R.T. Jarman

Bio: R.T. Jarman is an academic researcher from Central Electricity Generating Board. The author has contributed to research in topics: Chimney & Silt. The author has an hindex of 4, co-authored 8 publications receiving 51 citations.

Sea Carousel--A Benthic, Annular Flume

Abstract: A benthic annular flume (Sea Carousel) has been developed and tested to measure in situ the erodibility of cohesive sediments. The flume is equipped with three optical backscatter sensors, a lid rotation switch, and an electromagnetic (EM) flow meter capable of detecting azimuthal and vertical components of flow. Data are logged at rates up to 10·66 Hz. Erodibility is inferred from the rate of change in suspended sediment concentration detected in the annulus. The energy-density/wave number spectrum of azimuthal flow showed peaks in the energy spectrum at paddle rotation wave numbers (k) of 14 and 7 m −1 (macroturbulent time scales) but were not significant. Friction velocity ( U *), measured (1) at 1 Hz using a flush-mounted hot-film sensor, and (2) derived from measured velocity profiles in the inner part of the logarithmic layer gave comparable results for Ū * −1 . At higher values of U*, method (2) underpredicted by up to 20%. Method (1) showed radial increases in Ū * in the annulus for Ū y > 0·32 m s −1 . Radial velocity gradients were proportional to ( Ū y − 0·32 m s −1 ). Maximum radial differences in U * were 10% for Ū y = 0·5 ms −1 . Suspended sediment mass concentration ( S ) in the annulus resulted in a significant decrease (10·5%) in Ū * derived by method (1) over the range 0 S −1 . These decreases were not evident in method (2). Method (1) may, therefore, be subject to changes in stress sensor calibration with changes in S . Subaerial deployments of Sea Carousel caused severe substrate disturbance, water losses, and aeration of the annulus. Submarine deployments produced stable results, though dispersion of turbid flume water took place. Results clearly demonstrated the existence of ‘Type I’ and ‘Type II’ erosion documented from laboratory studies.

Sedimentary indicators of lake-level changes in the humid temperate zone: a critical review

Abstract: Evidence for lake-level changes derived from stratigraphic sequences in cores from littoral zones is reviewed in the context of lake sedimentation processes. These are illustrated with published case-studies which have used multiple-core data. Possible approaches for choosing optimum sites are examined. Sedimentation controls which may change over time are also considered; these include, wind strength and frequency, wind exposure, water depth and underwater slopes, sediment type and littoral vegetation. A final section discusses how lake-level studies can be optimised so that results can be used with confidence in paleoclimatic and paleohydrological reconstructions. Sedimentary data showing shifts in littoral vegetation along shallow underwater gradients in sheltered margins, and transitions between sediment compositions linked to specific hydrological conditions give the strongest lines of evidence.

Code manual for CONTAIN 2.0: A computer code for nuclear reactor containment analysis

Abstract: The CONTAIN 2.0 computer code is an integrated analysis tool used for predicting the physical conditions, chemical compositions, and distributions of radiological materials inside a containment building following the release of material from the primary system in a light-water reactor accident. It can also predict the source term to the environment. CONTAIN 2.0 is intended to replace the earlier CONTAIN 1.12, which was released in 1991. The purpose of this Code Manual is to provide full documentation of the features and models in CONTAIN 2.0. Besides complete descriptions of the models, this Code Manual provides a complete description of the input and output from the code. CONTAIN 2.0 is a highly flexible and modular code that can run problems that are either quite simple or highly complex. An important aspect of CONTAIN is that the interactions among thermal-hydraulic phenomena, aerosol behavior, and fission product behavior are taken into account. The code includes atmospheric models for steam/air thermodynamics, intercell flows, condensation/evaporation on structures and aerosols, aerosol behavior, and gas combustion. It also includes models for reactor cavity phenomena such as core-concrete interactions and coolant pool boiling. Heat conduction in structures, fission product decay and transport, radioactive decay heating, and the thermal-hydraulic and fission product decontamination effects of engineered safety features are also modeled. To the extent possible, the best available models for severe accident phenomena have been incorporated into CONTAIN, but it is intrinsic to the nature of accident analysis that significant uncertainty exists regarding numerous phenomena. In those cases, sensitivity studies can be performed with CONTAIN by means of user-specified input parameters. Thus, the code can be viewed as a tool designed to assist the knowledge reactor safety analyst in evaluating the consequences of specific modeling assumptions.

Erosion of Cohesive Sediments: Resuspension, Bed Load, and Erosion Patterns from Field Experiments

Abstract: New field data on cohesive sediment erosion is presented and discussed, with particular focus on partitioning the total erosion into resuspension and bed load. The data were obtained using a recently developed in situ flume of the National Institute of Water and Atmospheric Research, New Zealand. The erosion rate is estimated from direct measurements of bed surface elevations by acoustic sensors, whereas resuspension rate is obtained using data on sediment concentrations measured by optical backscatter sensors. The bed- load contribution to the total erosion rate is evaluated from the conservation equation for sediments. To test repeatability, the data from the in situ flume are compared with those from a previous version of the flume. The results show that comparative studies of in situ flumes and standardized deployment procedures enable direct comparison of experimental data on cohesive sediment erosion. Overall, the data show that a commonly used assumption that the erosion rate is equal to the resuspension rate is not always valid as bed load plays a significant role in cohesive sediment erosion. The data also highlight the importance of clay content and other sediment physical characteristics in the sediment mixture.