Session: 08-05-01 Internal Flows & FIV

Paper Number: 122474

122474 - Development of Two-Phase Flow-Induced Vibration Predicting Method for a Piping System With Elbows 

Gas-liquid intermittent two-phase flow in the piping system may cause piping vibration due to the repeating collision of liquid chunk onto the inner wall of elbow fittings. To design and monitor of piping system with elbows in Oil & Gas production plants or chemical plants, it is necessary to develop a prediction method for unsteady two-phase flow in the piping, vibration of the piping and the piping fatigue strength. Applications in Oil & Gas production plants include such kinds of piping system as jumpers, spools, flowlines and risers.
There are no established industry methods and tools so far that can be used by designers to calculate fatigue life, which is a critical design driver for deepwater applications. This is one of the objectives of the DeepStar funded study.
In this study, we developed the prediction method which combines three-dimensional two-phase flow simulation method for unsteady two-phase flow behavior and fluid force, one-dimensional beam model for vibration analysis and Dirlik's method calculation for fatigue analysis.
Three-dimensional two-phase flow simulation method was developed by implementing constitutive equations for interfacial interactions between gas and liquid phases into the platform of a commercial code, ANSYS Fluent. One-dimensional beam model was built and calculation was conducted by using ANSYS commercial code. Dirlik's method is one of the most famous and common methods to approximate probability density function of rainflow amplitude. These three types of calculation were carried out serially for each flow condition determined by gas and liquid velocities, pressure and temperature.
The subsea jumper piping was selected for the evaluation target in this study. The inner diameter is 145mm, the longest horizontal section is approximately 18m and the longest vertical section is approximately 10m. As a result of the eigen value analysis of the jumper piping, the natural frequencies in the out-of-plane direction, the in-plane horizontal direction, and the in-plane vertical direction were about 0.5 Hz, 1.0 Hz, and 2.0 Hz, respectively.
Several cases of unsteady two-phase flow CFD analysis were conducted to calculate excitation forces at each elbow of the jumper piping. In a slugging condition such as the case with gas superficial velocity of 2.66m/s and liquid superficial velocity of 2.6m/s, the intermitted two-phase flow was simulated in CFD analysis and the frequency of liquid chunk at an elbow was around 1Hz.
Vibration analysis for the cases was also conducted to evaluate dominant vibration modes and locations with larger stress based on the CFD analysis results. Fluid excitation force evaluated in the two-phase flow CFD were utilized as an input of vibration analysis.
Conducting the FIV analysis, the stress at each elbow was evaluated and the maximum stress in a slugging velocity condition was larger than that in other velocity conditions such as bubbly flow condition and stratified flow condition. Fatigue analysis in frequency domain was carried out to estimate the lifetime of elbow fittings, using the stress response spectrum in each elbow estimated by the vibration analysis.
Through those analysis, the effect of flow rate of gas and liquid phases on the fluid excitation force and vibration were also investigated.
Mitsubishi Heavy Industries would like to extend our sincere gratitude to the following individuals and organizations for their invaluable contributions to this project. Special appreciation goes to Nippon Foundation for the financial support and DeepStar Program for the technical guidance and program management. For the technical support and project support, the authors would like to thanks Yiannis Constantinides, Krishna Sambath, Henry Ren, from Chevron, Moussa Kane, Daniel Byrd from TotalEnergies, Puneet Agarwal from ExxonMobil and the technical chairs and subcommittee members from the DeepStar Fixed & Floating Offshore Production Subcommittee. Their expertise and commitment have been instrumental in the success of this project. The financial support and valuable technical discussion are fully acknowledged.

Presenting Author: Hiroaki Nakanishi Mitsubishi Heavy Industries, Ltd.

Presenting Author Biography: Hiroaki Nakanishi is an employee of Mitsubishi Heavy Industries, Ltd. His work focuses on multi
phase flow.

Authors:

Yoshiteru Komuro Mitsubishi Heavy Industries, Ltd.
Hiroaki Nakanishi Mitsubishi Heavy Industries, Ltd.
Yoshiyuki Kondo Mitsubishi Heavy Industries, Ltd.
Masashi Takemoto Mitsubishi Heavy Industries, Ltd.
Kazuo Hirota Mitsubishi Heavy Industries, Ltd.
Shunsaku Matsumoto Mitsubishi Heavy Industries, Ltd.
Tadashi Sugimura Mitsubishi Heavy Industries, Ltd.
Shintaro Honjo Mitsubishi Heavy Industries, Ltd.