本文選題：梢渦 + 梢渦空泡�。� 參考：《中國艦船研究院》2014年博士論文

【摘要】：隨著艦船航速的增加，螺旋槳將先后出現(xiàn)各種不同類型的空泡，艦船的臨界航速是指空泡最先起始時的航速，而螺旋槳梢渦空泡由于其尺度效應非常顯著，通常是最先起始的空泡�？张菀坏┊a(chǎn)生，螺旋槳的輻射噪聲會顯著增加，有時甚至會引起船尾的振動。水面艦船的臨界航速是低噪聲船舶的重要性能參數(shù)，因此，推遲梢渦空泡的起始對于提高艦船的安靜性是非常有必要的。在螺旋槳設(shè)計中，采用梢部卸載是一種典型的抑制梢渦空泡的有效措施。然而，該措施是以犧牲推進效率為代價的，而且其主要改變的是隨邊梢渦的強度，對導邊渦和局部梢渦的影響不明顯。研究槳葉梢部的幾何形狀，比如側(cè)斜形式、縱傾和厚度分布等參數(shù)對推遲梢渦空泡起始的影響也受到了螺旋槳設(shè)計者的關(guān)注，其工程應用性較強。 因此，本文研究的目的是建立一種能夠?qū)ι覝u空泡起始進行評估的方法，該方法可以對幾何變化影響梢渦空泡的起始進行有效性分析，可適用于多方案的相對比較；然后，從梢渦結(jié)構(gòu)和渦核壓力等流動機理出發(fā)，分析梢部幾何形狀對梢渦和梢渦空泡起始的影響。目前的研究主要包含了以下幾個方面： 首先，為了便于分析梢渦的流動結(jié)構(gòu)細節(jié)，設(shè)計了一只具有現(xiàn)代水面船螺旋槳葉片幾何輪廓及負荷特征的三維扭曲水翼，為研究螺旋槳梢渦特征的流動結(jié)構(gòu)提供了很好的對象。并且在中國船舶科學研究中心的空泡水筒利用LDV開展了梢渦區(qū)域的流場結(jié)構(gòu)、梢渦軌跡測量和梢渦空泡觀測試驗，獲得了豐富的梢渦速度場分布的數(shù)據(jù)，也為梢渦流動的數(shù)值模擬方法提供了豐富的試驗驗證數(shù)據(jù)。 其次，采用數(shù)值RANS方法模擬了水翼和螺旋槳的梢渦流動，對比分析了不同計算模型對計算結(jié)果的影響，認為采用邊界層網(wǎng)格和梢渦區(qū)域局部加密網(wǎng)格相結(jié)合的計算模型更有利于捕捉梢部區(qū)域的局部梢渦、導邊分離渦等不同類型渦的流動細節(jié)。然后，利用這樣的計算模型分析了梢部幾何參數(shù)對梢渦形成和渦流場特征的影響。為了定量評估梢渦空泡的起始，基于CFD計算結(jié)果，應用了一個簡化的渦模型來計算渦核內(nèi)的壓力分布。針對三維扭曲水翼，通過渦模型計算結(jié)果和空泡起始試驗測量結(jié)果的相關(guān)分析，獲得了修正系數(shù)‘K’。這個修正系數(shù)也被應用在了螺旋槳的算例中，與試驗結(jié)果的比較認為該評估方法可以用來分析評估梢渦空泡抑制效果的有效性，提供了一種可相對比較的方法。 在本文的研究中，通過梢部幾何的變化來實現(xiàn)抑制和推遲梢渦空泡的起始是最終的研究目標。為此，首先基于所設(shè)計的三維扭曲水翼，獨立分析了梢部局部的厚度分布變化、側(cè)斜和縱傾形式的變化對梢渦的影響。從流動變化上研究了推遲梢渦空泡起始的機理。梢部幾何的變化能夠延緩導邊分離渦卷入局部梢渦，使得梢部的橫向流動減弱。這些變化可以幫助減弱梢渦的強度，延遲梢渦空泡的起始。 最后，以三維扭曲水翼的研究結(jié)果為基礎(chǔ)，針對一個已有的參考螺旋槳，在保持原槳負荷分布不變的條件下，通過改變梢部的幾何參數(shù)重新設(shè)計了一個螺旋槳方案，該梢部幾何的變化包括了側(cè)斜形式、縱傾分布和梢部的厚度分布變化。這樣的改變目的是為了能夠相比于參考槳方案推遲梢渦空泡的起始。在空泡水筒中完成了參考槳和新設(shè)計槳的模型試驗，，設(shè)計目的實現(xiàn)了試驗結(jié)果的驗證，新設(shè)計槳的梢渦空泡起始得到了有效的推遲。數(shù)值計算結(jié)果也反映出了與試驗結(jié)果相同的趨勢，但數(shù)值計算結(jié)果仍然采用了三維水翼數(shù)值分析中相同的經(jīng)驗修正系數(shù)，這個修正系數(shù)的實用性問題還需要在未來的研究中更進一步的驗證。 本文的研究指出了一種通過幾何變化來推遲梢渦空泡起始的技術(shù)方向，根據(jù)數(shù)值分析結(jié)果，在螺旋槳設(shè)計階段能夠有效的評估梢渦空泡起始延遲效果的有效性，本文所提出的幾何變化措施具有較好的工程應用前景。
[Abstract]:With the increase of ship speed, the propeller will appear a variety of different types of vacuoles. The critical speed of the ship is the first speed when the cavitation first begins, and the propeller tip vortex cavitation is usually the first initiating bubble because of its very significant scale effect. Once the cavitation is produced, the radiation noise of the propeller will increase significantly, sometimes even even if the propeller is produced. It will cause the vibration of the ship's tail. The critical speed of the surface ship is an important performance parameter for the low noise ship. Therefore, it is necessary to postpone the start of the tip vortex vacuole to improve the quietness of the ship. In the design of propeller, the tip unloading is an effective measure to suppress the tip vortex cavitation. However, this measure is sacrificed. The influence of the tip vorticity on the edge vortex and the local tip vortex is not obvious at the cost of advancing efficiency, and the effect of the geometry of the tip of the paddle, such as the lateral form, the longitudinal tilt and the thickness distribution, on the delay of the tip vortex cavitation is also concerned by the propeller designers, and its engineering application Strong.
Therefore, the purpose of this study is to establish a method to evaluate the initiation of tip vortex cavitation. This method can be used to analyze the effect of geometric change on the initiation of tip vortex cavitation, and can be applied to the relative comparison of multiple schemes. Then, the tip geometry of the tip is analyzed from the tip vortex structure and the flow mechanism of the vortex core pressure. The influence of vortex and tip vortex cavitation initiation is studied.
First, in order to facilitate the analysis of the details of the flow structure of the tip vortices, a three-dimensional twisted hydrofoil with the geometric contour and load characteristics of the propeller blade of a modern surface ship is designed. It provides a good object for the study of the flow structure of the tip vortex characteristics of the propeller. The flow field structure of the vortex region, the tip vortex path measurement and the tip vortex cavitation observation test have obtained the abundant data of the tip vortex velocity field distribution, and also provide the abundant experimental verification data for the numerical simulation method of the tip vortex flow.
Secondly, the numerical RANS method is used to simulate the tip vortex flow of hydrofoil and propeller, and the influence of different calculation models on the calculation results is compared and analyzed. It is considered that the combination of boundary layer grid and local encrypted mesh in tip vortex region is more beneficial to capture the local tip vortices in the tip region and the flow of different types of vortices, such as the leading edge separation vortex and other types of vortices. Then, the effect of the geometric parameters of the tip on the tip vortex formation and the characteristics of the eddy current field is analyzed. In order to quantify the initiation of the tip vortex cavitation, a simplified vortex model is applied to calculate the pressure distribution in the vortex core based on the CFD results. The results are calculated by the eddy model for the three-dimensional twisted hydrofoil. The correction coefficient 'K' is obtained by correlation analysis of the measurement results of the initial cavitation test. The correction coefficient is also applied to the example of a propeller. Compared with the experimental results, the method can be used to evaluate the effectiveness of the effect of tip vortex cavitation suppression, and a relative comparison method is provided.
In this study, the ultimate objective of the study is to suppress and delay the initiation of tip vortex vacuoles through the variation of the tip geometry. First, based on the designed three-dimensional twisted hydrofoil, the influence of the variation of the thickness distribution on the tip part of the tip, the variation of the lateral and longitudinal forms on the tip vortices is independently analyzed. The mechanism of the initiation of the tip vortex cavitation. The variation of the tip geometry can delay the involvement of the leading edge vortex into the local tip vortices, making the lateral flow of the tip weakened. These changes can help to weaken the strength of the tip vortices and delay the initiation of the tip vortex vacuoles.
Finally, on the basis of the research results of the three-dimensional twisted hydrofoil, a propeller scheme is redesigned by changing the geometric parameters of the tip of an existing reference propeller to keep the load distribution of the original propeller unchanged. The variation of the tip geometry includes the side slope, the longitudinal inclination distribution and the thickness distribution of the tip. The purpose of the change is to delay the initiation of the tip vortex cavitation in comparison with the reference propeller scheme. The model test of the reference paddle and the newly designed paddle is completed in the vacuolar water tube. The design aims to verify the test results. The tip vortex cavitation in the newly designed paddle has been effectively pushed late. The numerical results also reflect the test knot. The same trend has been achieved, but the numerical results still use the same empirical correction coefficient in the three-dimensional hydrofoil numerical analysis. The practical problem of this correction factor needs to be further verified in future research.
In this paper, a technical direction to delay the initiation of tip vortex cavitation by geometric change is pointed out. According to the results of numerical analysis, the effectiveness of the effect of the initial delay effect on the tip vortex cavitation can be effectively evaluated in the design stage of the propeller. The geometric change measures proposed in this paper have a good prospect for engineering application.
【學位授予單位】：中國艦船研究院
【學位級別】：博士
【學位授予年份】：2014
【分類號】：U664.33;U661.1

【參考文獻】

相關(guān)期刊論文 前1條

1 LEE Jeung-Hoon;JUNG Jae-Kwon;LEE Kyung-Jun;HAN Jae-Moon;PARK Hyung-Gil;SEO Jong-Soo;;EXPERIMENTAL ESTIMATION OF A SCALING EXPONENT FOR TIP VORTEX CAVITATION VIA ITS INCEPTION TEST IN FULL-AND MODEL-SHIP[J];Journal of Hydrodynamics;2012年05期

本文編號：1937411