Representative Test Cases Research Articles

Evaluation of Direct Sunlight Availability Using a 360° Camera

One important aspect to consider when buying a house or apartment is adequate solar exposure. The same applies to the evaluation of the shadowing effects of existing buildings on prospective construction sites and vice versa. In different climates and seasons, it is not always easy to assess if there will be an excess or lack of sunlight, and both can lead to discomfort and excessive energy consumption. The aim of our project is to design a method to quantify the availability of direct sunlight to answer these questions. We developed a tool in Octave to calculate representative parameters, such as sunlight hours per day over a year and the times of day for which sunlight is present, considering the surrounding objects. The apparent sun position over time is obtained from an existing algorithm and the surrounding objects are surveyed using a picture taken with a 360° camera from a window or other sunlight entry area. The sky regions in the picture are detected and all other regions correspond to obstructions to direct sunlight. The sky detection is not fully automatic, but the sky swap tool in the camera software could be adapted by the manufacturer for this purpose. We present the results for six representative test cases.

Wetting characterisation on complex surfaces by an automatic open-source tool: DropenVideo

HypothesisInvestigating solid–liquid interactions to determine advancing and receding contact angles, and consequently contact angle hysteresis, is crucial for understanding material wetting properties. A reliable, automated, and possibly open-source tool is desirable, to standardize and automatize the measurement and make it user-independent. ExperimentsThis study introduces an open-source software, DropenVideo, as an extension of Dropen. DropenVideo automates frame-by-frame video analysis for the advancing and receding contact angle determination, by considering needle presence, contrast tuning, and compensating for missing drop edge data. Contact angles are calculated using convolution mask, circle, and polynomial fittings. An innovative feature in DropenVideo is the automatic protocol for identifying advancing and receding contact angles: (i) the advancing contact angle is determined as the average value during drop inflation; and (ii) the receding contact angle is determined from the frame of incipient motion during drop deflation. FindingsExploring the application of DropenVideo across a range of complex surfaces as representative test cases, we highlight existing challenges in interpreting wetting measurements by addressing different wetting scenarios. Our study demonstrates that employing frame-by-frame automatic analysis of contact angle measurement videos using DropenVideo significantly mitigates the potential risks of subjective bias associated with manual interpretation and enhances the precision of identified wetting characteristics.

Pure distortion of symmetric box beams with hinged walls

This paper is concerned with the analysis of the pure torsion and distortion of straight box beams with trapezial cross-sections and hinged walls. A one-dimensional mechanical model for this kind of system subjected to anti-symmetric loads on the end cross-sections and no warping constraints is developed. The distortional stiffness of the system is provided by the torsional rigidity of the wall panels. The cross-sectional kinematic condition for which torsion and distortion are uncoupled has been determined. Novel explicit expressions of the internal and external distortional moments, the distortion constant, and the distortional warping pattern have been deduced; they can be directly translated to the classical distortion theory. Results of representative test cases with different section shapes and loads show excellent agreement with finite element models using shell elements. The model is a first step to analyse bridge decks with a distortionable central cell for wind engineering applications. Finally, an extension of the model, including the distortional stiffness provided by the frame bending stiffness of the cross-section walls, is presented. The extended model is applicable to assess the large-scale torsional–distortional effects in long beams with closed cross sections.

Robust Autonomous Mobile Manipulation for Substation Inspection

Abstract The need for autonomous infrastructure inspections performed by mobile robots is becoming increasingly prevalent, to mitigate human error and inspect critical infrastructure with increased frequency, while reducing costs. Electric distribution substations contain a variety of high-power equipment that may occasionally fail, and we focus on inspecting pothead compartments as a representative test case. Frequent measurements of acoustic and transient earth voltage data can indicate degradation before failures occur. Handheld partial discharge (PD) sensors can gather these types of data. Measurements using PD sensors can be automated using a mobile manipulation platform with a custom end-effector. Accurate mapping, localization, and navigation are required to perform autonomous inspection tasks in indoor environments with unmanned ground vehicles. Computer vision and precise manipulator control are necessary for successful handheld sensor interactions. In this paper, we present and analyze a custom-integrated mobile manipulation system capable of performing these functions, which achieves a tradeoff between the small size needed to navigate through low-clearance areas, and the reach capabilities needed to collect the required measurements from pothead compartments.

High-fidelity simulation of the interaction between a blade cascade and an ingested vortex

The aim of this research is to analyze the flow generated by the interaction between a simplified linear blade cascade adapted from an industrial aircraft engine demonstrator and an ingested vortex with the aerodynamic characteristics of a ground vortex observed in experiments. Due to the lack of availability of experimental and high-fidelity numerical studies of this phenomenon in the literature, a representative academic test case with a high-fidelity hybrid RANS/LES resolution of turbulence, namely the Zonal Detached Eddy Simulation (ZDES) technique, is performed. After the description of the computational setup and the numerical parameters used, the instantaneous topology of this complex flow is discussed, especially the interaction of the compressor cascade with the dynamics of the vortex. The simulation shows the chopping of the vortex, its destabilization and its dislocation into turbulent structures downstream the blade cascade. Turbulence is finely resolved in the blade wake and in the chopped vortex by ZDES technique at a moderate computational cost thanks to the RANS treatment of attached boundary layers with an applicative value of Reynolds number (5⋅106). A URANS simulation is also performed and allows a good representation of the averaged vortical structures inside the vortex close to the phase-averaged reference simulation. Spectral analyses are performed on unsteady velocity signals from probes located inside and outside the vortex chopped by the blades, highlighting more intense axial velocity fluctuations from turbulent structures inside the transformed vortex than in the wake of the blades, these structures being convected downstream in the direction of the Outlet Guide Vane (OGV).

Mitigating cascading failure in power grids with deep reinforcement learning-based remedial actions

Power grids are susceptible to cascading failure, which can have detrimental consequences for modern society. Remedial actions, such as proactive islanding, generator tripping, and load shedding, offer viable solutions to mitigate cascading failure in power grids. The success of applying these solutions lies in the timeliness and the appropriate choice of actions during the rapid propagation process of cascading failure. In this paper, we introduce an intelligent method that leverages deep reinforcement learning to generate adequate remedial actions in real time. A simulation model of cascading failure is first presented, which combines power flow distribution and the probabilistic failure mechanisms of components to accurately describe the dynamic cascading failure process. Based on this model, a Markov decision process is formulated to address the problem of deciding on the remedial actions as the failure propagates. Proximal Policy Optimization algorithm is then adapted for the training of underlying policies. Experiments are conducted on representative power test cases. Results demonstrate the out-performance of trained policy over benchmarks in both power preservation and decision times, thereby verifying its advantages in mitigating cascading failure in power grids.

Lambert-Free Solution of Multiple-Gravity-Assist Optimization Problem

A new method to find optimized multiple-gravity-assist (MGA) interplanetary trajectories that does not require the solution of Lambert’s problem is presented. The method, applicable to MGA sequences with ballistic transfer arcs and flybys, exploits Godal’s hyperbolic locus of incoming and outgoing velocities connecting the different trajectory legs combined with the v∞ sphere flyby constraint. The intersection between the two loci, when it exists, can be used to find feasible candidate solutions for each interplanetary trajectory segment and can be obtained analytically after solving a quartic equation. A time-of-flight compatibility condition can then be introduced that replaces the classical C3-matching constraint for locating properly phased transfer arcs, whereby opening the door to a very significant improvement in computational efficiency. The implementation of the method and its applicability to interplanetary trajectory optimization and moon tours are discussed in detail using representative test cases.

Power Flow Solution on Multi-Terminal HVDC Systems: Supergrid Case

High Voltage Direct Current (HVDC) systems offer distinct advantages for the integration of offshore wind farms to inland grid system. HVDC transmission system based on Voltage Source Converter (VSC) enables multi-terminal use HVDC for the integration of large-scale wind power in the North Sea. That network requires a special formulation for power flow analysis as opposed to the conventional method employed on AC networks. This paper presents a sequential AC/DC power flow algorithm, which is proposed for the analysis of multi-terminal VSC HVDC (VSC-MTDC) systems. This sequential power flow method can be implemented easily in an existing AC power flow package and is very flexible when compared with unified methods. Gauss-Siedel is used to solve DC power balance equations, as it offers two keys advantages: very fast and simple computational implementation, and errors do not accumulate during the calculation. The algorithm is tested using the WSCC 3-machine, 9-bus system with a 3-terminal MTDC network and the results are compared with those obtained from DIgSILENT PowerFactoryTM demonstrating the validity of the proposed algorithm. As an aggregate value, a representative test case of the projected scheme for the phase I of the Supergrid project on the North Sea is presented. The proposed approach presented in this paper is used to calculate DC power flows for some scenarios.

The Optimization of a Subsea Pipeline Installation Configuration Using a Genetic Algorithm

The most commonly used subsea pipeline installation method is the S-Lay method. A very important and complex task in an S-Lay installation engineering analysis is to find the optimal pipelay vessel installation configuration for every distinctive pipeline route section. Installation loads in the pipeline are very sensitive to small changes in the configuration of the pipeline supports during laying and other influential parameters, such as the tensioner force, stinger angle, trim and draft of the pipelay vessel. Therefore, the process of an engineering installation analysis is very demanding, and there is a need for an automated optimization process. For that purpose, installation engineering methodology criteria and requirements are formalized into a nonlinear optimization problem with mixed continuous and discrete variables. A special tailored multi-objective genetic algorithm is developed that can be adjusted to any desired combination of criteria and offshore standards’ requirements. The optimization algorithm is applied to the representative test cases. The optimization procedure efficiency and quality of the achieved solution prove that the developed genetic algorithm operators and the whole optimization approach are adequate for the presented application.

Implementation and Validation of Explicit Immersed Boundary Method and Lattice Boltzmann Flux Solver in OpenFOAM

In this work, the explicit boundary-condition-enforced immersed boundary method (EIBM) and the lattice Boltzmann flux solver (LBFS) are integrated into OpenFOAM to efficiently solve incompressible flows with complex geometries and moving boundaries. The EIBM applies the explicit technique to greatly improve the computational efficiency of the original boundary-condition-enforced immersed boundary method. In addition, the improved EIBM inherits the accurate interpretation of the no-slip boundary condition and the simple implementation from the original one. The LBFS uses the finite volume method to discretize the recovered macroscopic governing equations from the lattice Boltzmann equation. It enjoys the explicit relationship between the pressure and density, which avoids solving the pressure Poisson equation and thus saves much computational cost. Another attractive feature of the LBFS lies in its simultaneous evaluation of the inviscid and viscous fluxes. OpenFOAM, as an open-source CFD platform, has drawn increasing attention from the CFD community and has been proven to be a powerful tool for various problems. Thus, implementing the EIBM and LBFS into such a popular platform can advance the practical application of these two methods and may provide an effective alternative for complicated incompressible flow problems. The performance of the integrated solver in OpenFOAM is comprehensively assessed by comparing it with the widely used numerical solver in OpenFOAM, namely, the Pressure-Implicit with Splitting of Operators (PISO) algorithm with the IBM. A series of representative test cases with stationary and moving boundaries are simulated. Numerical results confirm that the present method does not have any streamline penetration and achieves the second-order accuracy in space. Therefore, the present method implemented in the open-source platform OpenFOAM may have good potential and can serve as a powerful tool for practical engineering problems.

Assessment of a virtual boundary concept for efficient modeling of turbine film cooling

Film cooling is one of key technologies advancing the performance of gas turbine engines, which is extensively applied in the hot turbine component for thermal protection by injecting cooling air from numerous film holes. To achieve an optimal film cooling scheme, many iterations of the position, the diameter, and the orientation of the holes through computation simulations are required to well fit the aerodynamic profiles of the turbine blades. However, a conventional computational simulation that resolves each individual hole and its coolant supply channel implies substantial costs of computation resources. In this study, a novel film cooling modeling method that uses a virtual boundary to represent film holes is assessed by comparing to the conventional computational simulation in two representative test cases, involving flat-plate and turbine endwall inlet film cooling. Relevant experiments are carried out to provide experimental data for verifying the approach at various coolant injection rates. Generally, the virtual boundary model produces rather equivalent results to those predicted by the conventional simulation method. Though coolant concentration downstream of the holes is over-estimated by the virtual boundary model due to neglected in-hole mixing, the overall flow fields and film cooling performance are well captured, showing the feasibility of the novel strategy in accurately modeling film cooling in a much more efficient way by saving computational efforts. This novel concept thereby allows designers to modify the film hole geometries independently of the blade geometry and thus, is helpful to accelerate the design process of a film-cooled turbine or to assess multiple film cooling configurations more quickly, as compared to a conventional computation simulation.

Enhancing Performance of Software Testing Automation using Selenium Web Grid

Web application testing is crucial to ensuring software quality and dependability. Selenium, a popular open-source testing framework, is widely used for automating web browsers to perform various testing tasks. One of the key components of Selenium is Selenium WebGrid, a distributed testing infrastructure that allows running tests in parallel across multiple nodes. This paper presents a comprehensive study on measuring the performance of Selenium WebGrid. The objective is to evaluate its efficiency, scalability, and reliability in executing test scripts across different browsers and operating systems. The study compares the performance of Selenium WebGrid with other testing approaches, such as traditional Selenium Grid and single-node Selenium execution. The methodology employed in this study involves designing a set of representative test cases that simulate real-world scenarios. These test cases cover a range of typical web application functionalities, including form submissions, page navigation, and data validation. The performance metrics considered for evaluation include execution time, resource utilization, and test throughput. To measure the performance of Selenium WebGrid, a testbed environment is set up consisting of multiple nodes with different configurations. The test scenarios are executed on the WebGrid infrastructure, and the performance metrics are collected and analyzed. The results are then compared with those obtained from traditional Selenium Grid and single-node Selenium execution to identify the performance advantages and limitations of Selenium WebGrid. It demonstrates the improved scalability and efficiency of WebGrid in executing tests across multiple nodes simultaneously. The results also provide insights into the resource requirements and trade-offs associated with using Selenium WebGrid compared to other testing approaches. This work adds to the body of knowledge by presenting empirical data on Selenium WebGrid's performance characteristics. It serves as a valuable resource for software testing professionals and researchers interested in leveraging Selenium WebGrid for distributed web application testing.

Evaluation of advection schemes and surface tension model for algebraic and geometric VOF multiphase flow solvers

This paper addresses the validation and verification of numerical models for complex multiphase flows involving immiscible fluids. Specifically, the focus is on the dynamics of the interface between the fluids, which remains a challenge in many applications. Previous studies have primarily examined simpler flows with limited complexity, while real-world scenarios involve intricate interfaces and turbulent dynamics. To overcome this, a representative test case involving the motion of an oil cube within a water cube proposed by [12] is used. Different computational models using volume-of-fluid (VOF) approaches are validated and compared, with particular attention given to the influence of numerical schemes for convective terms. The impact of these schemes on integral quantities and interface dynamics is analyzed. Particular attention is paid at the surface tension contribution to the energy budgets, which is usually neglected in the available literature. Furthermore, it is shown here that, the model adopted for the surface tension is responsible for an additional contribution to numerical dissipation. To the authors' knowledge, it is the first time that a detailed analysis of such aspects is presented.

Enhancing Performance of Software Testing Automation using Selenium web grid

Web application testing is crucial to ensuring software quality and dependability. Selenium, a popular open-source testing framework, is widely used for automating web browsers to perform various testing tasks. One of the key components of Selenium is Selenium WebGrid, a distributed testing infrastructure that allows running tests in parallel across multiple nodes. This paper presents a comprehensive study on measuring the performance of Selenium WebGrid. The objective is to evaluate its efficiency, scalability, and reliability in executing test scripts across different browsers and operating systems. The study compares the performance of Selenium WebGrid with other testing approaches, such as traditional Selenium Grid and single-node Selenium execution. The methodology employed in this study involves designing a set of representative test cases that simulate real-world scenarios. These test cases cover a range of typical web application functionalities, including form submissions, page navigation, and data validation. The performance metrics considered for evaluation include execution time, resource utilization, and test throughput. To measure the performance of Selenium WebGrid, a testbed environment is set up consisting of multiple nodes with different configurations. The test scenarios are executed on the WebGrid infrastructure, and the performance metrics are collected and analyzed. The results are then compared with those obtained from traditional Selenium Grid and single-node Selenium execution to identify the performance advantages and limitations of Selenium WebGrid. It demonstrates the improved scalability and efficiency of WebGrid in executing tests across multiple nodes simultaneously. The results also provide insights into the resource requirements and trade-offs associated with using Selenium WebGrid compared to other testing approaches. This work adds to the body of knowledge by presenting empirical data on Selenium WebGrid's performance characteristics. It serves as a valuable resource for software testing professionals and researchers interested in leveraging Selenium WebGrid for distributed web application testing.

New methodology to model the atmospheric re-entry of a satellite with DEBRISK v3

In order to evaluate the possible casualty area caused by the atmospheric re-entry of a vehicle, CNES develops its own certification tool named DEBRISK. For more than 7 years, an important work has been carried out in the frame of DEBRISK v3 with the aim of reducing as much as possible the uncertainties on all the models influencing the survivability of debris.Given the significant advances in terms of modelling and observations from ground experiments, the methodologies and recommendations are evolving and improving. Several recommendations are discussed, specifically related to how to model a satellite and problematic equipment from a survivability point of view. Representative satellite test cases are presented, showing the evolution of the debris survivability with DEBRISK V3.

Enhanced Unsteady Vortex Lattice Aerodynamics for Nonlinear Flexible Aircraft Dynamic Simulation

Several modeling extensions and numerical improvements to the unsteady vortex-lattice method are discussed for the simulation of very flexible aircraft dynamics. In particular, fuselage aerodynamics are included by means of linear source panels, polar corrections are incorporated on the aerodynamics under potentially large deformations, and a new wake discretization scheme is derived to accelerate the computations. The theory behind each approach is detailed and successfully verified on representative test cases. The resulting modeling environment is then exemplified in a study of the flight dynamics of a flexible aircraft demonstrator model. Results indicate that, for large wing deformations, a noticeable effect of fuselage aerodynamic interference appears on the wing aeroelastic behavior. The polar corrections improve the drag estimations and allow capturing lift decrements due to stall onset at high induced angles of attack, which then affects the gust loads. The wake discretization scheme enables a reduction of the computational time for dynamic simulations on a full aircraft model by about 20% while keeping the arising error negligibly small.

Generalization to a wider class of entropy split methods for compressible ideal MHD

The high order entropy split methods of Sjögreen & Yee (2019, 2021), by entropy splitting of the compressible Euler (inviscid) flux derivatives for a thermally-perfect gas are based on Harten’s entropy function (Harten, 1983; Gerritsen and Olsson, 1996; Yee et al., 2000). Their formulation have been proven entropy conserving and stable by taking advantage of the homogeneity property of Euler flux, symmetrizable Euler flux derivatives and energy-norm stability in conjunction with high order classical spatial central, dispersion relation-preserving (DRP) (Bogey and Bailly, 2002; Brambley, 2016; Johansson, 2004) or Padé (compact) spatial discretizations (Hirsh, 1975) with summation-by-parts (SBP) operators (Strand, 1994). These high order entropy split methods not only preserve certain physical properties of the chosen governing equations but are also known to either improve numerical stability, and/or minimize aliasing errors in long time integration of turbulent flow computations without the aid of added numerical dissipation. The present work employs a new approach to obtain a wider class of high order entropy split methods that do not have the homogeneous property. The new method consists of a two-point numerical flux portion and a non-conservative portion in such a way that entropy conservation holds without requiring the homogeneity property of the compressible inviscid flux. For high order classical spatial central, DRP or Padé spatial discretizations, this new approach can be proven to be entropy conservative while at the same time allowing a wider class of symmetrizable inviscid flux derivatives. More importantly, we extend this new approach to derive a new entropy split method for the equations of ideal MHD. Representative test cases are illustrated with comparison among existing methods of the same high order of accuracy.

Elastemp — A workflow to compute the quasi-harmonic temperature dependent elastic constants of materials

Elastic constants characterize the stiffness of a material. A linear relationship between the stress and strain tensors in the limit of infinitesimal deformation is used to define and compute the elastic constants. Typically, this is computed at zero temperature by deforming the simulation box in one of the six directions and computing the stress tensor. Calculating elastic constants at finite temperature is more challenging owing to large fluctuations and thermal noise. Here, we introduce a semi-automated workflow — Elastemp, to obtain the quasi-harmonic elastic constants of materials as a function of temperature. The workflow integrates with electronic structure packages such as VASP and PHONOPY to get the quasi-harmonic energies. The workflow is capable of estimating the zero temperature elastic constants, thermal expansion coefficients of materials and temperature dependent elastic constants. The predictions for a set of representative test cases with different crystal symmetries (Al, Diamond, Titanium nitride (TiN) and α-Ti) are compared with experiments and used to demonstrate the efficacy of our workflow.

A hybrid lattice Boltzmann - Navier-Stokes method for unsteady aerodynamic and aeroacoustic computations

A hybrid numerical method coupling the standard lattice Boltzmann method and a compressible finite-volume Navier-Stokes solver is proposed in the context of unsteady aerodynamic and aeroacoustic simulations. The trend being towards more realistic and detailed simulations in a reasonable amount of CPU time, lattice Boltzmann and Navier-Sokes methods can be combined to solve the same problem. The present hybrid method relies on a zonal decomposition of the computational domain thus allowing to exploit the numerical features of both methods to their optimal extent in specific flow regions.The key issue when combining the lattice Boltzmann method with a Navier-Stokes solver is to ensure a smooth transition of the flow variables at the two-way coupling interface. While existing approaches consider overlapping meshes, a direct grid coupling is here derived. The mapping from the macroscopic flow variables to the set of lattice Boltzmann distribution functions is performed analytically thanks to a Chapman-Enskog expansion and draws a direct link to advanced regularised collision operators. Unsteady computations are enabled by coupling the lattice Boltzmann stream and collide algorithm with explicit and implicit Navier-Stokes time-stepping schemes. The hybrid method is then assessed on four time-dependent test cases representative of aerodynamic and aeroacoustic problems. The proposed approach is proven to yield very accurate results while keeping the numerical advantages of both methods and reducing the overall computational cost of direct noise computations.

A time-step-robust algorithm to compute particle trajectories in 3-D unstructured meshes for Lagrangian stochastic methods

Abstract The purpose of this paper is to propose a time-step-robust cell-to-cell integration of particle trajectories in 3-D unstructured meshes in particle/mesh Lagrangian stochastic methods. The main idea is to dynamically update the mean fields used in the time integration by splitting, for each particle, the time step into sub-steps such that each of these sub-steps corresponds to particle cell residence times. This reduces the spatial discretization error. Given the stochastic nature of the models, a key aspect is to derive estimations of the residence times that do not anticipate the future of the Wiener process. To that effect, the new algorithm relies on a virtual particle, attached to each stochastic one, whose mean conditional behavior provides free-of-statistical-bias predictions of residence times. After consistency checks, this new algorithm is validated on two representative test cases: particle dispersion in a statistically uniform flow and particle dynamics in a non-uniform flow.