scholarly journals Experimental and numerical studies of boat waterjets with increased seakeeping performance

2020 ◽  
Vol 4 (394) ◽  
pp. 31-42
Author(s):  
Valeriy A. Rodionov ◽  
Andrey V. Sverchkov ◽  
Alexey A. Rudnichenko ◽  
Fedor E. Mamontov ◽  
Andrey A. Ermolaev
Keyword(s):  
Weather Conditions ◽  
Discrete Variable ◽  
Bottom Section ◽  
Numerical Studies ◽  
Run Off ◽  
Variable Bottom ◽  
Seakeeping Performance ◽  
Sharp Force ◽  
Pressure Water ◽  
Better Than

Object and purpose of research. The object of the research is a fundamentally new waterjet, intended for installation on ships of increased seakeeping performance with discrete-variable bottom deadrise. The purpose of the research is to develop and test three waterjet designs that can be installed on vessels with large deadrise, operating in severe weather conditions. Materials and methods. Experimental data of waterjet tests as a part of self-propelled models obtained in deep-water and cavitation test tanks of KSRC. Numerical simulation of the flow in water conduits of full-scale vessel taking into account the waterjet performance. Main results. As a result of the performed experimental and computational studies, the characteristics of three waterjet designs with partial-pressure water inlets were obtained: two waterjets with isolated single-elbow water ducts and inlets on the bottom section with medium deadrise, "II"design; two waterjets with combined water duct and inlets on the bottom section with maximum deadrise and double jet, “X” design; single waterjet with bifurcating two-elbow water duct and a pair of water inlets on the bottom section with maximum deadrise, “Y” design. Conclusion. The studies have shown that all the developed innovative waterjet designs are practically equal to conventional ones (or even better than them), and air suction creates a smooth, rather than a sharp force decrease on the impeller. The preference is given to a high-pressure water inlet with a bifurcated water inlet and a combined water conduit, because in intense waves, even if one of the inlets is aerated, the vessel will not abruptly lose speed or run off the course.

scholarly journals Development of a standard range of waterjets for vessels with high seakeeping performance

2020 ◽  
Vol 4 (394) ◽  
pp. 13-20
Author(s):  
Nikolai V. Marinich ◽  
Rodionov А. Valeriy ◽  
Anastasia A. Koval ◽  
Andrey V. Sverchkov ◽  
Fedor E. Mamontov
Keyword(s):  
Weather Conditions ◽  
Severe Weather ◽  
Discrete Variable ◽  
Bottom Section ◽  
Variable Bottom ◽  
Seakeeping Performance ◽  
Cavitation Tunnel ◽  
Sharp Force ◽  
Pressure Water ◽  
Impeller Geometry

Object and purpose of research. The object of the research is a fundamentally new waterjet, intended for installation on ships of increased seakeeping performance with discrete-variable bottom deadrise. The purpose of the research is to develop and experimentally test the impeller and water duct for a variety of waterjet design possible for installation aboard vessels with large deadrise operating in severe weather conditions. Materials and methods. Test data for waterjet impellers obtained at KSRC Cavitation Tunnel for Special Propulsors. Main results. The study made it possible to select optimal impeller geometry and develop the shapes for water inlets and water ducts of three waterjet designs with partial-pressure water inlets: two waterjets with isolated single-elbow water ducts and inlets on the bottom section with medium deadrise, "II"design; two waterjets with combined water duct and inlets on the bottom section with maximum deadrise and double jet, “X” design; single waterjet with bifurcating two-elbow water duct and a pair of water inlets on the bottom section with maximum deadrise, “Y” design. Conclusion. The studies have shown that developed waterjet impeller features good hydrodynamic and cavitation characteristics, and possible air suction creates a smooth, rather than sharp, force decrease.

Effects of short-term rain events on mobile macrofauna living on seawalls

2007 ◽  
Vol 87 (5) ◽  
pp. 1069-1074 ◽  
Author(s):  
David J. Blockley ◽  
Victoria J. Cole ◽  
Julie People ◽  
M. Gabriela Palomo
Keyword(s):  
Temporal Variability ◽  
Weather Conditions ◽  
Short Term ◽  
Run Off ◽  
Sydney Harbour ◽  
Manipulative Experiments ◽  
Negative Effect ◽  
Artificial Rain ◽  
Rain Events ◽  
Term Rain

The distribution and abundance of intertidal organisms can be affected by short-term events, such as rain. We compared the effects of rain on intertidal mobile invertebrates in four common microhabitats with differing amounts of shelter (namely beds of oysters, coralline turf, bare patches and crevices) on sea walls in Sydney Harbour. There was an effect of rain on some, but not all taxa, although this was not consistent between locations or times. Effects of rain were observed for some species of gastropods and crustaceans, but not for polychaetes. Manipulative experiments using artificial rain indicated that rain, without the presence of run-off and independent of potential temporal confounding from differences in weather conditions, has a negative effect on abundances of amphipods in coralline turf. Pulse responses by mobile organisms to short-term rain events should be considered when designing experiments looking at temporal variability and processes responsible for observed patterns of distribution of marine organisms.

Effect of Geometry Changes in an Aggressive Turbine Exhaust Delivery System

2013 ◽  
Author(s):  
Shweta Dobhal ◽  
A. M. Pradeep ◽  
Bhaskar Roy
Keyword(s):  
Delivery System ◽  
Pressure Rise ◽  
Exhaust System ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
System A ◽  
Numerical Studies ◽  
Annular Diffuser ◽  
Better Than ◽  
Turbine Exhaust

The paper reports numerical studies carried out on an aggressive turbine exhaust delivery system. A typical industrial turbine exhaust system has been used as the baseline configuration. Several geometry modifications of the diffuser system were attempted to study their effect on the diffuser performance. The geometrical modifications used were 1) Blended shapes — a blended strut-hub geometry; 2) Repositioning of the struts; and 3) contoured hub end. The performance of the diffusers has been quantified in terms of total pressure loss and static pressure rise coefficient across the diffuser. The last stage turbine tip leakage flow has been simulated by using annular casing injectors applied ahead of annular diffuser. The effect of varying the rate of injection has also been analyzed. In addition, the effect of shortening the length of the diffuser was studied. Modification-2, as stated above, has been applied on the shortened aggressive diffuser and it was observed that with injection the performance of shortened aggressive diffuser is better than that of the baseline configuration.

ENVIRONMENTAL ASPECTS OF THE ARCO ANCHORAGE OIL SPILL, PORT ANGELES, WASHINGTON1

1987 ◽  
Vol 1987 (1) ◽  
pp. 407-410 ◽  
Author(s):  
June Lindstedt-Siva ◽  
Dilworth W. Chamberlain ◽  
Eugene R. Mancini
Keyword(s):  
Far East ◽  
Weather Conditions ◽  
Environmental Aspects ◽  
Water Jets ◽  
Environmentally Sensitive Areas ◽  
Effective Operation ◽  
Large Populations ◽  
Pressure Water ◽  
Spill Site ◽  
Environmentally Sensitive

ABSTRACT On December 21, 1985, the tanker Arco Anchorage ran aground in Port Angeles Harbor. Approximately 5,960 bbl (239,000 gal) of Alaska North Slope crude oil were released from two gashes in the ship's hull. Weather conditions permitted the effective operation of containment booms and skimmers. Once the vessel was secured, first priority during the response was protection of environmentally sensitive areas to the east of the spill site, including a National Wildlife Refuge with large populations of marine birds, fishes, and invertebrates. Heaviest shoreline contamination was on Ediz Hook in Port Angeles Harbor, but oil was observed as far east as Dungeness Bay and as far west as Neah Bay. Approximately 2,000 seabirds were known to be oiled during the spill. Removal of oiled debris was a successful cleanup strategy for all beaches except Ediz Hook, and concentrations of oil in the sediments returned to background levels within weeks. Oil penetrated into coarse sediments at the most heavily oiled sites on Ediz Hook. A unique cleanup method incorporating a combination of physical agitation and high-pressure water jets was devised to remove most of the entrained oil. Concentrations of oil in these sediments and biological recruitment are being monitored. Recommendations are made to further reduce the environmental impacts of such incidents.

Dispersal and monoecy in Atriplex cinerea (Chenopodiaceae)

2001 ◽  
Vol 49 (4) ◽  
pp. 501 ◽  
Author(s):  
Petrus C. Heyligers
Keyword(s):  
New Zealand ◽  
Weather Conditions ◽  
Published Data ◽  
Herbarium Specimens ◽  
Tasman Sea ◽  
Floating Object ◽  
Migrating Birds ◽  
Selection Of ◽  
Better Than ◽  
Seasonal Weather

Atriplex cinerea Poir., indigenous to southern coasts of Australia, has occasionally been found along the shores of Cook Strait, New Zealand. Buoyancy tests have shown that most fruits stay afloat less than 5 weeks. Published data from drift bottle and drift card experiments indicate that it takes at least 300 days for a floating object to cross the Tasman Sea. It is therefore unlikely that A. cinerea fruits have arrived in New Zealand unaided. Transport on rafts of flotsam or by migrating birds are mooted possibilities. Atriplex cinerea is dioecious or monoecious. Monoecious plants are self-compatible and thus one individual could start a new population. Inspection of herbarium specimens and plants in the field showed that there is at least a one in five and possibly a better than a one in three chance that a plant is monoecious. Atriplex cinerea is hexaploid. Some plants of A. canescens (Pursh) Nutt., a polyploid species from North America, change their gender from year to year owing to the sexually labile nature of tetraploid and hexaploid genotypes. Inherent genetic factors as well as seasonal weather conditions have an influence on these changes. It would be interesting to find out whether this also happens in A. cinerea. As A. cinerea is used for saltland rehabilitation, a study of its variability could benefit the selection of better-adapted strains.

scholarly journals Rock Breaking by Conical Pick Assisted with High Pressure Water Jet

2014 ◽  
Vol 6 ◽  
pp. 868041 ◽  
Author(s):  
Liu Songyong ◽  
Chen Junfeng ◽  
Liu Xiaohui
Keyword(s):  
Numerical Simulation ◽  
High Pressure ◽  
Hard Rock ◽  
Rock Breaking ◽  
Water Jet ◽  
Cutting Efficiency ◽  
Conical Pick ◽  
Pressure Water ◽  
High Pressure Water Jet ◽  
Better Than

In the process of hard rock breaking, the conical pick bears great cutting force and wear, and the cutting efficiency is lower. Thus different combination ways of water jet and conical pick were proposed to solve this issue; for instance, water jet placed in the front of pick (JFP) and water jet through the center of pick (JCP) was researched by numerical simulation and experiments in this paper. First, the models of rock breaking were built based on SPH combined with finite element method. Then, the stress distribution of rock and the cut force of pick were analyzed when the rock broken by the conical pick assisted with the high pressure water jet. It indicates that the effect of the JCP on rock breaking is better than the JFP. At last, experiments about rock breaking with a conical pick and the JCP were conducted to verify the reliability of the simulation. It indicates that the rock breaking with the assistance of high pressure water jet cannot only reduce the pick force, but also increase the rock crushing volume.

Establishment of four pasture grasses and Siratro from seed oversown into dense and open speargrass pastures

1984 ◽  
Vol 24 (126) ◽  
pp. 360 ◽  
Author(s):  
SJ Cook
Keyword(s):  
Seedling Emergence ◽  
Weather Conditions ◽  
Panicum Maximum ◽  
Brachiaria Decumbens ◽  
Heteropogon Contortus ◽  
Pasture Grasses ◽  
Macroptilium Atropurpureum ◽  
Signal Grass ◽  
Native Pastures ◽  
Better Than

In two experiments, seed of Gayndah and Biloela buffel grass (Cenchrus ciliaris), green panic (Panicum maximum var. trichoglume), signal grass (Brachiaria decumbens) and Siratro (Macroptilium atropurpureum) was broadcast into a range of seedbeds imposed on native speargrass (Heteropogon contortus) pastures that had either been cleared of trees 4-5 years before sowing (C) or had the trees killed at sowing (K). The seedbeds were: untreated control (NP); mown to 3 cm before and at sowing (M); M followed by regular clipping (MD); burnt (B); B followed by regular clipping (BD); and herbicide (H). Seed was also sown into a cultivated seedbed (P) in C. The number of plants established 15-16 months after sowing was highest in the cultivated seedbed and lowest in seedbeds where competition from the native grasses was greatest. Competition was greater in C than in K, the native pastures in C having about three times more dry matter than those in K. Burning reduced competition but also reduced seedling emergence. It increased establishment slightly in K but not in C. The M and MD treatments failed to increase establishment over that of the NP control. Herbicides reduced competition and increased establishment in C and K, but only for signal grass and Siratro in C when drier conditions occurred in the second experiment. Siratro established better than the grasses in the presence of competition when weather conditions were favourable, but there was little Siratro or grass establishment when water deficits occurred soon after emergence, especially in C

Discussion on Operation Mode of Long Distances Gravity-Fed Pressure Diversion Project

2012 ◽  
Vol 433-440 ◽  
pp. 7125-7130
Author(s):  
Man Lin Zhu ◽  
Yan He Zhang ◽  
Tao Wang
Keyword(s):  
Operation Mode ◽  
Middle Part ◽  
Pipeline System ◽  
Long Distance ◽  
Working Pressure ◽  
Pipe Length ◽  
Hydraulic Conditions ◽  
Fluid Transients ◽  
Pressure Water ◽  
Better Than

The characteristics of long distance gravity-fed pressure water-conveying projects are long pipe length, huge changes in rise and down of pipeline arrangement, and complex hydraulic conditions. It is the water hammer that mainly influences the safe operation of such projects. Based on a real long distance gravity-fed pressure water conveying pipeline system, fluid transients processes under different operation modes were analyzed by using the method of characteristics. The pipeline longitudinal arrangement is high in two ends and low in the middle part. The research puts forward that for such pipeline arrangement using valve set in the midway of the pipeline to control the system is evidently better than that of valve at the downstream end of pipeline. In this way, pipeline working pressure can be effectively reduced, in turn, the pipe pressure grade can be decreased and the investment of the project can be reduced.

scholarly journals Ship Speed Measurement

1975 ◽  
Vol 28 (3) ◽  
pp. 368-370
Author(s):  
C. A. Robinson
Keyword(s):  
Weather Conditions ◽  
Current Data ◽  
Ocean Current ◽  
Forward Speed ◽  
Related Information ◽  
Speed Measurement ◽  
Using Data ◽  
Ship Speed ◽  
Naval Architect ◽  
Better Than

If an analysis is made of the speed of a ship using data recorded in log-books the results are extremely disappointing, and do not reflect the accuracies of the instrumentation in use. Even data from a satellite navigator, where the speeds should have an accuracy of better than I per cent, give a I-knot band in recorded speed; in a 20-knot ship this is 5. per cent. Such inaccuracies require explanation.To begin with one must ask what is meant by ship's speed, and different interpretations come from different people. The navigator is concerned with speed over the ground, while the naval architect or marine engineer is mainly interested in the forward speed of the ship through the water. On the other hand a compiler of ocean current data will require both the speed over the ground and the speed made good through the water, but the latter must take leeway into account. Finally, a weather routing consultant is looking for the actual forward speed the ship can achieve through the water in the prevailing weather conditions. All users of speed data may require other related information, such as the ocean currents and the leeway characteristics of the ship, which can in fact only be compiled from ship speed data. At the present time all these different requirements have to be satisfied by the speeds measured at sea and recorded in the logbooks and their abstracts. Ships' officers compile these records, but by the nature of their work they are biased towards the navigational concept of speed.

scholarly journals A Prototype solar tracking system design and implementation

2020 ◽  
Vol 12 (01) ◽  
pp. 32-37
Author(s):  
Abbas F. Nori ◽  
◽  
Faisel G. Mohammed
Keyword(s):  
System Design ◽  
Tracking System ◽  
Weather Conditions ◽  
Electricity Production ◽  
The Sun ◽  
Design And Implementation ◽  
Optical Detector ◽  
Solar Tracking ◽  
Fixed System ◽  
Better Than

In this work comparison between the results of the first systems is a fixed solar and the second is the sun tracking in an attempt to increase the proportion of electricity production. Here a microcontroller (Arduino) and the light-dependent resistor (LDR) photo detector is used in this tracker. And then compare the results in different weather conditions and on different days to test the efficiency of the two systems. The efficiency of the tracking system is better than the fixed system by 12.3% on a sunny day and 4.9% on a partly cloudy day. However, it failed by 3.3% on a cloudy day. With a sunny day preference in the tracking system at 6.9% of partially cloudy days, and 12.1% with partially cloudy to a cloudy day. And verified from The efficiency of the work of the microcontroller (Arduino) system and the optical detector (LDR).

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