發(fā)布時間：2018-07-25 08:35

【摘要】：水下航行體上的附著空泡極大的改變了周圍流場結(jié)構(gòu),對航行體的水動力性能有重要影響,因此受到學者的廣泛重視。在試驗中發(fā)現(xiàn),當航行體在水下用高壓氣體從發(fā)射筒中彈射出去時,航行體穿越的并不是靜止的單一水介質(zhì)流場,而是筒口泄氣射流與周圍水流體相互摻混后的非定常水汽混合復雜流場。航行體在這種水氣摻混流場中的空化與單一水介質(zhì)中有很大不同,空泡在航行體上的產(chǎn)生、附著及演化過程受到水氣摻混流場結(jié)構(gòu)的重大影響,隨之也對航行體的水動力及彈道帶來復雜變化。目前對空泡開展的研究,多是針對單一水介質(zhì)中的空泡,而對水氣混合流場誘發(fā)的空泡,尚未進行綜合研究。因此,對這方面開展研究具有重要的工程應(yīng)用價值。水氣摻混的流場結(jié)構(gòu)復雜多樣,其中既有摻混比較均勻的流動,也含有大大小小氣泡的流動,不同流動結(jié)構(gòu)對空泡發(fā)展有不同的影響。為了簡化機理研究,本文將對水氣摻混結(jié)構(gòu)簡化為兩種典型的基本結(jié)構(gòu):一是水氣摻混均勻的單相結(jié)構(gòu),二是具有明顯水氣分界面的大氣泡結(jié)構(gòu);然后利用數(shù)值模擬方法,分別研究了航行體穿越這兩種水氣混合流場結(jié)構(gòu)的空泡產(chǎn)生、演化發(fā)展及水動力特性。航行體穿越水氣均勻混合流場時,空泡受速度與含氣率的綜合影響。由于水氣混合介質(zhì)的聲速下降很大,在水汽混合流場中有可能出現(xiàn)超聲速流動,航行體上不僅會出現(xiàn)空泡,而且還會產(chǎn)生激波。激波與空泡發(fā)生相互作用,結(jié)論是:航行體頭部前面產(chǎn)生的脫體激波削弱了空化效應(yīng),使得空化區(qū)域減小;受空泡外形影響,空泡分離面位置產(chǎn)生膨脹波,而空泡末端出現(xiàn)彎曲形狀的斜激波;當含氣率超過一定值,空泡將閉合在斜激波面上而不是航行體表面上,體現(xiàn)在空泡尾端壁面逆壓梯度趨于平緩,沒有明顯的閉合高壓出現(xiàn)。航行體穿越筒口泄氣產(chǎn)生的膨脹氣泡時,氣泡在一定條件下有可能附著在航行體上形成附著空泡。通過研究不同頭型航行體穿越氣泡的過程發(fā)現(xiàn),頭型對氣泡附著過程的影響極大:對于易空化的鈍頭型,氣泡容易附著在航行體上形成附著空泡。對于不易空化或細長頭型,氣泡受到擾動后就很快與航行體分離。文中初步分析了氣泡的附著機理和條件。以上研究可對航行體的外形設(shè)計及水動力預報提供參考。
[Abstract]:The attached cavitation on the underwater vehicle greatly changes the structure of the surrounding flow field and has an important influence on the hydrodynamic performance of the vehicle. Therefore, the scholars pay much attention to it. In the experiment, it is found that when the vehicle ejected from the launching tube with high pressure gas under water, the navigation body was not a static single water flow field. It is a complex flow field of unsteady water vapor mixed with the mixing of the deflated jet and the surrounding water fluid. The cavitation in this water and gas mixing field is very different from that in a single water medium. The formation of the cavitation on the vehicle, the process of attachment and evolution is greatly influenced by the structure of the mixed flow field of water and gas, and then to the navigation body. Hydrodynamics and ballistics bring complex changes. At present, the research on vacuoles is mostly aimed at the vacuoles in a single water medium, but it has not been studied synthetically for the vacuoles induced by the mixed flow of water and gas. Therefore, it is of great engineering application value to carry out this research. The flow structure of the mixture of water and gas is complex and diverse, in which the mixing ratio is not only complex. In order to simplify the mechanism study, this paper will simplify the mixing structure of water and gas into two typical basic structures: one is the homogeneous single-phase structure with water and gas mixing, and the two is a large bubble structure with obvious water and gas interface; The numerical simulation method is used to study the bubble generation, evolution and hydrodynamic characteristics of the two kinds of water vapor mixed flow field structure. The cavitation is influenced by the velocity and gas content when the vehicle passes through the homogeneous mixed flow field of water and gas. The supersonic flow can occur, not only the cavitation appears on the vehicle, but also the shock waves. The shock wave is interacting with the vacuoles. The conclusion is that the detachment shock produced in front of the head of the vehicle weakens the cavitation effect and reduces the cavitation area, which is influenced by the shape of the vacuoles, and produces the expansion wave in the position of the vacuolar separation surface, and the end of the vacuoles appears. When the gas content exceeds a certain value, the bubble will be closed on the oblique shock surface rather than on the surface of the vehicle, and the reverse pressure gradient tends to be slow, and there is no obvious closed pressure. The bubbles may be attached to the air under certain conditions. An attachment cavitation is formed on a row. Through the study of air bubbles through different head types, it is found that the head type has a great influence on the process of air bubble attachment: for the blunt type of easy cavitation, the bubbles easily attach to the aircraft to form an attached vacuole. For the air bubbles that are not easy to be cavitation or slender head, the bubbles are quickly separated from the aircraft. The mechanism and conditions of bubble attachment are preliminarily analyzed. The above research can provide reference for the shape design and hydrodynamic prediction of the vehicle.
【學位授予單位】：中國艦船研究院
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：U661.1

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