Semi-vertical Angle Research Articles

Modeling of the shape of Taylor cone in EHD printing based on backpropagation neural network and genetic algorithm

Electrohydrodynamic (EHD) printing has been recognized as a promising additive manufacturing technology with superior pattern resolution and economic viability. The shape of Taylor cone is deemed a pivotal element for the amplification of deposition efficiency, and the maintenance of consistent operational steadiness in EHD printing. The correlations between diverse operating parameters and the shape of Taylor cone are presently not well investigated. In this paper, modeling of relationships between operating parameters and the shape of Taylor cone was conducted with a backpropagation neural network (BPNN) and a genetic algorithm optimized backpropagation (GA-BP) neural network. Taylor cone semi-vertical angle and the meniscus height were employed as two indexes to characterize the shape of Taylor cone. The prediction accuracies of BPNN model and GA-BP model were 92.79 % and 95.46 %, respectively. The GA-BP model demonstrated higher precision in forecasting the shape of Taylor cone. A predictive framework for the shape of Taylor cone was proposed, which provided a practical tool for process optimization in EHD printing.

Scaled-Up Multi-Needle Electrospinning Process Using Parallel Plate Auxiliary Electrodes.

Electrospinning has gained much attention in recent years due to its ability to easily produce high-quality polymeric nanofibers. However, electrospinning suffers from limited production capacity and a method to readily scale up this process is needed. One obvious approach includes the use of multiple electrospinning needles operating in parallel. Nonetheless, such an implementation has remained elusive, partly due to the uneven electric field distribution resulting from the Coulombic repulsion between the charged jets and needles. In this work, the uniformization of the electric field was performed for a linear array of twenty electrospinning needles using lateral charged plates as auxiliary electrodes. The effect of the auxiliary electrodes was characterized by investigating the semi-vertical angle of the spun jets, the deposition area and diameter of the fibers, as well as the thickness of the produced membranes. Finite element simulation was also used to analyze the impact of the auxiliary electrodes on the electric field intensity below each needle. Implementing parallel lateral plates as auxiliary electrodes was shown to help achieve uniformization of the electric field, the semi-vertical angle of the spun jet, and the deposition area of the fibers for the multi-needle electrospinning process. The high-quality morphology of the polymer nanofibers obtained by this improved process was confirmed by scanning electron microscopy (SEM). These findings help resolve one of the primary challenges that have plagued the large-scale industrial adoption of this exciting polymer processing technique.

Capture Power Prediction of the Frustum of a Cone Shaped Floating Body Based on BP Neural Network

How to improve the power generation of wave energy converters (WEC) has become one of the main research objectives in wave energy field. This paper illustrates a framework on the use of back propagation (BP) neural network in predicting capture power of the frustum of a cone shaped floating body. Mathematical model of single floating body is derived, and radius, semi-vertical angle, mass, submergence depth, power take-off (PTO) damping coefficient, and stiffness coefficient are identified as key variables. Commercial software ANSYS-AQWA is used for numerical simulations to obtain hydrodynamic parameters, and then capture power is calculated by these parameters. A database containing 100 samples is established by Latin hypercube sampling (LHS) method, and a simple feature study is conducted. A BP neural network model with high accuracy is designed and trained for predictions based on built database. The results show that forecasting results and desired outputs are in great agreement with error percentage not greater than 4%, correlation coefficient (CC) greater than 0.9, P value close to 1, and root mean square error (RMSE) less than 139 W. The proposed method provides a guideline for designers to identify basic parameters of the floating body and system damping coefficient.

Effect of non-uniform heating and viscous dissipation on natural convective flow of Casson fluid over a vertical cone

The non-Newtonian fluid flows find its applications in the production of paints, pharmaceutical products, synthetic lubricant and biological fluid. Because of the significance of this aspect, the present paper describes the consequence of non-uniform surface heating on the natural convection of the Casson fluid past a vertical cone with a viscous dissipation effect. Firstly, the governing partial differential equations are derived in the dimensionless form. After that, the numerical solution is obtained using the Crank–Nicolson technique of the finite difference method. The obtained numerical solutions for the temperature profiles, velocity profiles, local Nusselt number and local skin friction are displayed by employing the graphs in order to judge the impact of the governing physical parameters of the model such as the Casson fluid parameter, Grashof number, Eckert number and semi-vertical angle of the cone. The major result is found that the velocity and temperature profiles are more at the center of the lateral side of the cone.

Influence of Ferrofluid Lubrication on Longitudinally Rough Truncated Conical Plates with Slip Velocity

The study focuses on analyzing the effect of slip velocity in the case of a Ferrofluid squeeze film when the surface of truncated cone-shaped plates has a longitudinal roughness. Each oblique to the bottom plate was utilized by the external magnetic field. The bearing surface has a roughness that is designed with the help of a random stochastic variable having a nonzero mean, skewness and variance. The load carrying ability of a bearing system’s surface is determined by calculating the dispersal of pressure in the system, which is calculated by using the associated stochastically average Reynolds’ equation. The graphs obtained from the study shows that there is a correlation between the longitudinal surface roughness and the bearing system performance. The magnetic fluid lubrication has a positive impact on a system’s bearing capacity. However, the load bearing capacity declines as a result of the effect of slip. A high negative skewness of the surface roughness also has a positive impact on a bearing’s load carrying capacity. One interesting finding shows that contrasting to the results of transverse roughness, standard deviation positively impacts the load bearing capacity. This investigation suggests despite the im-portance of aspect ratio and semi vertical angle is significant for performance enhancement, it is also essential to maintain the slip at the lowest level.

Natural convective heat transfer analysis of MHD unsteady Carreau nanofluid over a cone packed with alloy nanoparticles

The present numerical simulations are carried out to investigate the effect of viscous dissipation, temperature dependent viscosity and heat source/sink on magnetohydrodynamics (MHD) unsteady Carreaue nanofluid over a cone filled with different alloy nanoparticles. We considered two different types of alloy nanoparticle namely nickel chromium iron alloy (Nimonic 80A) and titanium aluminum vanadium alloy (Ti%6Al%4V). The governing equations of the flow are solved using the Runge-Kutta and Newton's method. The present numerical results are compared with the previous study and found agreement with the uncertainty of ±2.5%. Effects of various non-dimensional parameters such as Eckert number, power index parameter, volume fraction, heat source/sink parameter, viscous variation parameter and semi-vertical angle of the cone on the momentum and thermal boundary layer including the friction factor coefficients and local Nusselt number are presented and analyzed for two different alloy considered in the present study. It is found that the viscous variation parameter enables to enhance the heat transfer rate. The Ti%6Al%4V alloy has higher friction factor coefficient along the azimuthal direction of the flow while Nimonic 80A alloy boosts up the friction coefficient along the tangential direction. It is worth to mention that the heat transfer rate of Nimonic 80A alloy is higher than that of Ti%6Al%4V alloy. Hence, Nimonic 80A alloy signifies a better thermal performance than the Ti%6Al%4V alloy.

Theoretical model for predicting uniaxial stress-strain relation by dual conical indentation based on equivalent energy principle

For conical indentation, the strain energy is a function of the semi-vertical cone angle, the indentation depth and the stress-strain relation. According to equivalent energy principle of representative volume elements (RVE) and the classical cavity assumption for material deformation region, the function with dual-parameters about volume and deformation is theoretically derived in the present study. This original equivalent-energy indentation model (EIM) is capable of forward-predicting load-depth relation and reverse-predicting uniaxial stress-strain relation for ductile materials only based on loading part of indentation. Further analyses show that the forward and reverse predicted results from EIM method are in excellent agreement with those by finite element analyses (FEA). Macro conical indentation experiments on five types of metals have been conducted using conventional indenters which are similar to Rockwell sclerometer. Consequently, the stress-strain relations predicted by EIM are quite close to those from standard tensile tests.

Numerical study of effect of induced magnetic field on transient natural convection over a vertical cone

In the present paper, an analysis has been performed to study the influence of induced magnetic field on the transient free convective flow of an electrically conducting and viscous incompressible fluid over a vertical cone. The coupled nonlinear partial differential equations governing the transient flow have been solved numerically by using the implicit finite difference method of Crank–Nicolson type. The influence of magnetic parameter, magnetic Prandtl number and semi-vertical angle of the cone on the velocity and induced magnetic field profiles has been illustrated graphically. Also, the local as well as average skin-friction and Nusselt number has been presented graphically. For result validation, we have done a comparative study and the present results are found to be in very good agreement with available results.

Investigation on the Geometric Imperfections driven Local Buckling Onset in Composite Conical Shells

Buckling is a critical failure phenomenon for structures, and represents a threat for thin shells subjected to compressive forces. The global buckling load, for a conical structure, depends on the geometry and material properties of the shell, on the stacking sequence, on the type of applied load and on the initial geometric imperfections. Geometric imperfections, occurring inevitably during manufacturing and assembly of thin-walled composite structures, produce a reduction in the carrying load capability with respect to the design value. This is the reason why investigating these defects is of major concern in order to avoid over-conservative design structures. In this paper, the buckling behavior a conical structure with 45° semi-vertical angle is numerically investigated. The initial imperfections are taken into account by using different strategies. At first, the Single Perturbation Load Approach (SPLA), which accounts for defects in the form of a lateral load, normal to the surface, has been adopted. Then, the actual measured defects have been applied to the structure by using the Real Measured Mid-Surface Imperfections (MSI) approach. Investigations on cylindrical shells using the first strategy have already shown the occurrence of a particular phenomenon called “local snap-through”, which represents a preliminary loss of stiffness. In order to better understand this phenomenon for conical shells, both the aforementioned techniques have been used to provide an exhaustive overview of the imperfections sensitiveness in conical composite shells. This study is related to part of the work performed in the frame of the European Union (EU) project DESICOS.

Numerical study of free convective MHD flow past a vertical cone in non-Darcian porous media

A numerical study of buoyancy-driven unsteady natural convection boundary layer flow past a vertical cone embedded in a non-Darcian isotropic porous regime with transverse magnetic field applied normal to the surface is considered. The heat and mass flux at the surface of the cone is modeled as a power-law according to qw(x) = xm and q*w (x) = xn respectively, where x denotes the coordinate along the slant face of the cone. Both Darcian drag and Forchheimer quadratic porous impedance are incorporated into the two-dimensional viscous flow model. The transient boundary layer equations are then non-dimensionalized and solved by the Crank-Nicolson implicit difference method. The velocity, temperature and concentration fields have been studied for the effect of Grashof number, Darcy number, Forchheimer number, Prandtl number, surface heat flux power-law exponent (m), surface mass flux power-law exponent (n), Schmidt number, buoyancy ratio parameter and semi-vertical angle of the cone. Present results for selected variables for the purely fluid regime are compared with the non-porous study by Hossain and Paul [9] and are found to be in excellent agreement. The local skin friction, Nusselt number and Sherwood number are also analyzed graphically. The study finds important applications in geophysical heat transfer, industrial manufacturing processes and hybrid solar energy systems.

Magnetic fluid based squeeze film between porous rough conical plates

We make an endeavor to study and analyze the effect of surface roughness on the performance of a magnetic fluid based squeeze film between conical plates. The lubricant used here is a magnetic fluid and the external magnetic field is oblique to the lower plate. The bearing surfaces are assumed to be transversely rough. The roughness of the bearing surface is modeled by a stochastic random variable with non-zero mean variance and skew-ness. The associated Reynolds' equation is solved with appropriate boundary conditions to get the pressure distribution, which is, then used to obtain the expression for load carrying capacity leading to the computation of the response time. The results are presented graphically as well as in tabular form. It is noticed that although the bearing suffers owing to transverse surface roughness, the load carrying capacity registers an increase in the case of negatively skewed roughness. Even the negative variance causes an increase in the load carrying capacity. It is observed that the reduction in the load carrying capacity induced by the porosity and the standard deviation can be neutralized up to certain extent by the positive effect of the magnetization parameter μ^* with suitable values of the semi-vertical angle ω in the case of negatively skewed roughness. A close scrutiny of some of the results presented graphically makes it clear that the positive effect of variance dominates the effect of the skew-ness whose impact is slightly better than that of the magnetization parameter. It is needless to say that the performance of the rough bearing with the magnetic fluid lubricant is definitely better than the one with conventional lubricant. This article reveals that there is a scope for enhancing the performance of the bearing system considerably by choosing a suitable combination of the magnetization parameter and semi-vertical angle of the cone in the case of negatively skewed roughness especially when negative variance is involved.

Free Convective MHD Flow Past a Vertical Cone with Variable Heat and Mass Flux

A numerical study of buoyancy-driven unsteady natural convection boundary layer flow past a vertical cone embedded in a non-Darcian isotropic porous regime with transverse magnetic field applied normal to the surface is considered. The heat and mass flux at the surface of the cone is modeled as a power law according to qwx=xm and qw*(x)=xm, respectively, where x denotes the coordinate along the slant face of the cone. Both Darcian drag and Forchheimer quadratic porous impedance are incorporated into the two-dimensional viscous flow model. The transient boundary layer equations are then nondimensionalized and solved by the Crank-Nicolson implicit difference method. The velocity, temperature, and concentration fields have been studied for the effect of Grashof number, Darcy number, Forchheimer number, Prandtl number, surface heat flux power-law exponent (m), surface mass flux power-law exponent (n), Schmidt number, buoyancy ratio parameter, and semivertical angle of the cone. Present results for selected variables for the purely fluid regime are compared with the published results and are found to be in excellent agreement. The local skin friction, Nusselt number, and Sherwood number are also analyzed graphically. The study finds important applications in geophysical heat transfer, industrial manufacturing processes, and hybrid solar energy systems.

Unsteady Free Convective Heat and Mass Transfer Past a Vertical Cone in Non-Darcian Porous Media

A numerical solution of transient laminar free convective heat and mass transfer in a viscoelastic fluid past a vertical cone in non-Darcian porous media in the presence of thermal radiation is presented. The Walters-B liquid model is employed to simulate medical creams and other rheological liquids encountered in biotechnology and chemical engineering. This rheological model introduces supplementary terms into the momentum conservation equation. The dimensionless governing equations of the flow are solved by an implicit finite difference scheme of Crank-Nicolson type. The velocity, temperature and concentration fields have been studied for the effect of radiation parameter, viscoelasticity parameter, Prandtl number, Schmidt number, buoyancy ratio parameter, Darcy number, Grashof number, Forchheimer number and semi vertical angle. The local skin friction, Nusselt number and Sherwood number are also presented and analyzed graphically. The numerical results are validated by comparisons with previously published work and are found to be in excellent agreement.

Numerical Study of Free Convection Flow past a Vertical Cone with Variable Heat and Mass Flux

ABSTRACT A numerical study of buoyancy-driven unsteady natural convection boundary layer flow past a vertical cone embedded in a non-Darcian isotropic porous regime with transverse magnetic field applied normal to the surface is considered. The heat and mass flux at the surface of the cone is modeled as a power-law according to () m q x x w  and * () n q x x w  respectively, where x denotes the coordinate along the slant face of the cone. Both Darcian drag and Forchheimer quadratic porous impedance are incorporated into the two-dimensional viscous flow model. The transient boundary layer equations are then non-dimensionalized and solved by the Crank-Nicolson implicit difference method. The velocity, temperature and concentration fields have been studied for the effect of Grashof number, Darcy number, Forchheimer number, Prandtl number, surface heat flux power-law exponent (m), surface mass flux power-law exponent (n), Schmidt number, buoyancy ratio parameter and semi-vertical angle of the cone. Present results for selected variables for the purely fluid regime are compared with the published work nonand are found to be in excellent agreement. The local skin friction, Nusselt number and Sherwood number are also analyzed graphically. The study finds important applications in geophysical heat transfer, industrial manufacturing processes and hybrid solar energy systems.

EFFECT OF TRANSVERSE SURFACE ROUGHNESS ON THE PERFORMANCE OF HYDROMAGNETIC SQUEEZE FILM BETWEEN CONDUCTING TRUNCATED CONICAL PLATES

An attempt has been made to study and analyze the behavior of a hydromagnetic squeeze film between conducting porous transversely rough truncated conical plates. The associated Reynolds' equation is solved with appropriate boundary conditions to investigate the behavior of performance characteristics. The results indicate that the performance of the bearing system gels enhanced vis-a-vis a bearing system working with a conventional lubricant. This article reveals that the negative effect induced by porosity and standard deviation can be overcome completely by the positive effect of the magnetization parameter and conductivities by choosing suitable aspect ratio and the semi-vertical angle in the case of negatively skewed roughness.

Effecting Factors Study for Powder Flow Characteristics

To understand the influence of external factors on powder flow process from the hopper, and to get the prerequisite to control the flow rate, by doing a lot of experiments. In this paper, the size distribution regulation was acquired by SCIROCCO 2000 (dry method) laser granulometry, and then the affection on flow rate from many external factors were separate considerations. As resluts, when the semi-vertical angle was smaller, the flow type was whole flow; the relation between way dimension of feed opening and flow is nonlinearity; the rate between hopper weight and way dimension of feed opening could affect the flow when it was smaller than 5; the flow was stable when the ratio between the powder depth and way dimension of feed opening is bigger than 1.5. At the same time, it would be one effective indirect measurement method by measuring the way dimension of feed opening under special condition.

Performance of hydromagnetic squeeze films between conducting porous rough conical plates

An endeavor has been made to discuss the behavior of hydromagnetic squeeze film between two conducting rough porous conical plates. The plates are considered to be electrically conducting and the clearance space between them is filled by an electrically conducting lubricant. A transverse magnetic field is applied between the plates. Efforts have been made to solve the concerned Reynolds’ equation with the associated boundary conditions to get the pressure distribution. This in turn, is used to obtain the expression for load carrying capacity leading to the calculation of the response time. The results are presented graphically as well as in tabular form. It is suggested by the results that the bearing system records an enhanced performance as compared to that of a bearing system working with a conventional lubricant. It is noticed that the pressure, load carrying capacity and the response time increase steadily with increasing values of the magnetization parameter. In general, the bearing suffers owing to transverse surface roughness. However, the negatively skewed roughness tends to better the performance of the bearing system marginally. This performance gets further improved especially, when the negative variance is involved. It is observed that the semi-vertical angle increases the load carrying capacity. Besides, the conductivity also increases the load carrying capacity significantly. In addition, it is revealed that the negative effect induced by the porosity can be neutralized to a nominal extent by the positive effect of the magnetization parameter in the case of negatively skewed roughness in the presence of negative variance. Thus, this study provides ample scopes for improving the performance of the bearing system considerably by choosing a suitable combination of magnetization parameter, semi-vertical angle and the conductivities of the plates.

Unsteady Laminar Free Convection from a Vertical Cone with Uniform Surface Heat Flux

Numerical solutions of, unsteady laminar free convection from an incompressible viscous fluid past a vertical cone with uniform surface heat flux is presented in this paper. The dimensionless governing equations of the flow that are unsteady, coupled and non-linear partial differential equations are solved by an efficient, accurate and unconditionally stable finite difference scheme of Crank-Nicolson type. The velocity and temperature fields have been studied for various parameters Prandtl number and semi vertical angle. The local as well as average skin-friction and Nusselt number are also presented and analyzed graphically. The present results are compared with available results in literature and are found to be in good agreement.

Unsteady Laminar Natural Convection from a Non-Isothermal Vertical Cone

Natural convection effects of the numerical solution for unsteady, laminar, free convection flow over an incompressible viscous fluid past a non-isothermal vertical cone with surface temperature T′w(x) = T′∞ + axn varying as power function of distance from the apex (x = 0) is presented here. The dimensionless governing equations of the flow that are unsteady, coupled and non-linear partial differential equations are solved by an efficient, accurate and unconditionally stable finite difference scheme of Crank-Nicolson type. The velocity and temperature fields have been studied for various parameters Prandtl number, semi vertical angle 0◦ < φ < 90◦ and n. The local as well as average skin-friction and Nusselt number are also presented and analyzed graphically. The present results are compared with available results in literature and are found to be in good agreement.

On the integrability of the motion of a heavy particle on a tilted cone and the swinging Atwood machine

In the present note we study the motion of a particle under uniform gravity on a tilted smooth cone. We point out some integrable cases of that problem. In particular, we establish that motion on the cone with semi-vertical angle π/6 and one generator vertical is integrable. Moreover, we show that the swinging Atwood machine is equivalent to a special version of the motion on the tilted cone. This analogy makes it easier to analyze motion of SAM from a geometrical point of view.