Fundamental Conservation Principles Research Articles

Lid driven flow and heat transfer due to various positions of slit in a square cavity: FEM approach

A detailed analysis of flow and heat transfer due to moving slit within the various positions of the square cavity is discussed. The slit is strategically positioned and examined at three distinct locations within the square cavity i.e. left, middle and right. Constraints of the square cavity are defined for horizontal and vertical walls. The top horizontal wall is considered to be adiabatic while the other three walls of the cavity are cold. The upper surface of slit is heated and movable towards the left side of the square cavity while the other three walls are immovable and cold. The fluid flow dynamics and heat transfer within the enclosed cavity are governed by fundamental principles of mass, momentum and energy conservation. These governing principles manifest as intricate mathematical equations, specifically nonlinear partial differential equations accompanied with boundary conditions. The key parameters under consideration include the Reynolds number (250≤Re≤1500) and Richardson number (0.01≤Ri≤5) at a fixed Prandtl number (Pr=6.2). These parameters are analysed through variations in velocities, temperature profiles, isotherms and streamlines. In the computational framework, the momentum and temperature equations are addressed through quadratic interpolation, while linear interpolation is applied to handle the pressure equation. The numerical solution, utilizing Newton's technique and the PARADISO solver, is rigorously validated against existing research methodologies, establishing its methodological reliability. Higher Reynolds numbers shift the primary vortex towards the middle and create corner recirculation zones, more uniform heat distribution, while higher Richardson numbers increase buoyancy forces, reducing isotherm contours and affecting heat distribution. The local Nusselt number increases with the increase in Reynolds numbers but shows small changes with the increase in Richardson number. The value of Nusselt number decreases as the position of slit changes from left to right.

Four-dimensional hemodynamic prediction of abdominal aortic aneurysms following endovascular aneurysm repair combining physics-informed PointNet and quadratic residual networks

Hemodynamic parameters can provide surveillance for the risk of complication of abdominal aortic aneurysms following endovascular aneurysm repair (EVAR). However, obtaining hemodynamic parameters through computational fluid dynamics (CFD) has disadvantages of complex operation and high computational costs. Recently proposed physics-informed neural networks offer novel solutions to solve these issues by leveraging fundamental physical conservation principles of fluid dynamics. Based on cardiovascular point datasets, we further propose an integration algorithm combining physics-informed PointNet and quadratic residual networks (PIPN-QN) that is capable of mapping sparse point clouds to four-dimensional hemodynamic parameters. The implemented workflow includes generating point cloud datasets through CFD simulation and dynamically reproducing the three-dimensional flow field in the spatial and temporal dimensions through deep learning. Compared with physics-informed PointNet (PIPN), the PIPN-QN reduces the mean square error of pressure and wall shear stress by around 32.1% and 33.1% and anticipates hemodynamic parameters in less than 2 s (14 400 times faster than CFD). To address the challenge of big data requirements, we quantify the universal flow field using a reduced number of supervision points, as opposed to the large number of point clouds generated from the CFD simulation. The PIPN-QN can meet the real-time hemodynamic parameters obtained from patients with abdominal aortic aneurysms following EVAR with higher accuracy, faster speed, and lower training costs.

Exploring pressure, temperature, and flow patterns in ciliated microfluidic systems

The integration of cilia-induced flow, nanofluids, and the inclusion of cobalt ferrite particles holds significant promise in fluid dynamics, heat transfer, and nanotechnology, offering potential breakthroughs in various technological and material applications. We explore the behavior of cilia-induced flow in a nanofluid confined within an annular domain, employing the Williamson fluid model to characterize the behavior of cobalt ferrite (CoFe2O4) nanoparticles. Our analysis is based on a mathematical treatment rooted in fundamental mass, momentum, and energy conservation principles while considering physical constraints (low Reynolds number and long wavelength) and adopting a dimensionless approach. By applying regular perturbation techniques, we derive series solutions for velocity and temperature profiles, providing insight into the complex interplay among cilia-generated flow, nanofluid properties, and the influence of Cobalt ferrite nanoparticles within the annular configuration. In particular, we uncovered clear correlations among cilia length, amplitude ratio, flow rate, and the Prandtl number with temperature distribution. Also, we observed substantial reductions in temperature trends under Weissenberg numbers and particle volume fractions.

Reexamining the Estimation of Tropical Cyclone Radius of Maximum Wind from Outer Size with an Extensive Synthetic Aperture Radar Dataset

Abstract The radius of maximum wind Rmax, an important parameter in tropical cyclone (TC) ocean surface wind structure, is currently resolved by only a few sensors so that, in most cases, it is estimated subjectively or via crude statistical models. Recently, a semiempirical model relying on an outer wind radius, intensity, and latitude was fit to best-track data. In this study we revise this semiempirical model and discuss its physical basis. While intensity and latitude are taken from best-track data, Rmax observations from high-resolution (3 km) spaceborne synthetic aperture radar (SAR) and wind radii from an intercalibrated dataset of medium-resolution radiometers and scatterometers are considered to revise the model coefficients. The new version of the model is then applied to the period 2010–20 and yields Rmax reanalyses and trends that are more accurate than best-track data. SAR measurements corroborate that fundamental conservation principles constrain the radial wind structure on average, endorsing the physical basis of the model. Observations highlight that departures from the average conservation situation are mainly explained by wind profile shape variations, confirming the model’s physical basis, which further shows that radial inflow, boundary layer depth, and drag coefficient also play roles. Physical understanding will benefit from improved observations of the near-core region from accumulated SAR observations and future missions. In the meantime, the revised model offers an efficient tool to provide guidance on Rmax when a radiometer or scatterometer observation is available, for either operations or reanalysis purposes.

Proposal of an innovative model for fire prevention assessment in Cultural Heritage Protection. Research study in Italy

The complexity of cultural heritage has often led to the belief that fire safety regulations enacted for civil constructions could be derogated due to their invasiveness in relation to the artistic peculiarities of historical assets. In many cases, the lack of effective interventions has resulted in the loss of significant historical and architectural assets, destroyed by fires over the centuries. This research aims to reconcile the regulatory parameters of fire prevention with the fundamental principles of restoration and conservation, following a performance-based approach. Building upon the Italian regulatory framework, this study develops an integrated method that adheres to both the parameters of the “Vertical Technical Rule” on historical buildings and the conservation cases associated with them. The proposed model is the result of a multiparametric evaluation based on the intersection of 3 objectives, 7 sub-objectives, and 10 strategies, defining 70 actions based on the main objective to be pursued. The methodology was applied to two case studies in Southern Italy. The results demonstrate that it is possible to ensure fire safety while preserving the unique characteristics of historical buildings through minimally invasive interventions. Furthermore, the results, which are almost identical between the two case studies, demonstrate that the methodology is applicable to each type of protected asset, including museums or galleries, buildings for exhibitions or shows, libraries, and archives, and historical churches.

МЕТОДИЧНІ ОСОБЛИВОСТІ УЗАГАЛЬНЕННЯ ЗНАНЬ ШКОЛЯРІВ ПРО ФУНДАМЕНТАЛЬНІ ФІЗИЧНІ ПРИНЦИПИ

The article is devoted to solving the urgent, complex and multifaceted problem of increasing of the level and quality of fundamental training of schoolchildren in physics in modern educational conditions. The author notes that the solution of this problem requires the implementation of methodical approaches and learning technologies that will provide students with a purposeful and consistent mastery of a system of organically interconnected subject, worldview and methodological knowledge, followed by their generalization with the help of relevant physical principles at the level of modern physical pictures of the world. In this regard, the author determined the sequence of studying the material and highlighted the theoretical and methodological aspects of generalizing students' knowledge about the fundamental physical principles of relativity, conservation and atomism, which should be the focus of teachers' attention both during the educational process and at the final classes on the relevant topics. Schoolchildren's awareness of the physical essence of the principle of relativity contributes not only to the understanding of the general laws of mechanical motion and the interaction of bodies in different reference systems, but also expands and deepens knowledge of two basic scientific concepts (mass, energy) and forms an idea of a single four-dimensional space-time continuum that encompasses. Students' understanding of the fundamental importance of the principle of conservation is connected not only with the unity of space-time, but also with the symmetry of space, symmetry of interactions, and symmetry of laws. Elucidation by students of the physical essence of the fundamental principle of atomism involves a consistent awareness of the discrete structure of matter, electromagnetic radiation, the discreteness of the physical characteristics of micro-objects. It is noted that students' understanding of the physical essence and methodological significance of the latter will not only correspond to the development trends of modern physical science, but will also contribute to increasing the level of subject competence, the formation of a scientific worldview, and will be a guarantee of the success of further education and future professional growth. Key words: fundamental physical principles, systematization and generalization of schoolchildren's knowledge, scientific outlook, subject competence of students in physics.

Numerical and thermo-energy analysis of cycling in automotive air-conditioning operating with hybrid nanolubricants and R1234yf

Studies on automotive air-conditioning (AAC) systems involving compressor on-off cycling are still limited. This study focuses on improving the cycling of the AAC system using hybrid nanolubricants and hydrofluoroolefin-1234yf refrigerant. A dynamic model for an AAC system with a thermostatic switch that controls the on-off compressor was developed. The model was built in MATLAB Simulink and based on the state-space model using the fundamental conservation principles at the condenser, evaporator, and expansion valve. The experimental data were used to calculate the AAC system pressure, compressor, heat transfer coefficient of the condenser-evaporator, and expansion valve setting. The validation of the experimental data and the predicted data by the simulation suggested that the dynamic model could predict the AAC system’s performance within ±5% deviation. The AAC system operating with Al2O3-SiO2/PAG nanolubricants has a lower temperature cycling frequency than the AAC system with the original PAG lubricant, representing less energy consumed. In addition, the AAC system with hybrid nanolubricants was performed with lower power consumption and significantly higher cooling capacity than the original system. The present simulation confirmed the feasibility of hybrid nanolubricants for application in an AAC system with a thermostatic switch.

Numerical study on the straight, helical and spiral capillary tube for the CO2 refrigerant

A numerical study has been carried out for straight, spiral and helical capillary tubes and their performance has been compared with CO2 refrigerant. The numerical models are developed based on the fundamental conservation principles of mass, momentum, and energy. Within this, outer loop, the ordinary differential equations are solved from the inlet to the exit of the capillary tube. The study has been carried out to calculate the mass flow rate by bisection method where the mass is iteratively calculated at the specified capillary length or vice versa. In-house coding programming employs the finite difference approach for numerical solutions. The characterization of the capillary tube has been done by calculating the length for the given mass or by calculating mass for the given length. The comparison of the straight capillary with helical capillary tube (50 mm coil diameter) and spiral capillary tube (50 mm pitch) has been reported. For a change in tube diameter, surface roughness, and length, the percentage reduction in mass flow rate in capillary tubes (straight, helical, and spiral) is calculated. The percentage reduction in mass in a helical capillary tube compared to the straight capillary tube is about 7–9 %. The percentage reduction in mass in a spiral tube compared to the straight capillary tube is nearly 23–26 %. Additionally, the percentage reduction in mass in a spiral tube compared to the helical capillary tube is almost 17–19 %. Additionally, the percentage reduction in length in a spiral tube compared to straight capillary tube ranges from 37 % to 43 %. Similarly, the percentage reduction in length in a spiral tube compared to helical capillary tube is ranging from 25 % to 32 %

Treasures gutted by fire. Fire safety design awareness as a consequence of historic building accidents and disasters

Many of the emblematic buildings of historical importance that have been constructed throughout human history still survive today. However, a significant number has been destroyed by fire. Despite the impact this loss has on cultural heritage, important lessons can also be learnt, enhancing our understanding on how fires develop in historical structures and why they occur in the first place. A review of the existing fire design approaches, in conjunction with the heritage building values and fundamental conservation principles, initiates a dialogue in terms of acceptable interventions and fire protection solutions. The aim of this study is to provide contemporary scientists, conservation professionals and building owners with an insight of how building physics affect the fire performance of historic structures, highlight common risks following a thorough literature review and discuss the role of the fire and conservation engineer.

Physical principles of venous hemodynamics and its mathematical modeling

In physiological conditions, the cardiovascular system (CVS) is a closed circulatory system comprising a pump (the heart), a conduit system (vasculature), and a continuum media (blood) moving through the system. The heart is a major source of energy in this system. It pumps the blood through the two connected loops. From the mechanical point of view, CVS can be represented as a network of flexible tubes filled with a viscous incompressible fluid driven by a periodic energy source. The fluid dynamics are described by Navier-Stokes's equations, representing the fundamental physical principles of mass and momentum conservation. These equations allow computation of the blood velocity field and pressure depending on the forces exerted to the fluid's surface (surface forces) and to a unit portion of the fluid (mass forces). Equations of structural dynamics describe the motion of the vascular wall. The state-of-the-art models incorporate fluid and structure interaction (FSI). The blood flow in various parts of CVS has different features that must be considered during computational simulations. Elastic properties of the veins and arteries are different. The structural features of veins (valves) limit the backward flow. The geometry of venous cross-sections may be circular, elliptic, and dumbbell-shaped. It changes the flow characteristics. Blood rheology plays a significant role in venous flows. According to the mass conservation law, the work of the heart pump provides energy for the arterial flow and determines venous return to the heart atria. Venous hemodynamics comprises a lot of various processes with different physical and biological origins. Complex analysis of a patient requires computational simulations, which provide medical experts with a basis for prognosis and optimal surgical treatment. In this work, we review basic physical principles and modern mathematical models of venous hemodynamics. In conclusion, the blood flow in veins can be considered as a mechanical process. It obeys the fundamental physical principles and can be described by the well-known mathematical models of continuum mechanics. Thus, the flow characteristics can be simulated and predicted in various healthy and pathological conditions basing on the boundary conditions and material properties of the blood and veins.

Performance Evaluation of PFR and CSTR 1- Reactor Tank for Formaldehyde Petrochemical Production

CSTR 1-reactor tank and PFR plug flow reactor for the production of formaldehyde are two reactors subjected to performance studies. The research models were derived from the fundamental principles of conservation of mass and energy balance; and qualitative kinetic optimum model for the determination of yields for the dehydrogenation and partial oxidation of methanol in the two reactors at 600-6500C. The data obtained for model evaluation were statistically regressed to adopt it as engineering data which is adequate for applications in the evaluation process. The design models for the CSTR 1-reactor tank and PFR plug flow reactor reactors were appropriately solved. The results obtained on the two reactors parameters are given as follows: CSTR 1-reactor tank volume 2.85m3, Height 5.69m, Space-time 0.12hr, Space-velocity 0.67/hr, pressure drop and heat generated per unit volume 2.34*107J/m3. Similarly, PFR volume 1.26m3, Height 12.58m, Space-time 0.225hr, Space-velocity 0.182/hr, pressure drop 3.73*10-8 and heat generated per unit volume 1.17*108 J/m3, And, innovatively, results of optimal yields Yopt calculation for CSTR 1-reactor tank and Plug flow reactor PFR showed that the yields obtained for the two reactors are 69% and 87% and compare favorably with operational yields of the production process which stood at 78.5% and 80.1%. From the results PFR provide a better volume for the production of formaldehyde at 87% conversion of 1.26m3. Hence, the PFR has a better performance for the production of formaldehyde with 87% feed conversion.

On the Observed Inverse Relationship between Rainfall Amount and Dissolved Mineral Content

AbstractRainfall samples collected on the high plains of West Texas exhibit a high degree of variability with respect to the concentration of dissolved solids. That such variations should occur is to be expected, but there remains some uncertainty regarding factors that influence the ionic composition of individual samples. Measurements often show a distinct decrease in concentration with increasing precipitation amount. The reason for this inverse relationship is not intuitively obvious; however, it can be explained from a theoretical perspective. A theory was proposed that describes the concentration of dissolved solids in a collected rainfall sample. The theoretical basis of the derived equation rests upon fundamental principles of conservation of fluid volume and conservation of mass. This equation, which provides valuable insight into the process, suggests that if the rain sampling tube is absolutely clean at the start of a rain event, then the rainfall sample will not be altered by its collection and, therefore, will provide a true measure of rainfall chemistry. However, if windblown dust or other impurities are allowed to deposit in the rain gauge prior to or during the early stages of a rain event, then the concentration of dissolved solids can be very large for small sample volumes and not at all representative of the true concentration within the rain cloud. Results suggest that impurities in the rain sample can be appreciably diluted by the addition of relatively pure rainwater such that the concentration will asymptotically approach the true concentration as the rainfall sample volume increases.

Thermodynamic study of the simultaneous production of electrical power and refrigeration capacity from regasification of liquefied natural gas

The simultaneous production of electrical power and refrigeration capacity from regasification of liquefied natural gas (LNG) is studied. Typical regasification systems, such as open rack vaporizers and submerged combustion vaporizers, do not envisage the possibility of recovering the LNG cryogenic energy to produce refrigeration or electrical power. This paper focuses on a regasification-cogeneration process, already reported in the literature, from the University of Palermo, Italy, that prioritizes the recovery of refrigeration heat transfer rate, with electrical power generation being regarded as a process by-product. A simple thermodynamic analysis compares the traditional and the cogeneration regasification processes by means of their energy utilization and exergy efficiency. An innovative approach is here employed where, in addition to the system thermal performance, refrigeration load demand is also taken into account as an independent variable. Fundamental principles of mass and energy conservation are applied to provide a description of the system thermal behavior, in terms of the independent electrical and cooling power demands. Model results show that significant improvement on system efficiency can be attained with the recovery of the cryogenic exergy of LNG, particularly when refrigeration and regasification thermal power load demands are of the same order of magnitude.

Predator Persistence through Variability of Resource Productivity in Tritrophic Systems.

The trophic structure of species communities depends on the energy transfer between trophic levels. Primary productivity varies strongly through time, challenging the persistence of species at higher trophic levels. Yet resource variability has mostly been studied in systems with only one or two trophic levels. We test the effect of variability in resource productivity in a tritrophic model system including a resource, a size-structured consumer, and a size-specific predator. The model complies with fundamental principles of mass conservation and the body-size dependence of individual-level energetics and predator-prey interactions. Surprisingly, we find that resource variability may promote predator persistence. The positive effect of variability on the predator arises through periods with starvation mortality of juvenile prey, which reduces the intraspecific competition in the prey population. With increasing variability in productivity and starvation mortality in the juvenile prey, the prey availability increases in the size range preferred by the predator. The positive effect of prey mortality on the trophic transfer efficiency depends on the biologically realistic consideration of body size-dependent and food-dependent functions for growth and reproduction in our model. Our findings show that variability may promote the trophic transfer efficiency, indicating that environmental variability may sustain species at higher trophic levels in natural ecosystems.

Characterization and simulation of an open piston compressor for application on automotive air-conditioning systems operating with R134a, R1234yf and R290

A semi-empirical characterization and simulation model for automotive air-conditioning open piston compressor is developed. The model is based on fundamental conservation principles and takes into account pressure drop and heat transfer in suction and discharge passages. Fundamental conservation principles equations, as well as volumetric and isentropic efficiencies, pressure drop, heat transfer and property equations are combined to form a system of non-linear algebraic equations. They are worked out so as to identify constants that are sole characteristics of the compressor and should not vary with different operating conditions or refrigerants. A numerical method determines such constants from existing experimental data, thus characterizing the compressor. Experimental data were obtained from tests carried out by Navarro et al. (2013) for an open piston compressor running with fluids R134a, R1234yf and R290. First, the experimental data were employed to determine the characterization parameters of the compressor. Then, the simulation model, with the R134a-based parameters, was applied to simulate the compressor operation with R1234yf and R290. Good agreement was obtained between predicted and experimental values, proving the suitability of the model for the study of new refrigerants.

Theoretical calculation of the characteristics of annular flow in a rectangular narrow channel

A mathematical separated flow model has been developed that is applicable to the annular two-phase flow in the rectangular narrow channels with peripheral heating. The theoretical annular flow model is based on the fundamental conservation principles: the mass, momentum and energy conservation equations of liquid film, and the momentum conservation equation of the vapor core. Through numerically solving the closed equations, boiling heat transfer coefficient, axial pressure gradient, liquid film thickness and velocity profiles in the liquid film are obtained. A good agreement has been found through comparing the experimental data and theoretically predicted results. The liquid film thickness will decrease with the increase of heat flux and channel width, while increases with increasing flow rate and channel height. The velocity profile in the liquid film is not linear when the thickness of the liquid film is not very thin and it increases with increasing heat flux, while decreases with the increase of mass flow rate and channel size. The effects of heat flux and channel width on velocity in the liquid film are larger than that of mass flow rate. The velocity in liquid film tends towards linear, when the liquid film is mainly in the laminar boundary layer.

Oblique reflection of a laser pulse from a perfect elastic mirror

An oblique reflection of a laser pulse from a fully reflective mirror is treated using the fundamental nonrelativistic conservation principles of energy and momentum. Since the mirror is considered as an elastic object, the reflection of light gives rise to an elastic wave with measurable amplitude that propagates within the mirror. Our results predict a larger Doppler shift in the reflected pulse for the most common setting, when the mirror is initially at rest, compared to the results obtained when the mirror is treated as rigid.

Theoretical study on the characteristics of critical heat flux in vertical narrow rectangular channels

Abstract A mathematical separated flow model of annular upward flow has been developed to predict the critical heat flux (CHF) in uniformly heated vertical narrow rectangular channels. The theoretical model is based on fundamental conservation principles: the mass, momentum, and energy conservation equation of the liquid film and the momentum conservation equation of the vapor core together with a set of closure relationships. The comparisons between the theoretically predicted results and the experimental data demonstrate that a good agreement between them has been achieved. With the applications of the present model, the influences of several parameters (such as system pressure, inlet mass flux and channel size) on the CHF in rectangular channels are analyzed, and the CHF is compared with that in annular channels.

Numerical study on annular tube once-through steam generator using compressible flow model

The once-through steam generator is an essential component of the integrated nuclear power system. A compressible model with fixed boundaries was applied to study the thermo-hydraulic characteristics of an annular tube once-through steam generator. The present model follows the three fundamental conservation principles in the lumped parameters form, and adopts special method for the primary flow distribution in the annular tube. The Gear algorithm is adopted to solve the differential equations. The steady-state and transient results show that the proposed model can successfully simulate the transient processes with large disturbances in the steam generator. Comparisons between the compressible and incompressible flow models indicate that the compressible flow model is necessary to the steam generator transient simulation.

A fundamental approach to specify thermal and pressure loadings on containment buildings of sodium cooled fast reactors during a core disruptive accident

Reactor Containment Building (RCB) is the ultimate barrier to the environment against activity release in any nuclear power plant. It has to be designed to withstand both positive and negative pressures that are credible. Core Disruptive Accident (CDA) is an important event that specifies the design basis for RCB in sodium cooled fast reactors. In this paper, a fundamental approach towards quantification of thermal and pressure loadings on RCB during a CDA, has been described. Mathematical models have been derived from fundamental conservation principles towards determination of sodium release during a CDA, subsequent sodium fire inside RCB, building up of positive and negative pressures inside RCB, potential of in-vessel sodium fire due to failed seals and temperature evolution in RCB walls during extended period of containment isolation. Various heating sources for RCB air and RCB wall and their potential have been identified. Scaling laws for conducting CDA experiments in small-scale water models by chemical explosives and the rule for extrapolation of water leak to quantify sodium leak in reactor are proposed. Validation of the proposed models and experimental simulation rules has been demonstrated by applying them to Indian prototype fast breeder reactor. Finally, it is demonstrated that in-vessel sodium fire potential is very weak and no special containment cooling system is essential.