1963a. An antarctic fish with unusually low metabolism. Ibid. 44(3) :557-564. . 1963b. The biological laboratory and field research facilities at the United States Station. Antarctica. Polar Record 11(75):713-718. 1964. Respiratory metabolism and ecological characteristics of some fishes in McMurdo Sound, Antarctica. In Biology of the Antarctic Seas. Am. Geophysical Union, Antarct. Res. Ser. 1:33-62.

The biological laboratory and field research facilities at the United States “McMurdo” station, Antarctica

In 1958, at the close of the International Geophysical Year, the National Science Foundation (NSF) of the United States initiated long-term plans for the support of Antarctic biological research. These plans included the erection and outfitting of a modest, but modern, biological laboratory at the United States station at “McMurdo” on Ross Island in the late summer and early winter 1959. With the increasingly diversified biological research programmes, and with the active construction and supply programmes in subsequent years, the biological laboratory has now become one of the largest Antarctic research facilities for a single scientific discipline.