Velocity Coefficient Research Articles

Linear and nonlinear ultrasound parameters attributed to anisotropy in granite

AbstractThe anisotropic nature of granite, a key factor affecting its mechanical properties, is inherently governed by its mineral alignment and the presence of orthogonal cleavage planes: rift, grain, and hardway. This study examines how these cleavage planes influence anisotropy, particularly in the context of microcracking formation and acoustic properties. A new measurement procedure for the acoustic nonlinearity parameter ($$\:\beta\:$$) is developed to address the well-known limitations of conventional linear ultrasound methods, including wave velocity and attenuation coefficient, in detecting microstructural changes induced by existing cleavage planes. Unlike other parameters, $$\:\beta\:$$ exhibits remarkable changes depending on the plane type, highlighting its high sensitivity to the mineral distribution in each cleavage plane and to the microcracks. A correlation between the linear and nonlinear parameters provides further evidence of the superiority of $$\:\beta\:$$ in detecting inherent microscale defects that develop in each plane and affect the anisotropic characteristics of granite. The findings of this study confirm that nonlinear ultrasound is capable of elucidating the mechanisms underlying the origin of anisotropy in granite due to microcracks, with broader implications for understanding unidentified chemical and mechanical phenomena in geological materials.

Interrelationship Between Emergence and Yield Parameters in Mung Bean: Implication for Selection

Abstract Rapid and uniform seed germination and seedling emergence have been associated with grain yield under diverse environmental conditions. Twenty-one (21) mung bean accessions were evaluated at Ile-Ife and Kishi out-stations of the Institute of Agricultural Research and Training (IAR & T), Nigeria, to identify the emergence parameter(s) that could be selected for improvement of mung bean for yield. The experiment was laid out in a randomized complete block design (RCBD) in three replications. Data were collected on emergence and yield parameters and analysed using the Statistical Analysis Software (SAS). Mean, heritability, and correlation coefficient were estimated. Path coefficient analysis was used to partition correlations into direct and indirect effects using seed yield as the dependent variable. Heritability estimate was moderate to high for most of the traits. Accessions 3, 6, 14 and 15 with high pod and seed yield had also high values of coefficient of velocity of emergence (CVE) and emergence percentage (E%). All emergence parameters except emergence energy had significant correlation with yield traits. CVE and Emergence Index (EI) had strong positive correlation with number of seeds.pod-1 and pod yield. When only the emergence parameters were considered, CVE had highest direct effect (0.74) on seed yield followed by E% (-0.73) and EI (0.70). Total indirect effects of EI and CVE accounted for only 6.06% and 11.9% of the total correlation, respectively. It therefore suggests that EI and CVE are emergence parameters that could be selected for at early stage in improvement of mung bean for yield.

The Effect of the Nozzle Blade Pitch on the Velocity Coefficient of the Inflow Turbine with Partial Bladings of the Runner

The Effect of the Nozzle Blade Pitch on the Velocity Coefficient of the Inflow Turbine with Partial Bladings of the Runner

Effect of Different Seed Treatment on Germination of Fishtail Palm (Caryota urens) under Naturally Ventilated Poly-house Conditions

An investigation was conducted to study the effect of different seed treatments comprising of mechanical scarification, chemical and plant growth regulator on germination of Fishtail palm (Caryota urens) seeds under naturally ventilated poly-house at sheth D. M. Polytechnic in Horticulture College, Anand Agricultural University, Vadodara during 2021 to 2023. There were total 12 treatments under study which was replicated trice and statistically analysed by completely randomized design at 90 days after sowing. The results revealed that treatment T12 i.e. seeds treated with GA3 1000 ppm for one day recorded significantly lesser days to initiation of germination (46.33 days) along with higher germination percentage (86.67 % and 85.00 %), germination rate index (5.90 %/day and 5.70 %/day) and germination index (255 and 243.67), coefficient of velocity of germination (6.18 and 6.02), timpson’s germination index (1275 and 1218), modified timpson germination index (42.50 and 40.61) and survival percentage (88.33 and 86.67) at 90 days after sowing during first and second year respectively. While, seed without any treatment kept in open condition treatment T1 showed poor performance in germination percentage as well as survival percentage. Thus, Fishtail palm (Caryota urens) seeds soaked in solution of 1000 ppm GA3 along with sowing them in polybags and kept under NVPH condition provides better germination and survival.

Chaos and attraction domain of fractional Φ6‐van der Pol with time delay velocity

This article investigates the chaotic analysis and attractive domain of a fractional‐order ‐van der Pol with time delay velocity under harmonic excitation. Firstly, eight different types of bifurcation states of the system under different parameters are calculated by using the undisturbed system. Secondly, the Melnikov method is used to explore the effect of time delay velocity on the threshold of chaos in the Smale horseshoe sense under the double‐well potential and three‐well potential of the system. Finally, through numerical analysis of the phase diagram, bifurcation diagram, and maximum Lyapunov exponent, the influence of time delay velocity on system chaos is studied. The results indicate that an increase in the delay velocity coefficient will lead to the system transitioning from a chaotic state to a periodic state, while an increase in the delay velocity term will lead to the system transitioning from a periodic state to a chaotic state. In the study of system bifurcation, it is found that the position of the equilibrium points of the system changes during periodic motion. Therefore, cell mapping is used to draw the attractive domain of the system is studying the influence of initial conditions on the equilibrium point of the system and the results show that there is a close relationship between the attraction domain and the process of chaos occurrence.

Influence of energy-saving devices on the hydrodynamic characteristics of a waterjet-propelled ship: Experimental and numerical investigation

Installing stern energy-saving devices can help conserve energy and enhance ship speed, particularly for medium-to-high-speed ships. This study focuses on a waterjet-propelled ship and examines the performance of two energy-saving devices: the interceptor and stern flap. The investigation involves conducting a comparative analysis through towing-tank experiments and utilising Reynolds-averaged Navier–Stokes (RANS) numerical methods. The findings suggest that incorporating energy-saving devices alters the capture flow of the waterjet-propelled ship. Furthermore, these devices reduce ship resistance, resulting in a maximum decrease in the impeller speed of the self-propulsion point up to 5%. Following the installation of energy-saving devices, the propulsion efficiency of the waterjet-propelled ship demonstrates an enhancement ranging from 0.5% to 5.7%. This increase in propulsion efficiency emerges as a principal factor contributing to the energy savings facilitated by the stern energy-saving device. Upon comparison, it was found that within the Fr range of 0.3–0.5, the stern flap exhibited a superior energy-saving effect. Conversely, when Fr exceeded 0.5, the interceptor demonstrated a more pronounced energy-saving effect. Finally, the mechanisms of the stern energy-saving devices are elucidated based on the momentum velocity coefficient, thrust deduction fraction, and changes in the internal and external flow fields of the waterjet-propelled ship.

Rotational Taylor dispersion in linear flows

The coupling between advection and diffusion in position space can often lead to enhanced mass transport compared with diffusion without flow. An important framework used to characterize the long-time diffusive transport in position space is the generalized Taylor dispersion theory. In contrast, the dynamics and transport in orientation space remains less developed. In this work we develop a rotational Taylor dispersion theory that characterizes the long-time orientational transport of a spheroidal particle in linear flows that is constrained to rotate in the velocity-gradient plane. Similar to Taylor dispersion in position space, the orientational distribution of axisymmetric particles in linear flows at long times satisfies an effective advection–diffusion equation in orientation space. Using this framework, we then calculate the long-time average angular velocity and dispersion coefficient for both simple shear and extensional flows. Analytic expressions for the transport coefficients are derived in several asymptotic limits including nearly spherical particles, weak flow and strong flow. Our analysis shows that at long times the effective rotational dispersion is enhanced in simple shear and suppressed in extensional flow. The asymptotic solutions agree with full numerical solutions of the derived macrotransport equations and results from Brownian dynamics simulations. Our results show that the interplay between flow-induced rotations and Brownian diffusion can fundamentally change the long-time transport dynamics.

Physical and mechanical properties of concrete containing plastic tube fibers

Plastic tube fibers (PTFs) are one form of plastic waste resulting from the production of plastic mats that end up in the landfill. Until today, no attempt has been made to explore the applicability of PTFs as a construction material for a circular economy. This paper investigates the applicability of PTFs as fibers in fiber-reinforced concrete (FRC) production. A series of tests are carried out to investigate the effects of volume fractions (VFs) and the length of the fibers on the physical and mechanical properties of FRC-containing PTFs. The effects of the length and VFs on the unit weight, compressive strength, flexural strength, tensile strength, pulse velocity, thermal conductivity, and microstructure of FRC are examined. Three different lengths of fibers of 20 mm, 30 mm, and 50 mm, and VFs of PTFs of 0 %, 0.5 %, 1 %, and 1.5 % are studied. Results show that although the mechanical properties of concrete decrease as the VFs increase from 0 % to 1.5 %, the rate of reduction becomes smaller as the length of the fiber becomes larger. The maximum reduction of compressive, tensile, and flexural strength was found to be as high as 35 %, 25 %, and 35 % compared to the control sample obtained for 20 mm fiber length having 1.5 % VFs. Formulas to predict the tensile and flexural strengths of concrete containing PTFs as a function of the compressive strength are proposed and found to be providing satisfactory results. From a microscopic view, it is seen that the sample containing higher VFs shows less density and homogeneity of concrete which leads to an increase in the micropores of the concrete. Furthermore, the ultrasonic pulse velocity and attenuation coefficient decrease as the VFs of PTFs increase.

The influence of longitudinal duct profiling on unsteady gas dynamics and the heat transfer of pulsating gas flows in the outlet system of reciprocating-engine

Heat machines based on reciprocating-engines remain in demand in various fields of engineering and technology. Therefore, further research is needed to improve the efficiency, reliability, and environmental friendliness of engines. The thermomechanical improvement of non-stationary processes in outlet systems is an appropriate way to improve engine performance. The purpose of this research is to obtain and analyse the gas-dynamic and heat transfer characteristics of pulsating gas flows in an outlet system with ducts of various designs, using a laboratory model to simulate the outlet process in an engine. Thermal anemometry is used to receive data on the instant velocity values and local heat transfer coefficient of unsteady flows in ducts. The article examines two designs of outlet ducts, namely cylindrical (basic) and conical (with a taper of 0.0225) ducts. Spectral analysis of velocity, pressure and heat transfer coefficient pulsations, assessment of turbulence intensity, and calculation of flow characteristics of pulsating flows were performed to obtain detailed information on gas dynamics in the outlet system. The use of a conical duct (in comparison with a cylindrical one) leads to a slight increase in the turbulence intensity by up to 12 %, a decrease in the heat transfer coefficient by 15–20 %, and a change in volumetric gas flow within ± 7.5 %. Thus, the use of a conical duct will lead to the stabilisation of the flow in the outlet system, improved cleaning of the cylinder from outlet gases, a reduction in thermal stress, and a slight growth in the specific power of engines.

Modeling the transport and mixing of suspended sediment in ecological flows with submerged vegetation: A random displacement model-based analysis

Aquatic vegetation in rivers influences the flow structure, impacting the sediment transport in the river and further changing the ecosystem and geomorphologic evolution of the river. In this paper, an improved random displacement model (RDM) is proposed to investigate the concentration of suspended sediment (CSS) in flows with flexible submerged vegetation. Considering the effect of sediment resuspension on sediment transport, a probability model of sediment resuspension is embedded into the RDM so that the simulation process is more consistent with the natural cases. For the streamwise development of flow with flexible submerged vegetation, the flow is divided into a flow adjustment region and a fully developed region in the longitudinal direction. The vertical distributions of the flow velocity and turbulence diffusion coefficient were analyzed in these two regions, and they were incorporated into the RDM to simulate the along-flow development of the CSS. The simulated concentrations were compared with the experimental data. The mean relative errors (MREs) were below 15%, the root mean square errors (RMSEs) were below 0.20, and the Nash–Sutcliffe efficiencies (NSEs) ranged from 0.71 to 0.99, indicating that the improved RDM is plausible and reliable. In addition, the along-flow distribution of the sediment transport rate (STR) was analyzed. The rate exhibited a decreasing trend during the flow adjustment region and tended to stabilize during the fully developed region. This study provides a new way of thinking for research on sediment transport in rivers with aquatic vegetation, which is of great significance for achieving the sustainable development of river ecosystems and the optimal design of river channels.

Diffusion and mobility measurements for propane gas with a nanodosimetric detector

For the operation of nanodosimetric detectors with propane gas, it is essential to know the gas properties at room temperature, such as drift velocity, ion mobility, longitudinal and transversal diffusion coefficients. For propane gas there is only limited experimental data available for the ion mobility and transverse diffusion coefficients. In this work, the drift velocities and ion mobilities for propane were obtained over the reduced electric field range E/N from 24 to 212 Td (1 Td = 10−17 Vcm2) based on arrival time measurements. The reduced ion mobility K0 for propane was determined to be (0.71±0.09) cm2/Vs. The longitudinal diffusion coefficients were determined from the widths of the experimental arrival time spectra and found to be NDL = (3.7 ± 0.5)⋅1019 1/ms in the low field limit below 30 Td.The results presented in this work extend the range of available experimental data for propane, as well as introduce first experimental measurements of the longitudinal diffusion coefficient of propane.

Study of different theories of thermoelasticity under the propagation of Rayleigh waves in thermoelastic medium

The present research is on the propagation of Rayleigh waves in a homogenous thermoelastic solid half-space by considering the compact form of six different theories of thermoelasticity. The medium is subjected to an insulated boundary surface that is free from normal stress, tangential stress, and a temperature gradient normal to the surface. After developing a mathematical model, a dispersion equation is obtained with irrational terms. To apply the algebraic method, this equation must be converted into a rational polynomial equation. From this, only those roots are filtered out, which has satisfied both of the above equations for the propagation of waves decaying with depth. With the help of these roots, different characteristics are computed numerically, like phase velocity, attenuation coefficient, and path of particles. Various particular cases are compared graphically by using phase velocity and attenuation coefficient. The elliptic path of surface particles in Rayleigh wave propagation is also presented for the different theories using physical constants of copper material for different depths and thermal conductivity.

Error Estimates for First- and Second-Order Lagrange–Galerkin Moving Mesh Schemes for the One-Dimensional Convection–Diffusion Equation

A new moving mesh scheme based on the Lagrange–Galerkin method for the approximation of the one-dimensional convection–diffusion equation is studied. The mesh movement is prescribed by a discretized dynamical system for the nodal points. This system is related to the velocity and diffusion coefficient in the convection–diffusion equation such that the nodal points follow the convective flow of the model. It is shown that under a restriction of the time step size the mesh movement cannot lead to an overlap of the elements and therefore an invalid mesh. Using a piecewise linear approximation, optimal error estimates in the ℓ∞(L2)∩ℓ2(H01)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\ell ^\\infty (L^2) \\cap \\ell ^2(H_0^1)$$\\end{document} norm are proved in case of both, a first-order backward Euler method and a second-order two-step method in time. These results are based on new estimates of the time dependent interpolation operator derived in this work. Preservation of the total mass is verified for both choices of the time discretization. Numerical experiments are presented that confirm the error estimates and demonstrate that the proposed moving mesh scheme can circumvent limitations that the Lagrange–Galerkin method on a fixed mesh exhibits.

Three-dimensional solute transport in finite and curved porous media with surface input sources

In this paper, an analytical solution for three-dimensional solute transport in porous media between two curved surfaces is investigated. It is assumed that the groundwater velocity and dispersion coefficient vary with time and position. Groundwater velocity is not considered to be horizontal. The components of dispersion coefficient along the axes are considered to be proportional to the square of corresponding the position variable. The dispersion coefficient components along axes are proportional to the corresponding component of groundwater velocity in temporal aspects while former is squarely proportional to letter one in position components. It is assumed that the sources originate from two curved surfaces. The nature of the source on the two surfaces is the same, but there may be a variation in potential. Initially, the aquifer's domain is supposed to be uniformly polluted. The Laplace Integral Transformation Technique (LITT) is used to obtain analytical solutions. Numerical examples are given to demonstrate the effects of various factors on the solute concentration profile in a system where advection and dispersion play important roles.In addition, the sub-case of horizontal flow is also discussed. The model is extremely useful in analyzing and dealing with widespread surface sources of groundwater pollution in simulated agricultural fields or urban dumping areas.

ENHANCING GERMINATION AND SEEDLING VIGOR IN NIGELLA SATIVA: THE IMPACT OF NANO IRON OXIDE AND PHOSPHORUS PRIMING

Nigella sativa, commonly known as black cumin, is known for its health benefits due to its rich content of compounds like thymoquinone. This study explored the effects of various seed priming methods on Nigella sativa seeds, including control (unprimed), distilled water, nano iron oxide (Fe₂O₃), phosphorus (P), and a combination of Fe₂O₃ and P. We assessed how these treatments influenced several key aspects of seed germination: germination rate (GR), mean germination time (MGT), germination index (GI), coefficient of velocity of germination (CVG), and vigor index (VI).Our results showed that seeds treated with Fe₂O₃ nanoparticles had the highest germination rate at 93.5% and germinated faster than seeds from other treatments. This suggests that Fe₂O₃ nanoparticles effectively speed up the germination process. However, despite the improved germination rate, the seeds treated with Fe₂O₃ did not exhibit the highest seedling vigor; the control seeds had the highest vigor index, indicating that while Fe₂O₃ accelerates germination, it does not enhance seedling health as much as the untreated seeds. Additionally, there were no significant differences in the germination index and coefficient of velocity of germination between the treatments, suggesting these parameters were less influenced by the priming methods.In summary, nano-priming with Fe₂O₃ is effective for speeding up seed germination but does not necessarily improve seedling vigor. These findings provide valuable insights into how different priming techniques can be optimized to enhance seed performance and plant growth under various conditions.

Examining three distinct rheological models with flexoelectric effect to investigate Love‐type wave velocity in bedded piezo‐structure

AbstractThe transference of the surface seismic wave at the loosely bonded common interface of a visco‐piezo composite structure is examined in the current work. With the flexoelectric effect taken into account, the structure is composed of a viscoelastic layer embedded on a piezoelectric substrate. The shear stiffness of the upper layer is thought to be described by a Kelvin–Voigt model. An analytical separable of variable method is used to derive the complex dispersion relation for both electrically open and short circuit scenarios. A numerical example is presented to demonstrate the significant influence of several influencing parameters on the wave's phase velocities and attenuation coefficients. Additionally, a graphic comparison of three rheological models – the Maxwell, Newton and Kelvin–Voigt models – is covered. Results indicate that the attenuation curve pertaining to the Maxwell and Newton model is lowest than on the Kelvin–Voigt model. Some major outcomes are highlighted here as: the prominent influence of bonding parameter is well‐proportional to the phase velocity and inversely proportional to the attenuation coefficient, and flexoelectricity has an intensive impact on both phase velocity and attenuation coefficient curves. This theoretical study leads to understanding the piezo‐flexo coupling and its potential application to design the sensors, actuators, energy harvesters and nano‐electronics.

Generation of GHz surface acoustic waves in (Sc,Al)N thin films grown on free-standing polycrystalline diamond wafers by plasma-assisted molecular beam epitaxy

Abstract Telecommunication of the next generation demands filters that can operate in the 10 GHz range with sufficient bandwidths. For surface-acoustic-wave (SAW) devices this prerequisite translates into high sound velocities and high piezoelectric couplings. Wurtzite AlN on diamond, which exploits the strong piezoelectricity of AlN with the very high SAW velocity of diamond, has been considered a promising platform. A significant boost (up to a factor of 4) of the piezoelectric response can be obtained by alloying AlN with Sc. Here, the main challenge lies in the synthesis of highly-oriented thin (Sc,Al)N films on diamond. In this work, we aim at establishing a platform for SAW devices using plasma-assisted molecular beam epitaxy for the deposition of Sc0.2Al0.8N on diamond. We investigate the structural properties related to SAW generation gearing towards applications at high frequencies. To this end, we prepare (Sc,Al)N thin films using plasma-assisted MBE on polished polycrystalline diamond wafers and demonstrate the efficient generation of SAW modes with frequencies up to 8 GHz. Systematic studies of the dependence of the SAW velocity and electromechanical coupling coefficient on the Sc0.2Al0.8N film thickness is presented for various SAW modes. Our result demonstrates the potential of this material combination for future application that requires large bandwidth in the ultra-high frequency range.

Electro-magnetohydrodynamic (EMHD) Darcy–Forchheimer flow of Sutterby nanofluid with variable thermal conductivity over a stretching sheet: Finite difference approach

This paper examines the enactment of a two-dimensional, steady, non-Newtonian nanofluid flow over a stretching sheet. The utilization of magnetic influences acting in the direction normal to the Darcy–Forchheimer boundary layer flow of the Sutterby nanofluid with variable thermal conductivity is taken into consideration. This study takes into account the effects of thermophoresis and Brownian motion. The study found that a 15% increase in magnetic field strength resulted in a 10% increase in heat transfer rate. Similarly, a 20% increase in nanoparticle volume percentage causes a 12% increase in the convective heat transfer coefficient. The problem’s model is formulated in the form of partial differential equations (PDEs), transformed via similarity transformation into nonlinear ordinary differential equations (ODEs). Applying the finite difference method yields the solution to reduced equations. EMHD Darcy–Forchheimer flow and nanofluid dynamics are combined in cutting-edge technology. This is important for many industrial and technical applications. Moreover, providing a strong computational framework provides a precise simulation of the flow behavior. By providing insights into the intricate interactions between electromagnetic forces, porous medium effects, and variable thermal conductivity in nanofluids flow across a stretched sheet, this study makes an essential contribution to the science of fluid dynamics. This research is very significant and enlightening for researchers and professionals who are interested in the design and optimization of heat transfer systems. The fluid flow is examined thoroughly and graphically, and the relationship between the profiles of velocity, temperature, and concentration and other important physical limitations is investigated. The effect of various physical parameters on concentration, velocity, temperature, skin friction, Nusselt number and heat flow coefficient is verified and examined using graphs and tables.

Rayleigh wave propagation in a modified couple stress visco-thermoelastic diffusion medium

The present investigation is devoted to Rayleigh wave propagation in modified couple stress visco-thermoelastic medium with mass diffusion under Lord–Shulman and Green–Lindsay theories of thermoelasticity. After formulating the problem mathematically, the secular equation is derived for stress free, insulated, and impermeable boundary. The wave characteristics like phase velocity and attenuation coefficient have been obtained numerically by developing numerical algorithm. For a particular material, the numerically simulated results are shown graphically to display the physical meaning of the phenomenon. The current inquiry also leads to several specific cases of interest. A comparison has been conducted with the earlier findings that suggested how the additional parameters might affect the phenomena of Rayleigh waves propagating. The results obtained indicate to the strong impact for the diffusivity and viscosity of Rayleigh thermoelastic waves propagation and applicable on the related phenomenon in geology, geophysics, acoustics, astronomy, and geophysics and agreement with the physical meaning of the phenomenon.

Modelling and Analysis of Evacuated Tube Solar Collector Working with Hybrid Nanofluid

This research study is concerned with developing a mathematical model for an Evacuated Tube Solar Collector (ETSC) that utilizes a Hybrid Nanofluid flow in a manifold. The model consists of a set of the partial differential equations that, using the dimensional analysis approach, are reduced to a dimensionless system. The exact solution method, assisted by the Mathematica program, is used to solve the system. The study examines the impact of certain factors on flow and heat transmission, including horizontal velocity, temperature variation, heat source, magnetic field, Prandtl Number, and Eckert Number, and provides a detailed analysis of the results. The key findings of the analysis revealed that an increase in hybrid nanoparticle volume effects in a reduce in velocity and heat transfer coefficient. Additionally, elevated heat source and Prandtl number correspond to an increased heat transfer coefficient.