Full Dynamic Analysis Research Articles

Updated Forecast for TRAPPIST-1 Times of Transit for All Seven Exoplanets Incorporating JWST Data

The TRAPPIST-1 system has been extensively observed with JWST in the near-infrared with the goal of detecting atmospheric transit transmission spectra of these temperate, Earth-sized exoplanets. A byproduct has been much more precise times of transit compared with prior available data from Spitzer, Hubble Space Telescope, or ground-based telescopes. In this note we use 23 new timing measurements of all seven planets in the near-infrared from five JWST observing programs to better forecast and constrain the future times of transit in this system. In particular, we note that the transit times of TRAPPIST-1h have drifted significantly from a prior published analysis by up to tens of minutes. Our newer forecast has a higher precision, with uncertainties ranging from 7 to 105 s during JWST Cycles 4 and 5. This forecast will help to improve planning of future observations of the TRAPPIST-1 planets, while we postpone a full dynamical analysis to future work.

Design of isolated buildings to achieve targeted collapse limits through Gaussian process modeling

Design of isolated buildings to achieve targeted collapse limits through Gaussian process modeling

A Perspective on the Process and Turbomachinery Design of Compressed Air Energy Storage Systems

Abstract The present paper will describe the Baker Hughes experience in the development of the turbomachinery equipment for Hydrostor's advanced compressed air energy storage (A-CAES) system. At the core of a compressed air energy storage (CAES) plant, there is an air compressing system, followed by an air expander used to recover the stored energy. To achieve a reliable and effective solution, the expander is obtained from the architecture of Baker Hughes steam turbines, which was adapted to match the specific process needs. The criticalities that were addressed and solved to derive the expanders from the original steam turbine are presented. Specifically, the paper describes the activities performed to optimize the inlet and exhaust sections of each segment, the development of the blades for high atmospheric volume flow, and the implications that thermal transients have on the machine reliability. The inlet and exhaust sections were arranged according to the layout constraints, which were set to mitigate the effects of the thermal stresses and to reduce the weight to facilitate the machine transportation, while maintaining high aero-performance. As for the expander, a single-body configuration was selected to optimize capital expenditures and reduce leakage to atmosphere. A new set of blades derived from Baker Hughes's Steam Turbine stages were developed. This new stage is characterized by rotating blades with high radius ratio (HRR); therefore, an optimization strategy was adopted to include the mechanical constraints from the beginning of the design cycle and obtain a final geometry that can be used with different flow path and operating conditions. Finally, the three-dimensional full Navier Stokes Computational fluid dynamics analysis was used to assess the performance of the new stages in nominal and off-design conditions. A detailed analysis of the thermal transient of the expander parts with finite element analysis methods was performed to assess the life expectations of the equipment. The finite element analysis results are discussed in the paper to show the capability of the machine to sustain an extremely fast start up sequence. Compressor train is characterized by a multiple body configuration. A detailed optimization was performed to improve the efficiency and the availability of the selected solution. The low-pressure axial compressor discharge section has been optimized to reduce losses and a detailed study of rotor has been performed to evaluate the capability to withstand a high number of start and stop cycles.

Reconstruction of the real 3D shape of the SARS-CoV-2 virus

The photographs of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus taken by electron transmission microscopy and cryoelectron microscopy provide only a 2D silhouette. The viruses appear to look like distorted circles. The present paper questions the real shape of the SARS-CoV-2 virus and makes an attempt to give an answer. Is this a general ellipsoid, a spheroid with rotational symmetry, a sphere, or something else? The answer requires the application of tools from three different disciplines: structural mechanics, microbiology, and statistics. A total of 590 virus photographs taken from 22 recently published papers were examined. From this experimental data pool, the histogram of diameter ratios was built from the 283 measurements where the virus images could be approximated as ellipses. The curve peaks at the diameter ratio of 1.22. The transformation equation for the spatial shape to the planar shade was derived for a fixed light source of the microscope. This equation involves an unknown orientation of the viruses with respect to the microscope. Two sets of models were developed, one with a uniform distribution of the virus orientation and the other with the orientation defined by the normalized beta distribution. In both sets of models, the unknown diameter ratio of the spheroidal virus was regarded as a random realization from translated gamma distributions. The parameters of the distribution of the kernel functions were determined by minimizing the mean square difference between the predicted and measured 2D histograms. The information included in the measured histograms was found to be insufficient to find an unknown distribution of the virus's orientation. Simply too many unknown parameters render the solution physically unrealistic. The minimization procedure with a uniform probability of virus orientation predicted the peak of the aspect ratio of the 3D spheroid at 1.32. Based on this result, models of the virus will be developed in the continuation of this research for a full dynamic analysis.

Kinetic analysis of cardiac dynamic 18F-Florbetapir PET in healthy volunteers and amyloidosis patients: A pilot study

Kinetic analysis of cardiac dynamic 18F-Florbetapir PET in healthy volunteers and amyloidosis patients: A pilot study

Driving Strategies for Omnidirectional Mobile Robots with Offset Differential Wheels

In this work, we present an analysis of, as well as driving strategies and design considerations for, a type of omnidirectional mobile robot: the offset-differential robot. This system presents omnidirectionality while using any type of standard wheel, allowing for applications in uneven and rough terrains, as well as cluttered environments. The known fact that these robots, as well as simple differential robots, have an unstable driving zone, has mostly been dealt with by designing driving strategies in the stable zone of internal dynamics. However, driving in the unstable zone may be advantageous when dealing with rough and uneven terrains. This work is based on the full kinematic and dynamic analysis of a robot, including its passive elements, to explain the unexpected behaviors that appear during its motion due to instability. Precise torque calculations taking into account the configuration of the passive elements were performed for better torque control, and design recommendations are included. The stable and unstable behaviors were characterized, and driving strategies were described in order to achieve the desired performance regarding precise positioning and speed. The model and driving strategies were validated through simulations and experimental testing. This work lays the foundation for the design of better control strategies for offset-differential robots.

Investigation of dynamic responses of three-sided underpass culvert under near-fault and far-fault ground motions considering soil-structure interaction

Investigation of dynamic responses of three-sided underpass culvert under near-fault and far-fault ground motions considering soil-structure interaction

Research on dynamic responses of mooring line system of semi-submersible platforms in Vietnam sea conditions using random model

Recently, due to the nearshore oil fields in Vietnam were nearly exhausted, oil and gas extraction proceeds to deeper water areas using the mooring floating offshore structures. Therefore, the durability of the mooring system in deep water should be studied through determining the dynamic tension of the mooring line system using random wave models. However, full stochastic dynamics analysis for mooring line system takes up a lot of time and requires large computing resources. This paper is going to study the hydrodynamic interaction of random waves onto a semi-submersible platform, thereby analysing the dynamic responses in time domain of the mooring system using the “time window” method to optimize computational time and computing resources. This method performs the dynamic simulations around the maximum quasi-dynamic tension values to determine the dynamic tension and the dynamic amplification factor (DAF) of a maximum load-bearing mooring line, thereby evaluating the dynamic responses for the whole mooring system. The method is applied to calculate for a semi-submersible platform in Dai Hung field in Vietnam Sea.

Three-Dimensional Electromagnetic and Structural Analysis of Disruptions in the COMPASS Upgrade Vacuum Vessel

Structural analyses of disruptions and the electromagnetic (EM) analyses to support them typically use symmetry to produce a manageable model size. Nonaxisymmetric halo loads require larger analysis models. In this paper, the results of transient EM analyses of halo strikes during a vertical displacement event are presented. The plasma motions and halo characteristics are prescribed based on analyses performed by the Institute of Plasma Physics of the Czech Republic. The time transient EM solution provides loads to a full three-dimensional transient dynamic analysis of the vacuum vessel. The responses to large lateral halo loads are altered and mitigated by the mode responses of the vessel. Dynamic load factors are computed for specific locations in the vessel and supports.

Coupled dynamic characteristics of 10 MW semi-submersible offshore wind turbine under typical operation, extreme, and fault conditions

The Technical University of Denmark (DTU) 10 MW wind turbine is selected as the object of this study. The braceless semi-submersible platform for the National Renewable Energy Laboratory 5 MW wind turbine is upscaled to support the DTU 10 MW wind turbine. The servo control system of the 10 MW semi-submersible wind turbine is redesigned. Furthermore, torque control is performed below the rated wind speed to achieve maximum power capture, and the gain scheduling proportional integral (GSPI) control method is performed above the rated wind speed to realize the design of the variable propeller control system. This ensures the safe operation of the floating wind turbine above the rated wind speed. The reliability of the designed servo control system is verified by a full coupling dynamic response analysis with the designed servo control system, aerodynamics, and hydrodynamics under the combined action of wind and waves. The coupled dynamic characteristics of the 10 MW semi-submersible wind turbine under different conditions are analyzed, including operational, extreme, and fault situations. The results show that the servo control system effectively controls the motion response of a 10 MW floating offshore wind turbine (FOWT). Turbulent wind has an obvious excitation effect on the surge and pitch of the FOWT, whereas the heave motion is primarily excited by wave loads. Different fault conditions can cause different motion and structural responses. Furthermore, the tower top bending moment is greatly affected by the imbalance of aerodynamic load, and the surge, pitch motion, tower base bending moment, and mooring tension of the FOWT are affected by different fault conditions to varying degrees. In addition, the heave motion is generally barely affected by the fault conditions.

An optimisation methodology for suspended inter-array power cable configurations between two floating offshore wind turbines

An optimisation methodology for suspended inter-array power cable configurations between two floating offshore wind turbines

Seismic Behaviour of Shallow Tunnelling Method Tunnels Accounting for Primary Lining Effects

The shallow tunnelling method (STM) is usually used to construct shallow tunnels buried in soft ground. It consists of primary lining and secondary lining (tunnel). In the seismic design of STM tunnels, it is usually assumed that the secondary lining (tunnel) is resistant to all seismic effects. However, the soil–primary–secondary lining system may generate complex interaction phenomena during ground shaking. Compared with the case where the primary lining is not considered, the existence of the primary lining alters the seismic response of the secondary lining (tunnel). The paper attempts to investigate this complex interaction, focusing on the response of the secondary lining (tunnel). The full dynamic time history analysis is adopted to investigate the interaction in the transversal direction. A case history of the Hohhot (China) arched STM tunnel buried in a stratified soil deposit has been analyzed. Two tunnel configurations for a two-dimensional plane strain model of STM tunnels in Hohhot are studied and compared, including a model with primary lining and one without primary lining. A numerical parametric analysis was conducted to elucidate critical response characteristics of STM tunnels. Salient parameters that may affect the dynamic response of the tunnel were studied, including the characteristics of ground motion, the characteristics of contact interface, the characteristics of the soil, and the characteristics of the tunnel lining. The response characteristics of the tunnel are compared and discussed, including horizontal acceleration, deformation mode, lining internal force, and lining damage. The results show that the primary lining has a significant influence on the magnitude and distribution of the seismic response, especially considering the nonlinearity of the soil and the nonlinear characteristics of the tunnel lining. The effect of primary lining on the seismic response is about 5%–35 %.

Modeling and analysis technique of the hoisting system in the monorail crane

The monorail crane system (MCS) is a part of the ITER neutral beam remote handling system (NBRHS) in the neutral beam (NB) cell to lift and transport the components during their remote maintenance. The MCS is composed of four hoisting systems at each corner of the crane trolley, which are driven by two independent hoisting motors and gear chains. As the MCS works in a radiation controlled area where human worker access is strictly forbidden and there are lots of important components inside the NB cell, the structural and dynamic behaviors of the MCS are crucial that need to be verified. This paper describes a modeling and analysis technique of the hoisting system in the monorail crane. The hoisting system includes two drums and one balancer with a payload attached on it. The kinematic and dynamic model of the hoisting system is developed both for a non-extendable rope and for an extendable rope. Differential–Algebraic Equations (DAE) are constructed and its solution technique is described. Free body pendulum response is analyzed to verify the dynamic model and the solution technique. The dynamic equations with the realistic one quarter model of the hoisting unit are developed considering the rope flexibility. Synthesized seismic accelerogram is applied as the excitation forces. The time response of the balancer and the payload is calculated. The result shows that the dynamic model captures the six degree of freedom motion of the balancer and payload well during the seismic events. This methodology is applicable to develop a full multi body dynamic analysis model of the monorail crane. • The monorail crane system (MCS) is a part of the ITER neutral beam remote handling system (NBRHS) in the neutral beam (NB) cell to lift and transport the components during their remote maintenance. • A modeling and analysis technique of the hoisting system in the monorail crane is described by using the multi-dynamic modeling technique considering rope kinematics around the lifting drums. The kinematic and dynamic model of the hoisting system is developed both for a non-extendable rope and for an extendable rope. • The dynamic equations with the realistic one-quarter model of the hoisting unit are developed considering the rope flexibility. Free body response and seismic responses are calculated. Synthesized seismic accelerogram is applied as the excitation forces. The time response of the balancer and the payload is calculated. • The result shows that the dynamic model captures the six degree of freedom motion of the crane well during the seismic events. This methodology is applicable to develop a full multi body dynamic analysis model of the monorail crane.

Optimal disc brake design for reducing squeal instability using slip-dependent complex eigenvalue analysis

• Proposal of the new optimization methodology for squeal reduction in a brake system. • Applying the slip-dependent stability analysis combining with the model-based design. • Targeting maximum squeal instability reduction during entire braking scenario. • Effectiveness verified by comparing the average maximum power of each design. This paper proposes an improved disc brake system optimization method for squeal instability reduction using slip-dependent eigenvalue results. Although complex eigenvalue analysis is widely used for minimizing brake squeal instability, conventional optimization approaches still have the limitation of not being able to reflect slip rate-varying squeal instability characteristics. While relative angular velocity between the pad and disc declines due to braking, disc brake system instability gradually increases up to a specific peak velocity point and decreases until the vehicle stops, which means a maximum instability point exists during the braking process. Therefore, instability optimization should target the prevention of a maximum value during a braking scenario. The proposed optimization formulation is conducted considering maximum instability during full braking. To obtain braking time profiles, a model-based design method is employed and utilized instead of full finite element transient dynamic analysis to reduce computational cost. Kriging surrogate modeling is also used for solving the optimization problem and better express the multi-variable squeal problem. The proposed optimal design method produces minimal squeal instability during the full vehicle braking time range. The effectiveness of the proposed disc brake optimal design is demonstrated via acceleration power value comparison of the structure acceleration with that derived by conventional optimization approach.

Dynamic behaviour of pre-stressed concrete transmission poles under synoptic wind loading

A numerical model capable of predicting the dynamic response of pre-stressed concrete transmission poles under both the mean and fluctuating components of synoptic wind loads is developed in this study. A full non-linear dynamic analysis is conducted under a time history variation of wind velocity. The peak total responses, such as conductors’ reactions and poles’ base moments, are determined from this analysis. The same analysis is repeated in a quasi-static manner. Dynamic amplification factors (DAF), defined as the ratio between the maximum response based on a non-linear dynamic analysis and the corresponding value based on a quasi-static analysis, are calculated for the poles and the conductors to quantify the dynamic impact of synoptic wind loads. This factor is used to assess the importance of including the resonant component while estimating the response of the transmission poles. In addition, gust response factors (GRF) defined as the ratio between the peak and mean responses are evaluated and compared to GRF recommended by ASCE-74 (2010). A parametric study is conducted on three pre-stressed concrete transmission line systems. The mean value of the incoming wind speed is the main variable included in the parametric study. It is found that the resonant effect is dominant in the conductors at low wind speeds and the poles exhibit high dynamic response at higher wind speeds.

Dynamical Analysis and Optimization of a Generalized Resource Allocation Model of Microbial Growth

Gaining a better comprehension of the growth of microorganisms is a major scientific challenge, which has often been approached from a resource allocation perspective. Simple mathematical self-replicator models based on resource allocation principles have been surprisingly effective in accounting for experimental observations of the growth of microorganisms. Previous work, using a three-variable resource allocation model, predicted an optimal resource allocation scheme for the adaptation of microbial cells to a sudden nutrient change in the environment. We here propose an extended version of this model considering also proteins responsible for basic housekeeping functions, and we study their impact on predicted optimal strategies for resource allocation following changes in the environment. A full dynamical analysis of the system shows there is a single globally attractive equilibrium, which can be related to steady-state growth conditions of bacteria observed in experiments. We then explore the optimal allocation strategies using optimization and optimal control theory. We show that the solutions to this dynamical problem have a complicated structure that includes a second-order singular arc given in feedback form, and characterized by i) Fuller's phenomenon, and ii) the turnpike effect, producing a very particular asymptotic behaviour towards the solution of the static optimization problem. Our work thus provides a generalized perspective on the analysis of microbial growth by means of simple self-replicator models.

Efficient seismic risk assessment of irregular steel‐framed buildings through endurance time analysis of consistent fish‐bone model

SummaryThe seismic risk framework of building structures has been presented to reduce earthquake‐induced adverse consequences. In this context, probabilistic analysis of engineering demand parameters (EDPs) is always associated with many uncertainties and high computational demand for use in practical applications. This study has been presented to efficiently estimate the distribution of EDPs in probabilistic seismic risk assessment of irregular steel moment‐resisting frames (SMRFs). For this purpose, the incorporation of the consistent fish‐bone (CFB) model and the endurance time (ET) analysis method has been used. The proposed method (i.e., CFB‐ET) has a substantial impact on reducing the complexities of the new generation of performance‐based earthquake engineering (PBEE) by significantly reducing the degrees of freedom (DOFs) of the original building and the number of required nonlinear time history analyses (NLTHAs). The efficiency of the proposed method has been evaluated using three 3‐, 9‐, and 20‐story SMRFs irregular in bay lengths and three other SMRFs with the same number of stories but irregular in height. In this evaluation, the maximum structural response at all seismic intensity levels up to the collapse stage and also the structural response profile along the building height at service‐level earthquake (SLE), design‐based earthquake (DBE), and maximum credible earthquake (MCE) seismic intensity levels have been investigated. Next, the efficiency of the proposed method in seismic risk assessment is investigated by using seismic fragility and vulnerability curves. The results of these evaluations have been compared with the full incremental dynamic analysis (IDA) of the full DOF model of the building (i.e., SMRF‐IDA) under 44 far‐field ground motions of FEMA P‐695 in terms of computational accuracy and effort. Furthermore, a new approach to estimating the dispersion of the structural response in the ET method has been proposed, whose efficiency has been investigated in the above‐mentioned evaluations. The results show that the proposed method allows for using the new generation of PBEE in engineering applications by significantly reducing computational demand and having sufficient accuracy in the seismic assessment process.

Macroscale modelling of the orthotropic shear damage in the dynamics of masonry towers by RBSM

• Unique orthotropic shear response of the masonry can be accounted by a rigid body-spring model. • Different shear strength and internal friction, parallel and normal to the plane of the bed joints. • Comparison of these different constitutive assumptions to explain of a vertical pattern of cracks along masonry towers. • Numerical analyses show a better capability to predict the crack pattern of an idealized tower. The peculiarity of a rigid body-spring model (RBSM) is exploited to predict and explain a specific damage pattern and failure that is often observed in ancient masonry towers subjected to seismic events. In fact, the full understanding of the frequent appearence of a vertical pattern of cracks along the height of these buildings, which could be viewed as a macroscopic mode II shear fracture, would require to overcome the macroscopic approach based on the standard Cauchy solid continuum. The research focuses on the orthotropic shear response of the masonry material, related to its bond/texture pattern, which is here accounted by a RBSM that allows to assign, heuristically, a different shear strength and internal friction, parallel and normal to the plane of the mortar bed joints. This specific feature, in the context of a set of full dynamical analyses, appears to be a key to predict the crack pattern and failure of an idealized masonry tower, in accordance with the surveys of real towers subjected to strong ground motions.

Identification of Road Profile Parameters from Vehicle Suspension Dynamics for Control of Damping

Concept of symmetry covers physical link between road profile form, vehicle dynamic characteristics, and speed conjunction. Symmetry frame between these items is asymmetric itself and has no direct expression, but it affects a vibration level on the vehicle and driving comfort. Usually, we can change only the vehicle’s speed to achieve desired vibrations level of the driver and passengers. Recently, vehicle dynamic characteristics can be changed depending on its damping system structure, but these solutions are limited by construction and control possibilities and evidently represented by symmetric dependency between road input and the resulting acceleration of the vehicle. The main limitation of this process is to have a reliable value of the existing road profile that is mainly defined by road category but unpredictable for each road distance. Functional road profile calculations are provided in this article, where power spectral density (further-PSD) and waviness of the road play the main role in delineating road profile parameters. Furthermore, the transfer function system was created using full car dynamic model analysis. Values on vehicle suspension’s effects on acceleration were obtained from vehicle speed and road roughness. Acceleration values and transfer function were used to calculate PSD value quickly and practically. This calculated result can be formed as a control value to the vehicle damping control. In addition, the provided methodology became useful to determine road quality for adjustment of vehicle suspension parameters and set safe driving characteristics, which became part of driver assistant systems or autonomous driving mode.

Nonintrusive reduced order model for parametric solutions of inertia relief problems

AbstractThe Inertia Relief (IR) technique is widely used by industry and produces equilibrated loads allowing to analyze unconstrained systems without resorting to the more expensive full dynamic analysis. The main goal of this work is to develop a computational framework for the solution of unconstrained parametric structural problems with IR and the Proper Generalized Decomposition (PGD) method. First, the IR method is formulated in a parametric setting for both material and geometric parameters. A reduced order model using the encapsulated PGD suite is then developed to solve the parametric IR problem, circumventing the so‐called curse of dimensionality. With just one offline computation, the proposed PGD‐IR scheme provides a computational vademecum that contains all the possible solutions for a predefined range of the parameters. The proposed approach is nonintrusive and it is therefore possible to be integrated with commercial finite element (FE) packages. The applicability and potential of the developed technique is shown using a three‐dimensional test case and a more complex industrial test case. The first example is used to highlight the numerical properties of the scheme, whereas the second example demonstrates the potential in a more complex setting and it shows the possibility to integrate the proposed framework within a commercial FE package. In addition, the last example shows the possibility to use the generalized solution in a multi‐objective optimization setting.