Hydrodynamics Interactions on Vortex-Induced Motions of a Multi-Body Floating System

2019 ◽  
Author(s):  
Yibo Liang ◽  
Longbin Tao
Keyword(s):  
Horizontal Plane ◽  
Numerical Data ◽  
Hydrodynamic Interactions ◽  
Gap Ratio ◽  
Floating System ◽  
Preliminary Study ◽  
Drag And Lift ◽  
Lock In ◽  
Multi Body ◽  
Floating Platforms

Abstract In this study, numerical analysis has been carried out to investigate the hydrodynamic interactions of two multi-columns platforms. The objective of the work is to preliminarily evaluate the feasibility of a tension-leg-platform (TLP) dry tree unit (DTU) with tender assisted drilling (TAD) from the aspect of vortex-induced motions, characterized by the current. Two multi-columns floating platforms with a small gap ratio (28% of the overall platform width) are numerically simulated with the scenario of 3 degree-of-freedom (DOF) on the horizontal plane (including transverse, in-line and yaw motions). A comprehensive numerical simulation was conducted to examine the hydrodynamics interactions due to the flow over two floating platforms. Horizontal plane motions including transverse, in-line and yaw motions as well as drag and lift forces on both structures are discussed. The numerical data on the multi-body VIM interactions within the “lock-in” region will serve as a preliminary study for future coupled motions analysis of the TLP-TAD system design.

scholarly journals Effects of Gap Resonance on the Hydrodynamics and Dynamics of a Multi-Module Floating System with Narrow Gaps

2021 ◽  
Vol 9 (11) ◽  
pp. 1256
Author(s):  
Mingsheng Chen ◽  
Hongrui Guo ◽  
Rong Wang ◽  
Ran Tao ◽  
Ning Cheng
Keyword(s):  
Damping Ratio ◽  
Normal Wave ◽  
Hydrodynamic Interactions ◽  
Period Range ◽  
Artificial Damping ◽  
Potential Applications ◽  
Floating System ◽  
Parametric Studies ◽  
Multi Body ◽  
Narrow Gaps

Multi-module floating system has attracted much attention in recent years as ocean space utilization becomes more demanding. This type of structural system has potential applications in the design and construction of floating piers, floating airports and Mobile Offshore Bases (MOBs) generally consists of multiple modules with narrow gaps in which hydrodynamic interactions play a non-neglected role. This study considers a numerical model consisting of several rectangular modules to study the hydrodynamics and dynamics of the multi-module floating system subjected to the waves. Based on ANSYS-AQWA, both frequency-domain and time-domain simulations are performed to analyze the complex multi-body hydrodynamic interactions by introducing artificial damping on the gap surfaces. Parametric studies are carried out to investigate the effects of the gap width, shielding effects of the multi-body system, artificial damping ratio on the gap surface, and the dependency of the hydrodynamic interaction effect on wave headings is clarified. Based on the results, it is found that the numerical analysis based on the potential flow theory with artificial damping introduced can produce accurate results for the normal wave period range. In addition, the effects of artificial damping on the dynamics and connector loads are investigated by using a simplified RMFC model. For the case of adding an artificial damping ratio of 0.2, the relative heave and pitch motions are found to be reduced by 33% and 50%, respectively. In addition, the maximum cable and fender forces are found to be reduced by 50%, compared with the case without viscosity correction.

Time-Domain Simulation of a Multi-Body Floating System in Waves

2010 ◽  
Author(s):  
Xiaochuan Yu ◽  
Jeffrey M. Falzarano ◽  
Zhiyong Su
Keyword(s):  
Time Domain ◽  
Impulse Response Function ◽  
Hydrodynamic Interactions ◽  
Time Domain Simulation ◽  
Single Vessel ◽  
Close Proximity ◽  
Floating System ◽  
Response Amplitude Operators ◽  
Multi Body ◽  
Coefficient Method

It is important to study multi-body dynamics when analyzing the transfer of cargo between ships and platforms at sea. The hydrodynamic interactions should be considered in an accurate way to predict the relative motions between them. In this paper, the response amplitude operators (RAOs) of a single vessel will be compared with those of a multi-body system, considering different spacing between them. Further, the coupled hydrodynamic interactions among multiple vessels in close proximity are studied. Various levels of approximation, including the constant coefficient method (CCM) and the impulse response function (IRF) method, are employed to model the hydrodynamic interactions. Finally, the comparison between a single vessel and multi-body time domain simulation is also given.

With the Backlash Dynamics Simulation of a Crank-Slider Mechanism of the Internal Combustion Engine

2012 ◽  
Vol 215-216 ◽  
pp. 1081-1084
Author(s):  
Shao Jun Bo ◽  
Kui Ji ◽  
Juan Tian
Keyword(s):  
System Dynamics ◽  
Combustion Engine ◽  
Dynamics Simulation ◽  
Kinematic Pair ◽  
Body System ◽  
Nonlinear Characteristics ◽  
Preliminary Study ◽  
Multi Body ◽  
Dynamics Models ◽  
Crank Mechanism

On the basis of flexible multi-body system dynamics theory, we built flexible multi-body system dynamics models which include a backlash, and to a slider-crank mechanism as the research object, we made a preliminary study on the effect on the flexible components and the backlash of the kinematic pair on mechanical system dynamics characteristics. To consider the backlash of the kinematic pair and component of flexible space can show a preliminary research on the dynamic simulation, and focus on the backlash, friction and gravity field to influence in the dynamic characteristics of the system. The simulation results show that, due to the existence of backlash made the two components frequent collision in the process of the stretching, clearance, flexible and friction are closed, make the system nonlinear characteristics increased.

Numerical Investigation of Multistage Viscous Micropump Configurations

2005 ◽  
Vol 127 (4) ◽  
pp. 734-742 ◽  
Author(s):  
M. Abdelgawad ◽  
I. Hassan ◽  
N. Esmail ◽  
P. Phutthavong
Keyword(s):  
Flow Rate ◽  
Numerical Data ◽  
Future Research ◽  
Shear Stresses ◽  
Vertical Rotor ◽  
Viscous Micropump ◽  
Study Results ◽  
In Series ◽  
The Subject ◽  
Drag And Lift

The viscous micropump consists of a cylinder placed eccentrically inside a microchannel, where the rotor axis is perpendicular to the channel axis. When the cylinder rotates, a net force is transferred to the fluid because of the unequal shear stresses on the upper and lower surfaces of the rotor. Consequently, this causes the surrounding fluid in the channel to displace toward the microchannel outlet. The simplicity of the viscous micropump renders it ideal for micropumping; however, previous studies have shown that its performance is still less than what is required for various applications. The performance of the viscous micropump, in terms of flow rate and pressure capabilities, may be enhanced by implementing more than one rotor into the configuration either horizontally or vertically oriented relative to each other. This is analogous to connecting multiple pumps in parallel or in series. The present study will numerically investigate the performance of various configurations of the viscous micropumps with multiple rotors, namely, the dual-horizontal rotor, triple-horizontal rotor, symmetrical dual-vertical rotor, and eight-shaped dual-vertical rotor. The development of drag-and-lift forces with time, as well as the viscous resisting torque on the cylinders were studied. In addition, the corresponding drag, lift, and moment coefficients were calculated. The flow pattern and pressure distribution on the cylinders’ surfaces are also included in the study. Results show that the symmetrical dual-vertical rotor configuration yields the best efficiency and generates the highest flow rate. The steady-state performance of the single-stage micropump was compared to the available experimental and numerical data and found to be in very good agreement. This work provides a foundation for future research on the subject of fluid phenomena in viscous micropumps.

A Numerical Study on Hydrodynamic Interactions Between Large Numbers of Multiple Floating Bodies

2003 ◽  
Author(s):  
Yoshiyuki Inoue ◽  
Mir Tareque Ali
Keyword(s):  
Numerical Study ◽  
Computer Code ◽  
Hydrodynamic Forces ◽  
Hydrodynamic Interactions ◽  
Physical Aspect ◽  
Floating Bodies ◽  
Coupled Equations ◽  
Large Numbers ◽  
Exciting Forces ◽  
Multi Body

This paper investigates the hydrodynamic interactions between large numbers of multiple bodies floating in each other’s close vicinity. The physical aspect of hydrodynamic interaction is rather complicated and numerically sound scheme is highly recommended to study this complex phenomenon. In the present study, the 3D sink-source method has been adopted to determine the hydrodynamic forces by taking into account the effect of hydrodynamic interactions among the different floating bodies, and the coupled equations of motions are solved directly. The validation of the computer code developed for this purpose has been justified by comparing the present results with that of the published ones for simple geometrical shaped floating bodies. The numerical computations have been carried out for different numbers of various freely floating multi-body systems and the hydrodynamic interactions between the floating bodies have been studied by calculating the hydrodynamic forces, first order wave exciting forces and motion responses. Finally some conclusions have been drawn on the basis of the present analysis.

Preliminary Study of a Centrifugal Compressor With Counter-Rotating Impellers: Design and Performances Study

2020 ◽  
Author(s):  
Abed Cheikh Brahim ◽  
Khelladi Sofiane ◽  
Deligant Michael ◽  
El Marjani Abdel ◽  
Farid Bakir
Keyword(s):  
Centrifugal Compressor ◽  
Degrees Of Freedom ◽  
Numerical Data ◽  
Centrifugal Impeller ◽  
Through Flow ◽  
Aerodynamic Performances ◽  
Preliminary Study ◽  
And Performance ◽  
And Control ◽  
Selection Of

Abstract Turbomachinery with double counter-rotating impellers offer more degrees of freedom in the choice of design and control parameters compared to conventional machines. For these innovative machines, the literature review shows that more published works are available concerning axial type turbomachines than centrifugal ones. This work deals with a preliminary design and performance analysis applied to two counter-rotating impellers of a centrifugal compressor. We present here the design practice developed based on 0D/1D models, also coupled with optimization and stream-curvature through-flow methods to satisfy the selected design-criteria. An analyze of aerodynamic performances results are made and compared to those available experimental and numerical data of a baseline configuration, composed of one centrifugal-impeller and a volute. The compressor studied here includes a first conventional impeller with an axial inlet and a mixed or centrifugal outlet. The second impeller is designed parametrically and can be considered as a rotating-diffuser with a radial or mixed inlet and outlet. Ultimately, the numerical simulation results of a selection of candidate solutions are discussed.

With the Backlash Dynamics Simulation of a Crank-Slider Mechanism

2012 ◽  
Vol 479-481 ◽  
pp. 707-710
Author(s):  
Shao Jun Bo ◽  
Kui Ji
Keyword(s):  
System Dynamics ◽  
Dynamics Simulation ◽  
Kinematic Pair ◽  
Body System ◽  
Nonlinear Characteristics ◽  
Preliminary Study ◽  
Simulation Results ◽  
Multi Body ◽  
Dynamics Models ◽  
Crank Mechanism

On the basis of flexible multi-body system dynamics theory, we built flexible multi-body system dynamics models which include a backlash, and to a slider-crank mechanism as the research object, we made a preliminary study on the effect on the flexible components and the backlash of the kinematic pair on mechanical system dynamics characteristics. To consider the backlash of the kinematic pair and component of flexible space can show a preliminary research on the dynamic simulation, and focus on the backlash, friction and gravity field to influence in the dynamic characteristics of the system. The simulation results show that, due to the existence of backlash made the two components frequent collision in the process of the stretching, clearance, flexible and friction are closed, make the system nonlinear characteristics increased.

scholarly journals Flow Past a Fixed and Freely Vibrating Drilling Riser System with Auxiliaries in Laminar Flow

2021 ◽  
Vol 87 (3) ◽  
pp. 94-104
Author(s):  
Fatin Alias ◽  
Mohd Hairil Mohd ◽  
Mohd Azlan Musa ◽  
Erwan Hafizi Kasiman ◽  
Mohd Asamudin A Rahman
Keyword(s):  
Laminar Flow ◽  
Vortex Shedding ◽  
Oil And Gas ◽  
Reynold Number ◽  
Fundamental Study ◽  
Drag Forces ◽  
Gap Ratio ◽  
Auxiliary Lines ◽  
Lock In ◽  
External Loads

Drilling risers used in oil and gas operations are subjected to external loads such as wave and current. One of the phenomena that arise from the external loads is the Vortex-Induced Vibration (VIV), which affects the performance of the riser due to excessive vibration from the vortex shedding. A significant factor influencing the VIV is the design of the drilling riser and its auxiliary lines. Until now, the optimum geometrical size and gap between the auxiliary and the main riser are still very scarcely studied. In this paper, the main objective is to study the effects of the gap ratio (G/D) on the vortex shedding phenomenon on a fixed and freely vibrating riser. The riser system was modelled with a main drilling riser and six auxiliary lines with a constant diameter ratio (d/D) of 0.45 and gap ratio (G/D) = 0 to 2.0 in the laminar flow regime with Reynold Number, Re = 200. The simulations were conducted for Single Degree of Freedom (SDOF) using Computational Fluid Dynamics (CFD) software, Altair AcuSolve. It was found that the freely vibrating riser experienced higher lift and drag forces as compared to the fixed riser due to the synchronization (lock-in) of the shedding vibration and the natural frequencies. The lock-in phenomenon is normally observed on the drilling riser at different current directions. The forces are reduced when G/D is higher. The vortex shedding was significantly reduced for auxiliaries between 0.3 to 1.4. It is confirmed that by modifying the interaction of the vortices in the wake region with auxiliary lines, the hydrodynamic forces will be decreased. Finally, this fundamental study could potentially be used in the designing stage of an optimum drilling riser system by considering significant governing factors.

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