A series of physical models consisting of three different diameter pipes at the same 4% slope were studied at the Utah Water Research Laboratory (UWRL). Various combinations of air flow and head on the pipe were used to determine the effect of pipe diameter, head, and air flow on the behavior of air bubbles introduced into the pipes and to determine the venting capacity of the pipes. It was determined that neither bubble velocity nor bubble length changes with pipe diameter or head changes within the range tested. It was also determined that bubble velocity and length will increase with increased air flow. Bubble velocity also increased with increasing bubble length consistent with prior research. Overall the venting capacity of a pipe is dependent upon having a large enough pipe to prevent slug flow. A procedure was developed to aid in the sizing of submerged vent piping during the design of pipelines based on the data collected during this study and utilizing prior research.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20694号 / 工博第4391号 / 新制||工||1682(附属図書館) / 京都大学大学院工学研究科都市環境工学専攻 / (主査)教授 米田 稔, 教授 清水 芳久, 准教授 須崎 純一 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

This study combined documentation of four boat propeller scar types in Halodule wrightii seagrass beds in Mosquito Lagoon, Florida with manipulative field experiments to document scar recovery times with and without restoration. Scar types ranged from the most severe scar type (Type 1) with trench formation which had no roots or shoots in the trench, to the least severe (Type 4) scars that had no depth, intact roots and shoots shorter than the surrounding canopy. For 110 measured existing scars, the frequency of each scar type was 56% for Type 1, 10% for Type 2, 7% for Type 3, and 27% for Type 4. In the first manipulative experiment, experimental scars were created to document the natural recovery time of H. wrightii for each scar severity within one year. Type 4 scars recovered to the control shoot density at 2 months, while Types 1, 2, and 3 scars did not fully recover in one year. Mean estimated recovery for H. wrightii is expected in 25 months for Type 1, and 19 months for Types 2 and 3. For the second manipulative experiment, three restoration methods were tested on the Type 1 scars over a 1 year period. Restoration methods included: (1) planting H. wrightii in the scar trench, (2) filling the trench with sand, and (3) filling with sand plus planting H. wrightii. There was complete mortality of all transplants at 2 months and only 25% of scars retained fill sand after 1 year. With dense adjacent seagrass beds, natural recovery was more successful than any of my restoration attempts. Thus, I suggest that managers should concentrate on preventing seagrass destruction rather than restoration.

An experimental scale model study was conducted to investigate the onset of fluidelastic instability in a tube array subjected to axisymmetric jet flow. A tube array was constructed using aluminum tubes with 44.45 mm outer diameter, $D$, which were arranged in a square pattern with 88 mm pitch, $P$. The pitch to diameter ratio, $P/D$, was approximately 2.0. The tubes were flexibly mounted using threaded rod and tuned to a first mode natural frequency, $f_n$, of 9 Hz. Auxiliary damping devices were added to each tube, and tuned, to achieve a damping ratio, $\zeta$, of 1 % of critical. The mass damping parameter, $m(2 \pi \zeta)/(\rho D^{2})$, of the tube array was 27.9. The tube array was tested under uniform flow conditions in McMaster University's 2 ft wind tunnel to establish the critical reduced velocity, $V_{cr}/(f_n D)$, of 30.0 at the onset of fluidelastic instability. The uniform flow test established a basis for comparing the results with the existing literature and evaluating the validity of the proposed partial admission calculation. The tube array was also tested in open air using an axisymmetric jet, with two different physical arrangements, the first with the jet aimed between tubes and perpendicular to the tube spans and the second with the jet aimed at a tube face and perpendicular to the tube spans. In each case the jet flow velocity was incrementally increased to characterize the onset of fluidelastic instability. To characterize the flow dispersion through the tube array a series of velocity profile measurements were also collected. The measured velocity profiles were used to estimate the spanwise function of transverse average gap velocity, $\bar{V}(x)$, which was used to predict the equivalent critical uniform gap flow velocity, $V_{cr}$, using the concept of partial admission. The predicted $V_{cr}$ values showed reasonable agreement with the experimental results. However, the prediction method did indicate instabilities in tube rows where instability was not actually observed. A simplified prediction approach was developed which was based on using a predicted three dimensional velocity profile, $V(x,y)$, at the $z$ location of the first row tube gap, under the assumption of free field conditions, to calculate an estimate of the spanwise function of transverse average gap velocity, $\bar{V}(x)$. Although the predictions of $V_{cr}$ agreed reasonably well with the experimental results, first row instabilities were not observed in any of axisymmetric jet flow experiments. Therefore, this method can be used to estimate the the critical uniform gap velocity, $V_{cr}$, but not the spatial location of the instability. Based on the results of the experiments and calculations, adoption of the modified partial admission formula is recommended and possible avenues for further investigation and verification are suggested. / Thesis / Master of Applied Science (MASc)

No description available.

Yes / In this paper, an analytical model that represents the streamwise velocity distribution for open channel flow with submerged flexible vegetation is studied. In the present vegetated flow modelling, the whole flow field has been separated into two layers vertically: a vegetated layer and a non-vegetated free-water layer. Within the vegetated layer, an analysis of the mechanisms affecting water flow through flexible vegetation has been conducted. In the non-vegetated layer, a modified log-law equation that represents the velocity profile varying with vegetation height has been investigated. Based on the studied analytical model, a sensitivity analysis has been conducted to assess the influences of the drag and friction coefficients on the flow velocity. The investigated ranges of drag and friction coefficients have also been compared to published values. The findings suggest that the drag and friction coefficient values are non-constant at different depths and vegetation densities, unlike the constant values commonly suggested in literature. This phenomenon is particularly clear for flows with flexible vegetation, which is characterised by large deflection.

No / Vegetation remains to be an important factor that can hinder the river flow. It needs innovative management scheme, in order to adapt these changes and ensure sustainability of their multiple usages. Vegetation plays an important role in floods and droughts adaptation within river system to alleviate any flood that may propagates from river to its surrounding. Vegetation within river can also retard its flow to cause building-up of deposition, and further adding to uncertainty of water use under extreme droughts. Due to these, it is important to study and understand vegetation drag behaviour toward flow in order to prevent flood risk and water security with hydrological drought in the basin and any other negative impact caused by it. In this study, an analytical approach for river flooding has been studied by improved representation of drag coefficient CD in flow velocity distribution modelling. The analysis of flow parameters, i.e. Reynolds number, on the drag coefficient CD has been conducted. The presented model has been used and analysed in open channel flows with flexible vegetation. In modelling, the flexible vegetated channel layers were divided into vegetation, top of vegetation and water layer zones in the model. The balance of forces for each layer has been established by validation using different reported measured data. The modelling results showed reasonably corresponding prediction of velocity profile in flows with flexible vegetation.

Yes

Yes / The subject area of the Europe's Lost Frontiers project, the submerged landscape of Doggerland, is inaccessible and the data by which we can understand it is complex and hard for the non-specialist to understand. In order to be able to present the project at public events, an Augmented Reality sandbox was constructed, which records the shape of sand in a box, interprets it as a landscape inhabited by humans, animals and plants, and projects this simulated land back on to the sand. Different software packages can be used to highlight the effects of climate change or provide examples of the different types of evidence available to archaeologists researching submerged landscapes. The end result is an interactive, accessible display which attracts all ages and can be used as a starting point to conversation regarding the project's archaeological, scientific and technological aspects.

The numerous benefits that wetlands provide make them essential to ecosystem services and ecological functions. Historically, wetland losses have been caused by natural and anthropogenic changes. In Texas, nearly 50% of coastal wetland habitat has been lost since the 1930s and losses in the Lower Neches watershed have been some of the most extensive. Restoration is a way to mitigate these losses and can be accomplished in many ways. Each restoration design creates different aquatic habitats that can influence both submerged aquatic vegetation (SAV) and faunal communities. The restoration of the Lower Neches Wildlife Management Area (LNWMA) has created the conditions for the growth of the invasive submerged macrophyte, Myriophyllum spicatum (Eurasian watermilfoil) which may be competing with the native aquatic grass, Ruppia maritima (widgeongrass) for essential nutrients. In this study, an attempt was made to link restoration design with both SAV and aquatic fauna community structures by using a throw trap to characterize assemblages observed in three different types of restored marshes. We also performed two controlled mesocosm experiments in 0.5 gal aquariums to determine growth inhibition by M. spicatum on R. maritima. Analyses using Kruskal-Wallis non-parametric test determined that temporal variations in fauna and SAV community composition was greater than any restoration effect. Discriminant Function Analyses (DFAs) determined two to three key faunal species that best predicted association among restoration designs, but linear regressions could not determine any consistent relationship between individual species density and biomass of the dominant SAV species, M. spicatum. For the mesocosm experiments, M. spicatum inhibited the biomass production and branch count of R. maritima when the two species are grown together (ANOVA, p = 0.004 and 0.003, respectively). Changes in SAV assemblages due to competition and habitat characteristics could play a major role in determining faunal community. In order to minimize the temporal effect observed and better determine any habitat pattern that may be present, a much longer study is necessary.