DA-1型船用大抓力锚抓底性能研究

DA-1 anchor is a new type high holding power one for merchant ship use. There is a very little of research on its holding property by far and, further and deeper analyses have not been conducted on the holding mechanism in the world. In this project, studies are carried out on the characteristics of DA-1 anchor, which is about the key problems during anchor-dropping process by means of numerical simulation, model test and anchoring test at sea. A view point is put forward that the depth of anchor striking into seafloor (or penetration depth) will greatly affect the posture and holding power of the anchor, according to the fact which many anchors are dropped from above sea surface by their own weights in practice. So firstly, a mathematical model about the movement of a dropped anchor is built up to determine the speed of anchor when down to seabed. And then the penetration depth of anchor is tested and measured at sea. In accordance with the penetration depth, three cases will occur: the first is that the depth is too small to take into account, i.e. the anchor may be treated as lying on seafloor just like that in conventional study; the second is that the anchor is pulled out from the soils by chain tension after striking into seabed; the third is that the anchor strikes into seafloor so deep as to be buried by soils after a period of time. The holding process and holding power of anchor continues to be analyzed in line with three cases that are above-mentioned. The follow-up ability of ship's anchor is also discussed from model test results, by which how the anchor orientation pursues the chain tension (or wind or current direction) and then how the anchor keeps the holding power. Ultimately, the performance of anchor re-embedding into soils is researched by aid of the test at sea. In the whole studies, AC-14 anchor and Spek anchor are simultaneously taken into consideration for comparison each other. The finally comprehensive and systematical results of the holding properties of DA-1 anchor are brought out, which will provide a theoretical support for ship equipment and anchoring safety in the not far future.

DA-1锚是一种新型船用大抓力锚。关于其抓底性能的研究目前还很少，全面而深入的分析尚未展开。本项目以数值模拟、模型试验和实船锚泊试验为基本手段，围绕船舶抛锚过程中的几个关键环节，进行DA-1锚抓底机理研究。首次提出锚砸入底土深度(或贯入深度)大小将影响锚的抓底姿态和抓力大小。为此先建立锚下落运动数学模型，以便求解锚着底时的速度，并通过海上试验来测试锚的贯入深度。然后根据贯入深度大小，按锚平躺海底、锚砸入底土又被锚链拉出和锚砸入底土逐渐被泥土掩埋三种情况，分析锚的抓底过程和抓力大小。借助模型试验，探寻锚链拉力方向（或风、流方向）大幅度改变之后锚在土中跟着转向情况及抓力变化情况，来评判船用锚的追从性。通过海上试验，分析船舶走锚后锚再次啮土能力。整个研究过程还将AC-14锚和斯贝克锚纳入考虑，以便比对。最终做出全面而系统的DA-1锚抓底性能研究成果，为将来船舶舾装配备和锚泊安全提供理论依据。

自上个世纪90年代DA-1型船用大抓力锚诞生以来，围绕该锚的研究陆续展开，但对其性能总体上还认识不足。为此，以DA-1锚为研究对象，运用物模试验和理论分析方法开展了船用锚抓底性能和抛起锚性能研究。应用变质量物体动量定理建立了锚自由下落运动方程。通过物模试验初步研究了锚在软泥质底床上的贯入深度。为了配合实船试验，开展了船舶操纵控制、水下观测、锚泊船运动等研究。DA-1锚在沙质底床上的抓重比在6~9之间，在软泥底可达20~25。过大的抓底力会造成起锚困难，物模试验表明，软泥底床最大起锚破土力达到锚重的8倍左右；在沙质底床上，破土力大约为锚重的1.5~2.5倍之间。另外，在软泥底床当锚接近最大抓力时，啮土深度可达锚爪长度的1.5倍左右。DA-1锚在沙质底床走锚后再次啮土能力较强，但在软泥底床上再次啮土能力很差，主要原因是泥巴裹在锚爪与锚干上不易脱落，造成锚爪难以再次啮土。DA-1锚追随性较好，但比AC-14锚略差一点。在应急抛锚动抓力方面，DA-1锚也略逊于AC-14锚。这些数据将为船舶锚泊安全操作提供理论支持。研究成果共发表学术论文13篇，其中SCI收录5篇、EI收录4篇、中文核心期刊3篇、中文一般期刊1篇。