Conservation Of Mechanical Energy Research Articles

Two Dimensional Hydrodynamics Model with Evaporation for Coastal Systems

Introduction. The use of two-dimensional (2D) hydrodynamic models is relevant, despite the development of numerical methods of marine hydrodynamics focused on the use of three-dimensional spatial models. This is due to the modelling of hydrodynamic processes in shallow and coastal systems in solving practically important problems of predicting the transport of pollutants in suspended and dissolved forms. Evaporation for the Southern of Russia marine coastal systems (the Azov Sea, the Northern Caspian, etc.), and even more so in the coastal areas of the Red Sea, is a significant factor that affects not only the balance of water masses, but also makes changes in the momentum of the system and the distribution of the velocity vector of the aquatic environment. This effect is significant for coastal currents and shallow-water systems.Materials and Methods. The traditional method of converting the terms of the Navier-Stokes equations containing differentiation by horizontal spatial variables was used, involving the rearrangement of differentiation operations by horizontal spatial coordinates and integration by vertical coordinate when constructing a spatially two-dimensional model of hydrodynamics of marine coastal systems when integrated by vertical coordinate. This made it possible to avoid the appearance of non-physical sources of energy and momentum in the spatially two-dimensional model, which can be essential in traditional 2D models with significant depth differences characteristic of coastal systems. The implementation of the analogue of the law of conservation of the total mechanical energy of the system for the constructed 2D model is investigated.Results. Using the correct transformation of the 3D model (integration of the Navier-Stokes equations and continuity along a vertical coordinate, taking into account evaporation from a free surface), spatially two-dimensional models of hydrodynamics are constructed, for which the basic conservation laws, including mass and total mechanical energy of the system, are fulfilled. The implementation of an analogue of the law of conservation of total mechanical energy for various types of boundary conditions, including at the bottom, is investigated. The evaporation from the free surface is correctly accounted for not only in the continuity equation, but also in the equations of motion taking into account wind and waves.Discussion and Conclusion. 2D model of hydrodynamics has been constructed and studied, taking into account evaporation not only in the mass balance equation (continuity), but also in the Navier-Stokes equations of motion. The proposed model can be used for predictive modelling of hydrophysical processes, including the spread of pollutants in the aquatic environment of coastal systems and shallow reservoirs in relation to marine systems such as the Sea of Azov, the Northern Caspian Sea, coastal areas of the Red Sea, etc. Spatially two-dimensional models of marine hydrodynamics, without replacing three-dimensional models, can serve as a model basis for operational forecasting of situations in coastal systems and shallow-water objects using computing systems with relatively low performance and a moderate amount of RAM (5–10 Tflops, 2–4 TB, respectively).

How the air slows a closing book

When two flat surfaces approach each other, the fluid in between is accelerated and ejected from the sides at large speeds. This situation occurs often in everyday life, such as when you step in a puddle and create splashes of water, or when you clap your hands or close a book and create jets of air. For these systems, the inertia of the fluid resists the acceleration, creating large nonlinear forces on the flat surfaces. In this work, we study the case of a closing book. The fluid motion in this case is relatively easy to model, using the conservation of mechanical energy, and to measure using a MEMS gyroscopic sensor. This study reveals the unusual forces that occur when two plates collide in an experiment that can be performed by students at home.

Философское осмысление связи движения и взаимного положения материи как условия обратимости их изменений

The fact of existence of the limit of divisibility of matter, established earlier by the author, has an inevitable con-sequence of permanent loss by interacting matter of its motion. Since “heat death” due to this loss of motion has not occurred, therefore, there is a law providing restoration of motion. This law is the law of motion-position of matter. As an analog of the law of motion-position of matter, the article considers the law of conservation of mechanical energy, according to which kinetic energy (reflecting the motion of matter) can be reversibly trans-formed into potential energy (reflecting the mutual position of matter). The fundamental incompatibility of, on the one hand, the law of conservation of energy, corresponding to the relative description of being, and, on the other hand, the fact that motion is not irretrievably lost, corresponding to the absolute description of being close to absolute, is stated. The law of motion-position of matter in the assumption of birth of motion in the state of the greatest convergence of matter agrees with the existing cosmological ideas about the Big Bang and expan-sion of the Universe. The Universe in this case can be represented as an “energy independent” system. As the main problem, the study examines the determination of the mechanism of the growth of the velocity of material structures. The probable sought mechanism is the increase of (circumferential) rotational velocity at decreasing radius of rotation of material bodies, which can be rather complex material structures.

Assessing conceptual understanding of learning in energy and momentum by using Socrative online polling in physics classes

This research investigates the understanding and learning gains of students learning between online and onsite classes on topics of Energy and Momentum. In this study, twenty-five questions relating to Energy and Momentum, including Energy Concepts, Work Done by Gravitational Forces, Work Done by Nonconservative Forces, Conservation of Mechanical Energy, Momentum Concepts, Momentum Conservation, Completely Inelastic Collisions, and Applications of the Impulse-Momentum Theorem, were used. One hundred and ninety-five students from the Faculty of Engineering at Rajamangala University of Technology Lanna, Chiang Mai campus, were tested through online and onsite learning between 2021 and 2022, respectively. The collected data were evaluated using Socrative online polls. Statistics, including average percentage, standard deviation, and the normalized gain method, were used to analyze the understanding of learning between the pre-test and post-test of online and onsite classes. The results found that after classes, the mean of correct answers for online classes was 18.76 (SD = 2.81) and 20.68 (SD = 3.19) for onsite classes. The average normalized gain <g> for online classes was 0.01, and for onsite classes was 0.05. These results demonstrated that onsite learning was more effective than online learning.

An active hybrid Reynolds-averaged Navier–Stokes/large eddy simulation approach for gray area mitigation

During the transition from the RANS (Reynolds-Averaged Navier–Stokes) mode to the LES (Large Eddy Simulation) mode, i.e., in the so-called gray area, continuous hybrid RANS/LES approaches suffer from the well-known problem of excessively slow generation of resolved structures. Indeed, when the mesh is refined in the direction of the flow, the model is designed to reduce the modeled energy, but there is no mechanism to transfer the equivalent amount of energy into the resolved motion. Hence, the total turbulent energy and turbulent stresses are underestimated, which strongly affects the prediction of the mean flow. This also constitutes a violation of the conservation of mechanical energy, which can only be corrected by an active approach, i.e., an approach that allows the injection of resolved energy. The aim of this work is to develop such an active approach based on the introduction of a fluctuating volume force into the resolved momentum equation, similar to the anisotropic linear forcing (ALF) method proposed previously. The major difference with ALF is that the new method does not require target statistics obtained by a RANS computation but is based on a simple analysis of the rate of energy transfer related to variations in resolution, enabling the forcing to be extended to continuous hybrid RANS/LES. The application of the new method to the cases of a channel with or without periodic constriction shows a drastic improvement over the case without forcing. Although the method is applied herein to a particular hybrid RANS/LES approach (HTLES, hybrid temporal LES), it can easily be extended to any other approach, as long as a parameter identifies variations in resolution, and thus offers vast application prospects.

A four-tensor momenta equation for rolling physics

Relativistic four-tensor equation dJ μ ν = M μ ν dt is developed to analyse linear translation with rotation processes. The postulated cause-effect four-tensor equation, a relativistic generalisation for classical angular-impulse–angular-momentum variation equation dJ = Mdt, includes the Poinsot-Euler rotation (angular-impulse–angular-momentum variation) equation, Newton’s second law (linear-impulse–linear-momentum variation equation), and thermodynamics first law (work–energy equation). This four-tensor formalism is applied to describe three linear translation with rotation processes: a ring rolling on the floor by a horizontal force linear impulse and torque, fulfilling the rolling condition (mechanical energy conservation), a spinning ring placed on the ground until achieved the rolling condition (mechanical energy dissipation by friction), and a fireworks wheel ascending an incline (mechanical energy production by decreasing a thermodynamic potential).

Synergy principle and its application of endwall loss analyses in the turbine stator

The endwall flow significantly impacts the turbine performance behavior, and it is necessary to investigate the development of endwall secondary vortices and relevant losses. Inspired by the field synergy principle, the synergy between the velocity and the pressure gradient established by the three-dimensional mechanical energy conservation equation is innovatively applied to the endwall loss analysis in the stator of an axial-inflow turbine. In terms of the synergy equation, the loss is not only related to the viscous dissipation, but also the included angle (or the synergy angle) between the velocity vector and the pressure gradient vector. The physical content of the synergy angle suggests that the larger synergy angle is (i.e., the worse synergy), the higher losses should be. This conclusion has been validated by present numerical results, and an apparent positive correlation between the synergy angle and the losses could be perceived under time-averaged and transient conditions. The worse synergy could be observed at the passage rear part and the wake, where complex passage vortices and local separation exist. In these regions, the local velocity vector is not aligned with the bulk pressure gradient of the mainstream. Hence, the synergy angle has a marked rise, corresponding to the local high losses.

Theoretical and numerical analysis of the flow through a diffuser/nozzle element in pulsatile laminar conditions

Diffuser/nozzle pipes produce a directional flow resistance that is often exploited in microcirculation to generate a pumping action. This work presents an approximate time-dependent theoretical solution based on the mechanical energy conservation equation to predict the laminar flow rate through an ideal diffuser/nozzle pump. The theoretical solution is then used to characterize the dimensionless parameters that control the dynamics of the valveless pump in the pulsatile flow regime. A suitable numerical model is also implemented to solve the flow in a parametrized two-dimensional axial-symmetric domain subjected to an oscillating pressure, and its results are used to assess the theoretical solution. The pump dynamics and the main model parameters, such as the energy-loss coefficients, result in the following dependence on the ratios between the viscous force, the advective inertia, and the temporal inertia, i.e., the Reynolds (Red), Womersley (Wod), and Strouhal (St) numbers referred to throat diameter. In particular, The Womersley number plays an essential role in controlling the global energy loss when Red &amp;lt; 100. The flow transition is also investigated and found when Red exceeds a critical value, which increases with Wod. Finally, the pump efficiency is found to reach its maximum when the convective and temporal inertia become comparable, i.e., St=O(1), consistent with the observed range of St in real-world diffuser/nozzle pumps. This optimum range of functioning of the pump is also observed for cerebrospinal pulsatile flow in the Sylvius aqueduct, suggesting that the modeled mechanism is used to promote or enhance cerebrospinal fluid circulation.

The Relationships in the Law of Conservation of Mechanical Energy and the Ideal Gas Equation in Argon Molecules based on Moldy and Gnuplot

Science and technology have been progressing by leaps and bounds over the past few decades all over the world, resulting in the rapid development of advanced computer programs. Under such circumstances, we are able to prove plenty of theories in a new way with the help of different kinds of modern computer programs. For example, we are capable of investigating the relationship between kinetic energy and potential energy, as well as the connection between temperature and pressure, by applying computer programs to draw graphs. In this paper, moldy and gnuplot which are progressive computer programs are used to paint the graphs about the two relationships in the conservation law of mechanical energy and ideal gas equation respectively in argon gas with the help of the information obtained from the Internet. These two computer programs not only remove the burden of calculation, but also make the relationship clearer. In the end, this paper proves that the sum of kinetic energy and potential energy in argon molecules is invariable in a closed system under different temperatures. Pressure is also tested to have a positive linear association with temperature although the density changes when the argon gas is an ideal gas.

A power road by harvesting electromagnetic energy from moving object

There is a large amount of electromagnetic energy in modern life, but how to utilize the wasted electromagnetic energy from moving objects is still a difficult problem. Here, four 28 W fluorescent tube lamps can be lighted up when a car model slides on a simple power road (SPR) with an instantaneous power density of 11.6 W/m2. An energy-velocity model was proposed to utilize the electromagnetic energy in the constantly friction between the SPR and the car model. It was found that the electromagnetic energy generated by an object moving at a low speed increases with its speed. Besides, the instantaneous power generated by an object in a high-speed collision also increases rapidly with its speed. Moreover, the first SPR was successfully built in an actual road, which opens the door for solving the energy crisis. The energy-velocity model can be also used to explain the signal interference of high-speed railway and improve the positioning accuracy of missile, considerate that the electromagnetic energy produced by the object in motion. The new discovery may contribute to modifying the existing collision theory, conservation of mechanical energy, friction theory, Maxwell's equations, and electromagnetic technology.

Gyroscope oscillation depends on a rotor speed velocity

In engineering, all moving rotating objects exhibit gyroscopic effects resulting from the action of an external torque on a rotating object. Gyroscopic effects are the action of a set of inertial moments and movements of an object around three axes of a three-dimensional Cartesian coordinate system. Moments of inertia are created by centrifugal and Coriolis forces, as well as the moment of change in angular momentum, which is expressed by their kinetic energy. The values of the moments of inertia directly depend on the speed of rotation of the object and its rotation around the axes. A short-term effect of an external load on a running gyroscope with displaced support can be manifested by its oscillations. The physics of gyroscope oscillations is not well explained in publications. This article describes the oscillations of a gyroscope by the action of the external torque which is its potential energy converting into kinetic energy of the inertial torques of the gyroscope. The conversion is carried out by the principle of mechanical energy conservation which is the same as for oscillations of a spring with a load.

PENGARUH PENGUASAAN HUKUM KEKEKALAN ENERGI MEKANIK TERHADAP HASIL BELAJAR FISIKA MATERI POKOK MEKANIKA FLUIDA DI KELAS XI SMA NEGERI PADANGSIDIMPUAN

This study aimed to determine a general idea of mastering the law of conservation of mechanical energy and fluid mechanics, and then I see the influence of the law of conservation of mechanical energy mastery of the learning outcomes of the subject matter of physics of fluid mechanics in class XI of SMAN 8 Padangsidimpuan. The research was conducted using descriptive method.The population is all class XI student are 45 students. The sample is 45 students which are taken by total sampling technique. The data is collected by using test as an instrument. The writer uses statistic processes in analyzing data. They are descriptive analysis and inferential analysis by using the formula of “r” Product Moment and the formula of t test. After collecting the data, it is found the average of mastering the law of conservation of mechanical energy,can be categorized “pretty” .While the average value of the subject matter of physics learning outcomes of fluid mechanics 68.17 can be categorized “pretty”. The result of the analyzed data shows the score of ttest &gt; ttable (2,0 &gt; 1,67) . in other words, the score of ttest is bigger than ttable. So, the hypothesis is accepted. It means there is the influence of the law of conservation of mechanical energy mastery of the learning outcomes of the subject matter of physics of fluid mechanics in class XI of SMAN 8 Padangsidimpuan

Effect of Differentiated Approach in Inquiry-based Learning on Senior High School Students’ Conceptual Understanding of Work and Energy Topic

This study aims to investigate the effect of the differentiated approach on high school students' conceptual understanding of the work and energy topic. The research method used is a quantitative method. Two classes of 10th graders in one of the Senior High Schools in the Tangerang districts were chosen to be research participants with cluster random sampling. Data collection was done with learning style questionnaire and conceptual understanding item with a reliability 0.73. The experimental class applied Inquiry-based Learning with differentiation, while the control class applied Inquiry-based Learning without differentiation. The results of the different tests of students' conceptual understanding after learning showed a significant difference in the understanding of students' concepts in the two classes. The effect size score showed a large effect of a differentiated approach on students' conceptual understanding. The analysis of the level of students' conceptual understanding for each subtopic showed the Law of Conservation of Mechanical Energy having the most students at irresponsiveness level, while the subtopics with the highest number of students at the understanding level was the work subtopic. The percentage of students who studied with a differentiated approach at the highest understanding level is more than students without a differentiated approach in all subtopics. Although the application of the differentiated approach had obstacles in online learning, the differentiated approach applied in Inquiry based Learning has a positive impact in facilitating the diversity of student learning styles.

Effect of construction technology on air-lifting pump mining

The air-lifting pump has the advantages of low cost, strong reliability, simple structure and convenient maintenance, especially in the fields of deep-sea mining, oilfield mining and mineral mining under complex geological conditions. The construction technology and air intake mode not only play a decisive role in the performance of the air-lifting pump, but also greatly hinder the engineering application of the air-lifting pump. Here, the air-lifting pump is taken as the research object, and the river sand is used as the experimental transport medium. The particle concentration-efficiency model is established based on the mechanical energy conservation theorem. The working performance characteristic parameters of the air-lifting pump under different construction technologies are obtained by a three-axis motion control system. On this basis, the working performance characteristic parameters of the air-lifting pump under different intake modes are obtained by changing the intake mode. The results show that the particle concentration-efficiency model can well describe the efficiency of lifting solid particles by the air-lifting pump. When the sand depth is less than 200 mm, the concentration and efficiency of solid particles transported by the air-lifting pump in the horizontal movement construction are significantly better than those in the fixed position construction. In the same construction technology, the solid particle concentration of the air-lifting pump in uniform intake mode is better than that in non-uniform intake mode, while the transportation efficiency of the air-lifting pump in non-uniform intake mode is better than that in uniform intake mode. The research results of this paper can provide an important theoretical reference value for the air-lifting pump in practical engineering applications.

Design And Build A Practicum Equipment For The Law Of Conservation Of Mechanical Energy Of Rolling Objects

Using photo gate sensor technology and digital displays, the research team created a legal practicum for energy conservation. This study aims to replace manual practicum equipment that is prone to measurement errors during practicum. This practicum equipment is used to prove the law of conservation of mechanical energy in rolling objects. Practicum equipment is developed using a development research process that starts with identifying needs and continues through design, manufacturing, and testing. At the design stage, validation of design results is carried out, while at the manufacturing and testing stages, design specifications and performance (measurement of accuracy and precision) are carried out. Based on the results of design validation, a value of 0.85 with a valid category was obtained, while accuracy was 90.7%, with an average accuracy of 97.46%, and a relative error of 8.33%. The thoroughness of the practicum equipment for the law of conservation of mechanical energy of rolling objects is quite good. We are currently developing several pieces of practicum equipment with IoT-assisted smartphone displays.

A fully coupled thermo-hydro-mechanical model for fractured rock masses in cold regions

Freezing-thawing disasters are caused by the coupling effect of thermo-hydro-mechanical (THM) activity in rock masses at low temperatures, which seriously threatens the safety of rock mass engineering in cold regions. The accuracy of the coupled THM model is controlled by coupling parameters, such as the migration velocity of unfrozen water, equivalent thermal conductivity, and freezing point. The main difference in the THM coupling process between the frozen rock mass and frozen soil is the anisotropy caused by fractures, and the main difference between the frozen rock mass and normal rock mass is the existence of the ice-water phase transitions. In this paper, the governing equations for THM coupling of fractured rock masses at low temperatures are established, including the mechanical equilibrium equation, continuity equation and energy conservation equation. These equations include the effect of fractures, ice-water phase transitions, water migration and thermal expansion and contraction, which can also be degenerated to equations for rock masses without fractures. Then, the main parameters for the THM analysis are studied. The migration velocity of unfrozen water is closely related to the fractures, temperature, pressure, and phase transitions. Based on the energy conservation law, the expression of the equivalent thermal conductivity is proposed, which is a function of the geometric parameters of fractures, the thermal conductivity of each component, and the content of unfrozen water. Finally, the correctness of the proposed model are validated by Neaupane's experiment and an actual open-pit slope.

Carbon emission model of vehicles driving at fluctuating speed on highway.

Carbon emission changes significantly when the vehicle is driving at a variable speed. Given that the rule of vehicle carbon emissions under different driving behaviors is underexplored, this study filled this research gap by establishing a theoretical carbon emission model when vehicles are driving at fluctuating speed. The model was established based on the law of conservation of mechanical energy, the first law of thermodynamics, the theory of vehicle dynamics. Two passenger cars and three trucks were selected as typical vehicles. A field test was carried out under different driving behaviors with uniform acceleration. The proposed model can forecast the carbon emissions of vehicles that fluctuate in speed during travel and showed strong accuracy in model validation. As the speed fluctuation increased, the influence of acceleration on carbon emissions became more apparent. Gradient has a more significant influence on vehicle carbon emissions, followed by acceleration. By controlling the driving behavior of the vehicle on the round trip, the same carbon emissions as driving on a flat route at a constant speed can be achieved. The findings of this study will provide a theoretical basis for low-carbon transportation.

One Novel Dynamic-Load Time-Domain-Identification Method Based on Function Principle

In order to ensure the reliability of the structural design, it is necessary to know the external loads acting on the structure. In this paper, we propose a novel method to identify the dynamic loads based on function principles in the time domain. Assuming the external load remains constant within one micro segment, we establish a linear relationship between external load and structural response in the micro segments based on the mechanical energy conservation law. Next, the external load is obtained by solving the inverse problem in each micro-segment. Finally, the external load in the whole time domain is achieved by fitting the load-identification results in each micro segment. In order to verify the effectiveness and accuracy, single-force and two-force identification, and load identification with noise simulations, are performed on the structures, and the identification results are compared to the ones of the traditional time-domain method with a deviation of less than 5%. The proposed method can effectively solve the problem of cumulative errors in the time-domain method, while its resistance to noise interference is also strong. At last, we verify the experimental performance of the proposed method. The experimental results show the effectiveness and high accuracy of the proposed method. This work presents a first attempt to solve the structural dynamic load with an approach based on a function principle.

Principles of Classical Mechanics Describe Gyroscopic Effects

The unexplainable motions of the simple spinning top toy, boomerang, and other spinning objects attracted people since the time of ancient civilizations. The intricated motions of the rotating objects and the action of the unknown forces were named gyroscopic effects. The physicists and mathematicians tried to solve them beginning from the Industrial Revolution until our time. One gyroscopic effect which is the side motion of the spinning disc was described by L. Euler and presented in the world encyclopaedias as the fundamental principle of gyroscope theory. The origin of gyroscopic effects is more sophisticated than in published and simplified theories. Analytical solutions to other gyroscopic effects were described only in our times. The system of the interrelated inertial torques generated by the rotating mass acts on the spinning object based on the principle of mechanical energy conservation. This system presents the fundamental principles of gyroscope theory.

Maldistribution on a Vertical Manifold With Guide Vanes

Abstract Wall-Modeled Large Eddy Simulation (WMLES) has been used to study a subsonic vertical manifolds (VMs) in terms of maldistribution, i.e., how much the flow splitting deviates from an equal flow distribution between the outlets. The analyzed configuration is characterized by a wide-angle plane diffuser and by four outlets and it has been studied at high Reynolds number (Re*=10000, with Re*=u*Dh/ν, where u* is the friction velocity at the inlet, Dh=4A/P is the hydraulic diameter with A the cross-sectional area at the inlet and P the perimeter, ν is the kinematic viscosity). In the basic configuration, a jet flow develops in the diffuser with two stable flow separation regions at the inclined walls, which prevent an equal flow distribution at the outlets, and determine a maldistribution around ε=37%, where ε is a parameter that quantifies the flow rate deviation from an equal distribution. To increase the equal flow distribution between the outlets, guide vanes have been used. A conceptual model to reduce the maldistribution has been developed using the momentum and the mechanical energy conservation laws. The model uses as main parameter the relative distance between the guide vanes, and it allows to minimize ε. Taking advantage of this method, the maldistribution has been reduced from ε=11.20%, for the case of equally distributed guide vanes, to ε=0.32% in the optimized configuration. The methodology is of general use also for hydraulic systems.