Open Source Physics Research Articles

Experimental solution of a mechanical system with Tracker

A system of two masses joined by an inextensible rope that passes through two pulleys with negligible friction is a problem posed in university texts (Pérez, 1996) and this is an interesting exercise for students in the mechanical physics course. The analytical solution of the exercise allows a study of the conditions that must be present so that the mass released from rest when descending acquires sufficient tension to lift the other mass that rests on a table. The setup of the situation presented is simple and can be carried out in any classroom. In this article, an analytical solution to the problem is made using several methods and by using the Tracker software, information can be obtained that it allows an experimental solution to the problem posed and its study can be useful in mechanics courses. Tracker (Douglas, 2007) being a free video analysis and modeling tool based on the Java Open Source Physics (OSP) framework, allows obtaining complete information on the variables involved.

Numerical construction tests to assess the feasibility of placement grids for Cubipod Homogeneous Low-Crested Structures

Placement grid design is a key phase when constructing armor layers in mound breakwaters. Homogeneous Low-Crested Structures (HLCS) are low-crested structures designed as artificial reefs for marine colonization, coral reef regeneration and beach protection. The placement grid affects the construction feasibility, hydraulic stability and wave transmission of HLCS. This study presents a numerical methodology to simulate a realistic placement procedure for armor units during the construction of HLCS. This numerical simulator is based on the open-source physics engine Bullet Physics Engine (BPE), which applies Newton's laws of motion to rigid bodies. From an initial theorical placement grid for Cubipod HLCS, a series of numerical realistic unit placement tests are carried out to emulate the placement process at prototype scale; placement velocity and spatial deviation of crawler cranes are given parameters associated with each specific project. Considering the placement velocity and spatial deviation during construction, the quality of each specific placement grid is associated with the measured placement errors and the corresponding initial construction deviation to HLCS. This numerical methodology is valuable to understand the influence and the uncertaintly of the construction procedure of armor layers in mound breakwaters.

PolyVerif: An Open-Source Environment for Autonomous Vehicle Validation and Verification Research Acceleration

Validation and Verification (V&V) of Artificial Intelligence (AI) based cyber physical systems such as Autonomous Vehicles (AVs) is currently a vexing and unsolved problem. AVs integrate subsystems in areas such as detection, sensor fusion, localization, perception, and path planning. Each of these subsystems contains significant AI content integrated with traditional hardware and software components. The complexity for validating even a subsystem is daunting and the task of validating the whole system is nearly impossible. Fundamental research in advancing the state-of-the-art for AV V&V is required. However, for V&V researchers, it is exceedingly difficult to make progress because of the massive infrastructure requirements to demonstrate the viability of any solution. This paper presents PolyVerif, the world’s first open-source solution focused on V&V researchers with the objective of accelerating the state-of-the-art for AV V&V research. PolyVerif provides an AI design and verification framework consisting of a digital twin creation process, an open-source AV engine, access to several open-source physics based simulators, and open-source symbolic test generation engines. PolyVerif’s objective is to arm V&V researchers with a framework which extends the state-of-the-art on any one of the many major axes of interest and use the remainder of the infrastructure to quickly demonstrate the viability of their solution. Given its open-source nature, researchers can also contribute their innovations to the project. Using this critical property of open-source environments, the innovation rate of the whole research community to solve these vexing issues can be greatly accelerated. Finally, the paper also presents results from several projects which have used PolyVerif.

Movement and velocity of a particle in an inverse fluidized bed

The movement of particles in the fluidized bed primarily determines the mixing in the bed and determines the transfer intensities that occur between the particles and the fluid. Experimental monitoring of the velocity of the marked particle was performed in an inversely fluidized bed of polypropylene, polyethylene, and polystyrene particles. The velocity of the marked particle was monitored in a two-dimensional column, where water and an aqueous solution of glycerin were used as the fluidization medium. Using the Tracker Video Analysis program (Tracker Video Analysis, Open Source Physics, 2003), the mean velocity of the marked particle was determined, as well as the distance crossed by the marked particle in the x and y directions. The influence of fluidization medium viscosity and particle density on the velocity of the marked particle was investigated. The results of experimental investigations have shown that the particle velocity distribution approximately follows the Maxwell distribution. Comparison of the measured values of the mean velocity in the inversely and conventionally fluidized bed showed a certain deviation. In this paper, a correlation for determining the mean particle velocity in an inversely fluidized bed is proposed.

Physics engine based simulation of shear behavior of granular soils using hard and soft contact models

Physics engines have been widely used to simulate physical and mechanical processes in modern video games to create an immersive and realistic gaming experience. This study explores the feasibility of using an open-source physics engine, Chrono, as a discrete element method (DEM) platform to simulate shear behavior of granular soils. This study develops a series of pre-processing, servo-controlling, and post-processing functions to improve the Chrono platform, so that Chrono can generate soil specimens with designed packing densities, perform laboratory test simulations such as direct shear tests, and output stress-strain, fabric, and force chains. Traditional DEM codes use soft contact models (e.g., Hertzian contact model) to determine inter-particle contact forces, while most physics engines use a hard contact model (e.g., non-smooth contact dynamics) to determine inter-particle contact forces. The hard contact model enables physics engines to use large time steps in iterations without affecting the numerical stability and simulation accuracy, which remarkably accelerate simulation speeds compared with traditional DEM codes. Based on systematical comparisons between simulation results of two contact models and experimental results, this study demonstrates that the hard contact model can yield the shear behavior of granular soils observed in soft contact model simulations and laboratory tests.

Evaluation of Physics Frameworks for Building Web-Based Games

Recently, WebGL technology has shown a lot of potential for developing games. Since this technology is still relatively new, there is still much potential in the game development area that has not been explored yet. This paper explores the development of a game engine made with WebGL technology that integrates some physics frameworks for developing web-based 2D or 3D games. Specifically, we integrated three open source physics frameworks, which are Bullet, Cannon, and JigLib, into a WebGL-based game engine. We assessed these frameworks using some experiments, in terms of their correctness or accuracy, performance, completeness and compatibility. The results show that it is possible to integrate open source physics frameworks into a WebGL-based game engine, and Bullet is the best physics framework to be integrated into a WebGL-based game engine.

Feasibility of using a physics engine to virtually compact asphalt mixtures in a gyratory compactor

Optimization of asphalt mixtures in the laboratory is essential to maximize its performance in a pavement structure and reduce the likelihood of expensive premature failures. Several material and mixture variables affect the performance of an asphalt mixture. Evaluating the innumerable combinations of these variables in the laboratory to optimize an asphalt mixture is onerous. Computational models can supplement such laboratory-based optimization studies due to their capability of executing a broad range of parametric and probabilistic analyses. This study demonstrates the potential of using a physics engine to simulate the asphalt mixture compaction process. Physics engines were originally developed for animation and video games, however, with improvement in their accuracy, they are currently being used in many research areas. This study presents a computational model developed using an open source physics engine to virtually compact asphalt mixtures in a gyratory compactor. This model uses 3D laser-scanned representations of real aggregate particles and incorporates the viscous and cohesive nature of the asphalt mortar through customized subroutines. To demonstrate the feasibility of this model, the effect of the three key compaction parameters (i) angle of gyration, (ii) compaction pressure, and (iii) specimen height on the compaction characteristics were analyzed and compared with laboratory findings from various studies. Results suggest that the developed model can be used as a reasonably accurate means to simulate asphalt mixture compaction. This study also demonstrates that such simulations can be carried out using realistic and representative particle shapes in 3D, in a reasonable time using desktop computers.

Verifying North Korea’s Plutonium Production with Nuclear Archaeology

North Korea produced weapon-grade plutonium in its graphite-moderated 5-MWe reactor. Estimating the total production of fissile materials provides an important baseline for denuclearization efforts. Nuclear archaeology can improve such production estimates by measuring isotope ratios in the graphite moderator of the reactor. The accumulation of certain trace isotopes in the graphite enables to accurately estimate life-time reactor fluence which can then be related to plutonium production. This article uses the open-source reactor physics software ONIX to simulate the operation of the 5-MWe reactor. It discusses consolidated estimates of plutonium production from 1986 to 2020 based on publicly available operation history data. An updated mathematical framework to relate isotope ratio uncertainties to fluence uncertainties and its implementation in a special ONIX module for nuclear archaeology are also presented. The module is used to identify which isotope ratios should be measured in the 5-MWe reactor to minimize uncertainties on plutonium estimation.

Carbofuran affects behavior and metabolism of the Atlantic Forest lambari Deuterodon iguape, a native species from Brazil.

One of the major causes of aquatic biodiversity loss is the contamination of the environment by pesticides. Even though there is a considerable amount of studies on the subject, there are still few that deal with the effects of carbofuran on native species in Brazil. Although carbofuran is widely used in Brazil, its action on native organisms, such as the Atlantic Forest lambari Deuterodon iguape, has not yet been studied. This work aimed to evaluate the effects of exposure to carbofuran on the fish D. iguape, considering the behavior and specific oxygen consumption as end points. Opercular movements, dorsal fin movements, and swimming speed were analyzed as behavioral parameters. To assess specific oxygen consumption, fish were subjected to concentrations of 0.0, 0.05, 0.1, 0.25, and 0.5 mg/L, for 24 h. For behavior analysis, fish remained exposed to carbofuran at concentrations of 0.0, 0.01, 0.05, 0.1, and 0.5 mg/L, in periods of 0, 2, 24, and 48 h. The behavior was studied through filming, analyzed with the free software, Tracker 4.92 (Open Source Physics). The results demonstrate an increase in opercular movements (18% ± 2.65) and a decrease in dorsal fin movements (- 21.2% ± 2.97), as well as in swimming speed (- 58.3% ± 1.83) of the experimental groups compared to the control group. There was an increase in oxygen consumption of 58.4% in fish exposed to the highest concentration of carbofuran. Thus, it is concluded that carbofuran altered D. iguape's behavior and oxygen consumption. The species was sensitive to carbofuran concentrations and can be used as a bioindicator.

Quantifying Air Movement Induced by Natural Forces in an Isolated Structure in the Subsurface Infrastructure

This article describes the development and demonstration of a non-intrusive method for the quantitative determination of speed of air movement along the ground and inside an isolated subsurface structure, a type of confined space. Natural ventilation occurs continuously and reduces risk to entrants from contact with a hazardous atmosphere. One of the most important parameters still undetermined was the speed of air movement during the process. Small puffs of artificial “smoke” were used to visualize air movement. Tracker, an open-source physics program, provided the capability to analyze this movement. Measurement of air speed requires access to individual frames in the video, capability to move forward and backward, and the means to manipulate the image to highlight the “smoke”. Background subtraction, control of brightness and contrast, and conversion of color to greyscale were essential for obtaining these measurements. Measurements for a single opening indicated that flow along the ground was borderline turbulent (Reynolds number ~3000) and in the opening and inside the airspace, within the bounds of laminar flow (Reynolds number <2250). Video obtained during this work showed behavior observable in laboratory studies of Helmholtz resonators. Results provide the basis for a larger study of the ventilation process to facilitate design improvements.

Accelerated simulations of direct shear tests by physics engine

Physics engines, originally developed to simulate physical and mechanical processes in modern video games, are increasingly used as a scientific computational platform in many disciplines due to their high computational efficiency. This study explores the feasibility of using an open-source physics engine, Project Chrono, to simulate direct shear tests. This study develops a series of pre-processing, servo-controlling, and post-processing functions in Project Chrono to generate soil specimens with designed packing densities, perform direct shear tests, and output simulation results including stress–strain relations, fabrics, and force chains. To determine inter-particle contact forces, typical DEM codes use soft contact models, while most physics engines use hard contact models. The hard contact model enables physics engines to use large time steps in iterations without affecting the numerical stability and simulation accuracy, which remarkably reduces simulation time compared with typical DEM codes. Based on systematical comparisons between simulation results of two contact models, this study demonstrates that the hard contact model can yield the same direct shear test results observed in soft contact model simulations, but is ten times faster than the soft contact model for simulating the same number of particles. This study may provide DEM modelers with the physics engine as one more option for soil behavior simulation.

A geometrically exact isogeometric beam for large displacements and contacts

This work discusses an efficient formulation of a geometrically exact three-dimensional beam which can be used in dynamical simulations involving large displacements, collisions and non-linear materials. To this end, we base our model on the shear-flexible Cosserat rod theory and we implement it in the context of Isogeometric Analysis (IGA). According to the IGA approach, the centerline of the beam is parameterized using splines; in our work the rotation of the section is parameterized by a spline interpolation of quaternions, and time integration of rotations is performed using the exponential map of quaternions. Aiming at an efficient and robust simulation of contacts, we propose the adoption of a non-smooth dynamics formulation based on differential-variational inequalities. The model has been implemented in an open-source physics simulation library that can simulate actuators, finite elements, rigid bodies, constraints, collisions and frictional contacts. This beam model has been tested on various benchmarks in order to assess its validity in non-linear static and dynamic analysis; in all cases the model behaved consistently with theoretical results and experimental data.

Modeling of wave energy converters by GPUSPH and Project Chrono

This study presents a fully coupled numerical approach to study wave energy converters interaction with water waves. The open-source Smoothed Particle Hydrodynamics model GPUSPH is used to resolve wave dynamics and compute the hydrodynamic force on wave energy converters. The dynamics of wave energy converter is computed by the open-source physics engine, Project Chrono. The capability of the coupled numerical model to handle wave-body interaction is validated by considering a floating body in still water. The results show that the coupled model correctly predicts the balance between the floating body weight and the buoyancy force. Furthermore, the effectiveness of density diffusion method in reducing acoustic noise in a weakly compressible SPH model is also justified. In addition, the model is validated by laboratory experiment on floating body interaction with nonlinear wave packet. The model is then applied to simulate two types of wave energy converters. We conduct a thorough study of GPUSPH modeling of surface-piercing oscillating wave surge converter under waves. GPUSPH accurately predicts both wave gauge measurements and the device rotation as recorded in the laboratory. By virtue of the Project Chrono library we examine the power take-off scenario of the oscillating wave surge converter by introducing kinematic constraint into the system. The device performance under storm condition is further examined. We further present and simulate a conceptualized catenary mooring wave energy converter device, CSI-Device, under real sea states. We not only examine the interaction of CSI-Device with waves, but also we obtain the mooring force on the device that can facilitate the design of wave energy converters. We show that to maximize the energy extraction, it is important to design the device to have a natural frequency similar to the wave period of deployment site to maximize the swing motion of the pendulum. Finally the interaction of CSI-Device under different sea states with both relatively small and large wave heights are evaluated by placing the device in a directional spectral wave basin. Overall, this study shows that the open-source model GPUSPH is an efficient tool for modeling wave energy conversion devices in directional nonlinear sea states.

Study of oscillatory motion using smartphones and tracker software

The purpose of this contribution is to propose a workshop for acquiring data through the use of a smartphone, not necessarily high end, equipped with a camera and the required application installed. With a smartphone and the free Physics Toolbox application, it is possible to study the oscillatory motion of both simple and vertical pendulums. This is possible by measuring the components of acceleration on the three axes by means of a reading from the internal accelerometers of the smartphone. The vertical motion of the pendulum brings to light the concept of elasticity. Thanks to the Tracker software it is possible to study the damped oscillatory motion of a moving body on a semi-circular drive through the video analysis of the motion itself. Tracker is a free video analysis and modelling tool built on the Open Source Physics Java framework. Given the simplicity of the acquisition procedure and data analysis it is possible to study the motion of circular bodies of different sizes and materials in a short amount of time. The activity relating the vertical motion of the pendulum study also allows for the comparison between the classical procedure, using a stopwatch and both proposals procedures, using smartphones and Tracker. The analysis of subsequent data acquisition must be carried out using standard spreadsheet calculations by introducing the concept of error and the techniques to make it as small as possible. The use of the new widespread technologies allows students to approach the physical concepts even outside of a classic laboratory. The ease of use and low cost allow any school environment to propose activities to the entire class by offering more contemporary workstations and organizing groups of a few students.

Physics engine application to overturning dynamics analysis on banks and uniform slopes for an agricultural tractor with a rollover protective structure

Physics engines have become popular for the realistic animation of video games and movies to model the contact dynamics between two rigid bodies. However, the applicability of a physics engine to collect important physical information such as velocity during contact or impact dynamics of overturning vehicles remains unknown. This study is intended to ascertain whether or not the Bullet physics engine can simulate overturning behaviour of agricultural tractors with a roll over protective structure (ROPS) on a bank slope and on a uniform slope. Visual behaviour data and velocity transition during overturning processes are discussed based on the earlier reported experimental data. The results of vertical and lateral linear velocities, and roll angular velocity were evaluated in terms of Root Mean Square Error (RMSE), and the estimated average error was approximately 0.7. The behaviour time response was short in the simulation results because of the assumption of rigid-body contact. Moreover, the simulation results became smaller, but it is sufficiently accurate to predict the critical ROPS height (CRH) for various agricultural tractors. Therefore, results show that this open source physics engine has sufficient applicability to the overturning dynamics of agricultural tractors with ROPS on banks and uniform slopes.

Coordinated control architecture for motion management in ADAS systems

Advanced driver assistance systems U+0028 ADAS U+0029 seek to provide drivers and passengers of automotive vehicles increased safety and comfort. Original equipment manufacturers are integrating and developing systems for distance keeping, lane keeping and changing and other functionalities. The modern automobile is a complex system of systems. How the functionalities of advanced driver assistance are implemented and coordinated across the systems of the vehicle is generally not made available to the wider research community by the developers and manufactures. This paper seeks to begin filling this gap by assembling open source physics models of the vehicle dynamics and ADAS command models. Additionally, in order to facilitate ADAS development and testing without having access to the details of ADAS, a coordinated control architecture for motion management is also proposed for distributing ADAS motion control commands over vehicle systems. The architecture is demonstrated in a case study where motion is coordinated between the steering and the braking systems, which are typically used only for a single functionality. The integrated vehicle and system dynamics using the coordinated control architecture are simulated for various driving tasks. It is seen that improved trajectory following can be achieved by the proposed coordinated control architecture. The models, simulations and control architecture are made available for open access.

Simulation of partial differential equations models in Java

PurposeComputer simulations improve the knowledge of physical models and are widely used in teaching and research. Key aspects are to understand their solutions and to make interactive changes to the models, observing their effects in real-time. The drawback of creating interactive simulations of physical models is the high level of programming expertise required. The purpose of this study is to facilitate this task.Design/methodology/approachJava is the perfect language for this task; it yields high-quality graphics and is widely spread in the scientific community. Because many important physical models are described by means of partial differential equations (PDEs), the combination of Java with FreeFem++, a C++ PDE solver based on the finite element method, is considered.FindingsIn this study, a Java library is introduced to numerically solve PDE equations via a run-time connection with FreeFem++. The solution is encapsulated into Java objects that are ready to be used in different programming tasks. The library also includes new Java visualization elements for solutions and meshes in the context of the Open Source Physics project library. Together, the connection features and the visualization elements facilitate the creation of Java simulations by programming researchers. For those with less programming capabilities, this work has been included into Easy Java Simulations, a tool to further ease the creation of interactive simulations.Originality/valueThe present study approach allows simulating models given PDEs. The equations are solved either in local or in remote mode (e.g. by a network accessible to a high-performance computer) and visualized locally, providing a high degree of interactivity to the end user.

A Physics-Based Vibrotactile Feedback Library for Collision Events.

We present PhysVib: a software solution on the mobile platform extending an open-source physics engine in a multi-rate rendering architecture for automatic vibrotactile feedback upon collision events. PhysVib runs concurrently with a physics engine at a low update rate and generates vibrotactile feedback commands at a high update rate based on the simulation results of the physics engine using an exponentially-decaying sinusoidal model. We demonstrate through a user study that this vibration model is more appropriate to our purpose in terms of perceptual quality than more complex models based on sound synthesis. We also evaluated the perceptual performance of PhysVib by comparing eight vibrotactile rendering methods. Experimental results suggested that PhysVib enables more realistic vibrotactile feedback than the other methods as to perceived similarity to the visual events. PhysVib is an effective solution for providing physically plausible vibrotactile responses while reducing application development time to great extent.

SmartSIM - a virtual reality simulator for laparoscopy training using a generic physics engine.

Virtual reality (VR) training simulators have started playing a vital role in enhancing surgical skills, such as hand-eye coordination in laparoscopy, and practicing surgical scenarios that cannot be easily created using physical models. We describe a new VR simulator for basic training in laparoscopy, i.e. SmartSIM, which has been developed using a generic open-source physics engine called the simulation open framework architecture (SOFA). This paper describes the systems perspective of SmartSIM including design details of both hardware and software components, while highlighting the critical design decisions. Some of the distinguishing features of SmartSIM include: (i) an easy-to-fabricate custom-built hardware interface; (ii) use of a generic physics engine to facilitate wider accessibility of our work and flexibility in terms of using various graphical modelling algorithms and their implementations; and (iii) an intelligent and smart evaluation mechanism that facilitates unsupervised and independent learning.

Adapting smart phone applications about physics education to blind students

Today, most of necessary equipment in a physics laboratory are available for smartphone users via applications. Physics teachers may measure from acceleration to sound volume with its internal sensors. These sensors collect data and smartphone applications make the raw data visible. Teachers who do not have well-equipped laboratories at their schools may have an opportunity to conduct experiments with the help of smart phones. In this study, we analyzed possible open source physics education applications in terms of blind users in inclusive learning environments. All apps are categorized as partially, full or non-supported. The roles of blind learner’s friend during the application are categorized as reader, describer or user. Mentioned apps in the study are compared with additional opportunities like size and downloading rates. Out of using apps we may also get information about whether via internet and some other extra information for different experiments in physics lab. Q-codes reading or augmented reality are two other opportunity provided by smart phones for users in physics labs. We also summarized blind learner’s smartphone experiences from literature and listed some suggestions for application designers about concepts in physics.