第17卷第3期船舶力学Vol.17No.3 2013年3月Journal of Ship Mechanics Mar.2013 Article ID：1007-7294（2013）03-0306-07
Influence of Thrust Bearing Pedestal Form on
Vibration and Radiated Noi of Submarine
放飞中国梦演讲稿DING Ke,WANG Yong-sheng,WEI Ying-san
(Department of Mechanical Engineering,Naval University of Engineering,Wuhan430033,China)
Abstract:FEM/BEM method is ud to calculate the structure vibration and underwater radiated noi of the single-shell submarine which is full-scale caud by the propeller fluctuating thrust force.The influence of vibration and radiated noi caud by the propeller of the two kinds thrust bearing pedestal forms(flanged thrust bearing pedestal and common pedestal)is analyd and com鄄pared.The study shows that the flanged thrust bearing pedestal can reduce the underwater radiated noi up to25dB in frequency region except around28Hz.The common pedestal is combined with the submarine hull,it caus the longitudinal vibration and the lateral vibration,and the normal vi鄄bration is much stronger;but the flanged thrust bearing pedestal transfers the propeller fluctuating force equally t
o the submarine hull along the circumference,it mainly caus longitudinal vibration, only the head and tail of the hull cau normal vibration,and so the noi level is lower.
Key words:submarine;flanged thrust bearing;fluid-structure interaction;acoustic
radiation;Finite Element Method(FEM);Boundary Element Method(BEM) CLC number:TB532Document code:A doi:10.3969/j.issn.1007-7294.2013.03.011
1Introduction
With the development of detectability technology and the need of modern war,the stealth performance of submarine is becoming more and more important to navy of different countries. The U.S.Navy report-Technology for the United States Navy and Marine Corps,2000-2035, listed6kinds of key technology,the stealth technology is the first one.Last decades,China developed submarine stealth technology energetically,has got great advance,but still was dis鄄tanced by Europe,the U.S.and Russia.
Submarine noi is categorized into three main components-machine noi,propeller noi,and hydrodynamic noi.This paper mainly studies the cond component.Submarine moves through th
e water,creates asymmetric wake at the tail becau of the sail,tails and oth鄄er appendix structures.Vibration modes of a submarine hull are excited from the transmission of fluctuating forces through the shaft and thrust bearings due to the propeller rotating in an unsteady fluid[1].Pan[2]thought that the structural vibration arin by the propeller fluctuating forces through the thrust bearing is the main noi source of the low frequency underwater ra-
Received date：2012-06-08
Biography：DING Ke(1987-),male,master candidate of Naval University of Engineering,E-mail:******************;
WANG Yong-sheng(1955-),male,professor/tutor,E-mail:************************.
diated noi.Dylejko [3]investigated the influence of resonance changer by the transmission matrix approach.Kinns [4-5]studied the excitation of the hull vibration resulting from transmis 鄄sion through the propeller-shafting system.Feng [6]ud the FEM+BEM to study the charac 鄄teristics of the submarine tail vibra-noi,and drew the conclusion that the thrust bearing pedestal is the main transmission route under the longitudinal excitation.Cao,Zhang,Li et al.also investigated the longitudinal vibration of propeller-shafting system.But,only few people thought to change the structur
e form of thrust bearing pedestal.Cao and Zhang [7]ud the bulkheads replace the thrust bearing pedestal,and obtained a result that it could reduce the longitudinal vibration.Zhang [8]advanced that to u flanged thrust bearing pedestal instead of Michell (common pedestal),and ud FEM analyze the vibration transmission of propeller-shafting system,but his paper had not introduced the vibration respon and radiated noi of submarine hull under the propeller fluctuating force.Considering the scale effect and real pro 鄄peller fluctuating forces,this paper us FEM+BEM and real scale of Suboff model investigate the influence of thrust bearing pedestal form on vibration and underwater radiated noi of submarine.
2Basic theory
2.1Fluid-structure interaction theory
When the structure is placed in fluid,there is interaction between fluid and structure at their interface.The voice pressure acts on the structure as surface force.Then the vibration matrix equation of fluid-structure interaction is:
M s !"!"0籽f !"R M f !"#$U 咬%&P 咬%&’(*+,-+C s !"!"0!"0C f !"#$U 觶%&P 觶%&
’(*+,-+K s !"-!"
R T !"0K f !"#$%&U %&P %&=F s %&%&0%&(1)
where,M s !",C s !
"and K s !"are the mass matrix,damp matrix and stiffness matrix of struc 鄄ture,respectively.M f !",C f !
粗人"and K f !"are the equivalent mass matrix,equivalent damp ma 鄄trix and equivalent stiffness matrix of fluid,respectively.!"R is the interaction matrix between
fluid and structure,F s %&is the load force of structure,%&U and %&P are the displacement and
pressure of element nodes.
When structure is acted on by external force,the structure is excited to vibrate,the vi 鄄bration of the structure caus the surrounding fluid ’s interaction,it caus fluctuating pres 鄄sure,the fluctuating pressure acts on the structure again and affects the structure vibration,and this is the fluid-structure interaction phenomenon.At low frequency,it prents added fluid effect;at high frequency,it prents damp effect.
2.2Acoustic radiation theory
Becau of the structure vibration,the surface of structure and fluid caus interaction 第3期DING Ke et al:Influence of Thrust Bearing Pedestal (307)
which caus the fluid vibrating,and makes part of vibration energy transmit to surrounding,namely,forms the underwater radiated noi.Although FEM can be ud to predict the under 鄄water radiated noi,its size is very large,and has high requirement on computer.But BEM reduces the dimensions efficiently,only divides at the surface,then reduces the requirement on computer.
For the monochromatic voice field,if the surface of structure is smooth and the boundary normal vibration velocity is known,then Helmholtz integral equation [9]is:
滓乙p 乙乙Q 坠G P，乙乙Q 坠n +j 棕籽v n G P，乙乙Q 乙乙
kingman
d s=p 乙乙r r ∈E 12p 乙乙r r ∈S 0r ∈∈∈∈∈∈∈∈
I (2)where,E ,S and I are the exterior,surface and interior of structure,P and Q are the obrva 鄄tion point and the integral point on the surface of structure,G P，乙乙
Q =e -jkR /4仔R is the Green function of free space,k =棕/c is the wave number,R=P-Q ,v n is the no
rmal vibration veloc 鄄
ity，棕is the circular frequency,and 籽is the density of fluid.
After the discreteness of Helmholtz integral equation,the boundary element solution e 鄄quation is:
Ap=Bv n (3)
where,A and B are the coefficient matrices.
The paper us ANSYS to analyze the Suboff model,taking all the nodes vibration dis 鄄placement of hull,and us SYSNOISE to analyze the underwater radiated noi field.3Calculation of the submarine structure vibration respon
This paper ts up a model of single shell submarine bad on the databa of the Sub 鄄off.The total length is 78.408m,it concludes 6cabins divided by 5bulkheads,and is rein 鄄forced with ring stiffeners,longitudinal stiffeners and flat boards and the sail and tails are re 鄄inforced with beams and bars,as shown in Fig.1(a).This paper considers two cas.The Ca 1is flanged thrust bearing pedestal,as shown in Fig.1(a)and Fig.1(b).The Ca 2is common thrust bearing pedestal,as shown in Fig.1(c)and Fig.1(d).Fig.1(e)and Tab.1show that how the Suboff submarine structure elements me
sh.
(a)Ca 1:Flanged thrust bearing pedestal (b)Flanged form
308船舶力学第17卷第3
期
(c)Ca 2:Common thrust bearing pedestal (d)Common form
(e)Structure
Fig.1Submarine element meshing
The fluctuating force ud in this paper
neworientalcomes from the former result [10].The Suboff is
matched with a propeller,then a numerical
calculation of lf-propulsion is run,and get
the lf-propulsion point.The propeller fluctu 鄄
ating thrust force at the speed of 6kns is
shown in Fig.2,three wave crests are Axial
宾语从句的语序
modem是什么Passing Frequency (APF),Blade Passing Fre 鄄
love on topquency (BPF),and Double Blade Passing Fre 鄄
quency (2BPF).
Tab.1Element meshing Fig.2Propeller fluctuating thrust force calculated by CFD Element style Element number
Hull structure Flanged form
Common form SHELL63BEAM188FLUID30(prent)FLUID30(abnt)FLUID130SOLID4532326
14545
264801
4800
60035185134572852084800600
128Surface shell/Bulkheads/Flat boards Ring/Longitudinal stiffeners Prent fluid Abnt fluid Voice absorb face Pedestal
mesa
星期四的英文Fig.3shows that the quad velocity and react power of submarine hull under the fluctuat 鄄ing force,reprents the vibration intensity of hull and the distributing of vibration power at different frequency.As shown in Fig.3,both flanged and common thrust bearing form have wave 第3期DING Ke et al:Influence of Thrust Bearing Pedestal …
309
crest at the frequencies of APF,BPF and 2BPF.Below 60Hz except 28Hz,the respon of flanged form is smaller than the common form,it reprents that the flanged thrust bearing pedestal reacts smaller respon than the common form becau the flanged thrust bearing pedestal transfers the propeller fluctuating force equally to the submarine hull along the cir 鄄cumference,which mainly caus longitudinal vibration,only the head and tail of the hull are caud normal vibration,but the common one caus not only the longitudinal vibration but al 鄄so the lateral vibration.
good bye(a)Quad velocity (b)React power
Fig.3Vibration and radiated noi of submarine hull by unit force
Fig.4shows the vibration and radiated noi of submarine hull by unit force,it mainly reprents the nature frequencies of the hull.As shown in Fig.4,the vibration power mainly dis 鄄tributes in frequencies of 0-300Hz becau the vibration of submarine hull is mainly affected by stiffness impedance in low frequency;in middle-high frequency,it is damping impedance;at the critical frequency,it is mass impedance.The radiated noi power of common form is the biggest at 2BPF,but the flanged form is at 28Hz,which explains that why the respons 鄄es of flanged form under fluctuating force is bigger than the common form ’s.
(a)
Quad velocity
(b)React power Fig.4Vibration and radiated noi of submarine hull by fluctuating thrust force
Line spectrum 1in Fig.3(a),(b)corresponds with the 1in Fig.4(a),(b),it is the nature frequency of common form;line spectrum 2,3in Fig.3(a),(b)corresponds with the 1in Fig.2;line spectrum 4in Fig.3(a),(b)corresponds with the 2in Fig.4(a),(b),it is the nature fre 鄄quency of common form;line spectrum 5in Fig.3(a),(b)corresponds with the 3in Fig.4(a),(b),it is the nature frequency of flanged form;4,5and 6in Fig.4(a),(b)are the nature fre 鄄quencies of flanged and common form.310船舶力学第17卷第3期
