Dynamic Modelling of Deep-Water Riser With Slug Flow Based on ALE-ANCF

2020 ◽  
Author(s):  
Depeng Liu ◽  
Shangmao Ai ◽  
Liping Sun
Keyword(s):  
Slug Flow ◽  
High Speed ◽  
Dynamic Modelling ◽  
Internal Flow ◽  
Bending Moment ◽  
Time Domain Analysis ◽  
Load Model ◽  
Centrifugal Load ◽  
Load Component ◽  
Euler Bernoulli Beam

Abstract The internal flow in gas-liquid mixing riser often displays a flow pattern known as slug flow, in which gas and liquid are alternately distributed. Dynamic effects due to slug flow is normally most obvious in areas along the riser with high curvature, which is caused by the centrifugal load component. The global riser response to this excitation can be predicted by nonlinear time domain analysis using the load model as described for slug flow conditions. In this study, the riser with internal slug flow is modeled under the framework of Arbitrary-Lagrange-Euler (ALE) description by using the Absolute Node Coordinate Formula (ANCF). The riser is discretized into ANCF cable element based on the Euler-Bernoulli beam assumption, while one-dimensional moving medium modeling method with time-varying density is used to model slug element. Compared with other FEA models of riser subjected to internal flow, the ALE-ANCF model allow easily modeling of complex mass flow and has the advantages of high speed and high precision in handling large deformation of riser, especially for the compliant riser configurations. Numerical simulations of two simplified models are carried out to validate the developed model, then the dynamic response such as displacement, tension force and bending moment of the riser conveying slug flow are analyzed.

Tank Test and Numerical Simulation of Spar Type Floating OTEC

2021 ◽  
Author(s):  
Shunka C. Hirao ◽  
Jun Umeda ◽  
Kentaroh Kokubun ◽  
Toshifumi Fujiwara
Keyword(s):  
Numerical Simulations ◽  
Cold Water ◽  
Scaling Law ◽  
Internal Flow ◽  
Bending Moment ◽  
Floating Structure ◽  
Waves And Currents ◽  
Tank Test ◽  
Safety Assessments ◽  
Ocean Thermal Energy

Abstract National Maritime Research Institute, NMRI, had been studying the analytical method on safety assessments of floating power generation facilities for ten years more. As a part of these studies, an Ocean Thermal Energy Conversion (OTEC) was also studied in our institute. The OTEC normally has a very long and thick Cold-Water Pipe (CWP) with an unanchored end to pump up a large amount of cold-water continuously. From the viewpoints of the safety assessments of the OTEC operation, it is noteworthy to confirm the effect of the existing long pipe against a floating unit/body and an effect of internal flowing water. It is necessary, moreover, to consider the Vortex Induced Vibration (VIV) effect for floater motions and structural analysis of the pipe itself and a connecting point of the floating structure. In this paper, the results of model tests and numerical simulations of a spar type floating OTEC with a single CWP in waves and currents are presented. The CWP model was made of material fitting the scaling law for a planned full scale OTEC. The specific and unique phenomena of the floating OTEC were confirmed from the model test results. Based on the results of the tank tests and the numerical simulations, we confirmed the necessary items and arrangements for safety evaluations. In detail, the internal flow increased the bending moment at the connection point.

Visual Observation of Fragmentation Behavior on Molten Material Jet Surface in Coolant

2008 ◽  
Author(s):  
Yuta Uchiyama ◽  
Yutaka Abe ◽  
Akiko Fujiwara ◽  
Hideki Nariai ◽  
Eiji Matsuo ◽  
...  
Keyword(s):  
Water Surface ◽  
High Speed ◽  
Internal Flow ◽  
Core Material ◽  
Generation Process ◽  
High Speed Camera ◽  
Sodium Coolant ◽  
Molten Material ◽  
Fragmentation Behavior ◽  
Jet Breakup

For the safety design of the Fast Breeder Reactor (FBR), it is strongly required that the post accident heat removal (PAHR) is achieved after a postulated core disruptive accident (CDA). In the PAHR, it is important that the molten core material is solidified in sodium coolant which has high boiling point. Thus it is necessary to estimate the jet breakup length which is the distance that the molten core material is solidified in sodium coolant. In the previous studies (Abe et al., 2006), it is observed that the jet is broken up with fragmenting in water coolant by using simulated core material. It is pointed out that the jet breakup behavior is significantly influenced by the fragmentation behavior on the molten material jet surface in the coolant. However, the relation between the jet breakup behavior and fragmentation on the jet surface during a CDA for a FBR is not elucidated in detail yet. The objective of the present study is to elucidate the influence of the internal flow in the jet and fragmentation behavior on the jet breakup behavior. The Fluorinert™ (FC-3283) which is heavier than water and is transparent fluid is used as the simulant material of the core material. It is injected into the water as the coolant. The jet breakup behavior of the Fluorinert™ is observed by high speed camera to obtain the fragmentation behavior on the molten material jet surface in coolant in detail. To be cleared the effect of the internal flow of jet and the surrounding flow structure on the fragmentation behavior, the velocity distribution of internal flow of the jet is measured by PIV (Particle Image Velocimetry) technique with high speed camera. From the obtained images, unstable interfacial wave is confirmed at upstream of the jet surface, and the wave grows along the jet-water surface in the flow direction. The fragments are torn apart at the end of developed wave. By using PIV analysis, the velocity at the center of the jet is fast and it suddenly decreases near the jet surface. This means that the shear force acts on the jet and water surface. From the results of experiment, the correlation between the interfacial behavior of the jet and the generation process of fragments are discussed. In addition, the influence of surface instability of the jet induced by the relative velocity between Fluorinert™ and coolant water on the breakup behavior is also discussed.

scholarly journals Analysis and control of flow at suction connection in high-speed centrifugal pump

2017 ◽  
Vol 9 (1) ◽  
pp. 168781401668529 ◽  
Author(s):  
Wen-wu Song ◽  
Li-chao Wei ◽  
Jie Fu ◽  
Jian-wei Shi ◽  
Xiu-xin Yang ◽  
...  
Keyword(s):  
Flow Field ◽  
Centrifugal Pump ◽  
High Speed ◽  
Internal Flow ◽  
Orifice Plate ◽  
Centrifugal Pumps ◽  
Pressure Area ◽  
Negative Effect ◽  
And Control ◽  
Experimental Data Analysis

The backflow vortexes at the suction connection in high-speed centrifugal pumps have negative effect on the flow field. Setting an orifice plate in front of the inducer is able to decrease the negative effect caused by backflow vortexes. The traditional plate is able to partially control the backflow vortexes, but a small part of the vortex is still in the inlet and the inducer. Four new types of orifice plates were created, and the control effects on backflow vortexes were analyzed. The ANSYS-CFX software was used to numerically simulate a high-speed centrifugal pump. The variations of streamline and velocity vectors at the suction connection were analyzed. Meanwhile, the effects of these plates on the impeller pressure and the internal flow field of the inducer were analyzed. Numerically, simulation and experimental data analysis methods were used to compare the head and efficiency of the high-speed pumps. The results show that the C-type orifice plate can improve the backflow vortex, reduce the low-pressure area, and improve the hydraulic performance of the high-speed pump.

scholarly journals Effect of Slam Force Duration on the Vibratory Response of a Lightweight High-Speed Wave-Piercing Catamaran

2015 ◽  
Vol 59 (02) ◽  
pp. 69-84
Author(s):  
Jason John McVicar ◽  
Jason Lavroff ◽  
Michael Richard Davis ◽  
Giles Thomas
Keyword(s):  
High Speed ◽  
Bending Strength ◽  
Experimental Studies ◽  
Bending Moment ◽  
Higher Order ◽  
Acute Angle ◽  
Beam Model ◽  
Higher Order Modes ◽  
Hull Structure ◽  
Vertical Bending Moment

When the surface of a ship meets the water surface at an acute angle with a high relative velocity, significant short-duration forces can act on the hull plating. Such an event is referred to as a slam. Slam loads imparted on ships are generally considered to be of an impulsive nature. As such, slam loads induce vibration in the global hull structure that has implications for both hull girder bending strength and fatigue life of a vessel. A modal method is often used for structural analysis whereby higher order modes are neglected to reduce computational effort. The effect of the slam load temporal distribution on the whipping response and vertical bending moment are investigated here by using a continuous beam model with application to a 112 m INCAT wave-piercing catamaran and correlation to full-scale and model-scale experimental data. Experimental studies have indicated that the vertical bending moment is dominated by the fundamental longitudinal bending mode of the structure. However, it is shown here that although the fundamental mode is dominant in the global structural response, the higher order modes play a significant role in the early stages of the response and may not be readily identifiable if measurements are not taken sufficiently close to the slam location. A relationship between the slam duration and the relative modal response magnitudes is found, which is useful in determining the appropriate truncation of a modal solution.

Experimental Determination of Hydrodynamic Parameters of Air-Water Two-Phase Slug Flow in Horizontal Pipes

2012 ◽  
Author(s):  
Carlos H. Romero ◽  
María A. Márquez ◽  
Sissi D. Vergara ◽  
María T. Valecillos
Keyword(s):  
Slug Flow ◽  
High Speed ◽  
Electronic Device ◽  
Water System ◽  
Superficial Velocity ◽  
Two Phase ◽  
Horizontal Pipes ◽  
Type Pattern ◽  
Elongated Bubble

Two phase slug flow is the most common flow pattern for horizontal and near-horizontal pipelines. This study is designed to determine experimental velocities of elongated bubbles, lengths of liquid slugs and elongated bubbles, and slug frequencies for twenty flow rates combinations of a two phase air-water system that belong to a slug type pattern in horizontal pipes with a non invasive electronic device made of Photo-diodes (emitter) and photo-transistors (receiver) in a non visible length wave of 940 nanometers. The non intrusive electronic device is validated by simultaneously taking pictures with a high speed camera, (Kodak model Ektapro 4540 mx Imager, at shooting speed of 4500 frames per second, the picture resolution is 256 × 256 pixels), through a visualization cell filled with glycerin. This work is done with acrylic pipes of 0,03175 m inner diameter, to ensure complete flow development, the pictures are taken from a visualization cell located at a x/D = 249, the electronic device is located at x/D = 250. Air superficial velocity ranged between 0.156 and 0.468 m/s while water superficial velocity ranged between 0.159 and 1.264m/s. It is found that the non intrusive electronic device formed by photo diodes and photo transistors is an accurate technique that can be used in the determination of elongated bubble velocities, lengths and slug frequencies.

scholarly journals Dynamic Modelling and Analysis of the Microsegment Gear

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Yangshou Xiong ◽  
Kang Huang ◽  
Tao Wang ◽  
Qi Chen ◽  
Rui Xu
Keyword(s):  
High Speed ◽  
Load Capacity ◽  
Dynamic Performance ◽  
Dynamic Modelling ◽  
Weight Ratio ◽  
Load Condition ◽  
Main Idea ◽  
Heavy Load ◽  
Rotating Speed ◽  
Involute Gear

The development of technology requires higher load capacity, rotating speed, power-weight ratio, lower vibration, and noise with respect to the gear transmission. The new type microsegment gear’s tooth profile curve is composed of many microsegments. Previous researches indicate that the microsegment gear has a good static performance, while the dynamic behavior of the microsegment gear has never been investigated. This paper will focus on the dynamic performance of the gear. The profile deviation between microsegment gear and involute gear is regarded as a displacement excitation in the proposed dynamic model. The numerical analysis for three cases is conducted and the results shows that, in low-speed and heavy-load, medium-speed and medium-load conditions, microsegment gear and involute gear both exhibit a good performance, while, in high-speed and heavy-load condition, microsegment gear has a better performance than that of involute gear. The influence of backlash on the dynamic performance is also studied. It is found that the variation of backlash does not change the type of motion, but the vibration amplitude and the stability of the motion are much affected. The main idea in this paper is supposed to provide a novel method for the precision grinding of the microsegment gear.

Inverse Design of 3D Compressor Blades With Adjoint Method

2003 ◽  
Author(s):  
June Chung ◽  
Jeonghwan Shim ◽  
Ki D. Lee
Keyword(s):  
High Speed ◽  
Adjoint Method ◽  
Design Method ◽  
Computational Cost ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Internal Flow ◽  
Adjoint System ◽  
Inverse Design ◽  
Compressor Blades

A three-dimensional (3D) CFD-based design method for high-speed axial compressor blades is being developed based on the discrete adjoint method. An adjoint code is built corresponding to RVC3D, a 3D turbomachinery Navier-Stokes analysis code developed at NASA Glenn. A validation study with the Euler equations indicates that the adjoint sensitivities are sensitive to the choice of boundary conditions for the adjoint variables in internal flow problems and constraints may be needed on internal boundaries to capture proper physics of the adjoint system. The design method is demonstrated with inverse design based on Euler physics, and the results indicate that the adjoint design method produces efficient 3D designs by drastically reducing the computational cost.

Vibration Control of a Rigid and Flexible High-Speed Railway Vehicle

2020 ◽  
Author(s):  
Semiha Türkay ◽  
Aslı S. Leblebici
Keyword(s):  
High Speed ◽  
Low Frequency ◽  
Railway Vehicle ◽  
Allowable Limit ◽  
Low Frequencies ◽  
Railway Line ◽  
Power Spectral ◽  
Spectral Density Functions ◽  
The Right ◽  
Euler Bernoulli Beam

Abstract In this paper, the vertical carbody dynamics of the railway vehicle excited by random track inputs are investigated. The multi-objective ℋ∞ controllers for carbody weight of the actual, heavy and a mass confined in a polytopic range have been designed with the aim of reducing the wheel forces, heave, pitch and roll body accelerations of the vehicle. Later, the carbody mass is modelled as a free-free Euler Bernoulli beam and the low frequency flexural vibrations of the train body are examined. An omnibus ℋ∞ controller is synthesized to suppress both the rigid and low frequencies flexible modes of the railway vehicle. The performances of the ℋ∞ controllers are verified by using the passive and active suspension responses on the right and left rail track disturbances that are represented by the power spectral density functions authenticated for the stochastic real track data collected from the Qinhuangdao-Shenyang passenger railway line in China. Simulation results showed that all controllers exhibit a very good performance by effectively reducing the car-body accelerations in vicinity of the resonanat frequencies while keeping the wheel-rail forces in the allowable limit.

scholarly journals A New Conceptual Design and Dynamic Analysis of a Spar-Type Offshore Wind Turbine Combined with a Moonpool

Energies ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3737 ◽  
Author(s):  
Thanh Dam Pham ◽  
Hyunkyoung Shin
Keyword(s):  
Wind Turbine ◽  
Bending Moment ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Operational Conditions ◽  
Floating Offshore Wind Turbines

Floating offshore wind turbines promise to provide an abundant source of energy. Currently, much attention is being paid to the efficient performance and the economics of floating wind systems. This paper aims to develop a spar-type platform to support a 5-MW reference wind turbine at a water depth of 150 m. The spar-type platform includes a moonpool at the center. The design optimization process is composed of three steps; the first step uses a spreadsheet to calculate the platform dimensions; the second step is a frequency domain analysis of the responses in wave conditions; and the final step is a fully coupled simulation time domain analysis to obtain the dynamic responses in combined wind, wave, and current conditions. By having a water column inside the open moonpool, the system’s dynamic responses to horizontal and rotating motions are significantly reduced. Reduction of these motions leads to a reduction in the nacelle acceleration and tower base bending moment. On the basic of optimization processes, a spar-type platform combined with a moonpool is suggested, which has good performance in both operational conditions and extreme conditions.

Sign in / Sign up

Export Citation Format

Share Document