Numerical simulation and analysis of periodically oscillating pressure characteristics of inviscid flow in a rolling pipe

Abstract

Floating liquefied natural gas (LNG) plants are gaining increasing attention in offshore energy exploitation. The effects of the periodically oscillatory motion on the fluid flow in all processes on the offshore plant are very complicated and require detailed thermodynamic and hydrodynamic analyses. In this paper, numerical simulations are conducted by computational fluid dynamics (CFD) code combined with user defined function (UDF) in order to understand the periodically oscillating pressure characteristics of inviscid flow in the rolling pipe. The computational model of the circular pipe flow is established with the excitated rolling motion, at the excitated frequencies of 1–4 rad/s, and the excitated amplitudes of 3°–15°, respectively. The influences of flow velocities and excitated conditions on pressure characteristics, including mean pressure, frequency and amplitude are systematically investigated. It is found that the pressure fluctuation of the inviscid flow remains almost constant at different flow velocities. The amplitude of the pressure fluctuation increases with the increasing of the excitated amplitude, and decreases with the increasing of the excitated frequency. It is also found that the period of the pressure fluctuation varies with the excitated frequency. Furthermore, theoretical analyses of the flow in the rolling circular pipe are conducted and the results are found in qualitative agreement with the numerical simulations.

Key words： pressure fluctuation; rolling; floating production storage and offloading unit for liquefied natural gas (LNG-FPSO) offshore

Acknowledgements

This work was supported by the National High-Tech Research and Development Program of China (863 Program) (No.2006AA09Z317), and the Program for Distinguished Young Scholars of the Ministry of Education (NCET-07-0544).

Notation

a_{\mathrm{0}}	Acceleration of kinetic system/(m·s-2)
f	Body force/ (N·kg-1)
fi	Body force component/(N·kg-1)
BoldItalic	Normal vector
\mathrm{d}{\mathit{l}}^{\prime }	Pipe segment in kinetic system/m
P	Pressure/(N·m-2)
qw	Heat flux of wall/W
BoldItalic0	Vector of origins from inertial and kinetic systems/m
BoldItalic	Vector in kinetic system/m
t	Time/s
T	Temperature of fluid/K
BoldItalic	Flow velocity/(m·s-1)
ui	Velocity component/(m·s-1)
BoldItalicn	Normal velocity/(m·s-1)
BoldItalicr	Relative velocity/(m·s-1)
xi	Direction component/m
{\delta }_{ij}	Kronecker delta
ϵ	Surface force/(N·m-3)
{\theta }_{\mathrm{0}}	Amplitude of rolling/rad
\rho	Density/(kg·m-3)
\omega	Angular velocity/(rad·s-1)
{\omega }_{\mathrm{0}}	Angular velocity of rolling/(rad·s-1)

References

1 Gu Y, Ju Y L. LNG-FPSO: Offshore LNG solution. Frontiers of Energy and Power Engineering in China, 2008, 2(3): 249-255

2 Yan G, Gu Y. Effect of parameters on performance of LNG-FPSO offloading system in offshore associated gas fields. Applied Energy, 2010, 87(11): 3393-3400

3 Richardson E G, Tyler E. The transverse velocity gradient near the mouths of pipes in which an alternating or continuous flow is established. Proceedings of the Physical Society, 1929, 42(1): 1-15

4 Sexl T. On the annular effect discovered by E. G. Richardson. Zeitschrift fur Physik, 1930, 61: 349-362 (in German)

5 Womersley J R. Method for the calculation of velocity, rate of flow and viscous drag in arteries when the pressure gradient is known. The Journal of Physiology, 1955, 127(3): 553-563

PMID

6 Uchida S. The pulsating viscous flow superimposed on the steady laminar motion of incompressible fluid in a circular pipe. Zeitschrift für Angewandte Mathematik und Physik, 1956, 7(5): 403-422

7 Clamen M, Minton P. An experimental investigation of flow in an oscillating pipe. Journal of Fluid Mechanics, 1977, 81(3): 421-431

8 Hershey D, Song G. Friction factors and pressure drop for sinusoidal laminar flow of water and blood in rigid tubes. AIChE Journal. American Institute of Chemical Engineers, 1967, 13(3): 491-496

9 Ohmi M, Iguchi M. Flow pattern and frictional losses in pulsating pipe flow. Part 6: Frictional losses in a laminar flow. Bulletin of the JSME, 1981, 24(196): 1756-1763

10 Ohmi M, Iguchi M, Usui T. Flow pattern and frictional losses in pulsating pipe flow. Part 5: Wall shear stress and flow pattern in a laminar flow. Bulletin of the JSME, 1981, 24(187): 75-81

11 Donovan F M, McIlwain R W, Mittmann D H, Taylor B C. McIIwain R W, Mittmann D H, Taylor B C. Experimental correlations to predict fluid resistance for simple pulsatile laminar flow of incompressible fluids in rigid tubes. Journal of Fluids Engineering, 1994, 116(3): 516-521

12 Pendyala R, Jayanti S, Balakrishnan A R. Flow and pressure drop fluctuations in a vertical tube subject to low frequency oscillations. Nuclear Engineering and Design, 2008, 238(1): 178-187

13 Ishida T, Yoritsune T.Effects of ship motions on natural circulation of deep sea research reactor DRX. Nuclear Engineering and Design, 2002, 215(1,2): 51-67

14 Murata H, Sawada K, Kobayashi M. Experimental investigation of natural convection in a core of a marine reactor in rolling motion. Journal of Nuclear Science and Technology, 2000, 37(6): 509-517

15 Murata H, Sawada K, Kobayashi M () Natutal circulation characteristics of a marine reactor in rollling motion and heat transfer in the core. Nuclear Engineering and Design, 2002, 215(1,2): 69-85

16 Tan S C, Su G H, Gap P Z. Experimental and theoretical study on single-phase natural circulation flow and heat transfer under rolling motion condition. Applied Thermal Engineering, 2009, 29(14,15): 3160-3168

17 Pendyala R, Jayanti S, Balakrishnan A R. Convective heat transfer in single-phase flow in a vertical tube subjected to axial low frequency oscillations. Heat mass transfer 2008, 44(7): 857-864

18 Yan B H, Gu H Y, Yu L. Numerical research of turbulent heat transfer in rectangular channels in ocean environment. Heat and Mass Transfer, 2011, 47(7): 821-831

19 Gundogdu M Y, Carpinlioglu M O. Present state of art on pulsatile flow theory part 1: Laminar and transitional flow regimes. JSME International Journal, 1999, 42(3): 384-397

20 Gundogdu M Y, Carpinlioglu M O. Present state of art on pulsatile flow theory part 2: Turbulent flow regime. JSME International Journal, 1999, 42(3): 398-410

21 Özdinç Çarpinlioglu M. A critical review on pulsatile pipe flow studies directing towards future research topics. Flow Measurement and Instrumentation, 2001, 12(3): 163-174