Dynamic interaction of breaking waves and inverted sailing yachts: Explaining the efficacy of mast height retention relative to vertical centre of gravity     

Jonathan R. Binns  Paul A. Brandner 《Ocean Engineering》2008,35(17-18):1759-1768

The ability of a sailing yacht to re-right due to the effect of a breaking wave is investigated experimentally. Free and constrained physical models with varying mast height and centre of gravity were tested. To investigate the influence of retained mast height on sway force and roll moment, models were constrained by attachment to a force balance for sway motion tests in calm water and stationary tests in regular and breaking waves. Free model testing, with varying mast height and centre of gravity position, were carried out in breaking waves. For these tests, model motions in six degrees of freedom were measured using photogrammetry. The constrained tests showed that while the mast height had little effect on forces when stationary in waves it had a large effect when in sway motion. As models experience large sway motions when subject to a breaking wave the mast remnant plays a critical role in re-righting dynamics. This work demonstrates that re-righting probability is more dependent on mast height retention and wave characteristics than vertical centre of gravity. This conclusion has direct implications on re-righting safety assessment as the dominant design feature in most safety standards is the vertical centre of gravity.  相似文献   

Buoyancy leads to high productivity of the Changjiang diluted water: a note     

CHEN Chen-Tung Arthur 《海洋学报(英文版)》2008,27(6):133-140

Being the mightiest river emptying into the East China Sea （ECS） and the Pacific Ocean, compounded with the large increase of nitrogen and phosphorus input due to anthropogenic activities, the Changjiang River （Yangtze River） has become a dominating source of these nutrients to the estuary. The high nutrient concentrations notwithstanding, however, outside of the estuary the high biological productivity of the Changjiang diluted water （CDW） are most probably fueled mainly by nutrient-rich subsurface waters originating from the upwelled Kuroshio waters. This is because while the buoyancy of the CDW spreads it out on the ECS continen- tal shelf, the CDW entrains subsurface waters along with the nutrients. Nutrients thus supplied are several times more than those supplied by the Changjiang River.  相似文献   

基于现场监测的抗冰平台疲劳寿命估计     

王荣祥  张大勇  岳前进  刘圆 《海洋工程》2008,26(3)

基于安全寿命设计方法,根据现场监测得到的资料数据,论述了现役导管架平台冰激疲劳寿命的估算法.应用ANSYS软件建立JZ20-2MSW平台的有限元模型,计算该平台的年平均冰激疲劳损伤,从而得到剩余疲劳寿命,为平台的维修、报废等决策提供了依据.  相似文献   

地下矿产开采对天然气管道工程的安全影响评价   总被引：1，自引：1，他引：0       下载免费PDF全文

万继涛  胡松涛  韩祥银  张新文 《山东国土资源》2008,24(6)

西气东输天然气管道工程途经兖州市,穿越杨庄、杨村、兴隆庄等煤矿矿区,压覆煤层埋深变化较大。该文采用预测法对各煤矿在不同开采条件下分煤层对管道运营安全的危害程度进行了评价分析。通过计算表明,煤矿开采埋深越浅,煤层越厚,对管道危害越严重。兴隆庄煤矿3煤层、杨村煤矿煤16t、煤17开采对管道影响强烈,杨庄煤矿煤16t、煤17开采对管道影响中等,兴隆庄煤矿煤16t、煤17开采对管道运营影响小。  相似文献   

Assessing the effects of the Three Gorges Dam and upstream inflow change on the downstream flow regime during different operation periods of the dam     

Cong Jiang  Quan Zhang  Mingming Luo 《水文研究》2019,33(22):2885-2897

As the largest hydroelectric dam in the world, the Three Gorges Dam (TGD) has raised wide concerns over the environmental and ecological impacts since its dramatic effect on the downstream flow regime of the Yangtze River. Since 2003, the TGD has progressed from the initial operation period to the full operation period, with different effects on the downstream flow regime over each period. Although the upstream inflow change (USIC) of the TGD is a possibly additional factor affecting the downstream flow regime, this has drawn little attention. This study aims to quantify the individual contributions of the TGD and the USIC to the changes of the downstream flow regime over different operation periods of the dam. Using the Muskingum routing model and the Xin'anjiang rainfall–run‐off model, we reconstruct the discharge unregulated by the TGD for the post‐TGD period from 2003 to 2015. On this basis, the effects of the TGD and the USIC on the downstream flow regime are quantitatively assessed. Benchmarked against the flow regime during the pre‐TGD period from 1955 to 2002, it is found that the TGD and the USIC play considerable and comparable roles in affecting the downstream flow regime during the whole post‐TGD period from 2003 to 2015. Furthermore, the TGD appears to have a limited effect on the downstream flow regime during the initial operation period from 2003 to 2008 relative to the USIC. In contrast, during the full operation period from 2009 to 2015, the TGD plays a dominant role in changing the downstream flow regime, although the effect of the USIC cannot be neglected. The findings of this study are helpful to understand the exact impacts of the TGD on the downstream flow regime, thereby facilitating the development of a rational strategy for operating the dam.  相似文献   

秦皇岛水库区汛期人工增雨作业风险评估   总被引：1，自引：0，他引：1  

赵国石  陈连友 《气象科技》2007,35(2):274-277

采用河北省人工影响天气办公室研究的增水计算方法,对秦皇岛市的桃林口水库、洋河水库两大水库的水系流域在历年日最大降水(包括水文站、气象哨资料)条件下,如果进行人工增雨作业,可能增加的最大水量进行评估。结果表明,在汛期(6-9月)进行增雨作业不会给两大水库带来风险。根据气候变化分析认为,以增加水库蓄水为目的的人工增雨作业,最有效的办法是在汛期进行人工增雨作业。在汛期到来时,抓住一切有利天气连续作业,才能达到增加蓄水的目的。  相似文献   

PCB, PCDD/F and PBDE levels and profiles in crustaceans from the coastal waters of Brittany and Normandy (France)     

Bodin N  Abarnou A  Fraisse D  Defour S  Loizeau V  Le Guellec AM  Philippon X 《Marine pollution bulletin》2007,54(6):657-668

Polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were analysed in the muscle of various edible marine crustaceans (spider crab, edible crab, velvet swimming crab and Norway lobster) from the Brittany and Normandy coasts (France). The highest concentrations were measured in species collected from Antifer (Seine Bay). PCB and PBDE patterns in crustacean muscles were similar and independent of the geographical area with the predominance of the high chlorinated PCBs (CB153, 138, 118 and 180), and of a few PBDE congeners (BDE47, BDE99, BDE100 and BDE28). Oppositely, dioxin contamination differed with site. The major component in crustaceans from the Seine Bay was 2378-TCDF, whereas specimens from cleaner areas had higher relative concentrations of OCDD. Finally, the comparison of the spider crab contaminant profiles to those measured in mussel and sea bass highlighted two different trends: decapod crustaceans possess relatively strong capacity to metabolise PCBs and PBDEs; however these species might be used as bioindicators for dioxin pollution monitoring in the marine coastal environment.  相似文献   

饮水安全及水污染防治对策研究     

张云 《地下水》2010,32(3):99-100

介绍了我国水污染的现状、水污染的原因及水污染的影响,提出了饮水安全的重要性和防治水污染的措施。加强法制手段,保护水源,实行总量控制,提高污水处理技术,改进水处理工艺,加快水质安全监测系统的建立,确保饮水安全。  相似文献   

临时用电规程与野外机台的安全用电     

郭厚军  宫门零 《安徽地质》2010,20(2):143-146

临时性施工用电因作业时间短,用电器具的流动性大,作业环境比较差而成为施工作业管理的难点,这样的问题在地质队的野外作业机台表现的尤其突出。野外机台的临时用电主要包含两个方面的内容:一是技术措施,二是组织保障。  相似文献   

阿坝州壤塘县大骨节病区安全供水模式研究     

赵松江  李胜伟  唐升海 《四川地质学报》2010,30(3):323-325

通过调查研究阿坝州壤塘县已有供水措施及近期实施的地下水小型集中供水模式,从水质、水量、用水便捷程度等方面进行对比分析,探讨适合高寒高原区的安全供水模式,为改善病区生活饮用水条件提供借鉴。  相似文献