Model Test Study on Added Mass Coefficient of Four Buckets Foundation Ocean Platform

2011 ◽  
Vol 243-249 ◽  
pp. 4728-4732
Author(s):  
Hong Yan Ding ◽  
Xian Qing Liu ◽  
Jing Hua Diao ◽  
Pu Yang Zhang
Keyword(s):  
Natural Frequency ◽  
Model Test ◽  
Bottom Water ◽  
Water Pressure ◽  
Added Mass ◽  
Air Pressure ◽  
Test Study ◽  
Pitch Frequency ◽  
Mass Coefficient ◽  
Added Mass Coefficient

In this paper, the internal air pressure and bottom water pressure of the buckets, the acceleration of swaying, surging and heaving of platform were determined by the sensors fixed on the platform, as a naval bucket foundation platform for example. The motion rules of heave and sway of bucket foundations are studied with different drafts. The results of this test showed that the added mass coefficient of heave, roll and pitch are declined with the increase of the draft; the natural frequency of heave is constant with different drafts but the roll frequency and pitch frequency are consistent with the changes of the draft; the frequency of heave is larger than that of roll and pitch but the added mass coefficient of heave is lesser than that of roll and pitch.

Experimental Investigation on Added Mass Coefficient of a Truss Spar Subjected to Vortex-Induced Motions

2012 ◽  
Author(s):  
Hui Zhang ◽  
Jianmin Yang ◽  
Tao Peng ◽  
Haining Lu
Keyword(s):  
Natural Frequency ◽  
Oscillation Frequency ◽  
Added Mass ◽  
Model Tests ◽  
Response Frequency ◽  
Mean Oscillation ◽  
Study Results ◽  
Mass Coefficient ◽  
Truss Spar ◽  
Added Mass Coefficient

The prediction of response frequency of Truss Spars is important in the estimation of fatigue damage rates. Response frequency depends on the natural frequency of the structure which is influenced by the added mass. The 1:60 scale Truss Spar model tests have been conducted in towing tank at Zhejiang Ocean University (ZOU). The Truss Spar model consists of a hard tank with removable helical strakes, a truss section and a square soft tank. Model tests were carried out with simplified mooring system. In this study, results from the experiment subjected to uniform current were reported. The Reynolds numbers varied from 8E04 to 2E05. The mean added mass coefficient and the time-variable added mass coefficient were calculated. The results shown that the predicted natural frequency based on the measured added mass coefficient was approximately equal to the measured mean oscillation frequency. The added mass coefficient calculated from one oscillation cycle to the next varied considerably. The oscillation frequency from one oscillation to the next corresponded to the natural frequency including the added mass coefficient for the same cycle.

On the unsteady inviscid force on cylinders and spheres in subcritical compressible flow

2008 ◽  
Vol 366 (1873) ◽  
pp. 2161-2175 ◽  
Author(s):  
M Parmar ◽  
A Haselbacher ◽  
S Balachandar
Keyword(s):  
Mach Number ◽  
Compressible Flow ◽  
Propagation Speed ◽  
Added Mass ◽  
The Body ◽  
Mass Force ◽  
Unsteady Force ◽  
Mass Coefficient ◽  
Added Mass Coefficient ◽  
Cylinders And Spheres

The unsteady inviscid force on cylinders and spheres in subcritical compressible flow is investigated. In the limit of incompressible flow, the unsteady inviscid force on a cylinder or sphere is the so-called added-mass force that is proportional to the product of the mass displaced by the body and the instantaneous acceleration. In compressible flow, the finite acoustic propagation speed means that the unsteady inviscid force arising from an instantaneously applied constant acceleration develops gradually and reaches steady values only for non-dimensional times c ∞ t / R ≳10, where c ∞ is the freestream speed of sound and R is the radius of the cylinder or sphere. In this limit, an effective added-mass coefficient may be defined. The main conclusion of our study is that the freestream Mach number has a pronounced effect on both the peak value of the unsteady force and the effective added-mass coefficient. At a freestream Mach number of 0.5, the effective added-mass coefficient is about twice as large as the incompressible value for the sphere. Coupled with an impulsive acceleration, the unsteady inviscid force in compressible flow can be more than four times larger than that predicted from incompressible theory. Furthermore, the effect of the ratio of specific heats on the unsteady force becomes more pronounced as the Mach number increases.

Added mass coefficient of elastic rods in cylindrical fluid

2019 ◽  
Vol 342 ◽  
pp. 249-256
Author(s):  
Xie Teng ◽  
Liu Jianhu ◽  
Wang Haikun ◽  
Li Haitao ◽  
Pei Du ◽  
...  
Keyword(s):  
Added Mass ◽  
Elastic Rods ◽  
Mass Coefficient ◽  
Added Mass Coefficient

Added Mass of Elastically Mounted Rigid Cylinder in Water Subjected to Vortex-Induced Vibrations

2002 ◽  
Author(s):  
Andre´ L. C. Fujarra ◽  
Celso P. Pesce
Keyword(s):  
Added Mass ◽  
Leaf Spring ◽  
Technical Literature ◽  
Experimental Calibration ◽  
Rigid Cylinder ◽  
Vortex Induced Vibrations ◽  
Mass Coefficient ◽  
Added Mass Coefficient ◽  
The Cross ◽  
Technological Research Institute

Vortex Induced Vibrations (VIV) of elastically mounted rigid cylinders, with low mass-damping parameter values, are strongly dependent on the added mass coefficient. This paper aims to contribute to the technical literature by presenting some results from experiments carried out at University of Sa˜o Paulo – USP and at the Sa˜o Paulo State Technological Research Institute – IPT. A cantilevered rigid cylinder was mounted on an elastic (leaf spring) two-degree-of-freedom device. The device is not only an elastic support, but acts also as a special mechanical transducer to measure accelerations/forces/displacements in the stream-wise (x) and the cross-wise (y) directions. A comprehensive experimental calibration of such a device was carried out, both “in air” and “in water”. The added mass coefficient in the cross-wise direction was indirectly determined from forces and acceleration measurements as a function of the reduced velocity. Results from time-domain and frequency-domain analyses are compared with those obtained by Vikestad et al. (2000) [1].

scholarly journals Test Study on Airtight Capability of Filter Cakes for Slurry Shield and Its Application in a Case

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Fanlu Min ◽  
Wei Zhu ◽  
Shengquan Xia ◽  
Rui Wang ◽  
Daiwei Wei ◽  
...  
Keyword(s):  
Yangtze River ◽  
Filter Cake ◽  
Water Pressure ◽  
Air Pressure ◽  
Test Results ◽  
Test Study ◽  
Capillary Bundle ◽  
Slurry Shield ◽  
Filter Cakes ◽  
The Relationship

To learn the airproof capacity of filter cakes as opening chambers under air pressure, a series of tests were carried out. The variations of discharged water with air pressure and time were observed, and the relationship between airproof capacity of filter cakes and surrounding air pressure was analysed. The test results indicated that there were three stages as compressed air acting on filter cakes: completely not infiltration, a very small amount of infiltration, and penetration leakage. The certain air pressure between the first and second stages was called the airproofing value of filter cake. And a capillary bundle model was used to explain the mechanism of air tightness of filter cakes. In Nanjing Yangtze River Tunnel, a 5 cm thickness filter cake was formed in gravel sand, and its airproofing value was a little lower than 0.12 MPa. The air pressure used as opening chamber should be equal to the summation of water pressure in sand and airproofing value of filter cake. While the air pressure is larger than the summation, the filter cake would be gas permeable. The slurry formulation and airproofing value of filter cakes obtained in the tests were applied successfully in Nanjing Yangtze River Tunnel.

Wall Proximity and Curvature Effect on Added Mass Forces in Two-Phase Cross-Flow

2014 ◽  
Author(s):  
C. Béguin ◽  
T. Plagnard ◽  
S. Étienne
Keyword(s):  
Cross Flow ◽  
Added Mass ◽  
Two Phase ◽  
Averaged Equations ◽  
Flow Potential ◽  
Mass Coefficient ◽  
Added Mass Coefficient ◽  
A New Technique ◽  
Infinite Wall ◽  
Wall Proximity

This paper studies the effect of wall proximity and wall curvature on the added mass coefficient of a spherical bubble. Results are based on a semi-analytical method. This information is essential to completely characterize finely dispersed bubbly flows in two-phase cross flow. In such flows small spherical gas bubbles are present in a continuous liquid phase close to a cylinder. This paper uses solid harmonics to solve 3D potential flow around a bubble and a wall. A new technique is developed to calculate the flow potential around a sphere and a cylinder using solid harmonics. Several configurations were calculated: one bubble close to an infinite wall, one bubble close to a cylinder and one bubble close to a spherical wall. Our results are compared with previous studies. As expected added mass forces increase in the vicinity of the wall and for lower curvature. The main purpose of this work is to understand the effect of wall curvature and proximity on added mass. These results are suitable for further use, particularly as added mass models for multiphase flow averaged equations.

Void Fraction Effect on Added Mass in Bubbly Flow

2014 ◽  
Author(s):  
C. Béguin ◽  
É. Pelletier ◽  
S. Étienne
Keyword(s):  
Liquid Phase ◽  
Void Fraction ◽  
Bubbly Flow ◽  
Added Mass ◽  
Bubbly Flows ◽  
Averaged Equations ◽  
Mass Coefficient ◽  
Spherical Bubbles ◽  
Closure Relations ◽  
Added Mass Coefficient

This paper proposes a relation for the added mass coefficient of spherical bubbles depending on void fraction based on results obtained by a semi-analytical method. This information is essential to completely characterize finely dispersed bubbly flows, where small spherical gas bubbles are present in a continuous liquid phase. Most of the closure relations for Euler-Euler or Euler-Lagrange models are obtained from experiments involving single bubbles. Their applicability to systems with high void fraction is therefore questionable. This paper uses solid harmonics to solve 3D potential flow around bubbles. Several configurations were calculated for different numbers of particles and spatial arrangements. Our results are compared with previous studies. Depending on the model proposed by previous authors, added mass forces could increase or decrease with the void fraction. This paper solves these discrepancies. The main purpose of this work is to develop simple formulas fitting our semi-analytical results. These simple formulas are suitable for further use, particularly as added mass models for multiphase flow averaged equations.

scholarly journals The Added Mass Coefficient computation of sphere, ellipsoid and marine propellers using Boundary Element Method

2011 ◽  
Vol 18 (1) ◽  
pp. 17-26 ◽  
Author(s):  
Hassan Ghassemi ◽  
Ehsan Yari
Keyword(s):  
Boundary Element Method ◽  
Numerical Methods ◽  
Boundary Element ◽  
Mass Matrix ◽  
Added Mass ◽  
Experimental Results ◽  
Marine Propellers ◽  
Mass Coefficient ◽  
Added Mass Coefficient ◽  
Element Method

The Added Mass Coefficient computation of sphere, ellipsoid and marine propellers using Boundary Element Method Added mass is an important and effective dynamic coefficient in accelerating, non uniform motion as a result of fluid accelerating around a body. It plays an important role, especially in vessel roll motion, control parameters as well as in analyzing the local and global vibration of a vessel and its parts like propellers and rudders. In this article, calculating the Added Mass Coefficient has been examined for a sphere, ellipsoid, marine propeller and hydrofoil; using numerical Boundary Element Method. Since an Ellipsoid and a sphere have simple geometric shapes and the Analytical values of their added mass coefficients are available, so that the results of added mass matrix are obtained and evaluated, using the boundary element method. Then the added mass matrix is computed in a given geometrical and flow specifications for a specific propeller and its results are studied versus experimental results, which it's current numerical data In comparison with other numerical methods has a good conformity with experimental results. The most important advantage of the method in determining the added mass matrix coefficients for the surface and underwater vessels and the marine propellers is extracting all the added mass coefficients with very good Accuracy, while in other numerical methods it is impossible to extract all the coefficients with the Desired Accuracy.

Rolling motion of a sphere on a plane boundary in oscillatory flow

1976 ◽  
Vol 76 (4) ◽  
pp. 653-674 ◽  
Author(s):  
C. Samuel Martin ◽  
M. Padmanabhan ◽  
C. D. Ponce-Campos
Keyword(s):  
Oscillatory Flow ◽  
Added Mass ◽  
Inertial Range ◽  
Plane Boundary ◽  
Rolling Motion ◽  
Smooth Plane ◽  
Mass Coefficient ◽  
Added Mass Coefficient ◽  
Averaging Techniques

The rolling motion of a sphere on a smooth plane boundary in a simple-harmonic water motion has been analytically and experimentally investigated. For spheres having specific gravities ranging from 0·09 to 15·18 the sphere motion was found to be sinusoidal for both low and high values of the period parameter defined by Keulegan & Carpenter. The knowledge of the sphere motion, and hence the resultant force, allowed the determination of inertia and drag coefficients from Fourier-averaging techniques. Experiments in the inertial range yielded an added-mass coefficient of 1·2, compared with 0·67 from inviscid theory for translating spheres. For values of the period parameter greater than 30 the drag coefficient is reported to be approximately 0·74.

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