Effect Of Geometrical Shape Research Articles

Study on the effect of geometric shape on microswimmer upstream motion

The upstream motility of three microswimmer shapes (circular squirmer, squirmer rod, and elliptical squirmer) at the center of a Poiseuille flow is numerically investigated using the lattice Boltzmann method. Based on the stability and upstream ability, the swimming velocities and four motion states (stable motion, progressively unstable motion, unstable motion, and upstream failure) are summarized. The results show that the circular squirmer and squirmer rod are more stable than the elliptical squirmer; however, the elliptical squirmer has the greatest advantage in velocity and can swim up to twice as fast as the circular squirmer under the same conditions. The swimming type is also the key to influencing the motion state, which is reflected differently in the distinct microswimmer shapes. The increase in the Reynolds number (Re) and self-propelled strength (α) aggravates the motion instability; however, for elongated microswimmers, the aspect ratio (ε) plays a role in velocity rather than the motion state. Moreover, the upstream velocity of the pusher is always better than that of the puller, especially when Re increases. Notably, all microswimmers can maintain stable swimming when the preset velocity is twice the maximum velocity of the flow field. These findings can provide guidelines for the selection of design parameters and the appearance of microswimmers that resist complex incoming flows.

Postbuckling behavior of two-dimensional decagonal quasicrystal plates under biaxial compression

Two-dimensional (2D) decagonal quasicrystal (QC) plates are analyzed for their postbuckling behaviors when subjected to biaxial compressive loads in this research. The analysis using a combination of the first-order shear deformation theory (FSDT) along with von Kármán’s nonlinear equations of motion, while also accounting for the initial geometric imperfections. The governing equations for the QC plate are obtained through the application of the Hamiltonian variational principle, and the postbuckling equilibrium path for the four-sided plate with simply support is calculated using a two-step perturbation technique. The quasiperiodic structure and phonon-phason coupling in 2D decagonal QCs play a crucial role in determining their mechanical behavior. The numerical analysis explores the effects of geometric shape, phonon-phason coupling constants, initial geometric imperfections, and compressive forces on the postbuckling characteristics of the plates. Numerical simulations validate the theoretical model, demonstrating its accuracy. The application of FSDT, von Kármán theory, and the two-step perturbation method to QC plates, considering the complex interactions involving the phason field unique to quasicrystals, provides new insights into the intricate mechanical responses of QC plates under postbuckling conditions.

Investigation on vibration characteristics of rock based on circular plate and cylinder model: dimension, geometric shape and boundary condition

Abstract The declaration on the “natural frequency of rock” exists in many engineering areas, and it has caused many misunderstandings. Different from the mass-spring model usually used, the circular plate model and cylinder model are respectively established to clarify the relationship between the vibration characteristics (including natural frequency and vibration mode) and their influencing factors of rock by modal analysis. The effect of dimension, geometric shape, and boundary condition on the vibration characteristics of rock with plate structure is investigated, in which the semi-analytical solutions agree well with the simulation results. By using the cylinder model based upon the Lamé-Navier Eq., the effect of such influencing factors on the vibration characteristics of the block rock sample is further studied and verified by numerical simulation and experimental results. The results suggest that the natural frequency of “rock” (including the experimental rock sample) is strongly dependent on the dimension, geometric shape, and boundary condition. The resonance frequency observed in the excitation experiment is not only closely associated with the natural frequency of a specific order, but also dependent on the dominance of the particular vibration mode. These findings contribute to a better understanding of the rock-breaking mechanism under dynamic loads with a certain excitation frequency.

Investigation of influence of geometry of jet orifice of throttling device on formation of cavitation

Throttling devices are used in hydraulic systems both as regulating valves and to provide protective functions, which determines the relevance of developing such a design that will ensure their cavitation-free operation. The aim of the study is to investigate cavitation phenomena in single-stage throttling devices with different geometry of the jet orifices in order to identify the geometric shape capable of minimizing cavitation. The paper presents a study of the effect of different geometric shapes of the orifices of single-stage throttling devices on cavitation formation in the low-pressure areas. In addition, the objective of the study is to investigate the influence of physical quantities (velocity and pressure) on cavitation formation and to carry out a comparative analysis by means of which the influence of the correlation between the geometrical shape of the orifice of the jets, the velocity of the working medium and the pressure in the area of the orifice of the jets on the formation of cavitation zones in the areas of reduced pressure is clearly demonstrated. The computational experiment was conducted using Ansys CFX software and was based on the Rayleigh-Plesset mathematical model of cavitation. The study investigated the possibility of cavitation phenomena in single-stage throttling devices, and identified the geometric shape of the jet orifice that promotes cavitation-free operation of the single-stage throttling device. Thus, the results of the study show that the jet with a conical orifice minimizes the volume fraction of vapor, arising during cavitation processes, in single-stage throttling devices. The conducted research has practical significance and can increase the service life of single-stage throttling devices by minimizing the formation of cavitation zones in areas of low pressure.

The effect of toroidal geometrical shape on turbulent oscillations in a bidirectional vortex combustor

The paper reports on detailed studies of a bidirectional swirling flow structure in a toroidal vortex chamber under non-reactive and combustion conditions at the Reynolds numbers Re = 65,000 and Re = 10,000. The explanation of reduced velocity fluctuations near the head wall compared to simple cylindrical bidirectional chambers is also given. The studies were carried out using transient numerical simulations DES (Detached Eddy Simulation). The necessary experimental validation based on PIV (Particle Image Velocimetry) and temperature measurements were performed as well. The results show that fluctuations of all velocity components in the toroidal part of the chamber do not exceed 20% in non-reactive conditions and 10% in the combustion case. Additionally, temperature oscillations are less than 10% of the adiabatic stoichiometric temperature of propane-air mixture combustion. The studies of combustion at different equivalence ratios show that the rich combustion ϕ = 1.5 provides the most favorable conditions in terms of mixture ignition. Moreover, a large-scale backflow structure is formed beyond the outlet nozzle at rich modes that leads to an increase in combustion stability. This feature can be usefully applied in studies of mesoscale bidirectional arrays and developing multiport combustion chambers.

Synergistic effects of nanoparticle geometric shape and post curing on carbon-based nanoparticle reinforced epoxy coatings: Characterization, microstructure, and adhesion properties

Incorporating carbon-based nanoparticles and optimizing the curing conditions of epoxy nanocomposites are commonly employed as two practical strategies to achieve enhanced properties of epoxy coatings. This study investigated the synergistic effects of nanoparticle geometric shape and post curing on carbon-based nanoparticle reinforced epoxy coatings. Nanocrystalline diamonds (NCDs), carbon nanotubes (CNTs), and graphenes (GNPs) with spherical, cylindrical, planar geometric shapes were incorporated into epoxy coatings as 0-D, 1-D, and 2-D nano-fillers, respectively. For each nano-filler, epoxy coatings with and without post curing were synthesized and evaluated based on dispersion quality, viscosity, microstructure, and adhesion properties. Experimental results indicated that NCD reinforced epoxy coatings exhibited a more homogenous nanoparticle dispersion, lower viscosity, reduced porosity, and stronger pull-off adhesion, while GNP reinforced epoxy coatings achieved a higher lap shear strength. Although post curing was effective in reducing porosity and improving adhesion properties of epoxy coatings, its effect became less pronounced with the addition of nanoparticles.

Study of the effect of geometric shape on the quality of mixing: Examining the effect of length of the baffles

Study of the effect of geometric shape on the quality of mixing: Examining the effect of length of the baffles

Simulation of Heat Storage and Heat Regeneration in Phase Change Material

The present study explores numerically the energy storage and energy regeneration during Melting and Solidification processes in Phase Change Materials (PCM) used in Latent Heat Thermal Energy Storage (LHTES) systems. Transient two-dimensional (2-D) conduction heat transfer equations with phase change have been solved utilizing the Explicit Finite Difference Method (FDM) and Grid Generation technique. A Fortran computer program was built to solve the problem. The study included four different Paraffin's. The effects of container geometrical shape, which included cylindrical and square sections of the same volume and heat transfer area, the container volume or mass of PCM, variation of mass flow rate of heat transfer fluid (HTF), and temperatures difference between PCM and HTF were all investigated. Results showed that the PCMs in a cylindrical container melt and solidify quicker than the square container. The increase in mass flow rate and/or temperature difference decreases the time required for complete phase change. Paraffin's solidify quicker than they melt and store more energy than they release

On the importance of specimen’s geometric shape effects on the slake-durability index of limestones and grain size distribution of the sediment particles obtained during the test

The slake-durability test is one of vital test method used in engineering geological studies for evaluating resistant of rocks against wetting–drying cycles in humid environments. The result of the test is related to many parameters specially specimen’s geometric shape. In the present research, eight limestone samples used as common building stones in Iran have been selected and their mineralogical and physical properties have been measured in the laboratory. In order to determine the effect of specimen’s shape on the slake-durability index of the stones, laboratory specimens were prepared in seven various shapes including lump, rounded lump, cube, sphere, square prism, square-base plate, and rectangular cube which have different shape parameters. After performing the slake-durability tests, the samples were classified as very durable rocks according to Gamble and Franklin-Chandra classifications. The results indicated that specimen’s shape has essential effects on both rock durability and grain size distribution of the obtained sediment particles, so that the spherical and lump specimens shown the highest and lowest values of the slake-durability index, respectively. This means that more unregular dimensions, nonsphericity, and angularity of the specimens lead to decrease the slake-durability index which is highly correlated to the roundness (Rc) values of the specimens. The granulation parameters (D10, D30, D60, Cu, and Cc) of the obtained sediment particles were different for the tested samples. These parameters were recognized related to the specimen’s shape so that, the D60 and Cu are also highly correlated to the roundness (Rc) values of the specimens used in the slake-durability test.

Hybridized nanofluidic convection in umbrella-shaped porous thermal systems with identical heating and cooling surfaces

PurposeThis study aims to investigate the impact of different heater geometries (flat, rectangular, semi-elliptical and triangular) on hybrid nanofluidic (Cu–Al2O3–H2O) convection in novel umbrella-shaped porous thermal systems. The system is top-cooled, and the identical heater surfaces are provided centrally at the bottom to identify the most enhanced configuration.Design/methodology/approachThe thermal-fluid flow analysis is performed using a finite volume-based indigenous code, solving the nonlinear coupled transport equations with the Darcy number (10–5 ≤ Da ≤ 10–1), modified Rayleigh number (10 ≤ Ram ≤ 104) and Hartmann number (0 ≤ Ha ≤ 70) as the dimensionless operating parameters. The semi-implicit method for pressure linked equations algorithm is used to solve the discretized transport equations over staggered nonuniform meshes.FindingsThe study demonstrates that altering the heater surface geometry improves heat transfer by up to 224% compared with a flat surface configuration. The triangular-shaped heating surface is the most effective in enhancing both heat transfer and flow strength. In general, flow strength and heat transfer increase with rising Ram and decrease with increasing Da and Ha. The study also proposes a mathematical correlation to predict thermal characteristics by integrating all geometric and flow control variables.Research limitations/implicationsThe present concept can be extended to further explore thermal performance with different curvature effects, orientations, boundary conditions, etc., numerically or experimentally.Practical implicationsThe present geometry configurations can be applied in various engineering applications such as heat exchangers, crystallization, micro-electronic devices, energy storage systems, mixing processes, food processing and different biomedical systems (blood flow control, cancer treatment, medical equipment, targeted drug delivery, etc.).Originality/valueThis investigation contributes by exploring the effect of various geometric shapes of the heated bottom on the hydromagnetic convection of Cu–Al2O3–H2O hybrid nanofluid flow in a complex umbrella-shaped porous thermal system involving curved surfaces and multiphysical conditions.

Studying the Oscillating Flow around Unconfined Obstacle of Elliptical Cross-Section

The present paper focuses on the effect of geometric shape of a cylindrical body submerged in an oscillating flow by means of numerical investigations. The cylindrical body has an elliptic cross-section with a variation of its elliptic ratio (ratio between major and minor axes of the elliptic section). The flow direction is oriented along the major axis. Three regimes from (Tatstuno and Bearman) maps are studied namely, a symmetric regime A and two other asymmetric regimes D and F. The flow field structures, the Morison coefficients of longitudinal forces and the root mean square (r.m.s.) of transverse forces are computed with respect to the elliptic ratio variation. For the case of cylinders with slightly elliptic cross-section, vortices and pressure fields are very similar to those of a circular cylinder. For the case of regime A, the vortex shedding is always symmetric despite the unbreakable variation of the elliptic ratio. On the other hand, the reduction of the elliptic ratio weakens the asymmetry of the flow for regimes D and F. Moreover, the flow in each regime becomes completely symmetric at a given value of the elliptic ratio. In fact, the predicted longitudinal component of the force acting on the cylinder decreases with the reduction of this ratio. This results in the same manner on the behavior of Morison coefficients. With regard to the symmetric regime A, the transverse force does not manifest itself for all considered ratios. On the other hand, the transverse force in the case of asymmetric regimes decreases rapidly with increasing the ellipticity of the cylinder. The present study showed us that the inertia coefficient is sensitive to the vortex path; however, the drag coefficient is independent of the vortex path. Both coefficients depend simultaneously on Reynolds number and the geometric shape of the body.

Evaluation of CFD-predicted thermal comfort uncertainties based on a seated thermal manikin test case

The contribution presents the results of numerical simulation of 3D turbulent airflow and heat transfer around a seated thermal manikin in a model room with mixing ventilation. The main goal of the study is to evaluate the uncertainties caused by a CFD model. The room and the detailed thermal manikin geometry correspond to the experiment of P.V. Nielsen et al. (2007). The 3D computational model based on the RANS approach with the standard k-ε turbulence model is applied. The radiation effects are taken into account with the surface-to-surface radiation model. The study considers (1) the effect of the supply air flow rate variation and (2) the effect of the thermal manikin geometrical shape. For a particular parameters set, the results of numerical simulation are validated using the experimental data available (P.V. Nielsen et al.). The contribution is focused also on studying the effects of various heat transfer mechanisms on the airflow pattern and thermal comfort parameters: the baseline mixing ventilation scenario is compared with the buoyancy-dominated case.

Effect of geometric shapes of chimney weir on discharge coefficient

This study numerically investigated the effects of geometric parameters of chimney weirs on the discharge coefficient (Cd). Here, chimney weirs with apex angles 74°, 84°, 94.4°, 106° and 116° at two crest heights were examined. The RNG turbulence model was selected due to its greater accuracy compared to k-ε, k-ω and LES methods for these types of flows. With increasing discharge and crest height, the value of Cd decreases. The effect of constant Cd showed an increase in the percentage of discharge deviation from the discharge values obtained from numerical solution. Based on dimensionless variables such as ratio of water head to the crest height, the ratio of crest length to the crest height, the ratio of the vertical distance between weir crest and the first point where the weir slope changes to the crest height, and the vertex angle of the inverted triangle, non-linear polynomial regression relations were obtained. Highlights A numerical investigation of the discharge coefficient of Chimney weir with different geometry has been done using FLOW-3D software. Chimney weirs have high reliability in measuring discharge due to less sensitivity to changes in upstream water depth. This investigation improves the design of hydraulic control structures. New equation was developed for calculating the discharge coefficient of Chimney weir.

Numerical assessment of the effect of length, angle of attack, and type of ducts on hydrodynamic parameters of a linear-jet propulsion system

Achieving noble and more practical propulsion systems is still a major concern for engineers and researchers. Accordingly, many researchers have strived to opt for better and suitable system for the targeted vessels. One of the marine propulsion systems is linear-jet propulsion which includes rotor and stator. In this paper, the effects of geometrical shape of the duct in the form of different length and angle of attack for two types of the accelerating and decelerating ducts are comprehensively explored. Furthermore, section of rotor from Kaplan series are selected and the geometrical shape effects of the rotor on hydrodynamic performance of linear-jet propulsion system are also investigated. Therefore, to obtain the effects of the expressed parameters on the hydrodynamic characteristics of this propulsion system, Ansys-CFX software has been used. The governing equations of the studied problem are RANS equations and SST k-omega turbulent model is utilized. The obtained results are presented in the form of dimensionless coefficients of the forces applied on the propulsion system. The existing data for a ducted propeller are used to validate the numerical solution. Based on the results of the numerical solution, it is concluded that use of a decelerating duct increases the efficiency of the linear-jet system. On the other hand, the use of accelerating ducts reduces the hydrodynamic efficiency of the linear jet, so the performance is not desirable at high advance ratio. Therefore, the use of decelerating ducts in the linear-jet system is found to be the appropriate choice. Results further illustrate that, if the duct length increases, the generated thrust by the rotor increases. It is also concluded that, by increasing the angle of attack of the decelerating duct, the overall efficiency of the linear-jet propulsion system decreases.

Thermal conductivity and conductance of protein in aqueous solution: Effects of geometrical shape.

Considering the importance of elucidating the heat transfer in living cells, we evaluated the thermal conductivity κ and conductance G of hydrated protein through all-atom non-equilibrium molecular dynamics simulation. Extending the computational scheme developed in earlier studies for spherical protein to cylindrical one under the periodic boundary condition, we enabled the theoretical analysis of anisotropic thermal conduction and also discussed the effects of protein size correction on the calculated results. While the present results for myoglobin and green fluorescent protein (GFP) by the spherical model were in fair agreement with previous computational and experimental results, we found that the evaluations for κ and G by the cylindrical model, in particular, those for the longitudinal direction of GFP, were enhanced substantially, but still keeping a consistency with experimental data. We also studied the influence by salt addition of physiological concentration, finding insignificant alteration of thermal conduction of protein in the present case.

Effects of support type and geometric shape of steel tube on concrete-encased concrete-filled steel tube beam under low velocity impact

Concrete-encased concrete-filled steel tube (CEFST) beams prepared by placing steel tube in RC beam is a beam type that has widespread use. The current study examines the effects of steel tube geometry and support conditions on the behavior of CEFST beams under low velocity impact loading. First, CEFST beam specimens with different lengths and different tube section geometries (circular and square) were produced in the laboratory. These four test specimens with two different support conditions were exposed to low velocity impact load tests. Finite element models of the test specimens were created using Abaqus\\Explicit software. In the next stage, 4 finite element models were verified by the experimentally obtained damage conditions, maximum displacements, and support reaction forces. In the final stage, as parametric study 12 finite element models were prepared in addition to 4 verified models and analyzed under low velocity impact loading. In addition to experimental values, Von Mises stresses, Equivalent plastic strain, Friction energy, and Damage energy values were also obtained by the numerical study and thus the effects of steel tube geometry and support conditions were comparatively examined. The obtained results showed that CEFST beams with a square tube section exhibited better performance under a sudden load such as impact compared to the beams with a circular tube section. Moreover, both numerical and experimental results pointed out that the beam length beyond support has a positive impact on the performance of beam under impact loading.

Investigating the effects of reactant gas flow geometrical shape on the performance of solid oxide fuel cell

ABSTRACT Solid oxide fuel cells powered by renewable fuels will be a panacea for our current challenges to meet the global energy demand and mitigate climate changes stemming from the widespread use of carbon-rich fuels. Accordingly, this numerical investigation has examined the geometrical shape effects of reactant gas ducts, and the thickness of electrodes on solid oxide fuel cell performance. The model was also validated using the experimental result of a rectangular shape gas flow duct conducted at Dr. T. Nejat Veziroğlu Clean Energy Research Center of Niğde Ömer Halisdemir University in Türkiye. Thus, the finding of this work disclosed that the semicircular gas flow duct has outstanding performance following rectangular, trapezoidal and triangular geometrical shapes. The additional remarkable results of this work are that the shape of the reactant gas flow channel and the thickness of the cathode have more substantial effects on airflow than fuel flow under identical electrolyte thickness. The finding also revealed that a peak power density has been achieved when the thickness of an anode gets thicker up to a certain limit then it is sharply decreasing. On the contrary, the performance of the model is increasing as the thickness of the air electrode is increasing. 9 Solid oxide fuel cells powered by renewable fuels panacea for our current challenges to meet the global energy demand and mitigate climate changes stemming from the widespread use of carbon-rich fuels rectangular shape gas flow duct conducted at Dr. T. Nejat VeziroğluNiğdeHalisdemir peak power density has been achieved when the thickness of an anode gets thicker up to a certain limitis decreasingincreasing.

Aerodynamic influences of typical windbreak wall types on a high-speed train under crosswinds

The effect of windbreak wall types on their windproof effects on trains has been systematically investigated by comparing the flow field around a high-speed train behind three typical windbreak walls. These three typical windbreak walls are widely used along the windy railway lines in China, which include the earth embankment–type windbreak wall (EW), the road cutting–type windbreak wall (RW), and the straight reinforced concrete–type windbreak wall (SW). We compared the time-averaged crosswind-induced flows and aerodynamic performances of high-speed trains behind these three windbreak walls with the same height using numerical simulations. The results revealed that the windbreak wall geometric shape effects on the aerodynamic load coefficients varied according to the type of aerodynamic load and carriage marshalling positions but barely varied with yaw angles. The total drag coefficients of the train in the EW and RW were approximately 50–60% of that in the SW under the two smaller yaw angles and were only 30–40% for the largest yaw angle. For the absolute value of the side force and rolling moments coefficients, the maximum values for the head and middle cars both appeared in the RW, and the corresponding minimum values were obtained in the SW. The maximum and minimum values for the tail car were obtained at the SW and EW, respectively. The maximum of the rolling moment coefficient among three carriages in the SW was approximately 45–60% of that in the EW and only 30–40% of that in the RW. The time-averaged train surface pressure coefficient and flow patterns were similar between the EW and RW, which showed apparent differences from those in the SW. The SW provided a strong blocking effect on the incoming windward airflow and avoided the direct impact on the train. Compared with the RW, the uplifting effect of the EW's windward slope on the incoming flow further reduced the crosswind effect on trains. In addition, the dominating frequency characteristics of the aerodynamic loads were significantly affected by windbreak wall types. These findings provide a systematic understanding of the time-averaged aerodynamics of trains behind these three typical windbreak walls.

Effect of cracks on dynamical responses of double-variable-edge plates made of graphene nanoplatelets-reinforced porous matrix and sur-bonded by piezoelectric layers subjected to thermo-mechanical loads

This paper presents free vibration analyses and nonlinear dynamic responses of new complex edge contour non-rectangular plate structures with a part-through surface crack which the authors name as temporarily double-variable-edge (DVE) plates. The analytical results and numerical simulation are investigated in the Part I and it is expected that the experimental approach will be shown in Part II. The cracked plate made of a functionally graded porous (FGP) matrix structure and reinforced by graphene nano-platelets (GNPs) is covered by two piezoelectric layers and rested on a Winker-Pasternak elastic foundation. The material properties are determined by using the Halpin-Tsai micro-mechanical model, Gaussian Random Field (GRF) proposal, and the rules of mixtures. The governing equations are established based on the classical plate theory (CPT) and Galerkin's method which are convenient in analyzing the behaviors of complex edge contour plates. The obtained results are compared with those obtained from the existing Finite Element Method (FEM) to ensure the reliability and accuracy. In addition, the effects of geometrical shapes, crack parameters, applied voltages of piezoelectric layers, elastic foundations as well as thermal impacts are scrutinized. The obtained outcomes in the paper are promising for applications in the fields of aerospace, civil, and electronic engineering.

Numerical Investigation on the Effect of Geometric Shape and Outlet Angle of a Bladeless Fan for Flow Optimization using CFD Techniques

A three dimensional numerical study has been carried out to investigate the effect of various geometric shapes and slit angle on performance of the bladeless fan for various aerodynamic profiles. Aerofoils considered for the present study are E169, E473 and E479 which are then reformed into a typical bladeless fan arrangement. The numerical model of bladeless fan encompassing the outer domain is discretized tetrahedrally through finite volume approach using ANSYS ICEMCFD 20.0 and the necessary boundary conditions are specified in the ANSYS Fluent 20.0 pre-processor. The three dimensional fluid flow variations through and across the aerofoil have been simulated by solving the appropriate governing equations namely continuity and Reynolds Averaged Navier-Stokes equations (RANS). The turbulence induced in the fluid is modelled using SST k-ωmode of closure. Numerically predicted results of lift, drag and streamwise velocity decay along the jet centreline of a cylindrical channel are compared with literature and a very close agreement exists between the two. Upon validation, geometric shapes - circular and square cross section with aspect ratios of 1, 1,5 and 2 and slit angles of 20, 40, 60 and 80 degree for all the above three aerofoil configurations are analysed numerically for various inlet Reynolds number. Pressure, velocity contours and stream line across the bladeless fan are presented and discussed. From the study it is observed that Eppler 473 aerofoil profile with slit thickness of 1 mm and slit angle of 80° provided the maximum discharge ratio of 34.17 for an inlet mass flow rate of 80 LPS.