Study on the design method of distorted model testing for cementing casing string systems based on the similarity of stiffness and mass

Qi L., Yin Y., Wang L., Qu C., Yu Y., Xia X., Liu B.

Teja D.H., Muvvala P., Prashanth Nittala N.A., Bandhu D., Khan M.I., Saxena K.K., Khan M.I.

Guo Z., Ni Q., Cao R., Chen W., Dai H., Wang L.

Up to now, three-dimensional modeling for investigating the nonlinear dynamics of cantilevered pipes conveying fluid with arbitrary initial configurations is still unsolved. This study aims to establish a universal three-dimensional nonlinear dynamic model based on absolute node coordinate formulation (ANCF) and the generalized Lagrange equation. Through this three-dimensional model, static equilibrium configuration and stability analysis for a straight-curved planar pipe system are extensively explored. The results demonstrate that the static equilibrium configuration obtained by the three-dimensional ANCF is limited to the in-plane and hence, it is consistent with that predicted by the two-dimensional model. In terms of stability analysis, two critical flow velocities for flutter instability, namely, the in-plane and out-of-plane critical flow velocities are obtained. It is found that the out-of-plane critical flow velocity is much lower than its counterpart of the in-plane. Regarding on nonlinear dynamics, vibration shapes, time history curves and phase portraits are offered to display rich dynamical behaviors of the pipe system, which are strongly dependent on in-plane and out-of-plane initial conditions. The proposed nonlinear dynamic model in this study can deal with large-amplitude vibrations of pipes conveying fluid with arbitrary initial configurations in the three-dimensional sense, which provides a new thought for the dynamical analysis of nonconservative fluid-conveying pipe system.

G S., Prasad.CH V., Bhatti S.K., Venu.Madhav V.V., Saxena K.K., Khan M.I., Aloui Z., Prakash C., Khan M.I.

This study investigates the influence of multi-walled carbon nanotubes (MWCNTs) and hybrid biodiesel blends on the performance, combustion, and emission characteristics of a compression ignition engine. The hybrid biodiesel comprises waste frying oil methyl ester (WFOME), sesame oil methyl ester (SOME), and ultra-low sulfur diesel (ULSD) blended at 20%:80% by volume (B20). MWCNTs were added into B20 at 25 ppm and 50 ppm concentrations (B20-25MWCNT and B20-50MWCNT). Experimental analysis was conducted under varying engine loads and injection pressures, complemented by CFD simulations. Results demonstrate that the addition of MWCNTs significantly enhances B20 blend performance, with B20-50MWCNT exhibiting a 25% increase in brake thermal efficiency and a 17% reduction in brake specific fuel consumption compared to neat B20.Additionally, the incorporation of MWCNTs resulted in notable reductions in harmful emissions. NOx emissions for the B20+50MWCNT blend were reduced by up to 36% compared to diesel and 43% compared to B20. Smoke opacity and particulate emissions also showed significant decreases, highlighting the cleaner combustion facilitated by the presence of MWCNTs. The CFD simulations provided detailed insights into the combustion process, validating the experimental findings and elucidating the mechanisms behind the observed improvements. The enhanced fuel atomization, better fuel-air mixing, and catalytic properties of MWCNTs were identified as key factors contributing to the superior performance and reduced emissions.

Peng X., Yue B., Li G., Qiu Z., Yang H.

The increase in deep and ultra-deep wells demands higher drilling efficiency and more drilling safety. Since the undesired oscillation associated with the tripping in/out of the drill-string increases the risk of downhole safety, it is important to master the axial dynamics of the drill-string system and choose appropriate tripping parameters. In this study, the drill-string system during the tripping operation is modeled as a continuous Euler–Bernoulli beam with the equivalent mass-spring-damper at the top and free at the bottom. The finite element method is employed to solve the axial dynamics of the drill-string system. Then, the dynamic characteristics of the underground drill-string for different system parameters are investigated in detail. Moreover, a multi-objective optimization framework is proposed, aiming to find the optimal tripping parameters and reach a balance between drilling safety and drilling efficiency. The results show that the axial vibration of the drill-string brings about the dynamic load fluctuation of the system, which becomes more serious in the tripping out process. The proposed optimization procedure can reach a desired balance between drilling efficiency and drilling safety and obtain appropriate tripping parameters for different conditions.

Mao L., Chen X., Gao Y., Fu Q.

During the production of high-temperature, high-pressure (HPHT) gas wells, the gas entering the production tubing column induces vibration, which in turn leads to changes in the mechanical properties and safety of the tubing column. A dynamic model of the production string in an HPHT gas well was established to study the dynamic characteristics of its production string. The additional axial force caused by the transient temperature change and the nonlinear contact collision between the production string and the casing were considered. The Newmark-β method was used to solve the problem by analyzing and comparing the flow-induced vibration characteristics of the production pipe string. In this study, a gas well in the southwest Sichuan Basin was used as the research object to study the effects of gas production, packer setting position, and string wall thickness on the dynamic characteristics of the string. The results show that in the gas production process, intense vibrations are generated in the transverse and longitudinal directions of the tubular column. After high-velocity gas flows through the production tubing column, the vibrations at the wellbore inclination and the top of the tubing column are more intense. With the rise of production and the downward movement of the packer setting position, the vibration displacement and frequency of the tubing column increase. In addition, as the column's wall thickness increases, the column's stiffness rises, which, in turn, reduces the vibration of the column. When the gas production increases from 60×104 m3/d to 150×104 m3/d, the maximum transverse vibration displacement of the production string will increase by 22.2%-39.3%, while the frequency will increase by 15.3%-54.3%. When the wall thickness of the pipe column reaches 9.53mm and 10.92mm, it can be employed to enhance the safety factor of the string and extend the fatigue life of the string. This study provides a theoretical framework for field string protection and production guidance.

Du Y., Fan G., Chen G., Zhang Y., Wang D., Li X.

The distortion model may arise due to the inability to isometrically scale the thickness dimensions when utilizing similitude theory to develop scaling laws for large-scale concentrator units in the Space Solar Power Satellite. Previous works to address the distortion model neglect its negative impacts and persistent limits, resulting in insufficient prediction accuracy for prototype. To obtain scaling laws of the distortion model, this paper introduces a novel strategy called the performance-dominated separate similitude analysis, which significantly reduces the distortion model's negative impacts and persistent limits on similitude prediction. Firstly, performance parameters sensitive to the distortion model are generated by dimensional analysis and the governing equation method. Secondly, the distortion model is separated into two scaled models: complete and partial similitude, based on the sensitive performance parameters. Subsequently, the scaling laws of complete and partial similitude models are derived, respectively. Finally, the scaling laws of the distortion model are derived by combining the complete and partial similitude laws. The proposed method is validated through finite element model simulation for both the concentrator unit prototype and the distortion model. Results indicate that in the best case, the prediction error doesn't exceed 0.2%, and the prediction accuracy can be improved by up to 87.34% compared to the existing methods.

Peek R., Sequeiros O., Wu J., Witz M., Yin D., Lie H.

Bending strain data from 3 well-instrumented VIV model test programs on simply supported bare pipes under uniform flow are processed using rainflow counting to get fatigue damage rates directly. These are presented in terms a dimensionless fatigue-equivalent bending strain amplitude, ϵe, which for the structurally undamped simply supported span under constant axial force N undergoing small rotations depends on 5 dimensionless parameters, and only weakly on the fatigue resistance curve used. Existing and new approximations are discussed as assessed whereby the number of dimensionless parameters that affect ϵe may be reduced from 5 to 1. Thus a scaling approach is developed, whereby any VIV test can be scaled to represent any prototype at a current velocity determined by the scaling procedure. The procedure uses scaling only for the dynamic part of the response, and structural analysis for the static part. It works for single as well as multi-mode response. It is illustrated for a 150m-long prototype span subject to high currents. The test and/or scaling results are also compared to predictions by existing methods, including DNVGL-RP-F105 (“F105”) and Vivana. The example also illustrates how the proposed method can be used for partially strake-covered (“straked”) pipes, provided the strake coverage is similar for model and prototype. The scatter in the data gives an indication of the uncertainties involved in estimating VIV fatigue damage rates from limited experimental data where high-mode and multi-mode response is possible.

He F., Luo Z., Shi H., Yu C., Li L.

Similitude theory can be used to extrapolate the experimental data of a small, inexpensive, and easily tested model into design information for a large prototype. Scaling laws provide the relationship between a full-scale structure and its scale models. However, one challenging issue is the similitude of complex structure. To address the problem, an energy similarity method is presented based on the principle of conservation of power flow. The emphasis is to predict the vibroacoustic characteristic of beam-plate coupled structure in an effective and convenient way. The vibration response and radiated sound are investigated on the beam-plate coupled structure under random excitation. Numerical simulation and model test are both implemented, which validate the effectiveness and efficiency of the proposed method. Both aluminum and honeycomb materials are considered in beam-plate coupled structures. In addition, the comparison between the classic similitude method and the presented method (energy similarity) is illustrated. The results show that the energy similarity presented in this study can achieve a better performance in reproducing the vibroacoustic characteristic of beam-plate coupled structure than the classic similarity method.

Tarahomi M.A., Emamzadeh M., Ameri M.

Two-phase flow in pipelines is analyzed by experimental facilities and also numerical analysis. The experimental facilities are designed by scale-down field pipelines. Therefore, the accuracy of experimental data is strongly dependent on the scaling method. In this research, an approach for downscaling field pipelines into experimental facilities is proposed. The fluid flows in different scales for various flow patterns including Stratified, Stratified Wavy, Slug, Plug and Bubbly are numerically simulated and validated against full-scale experimental data. The results of the scaled-down model simulation are in excellent agreement with the full-scale facilities, affirming the robustness of the downscaling method. This research enhances the understanding of scaled-down experiments for various flow conditions.

Li L., Luo Z., He F., Zhou J., Ma H., Li H.

Li L., Luo Z., Wu F., He F., Sun K.

Similitude theory can be utilized to perform scaled experiments and facilitate the understanding of physical behaviors of large structures. However, the prediction accuracy in partial similitude is still needed to be improved. To address the problem, a partial similitude method is presented to improve the prediction accuracy. The vibration consistency is satisfied by developing the scaling laws of critical speed. In addition, the scaling laws of vibration response are developed after ensuring consistency. The ability and performance of the presented method are demonstrated using a simulation case study and an experiment case study. In both case studies, the presented method is utilized to reproduce the vibration responses of the prototype, which includes the predictions of resonant and non-resonant responses. Besides, the prediction results of the existing methods are also provided for comparison. In the numerical case, the errors of the proposed method are less than 3% in predicting the vibration amplitude. In the experimental case, the minimum and maximum errors are 0.1% and 14.4%, respectively. Moreover, the proposed method can achieve better performance than the current methods.

Qiu L., Li J., Wang Y.

In order to prevent the problem of freezing pipe fracture in the process of artificial freezing construction, taking the main shaft freezing project of Shandong Yuncheng Mine as the background and based on the similarity theory, the similarity model test of freezing pipe in the composite stratum of the active freezing section is carried out. The test results show that the distribution of freezing temperature field in sand layer and clay layer is “W”-shape, and the temperature at the interface of outer ring pipe is slightly higher than that of the inner ring pipe. The change rate of freezing temperature can be divided into three stages: rapid decreasing section, slow decreasing section, and stable section. Compared with the clay layer, the sand layer has the shorter freezing closure time and the lower freezing average temperature. The frozen pipe is always in the state of vertical compression in the clay layer, while in the state of vertical compression first and then vertical tension in the sand layer. The maximum compressive strain in the clay layer is −305 με, which is equal to the vertical compressive stress of 64.1 MPa. The maximum tensile strain in the sand layer is 406 με, which is equivalent to the tensile stress of 85.2 MPa. The bending direction of different freezing pipes is different in the different soil layers. The maximum bending strain of the frozen pipe in the clay layer is 779 με, which is 2.6 times the vertical strain at the same location, corresponding to the bending stress of 163.4 MPa and reaching 0.69 times of the yield limit of frozen pipe, while the bending strain in the sand layer is very small. The vertical strain and bending strain of freezing pipes at the interface of soil layers are very small, but the bending strain is still dominant.

Meng X., Qin C., Li J.

In this study, computational fluid dynamics was used to simulate the flow field of fluids through an elbow pipe. Subsequently, an elbow flowmeter was experimentally studied under the same conditions. The simulation results agreed well with the experimental data, with an error of < 10%. The turbulence model, difference scheme, and grid distribution used in the numerical calculation closely matched the actual flow state. Results showed that pressures inside and outside the elbow pipe exhibited the same trends at different flow rates. Pressures outside the elbow pipe gradually increased at the inlet of the elbow pipe, tended to be flat at ~ 30°, reached their maximum value at 60°, and began to decrease at 70°. The inner pressure dropped sharply at the sensor inlet, reached its minimum value near 30°, and then began to increase sharply. Overall distribution of the differential pressure showed a trend of first increasing and then decreasing, and the maximum differential pressure was ~ 30°. The feasibility of similarity theory was verified, laying a foundation for subsequent theoretical research involving elbow flowmeters.

Guo X., Li X., He Y., Liu J., Wang G., Mao L., Wang J.

Under deep-water test conditions, a riser-test pipe system (RTS) is subject to the vortex-induced effect on the riser, flow-induced effect on the test pipe, and longitudinal–transverse coupling effect. Further, the system is prone to buckling deformation, fatigue fracture, and friction perforation. A three-dimensional (3D) nonlinear vibration model of deep-water RTS was established using the micro-finite method, energy method, and Hamilton variational principle. Based on the elastic–plastic contact collision theory, a nonlinear contact load calculation method between the riser and test pipe was proposed. According to field parameters in the South China Sea and the similarity principle, a vibration test bench for the RTS was designed. The experimental measurement results and the calculation results obtained from the proposed vibration model and the single tubing vibration model developed in our recent study were compared. Based on this comparison, the correctness and effectiveness of the proposed vibration model of the deep-water RTS were verified. Then, the vibration characteristics of the RTS for the BY5-2-1 well in the South China Sea were analysed. The results demonstrate that, first, in the vibration fatigue analysis of the test pipe, the influence of its own local high-frequency vibration cannot be neglected. Second, long-term collisions will cause friction and wear failure in the RTS. In the safety analysis of the RTS, the wear problem of the RTS caused by the collision between the riser and test pipe cannot be neglected. Third, the position where the test pipe is prone to strength failure is mainly located in the upper and lower parts. The field designer should focus on the safety of the pipe at these locations. • A three-dimensional nonlinear vibration model of deep-water riser-test pipe system is established. • A nonlinear contact load calculation method between the riser and test pipe is proposed. • A similar experiment of RTS vibration is designed and completed to test the validity of vibration model. • The vibration characteristics of the RTS for the BY5-2-1 well in the South China Sea are analysed.