Dynamical Orbital Stability Analyses of Eclipsing Binaries with Additional Companions

In mechanics, viscoelasticity was the first field of applications in studying geomaterials. Further possibilities arise in spatial non-locality. Non-local materials were already studied in the 1960s by several authors as a part of continuum mechanics and are still in focus of interest because of the rising importance of materials with internal micro- and nano-structure. When material instability gained more interest, non-local behavior appeared in a different aspect. The problem was concerned to numerical analysis, because then instability zones exhibited singular properties for local constitutive equations. In dynamic stability analysis, mathematical aspects of non-locality were studied by using the theory of dynamic systems. There the basic set of equations describing the behavior of continua was transformed to an abstract dynamic system consisting of differential operators acting on the perturbation field variables. Such functions should satisfy homogeneous boundary conditions and act as indicators of stability of a selected state of the body under consideration. Dynamic systems approach results in conditions for cases, when the differential operators have critical eigenvalues of zero real parts (dynamic stability or instability conditions). When the critical eigenvalues have non-trivial eigenspace, the way of loss of stability is classified as a typical (or generic) bifurcation. Our experiences show that material non-locality and the generic nature of bifurcation at instability are connected, and the basic functions of the non-trivial eigenspace can be used to determine internal length quantities of non-local mechanics. Fractional calculus is already successfully used in thermo-elasticity. In the paper, non-locality is introduced via fractional strain into the constitutive relations of various conventional types. Then, by defining dynamic systems, stability and bifurcation are studied for states of thermo-mechanical solids. Stability conditions and genericity conditions are presented for constitutive relations under consideration.

Accurately grasping the stability characteristics of high earth-rockfill dam slopes is the key to the seismic safety evaluation of dams. In this research, the development and application of the common methods for slope stability analysis are reviewed firstly. Then, a three-dimensional dynamic time history stability analysis method is presented, and corresponding software is developed based on the sliding surface finite element stress method combined with the three-dimensional finite element dynamic response. This method makes the three-dimensional dynamic stability analysis efficient, and the effectiveness of this software is verified. Finally, the two-dimensional (2D) and three-dimensional (3D) dynamic stability analyses of a high concrete face dam are carried out, and the stability of the dam’s downstream slope under seismic load is studied. The results indicate that there are many differences between the results of the traditional 2D and 3D stability analyses. The time history of the safety factor, local safety behavior, overall shape and spatial position of the potential sliding body, and even the sliding process of failure can be captured with 3D stability analysis.

PurposeTandem wing aircrafts belong to an unconventional configurations group, and this type of design is characterised by a strong aerodynamic coupling, which results in lower induced drag. The purpose of this paper is to determine whether a certain trend in the wingspan impact on aircraft dynamic stability can be identified. The secondary goal was to compare the response to control of flaps placed on a front and rear wing.Design/methodology/approachThe aerodynamic data and control derivatives were obtained from the computational fluid dynamics computations performed by the MGAERO software. The equations of aircraft longitudinal motion in a state space form were used. The equations were built based on the aerodynamic coefficients, stability and control derivatives. The analysis of the dynamic stability was done in the MATLAB by solving the eigenvalue problem. The response to control was computed by the step response method using MATLAB.FindingsThe results of this study showed that because of a strong aerodynamic coupling, a nonlinear relation between the wing size and aircraft dynamic stability proprieties was observed. In the case of the flap deflection, stronger oscillation was observed for the front flap.Originality/valueResults of dynamic stability of aircraft in the tandem wing configuration can be found in the literature, but those studies show outcomes of a single configuration, while this paper presents a comprehensive investigation into the impact of wingspan on aircraft dynamic stability. The results reveal that because of a strong aerodynamic coupling, the relation between the span factor and dynamic stability is nonlinear. Also, it has been demonstrated that the configuration of two wings with the same span is not the optimal one from the aerodynamic point of view.

On-bottom stability analysis of subsea cables is commonly carried out in accordance with the leading industry practice for subsea pipelines "DNV-RP-F109". Similar to pipelines, the analysis method typically used is F109's Generalized Lateral Stability Method. However, this method is considered to be overly conservative for small diameter cables in shallow water applications such as the Arabian Gulf. Consequently, costly additional stabilization measures such as vast quantities of concrete mattresses are normally required. Given the flexible nature of cables, dynamic on-bottom stability analysis is considered to be a rational approach for optimizing the stabilization requirements. Dynamic on-bottom stability analysis is a known approach for subsea pipelines; however, its application is normally limited to extreme cases of environmental conditions where concrete coating requirements exceed practical limits. Hence, ADMA-OPCO has initiated a study to develop an FE model for dynamic on-bottom stability analysis of subsea cables. The outcome of ADMA-OPCO's study demonstrated that dynamic on-bottom stability represents the best approach for achieving cost-effective stabilization solutions for subsea cables. Hence, it is envisioned to become the norm for on-bottom stability analysis of subsea cables. The key features of the FE model are presented as well as general guidance for dynamic on-bottom stability analysis of subsea cables.

Sandwich composites with controllable cores have wide applications in aerospace structures. This paper presents a dynamic modeling and stability analysis of sandwich beams with a partially filled magneto-rheological (MR) fluid core covered by laminated composite face sheets in the supersonic flow regime. The equations of motion of the resulting system are formulated using energy expressions and the Hamilton principle. Finite element modeling is employed to solve the equations with different boundary conditions. Initially, free vibration analysis is performed and the effect of the magnetic field on the natural frequencies of the beam is reported. In order to minimize the weight, the magnetorheological fluid is filled at selected cells in the core layer. The locations and sizes of these cells affect the modal characteristics and flutter stability of the beam. Also, the impact of core layer thickness under different boundary conditions is studied. Furthermore, the influence of magnetic field on the critical pressure in supersonic flow regime is investigated using first-order piston theory to identify the unstable regions. The results revealed that the size and position of the MR section in the beam and the applied magnetic field strength drastically influence the natural frequencies of partially treated magnetorheological laminated sandwich beams. The influencing variables are identified from main-effect plots using analysis of variance study.

The offshore oil and gas industry requires pipelines to transport hydrocarbons from wells to processing facilities. Application of Mechanical Interference Fit Connection (MIFC) has been considered one of the optimization solutions in jointing of line pipes for pipeline installation, especially for offshore application. This method allows faster or less duration in pipe joining, which subsequently contributed to significant cost reduction in offshore pipeline installation. These pipelines are often subjected to harsh environmental conditions, including strong currents, waves, and seabed scouring. To ensure stability of pipeline on seabed, normally concrete coating is applied to provide sufficient weight for the pipeline. However, with concrete coated pipe, the faster joining rate by MIFC may be offset by longer duration to perform field joint coating due to longer field joint length required for MIFC to cater for clamping equipment to joint both-end of the pipes. This paper presents a case study of the dynamic on-bottom stability analysis of an offshore MIFC pipeline. The pipeline is a 12-inch diameter pipeline with a total length of 60 km. The pipeline is located in an offshore field with a water depth of ninety meters and 150 km away from shore. The dynamic on-bottom stability analysis is carried out to investigate the pipeline's response to environmental loads, including waves and currents. The dynamic on-bottom stability analysis is performed using a finite element analysis software package. The analysis considers the pipeline's structural behavior, seabed soil properties, and environmental loads. The results show that the MIFC joined pipeline is stable on seabed within the design envelope of the environmental loads without requirement of concrete weight coating. The maximum displacement and stress in the pipeline are well within the allowable limits, indicating that the pipeline's integrity is maintained. In addition, the study evaluates the effects of different parameters, such as seabed soil properties, current velocities, and wave heights, on the pipeline's dynamic response. In conclusion, this case study demonstrates that MIFC supported by dynamic on bottom stability analysis can be an effective solution for offshore pipeline jointing, providing stability and integrity on the seabed under the environmental design limit. The dynamic on-bottom stability analysis is an essential tool to investigate the pipeline's response to environmental loads and optimize the design and operation. Based on the findings of this study, we recommend that offshore pipeline engineers and designers may consider MIFC as a viable option for pipeline jointing. In overall, this case study contributes to the industry's knowledge and understanding of MIFC jointing for offshore pipelines, improving safety and efficiency in the offshore oil and gas industry.

A dynamic longitudinal stability analysis is made for a Canard (tail forward) type airplane in steady horizontal flight at Mach numbers of 1.7 and 1.3. Four different wing configurations (Fig. 1) are investigated: Case I. Delta wing with the Mach wave ahead of the leading edge. The planform of the delta wing is characterized by one-half the apex angle, w[subscript o]. In this case it has been taken to be 18°. Case II. Delta wing with the Mach wave ahead of the leading edge (w[subscript o] = 25°). Case III. Delta wing with the Mach wave behind the leading edge (w[subscript o] = 54°). Case IV. Rectangular, bi-convex, wing with an aspect ratio of 2. The shell or fuselage of the airplane consists of a conical nose and cylindrical afterbody with no boat tailing at the aft end. The stabilizing surface is hi-convex and rectangular in plan form with an aspect ratio of 2. Power is assumed to be supplied by a constant thrust jet motor. Other characteristics may be found in Table I. The design of the airplane is based on the Mach number of 1.7 at an altitude of 30,000 ft. and a gross weight of 10,000 lbs. Static stability is assumed to be the major design variable. The dynamic stability is first investigated for a static stability just sufficient to allow a four-g maneuver without exceeding a 20 degree angle of attack on the fin. Then the static stability is increased in multiples of 2, 3, and 4, to establish a trend. It is found that the effects of compressibility have a powerful influence on some of the coefficients of the stability quartic and hence on the dynamic stability, and that dynamic instability will result in certain cases regardless of the amount of static stability provided.

Submarine pipelines and umbilicals are essential elements of many offshore hydrocarbon developments. In general, the most economical approach is to lay the pipelines and umbilicals directly on the seafloor with adequate self-weight to avoid any requirement to perform secondary stabilisation work such as trenching. A fundamental design requirement for this scenario is to ensure adequate pipeline stability under extreme environmental loading conditions, as excessive lateral displacements may result in pipeline or umbilical damage. The commonly used and widely accepted recommended practice DNV-RP-F109 (Ref. 3) provides three design approaches with increasing levels of complexity to perform on-bottom stability design. These three design approaches are: Absolute Lateral Static Stability, Generalised Lateral Stability and Dynamic Lateral Stability Analysis. The first method is based on two dimensional (2D) force balance equilibrium equations while the second method is based on extensive dynamic modelling results of 2D pipeline models. These first two methods are intended to provide conservative on-bottom stability designs for rigid pipelines. The third method involves detailed finite element modelling of the pipeline under a time domain hydrodynamic loading. This paper highlights the DNV-RP-F109 recommended practice limitations with respect to the on-bottom stability design of flexible pipelines, umbilicals and cables. The paper presents a dynamic simulation methodology, in accordance with the recommended practice DNV-RP-F109, for on-bottom stability design of rigid pipelines, flexible pipelines, umbilicals and cables, together with specific sensitivity analyses and comparisons with the Absolute Stability method. The dynamic modelling results and comparisons presented in this paper highlight some limitations of the Absolute and Generalised methods for flexible pipelines, umbilicals and cables and illustrate the benefits of using the three dimensional (3D) dynamic stability analyses. The results of the sensitivity analyses clearly identify important parameters for the dynamic simulation, such as the hydrodynamic load correction due to the pipeline movements, the pipeline axial stiffness and the seabed passive soil resistance, that significantly affect the on-bottom stability behaviour. Refining the identified parameters input values will lead to more accurate and cost effective on-bottom stability design.

Quantitative assessment of the stability of slopes is very important for the evaluation of an earth fill dam in order to perform the intended function throughout the service life. This study presents the slope stability and analysis of the Koga earth fill dam. The analyses were carried out using finite element-based PLAXIS 2D software. The behavior of both the body and the foundation of the dam was described using the Mohr–Coulomb criterion. Based on the result of this study, the resulting factor of safety values during end of construction for both static and dynamic stability analysis was 1.6221 and 1.3592, respectively. For steady-state condition, the water level was fixed at normal pool level (2015.25 m). The factor of safety obtained for static stability analysis was 1.6136 and the dynamic analysis 1.3157. The rapid drawdown condition is analyzed with normal pool level of 2015.25 m lowered to 2008.5 m. The analysis results showed that the factor of safety for the static and dynamic analysis was 1.2199 and 1.0353, respectively. Using recommended design standards: United States Army Corps of Engineers, British Dam Society and the Canadian Dam Association the slope stability analysis of the Koga earth dam at all critical loading conditions are safe. The displacement result shows the maximum total displacements for static and dynamic analysis were 1.033% and 1.628% of the dam height, respectively. The displacement result coincides with Fell et al. (J Geotech Geoenviron Eng 129(4):307–314, 2003) standards.

The New Madrid earthquakes of 1811–12 reportedly triggered many landslides from the bluffs east of the Mississippi River. We use static and dynamic slope stability analyses to determine if landslides currently visible in this area were triggered by seismic shaking or if failure could have occurred in aseismic conditions. We apply this approach to a translational block slide representative of a group of old landslides that previous investigations showed probably were triggered in 1811–12. Slope-stability modeling of aseismic conditions shows that the slide could not have formed aseismically even in unrealistically high ground-water conditions. Dynamic stability analysis using Newmark’s method shows that the landslide would have experienced large displacements – sufficient to cause catastrophic failure – during earthquake shaking similar to that which occurred in 1811–12.

BackgroundThe dynamic on-bottom stability analysis represents a fundamental task in the design process of the subsea pipelines. Such analysis ensures the stability of the as-laid pipeline on the seabed against the lateral displacements, which are induced by the surrounding hydrodynamic forces. In this paper, the dynamic on-bottom stability analysis of a subsea pipeline is performed using finite element-based advanced offshore engineering simulation software called Flexcom. The latter predicts the pipeline response in a time-domain simulation based on a given environmental condition (i.e., the sea state, the soil frictional resistance, and the nonlinear behavior of the pipeline). A case study is conducted on a 22-in.-diameter pipeline, which is placed on a sandy soil in shallow water, under different loading combinations from two-dimensional irregular waves and a steady current.ResultsThe resultant maximum lateral displacements and the associated stresses decreased by increasing the concrete weight coating thickness. Pipeline response due to drag, lift, and inertia forces increased by increasing the total water particle velocity induced from the summation of wave-induced particle velocity and current velocity. Different random wave patterns generated from different random seed numbers assigned to wave components are important to verify the selection of the concrete weight coating thickness. Ignoring passive soil resistance reduced the total soil resistance significantly and resulted in conservative stability weight requirement.ConclusionsSeveral factors influence the pipeline stability such as pipeline submerged weight, hydrodynamic loads induced by random sea states, and soil friction model being used. The dynamic on-bottom stability analysis can optimize the design and results in less concrete weight coating if the actual case is modeled accurately; therefore, ignoring passive soil resistance reduced the prime advantage of this analysis compared to other simplified methods.

PurposeThe purpose of this paper is to present the results of a conceptual design of Martian aircraft. This study focuses on the aerodynamic and longitudinal dynamic stability analysis. The main research questions are as follows: Does a tailless aircraft configuration can be used for Martian aircraft? How to the short period characteristic can be improved by side plates modification?Design/methodology/approachBecause of a conceptual design stage of this Martian aircraft, aerodynamic characterises were computed by the Panukl package by using the potential flow model. The longitudinal dynamic stability was computed by MATLAB code, and the derivatives computed by the SDSA software were used as the input data. Different aircraft configurations have been studied, including different wing’s aerofoils and configurations of the side plate.FindingsThis paper presents results of aerodynamic characteristics computations and longitudinal dynamic stability analysis. This paper shows that tailless aircraft configuration has potential to be used as Martian aircraft. Moreover, the study of the impact of side plates’ configurations on the longitudinal dynamic stability is presented. This investigation reveals that the most effective method to improve the short period damping ratio is to change the height of the bottom plate.Practical implicationsThe presented result might be useful in case of further design of the aircrafts for the Mars mission and designing the aircrafts in a tailless configuration.Social implicationsIt is considered by the human expedition that Mars is the most probable planet to explore. This paper presents the conceptual study of aircraft which can be used to take the high-resolution pictures of the surface of Mars, which can be crucial to find the right place to establish a potential Martian base.Originality/valueMost of aircrafts proposed for the Mars mission are designed in a configuration with a classic tail; this paper shows a preliminary calculation of the tailless Martian aircraft. Moreover, this paper shows the results of a dynamic stability analysis, where similar papers about aircrafts for the Mars mission do not show such outcomes, especially in the case of the tailless configuration. Moreover, this paper presents the results of the dynamic stability analysis of tailless aircraft with different configurations of the side plates.

Assessment of offshore pipelines using dynamic lateral stability analysis

Dynamic stability analysis (DSA) software allows for computing transient and dynamic responses to a large number of potential grid system disturbances (contingencies). Typically, using past tools, DSA analysis is performed off-line since the simulation process took hours to compute the simulation of a large number of contingencies for a large interconnected power system. This paper presents a new online DSA tool using distributed computing, which dramatically reduces the computation time for on-line DSA calculations when there is a large number of contingencies to be investigated for a large interconnective power system. Grid operators will thus be able to use this new DSA tool to perform dynamic stability analysis on-line, for real-time operating conditions and for a large set of contingencies. The new DSA tool can also be used for studying the effectiveness of candidate operating procedures, system protection schemes or possible corrective or preventative operator control actions that could be used to control the grid during emergency conditions (terrorist induced or dasianaturepsila induced). This paper describes the technical approach used for the distributed computing architecture used in the new DSA tool. Extensive testing was performed using a 16,000 bus and a 20,500 bus system with a large number of contingencies. The computational time and performance test results from these tests are also described herein. The new on-line DSA tool can thus be used for performing on-line or off line dynamic stability analyses; and, the new tool can be used to validate appropriate corrective or preventative control actions, or operating procedures, a grid operator can use to mitigate various emergency conditions and to prevent potential large scale cascading blackouts.

This paper presents the dynamic voltage stability analysis of a 4-bus micro grid set-up with the implementation of the MicroGrid Voltage Stabilizer (MGVS). Dynamic voltage stability analysis of microgrid systems using MGVS was introduced in the literature on simulation level. However, implementation of the controller at hardware level have not been accomplished. This paper provides detailed information on implementing the MGVS to a 4-bus microgrid set-up and improvements on overall dynamic voltage stability. The implementation is performed in a lab environment using LabVolt and Texas Instruments equipment, along with MATLAB/Simulink interface. Several case studies are performed and relevant graphs showing the dynamic voltage stability analysis of the system data are presented in this paper. The 4-bus micro grid system is also simulated using the MATLAB based Power System Analysis Toolbox (PSAT). Furthermore, comparison between hardware and software results are presented and it validates the successful implementation of the MGVS.