Component-based Modeling and Simulation of Nonlinear Drill-string Dynamics

In this paper, we present a dynamic model for a generic drill-string. The model is developed with the intention for component-based simulation with coupling to external subsystems. The performance of the drill-string is vital in terms of efficient wellbore excavation for increased hydrocarbon extraction. Drill-string vibrations limit the performance of rotary drilling; the phenomenon is well-known and still a subject of interest in academia and in industry. In this work, we have developed a nonlinear flexible drill-string model based on Lagrangian dynamics, to simulate the performance during vibrations. The model incorporates dynamics governed by lateral bending, longitudinal motion and torsional deformation. The elastic property of the string is modeled by the assumed mode method, representing the elastic deformation, with a finite set of modal coordinates. By developing a bond graph model from the equations of motion, we can ensure correct causality of the model towards interacting subsystems. The model is analyzed through extensive simulations in case studies, comparing the qualitative behavior of the model with state-of-the art models. The flexible drill-string model presented in this paper can aid in developing system simulation case studies and parameter identification for offshore drilling operations.

Girder Longitudinal Movement and Its Factors of Suspension Bridge under Vehicle Load

Vehicle load may not only cause vertical deformation and vibration of suspension bridge but also lead to longitudinal deformation and vibration. And the longitudinal behavior is closely related to the durability of the girder end devices and the bending fatigue failure of suspenders. In this study, the longitudinal deformation behavior and longitudinal vibration of suspension bridge under vehicles, as well as the related influencing factors, are investigated. The underlying mechanism of girder longitudinal movement under the moving vehicles is revealed. Based on the simplified vehicle model of vertical concentrated force, the characteristics of main cable deformation and girder longitudinal displacement under vertical loads are analyzed first. Then, the longitudinal motion equation of the girder under vertical moving loads is derived. Finally, a single long-span suspension bridge is employed in the case study, and the girder longitudinal response and influencing factors are investigated based on both numerical simulation and field monitoring. Results indicate that the asymmetric vertical load leads to cable longitudinal deflection owing to the geometrically nonlinear characteristic of the main cable, leading to longitudinal movement of the girder. The results of field monitoring and numerical simulation indicate that the girder moves quasi-statically and reciprocates longitudinally with centimeter amplitude under normal operational loads.

Post-marathon decline in right ventricular radial motion component among amateur sportsmen

Introduction Running the marathon may be followed by post-exercise “cardiac fatigue” manifesting as transient right ventricular (RV) systolic and diastolic impairment. It is the thin-walled RV that is predominantly affected by the exercise-induced overload, with little if any, impact on the left ventricle (LV) [1]. The 2-D echocardiographic (ECHO) assessment of RV is challenging and may be incomplete since conventional measures reflect only the longitudinal motion (displacement of tricuspid annulus towards the apex) [2]. The mechanics of RV can be separated into two more components, anteroposterior (stretching RV wall by contracting septum) and radial (internal relocation of the RV free wall) [2]. The significance and relative contribution of motion components to global RV function may not be equal, and their interplay can vary depending on concomitant diseases [3]. Purpose We aimed to analyse the pathophysiology of RV exhaustion associated with a marathon run with 3-D ECHO, which allows precise estimation of all RV motion components and their contribution to RV global function. Methods The study included 34 healthy males (mean age of 40±8 years), amateurs, who finished the marathon in northern Poland. The 3-D ECHO was performed 2 weeks before (stage I), at the marathon finish line (stage II) and 2 weeks after the competition (stage III). According to the ReVISION method (Right ventricular separate wall motion quantification) the global RV function was decomposed to longitudinal (L_), anteroposterior (AP_) and radial (R_) [3]. By dividing componential ejection fractions (EF) with global RV EF, L_EFi, AP_EFi, and R_EFi ratios were obtained. Results When comparing results from stage I and III there were no significant differences (Table 1). The analysis revealed post-run decline in RV EF with no changes in LV EF. The quantification of the RV motion components showed reduction in R_EF after the marathon with no changes in AP_EF or L_EF. The relative contribution of componential EF to global RV function were permanent and was not influenced by the competition. Conclusions Marathon run resulted in transient RV dysfunction arising from decline in radial shortening. Noteworthy, the componential interplay between wall motion compartments was preserved in pre- and post-run assessment. The ReVISION method enables the comprehensive analysis of the competing RV. FUNDunding Acknowledgement Type of funding sources: Public grant(s) – EU funding. Main funding source(s): The study was supported by the project POWR.03.05.00-00-z082/18 co-financed by the European Union through the European Social Fund under the Operational Programme Knowledge Education Development 2014–2020

Stabilization of the vertical take-off of a rigid flying wing for an airborne wind energy system

Airborne wind energy is an emerging technology that harvests wind energy with flight systems connected via a tether to the ground. In the project “EnerGlider”, a flying wing is meant to fly fully automated by its own control units. This contribution discusses the challenges to control and trim this flying wing during vertical take-off and landing under the influence of a horizontal wind velocity. High wind velocities can lead to unstable and untrimmed states concerning the longitudinal motion of the flying wing. The paper analyzes the influence of design modifications of thrust vector and elevon area to enhance the flight envelope of the trimmed states to higher wind velocities. Besides, the tether force as additional control unit is considered for strong wind forces. It is demonstrated that a tether force acting behind the center of gravity can significantly enhance the robustness of the flight system concerning wind velocity. Moreover, the unstable flight states emerging during vertical take-off and landing can be stabilized with a flight control.

Case Studies in Physiology: Using premature ventricular contractions to understand the regulation of carotid artery longitudinal wall motion

Benign arrhythmias can be a useful tool to probe new hypotheses in physiology. We tested the control of longitudinal motion of the common carotid artery wall using observations from spontaneous premature ventricular contractions in a healthy male. Forwards wall motion remained unchanged despite large deviations in local blood velocity and backwards wall motion mirrored changes in pulse pressure, blood velocity, and cardiac motion, thereby revising our original hypothesis of the control of longitudinal wall motion.