Vertical Slender Cylinder Research Articles

Coupled effects of wave and depth-dependent current interaction on loads on a bottom-fixed vertical slender cylinder

Coupled effects of wave and depth-dependent current interaction on loads on a bottom-fixed vertical slender cylinder

The bioconvective flow of an Eyring-Powell nanoliquid: the influence of entropy

ABSTRACT The focus of the study in this article is the bioconvection in a nonlinear mixed convective flow of an Eyring–Powell nanoliquid over a vertical slender cylinder with entropy generation. The two-phase Buongiorno’s model is used to investigate the Brownian motion and thermophoresis mechanisms of nanoparticles. The Boussinesq approximation for the body force term in the equations, which govern the convection flow leads to nonlinear coupled partial differential equations (PDEs). Nonsimilar transformations are considered to handle the equations in the non-dimensional form. Further, the technique of Quasilinearization and the implicit finite difference method are utilized for numerical simulation of the mathematical solution of the problem. The heat transfer rate diminishes by about 75% when the Eckert number rises from −0.5 to 0.5. The microorganism density number is enhanced by about 19% as the bioconvection Lewis number increases from 1 to 2. The skin friction coefficient is higher for the Newtonian fluid as compared to the non-Newtonian Eyring–Powell fluid and it is decreased about 8% when fluid parameter varies from 0 to 0.1. The entropy generation intensifies for higher nanoparticles diffusion and microorganism’s density parameters. An excellent agreement is noticed when the current solutions are compared with the outcomes reported in the existing results.

Computation of Cattaneo-Christov heat and mass flux model in Williamson nanofluid flow with bioconvection and thermal radiation through a vertical slender cylinder

Nanofluids are in high demand in the medical, electrical, and engineering fields. Nanofluid flow is used in a variety of applications including industrial cooling and heating frameworks, hyperthermia, electronic device batteries, and related pharmaceutical administration systems. Because of their improved thermal properties, nanofluids are commonly used as coolants in heat exchangers also including heating systems, electronic cooling systems, and radiators. Many scientists have studied heat transfer via a cylinder. The current study uses a vertical thin cylinder to scrutinize the effects of activation energy, motile microorganisms, bioconvection, and WU's slip on the Williamson nanofluid. Brownian motion, thermal radiation, Cattaneo-Christov heat, mass flow, and thermophoresis are all considered. Using appropriate similarity variables, the structures of PDEs are translated into the structure of ordinary differential equations. Using the well-known shooting strategy (Bvp4c) in the mathematical program MATLAB, higher-order nonlinear differential equations (DEs) are reduced to first-order. The effects of important flow parameters are shown graphically and numerically. It is noted that the momentum distribution field is upsurged for mixed convection parameters and decreased for the fluid parameter. The thermal profile is declining for the Prandtl number while increasing for the thermal radiation parameter and heat source-sink parameter. It is also observed that the concentration distribution field decreased for the Lewis number and concentration relaxation parameter while boosted up for larger magnitude of activation energy and thermophoresis parameter. It is analyzed that the microorganisms profile is upsurged for bioconvection Rayleigh number while declined for Peclet number. A comparison with the reported results from available literature is also done, and an excellent agreement is found. The discovery has far-reaching ramifications in the fields of medicine, modern aircraft technology, and power generation. In this study, we combine metallic nanoparticles with the base fluid water. Metallic nanoparticles offer a wide range of uses in everyday life, including catalysts, biosensors, medicine, and medication delivery, soil pollutant removal, electronics, coatings, packaging, semiconductors, bioengineering, paints, telecommunications, cosmetics, automobiles, and water treatment.

Wake Effects on Wave-Induced Loads Acting on Cylinders in a Tripod Configuration

Comparative hydrodynamic loads caused by a focused wave acting on differently sized slender vertical cylinders placed in a wave canal were predicted at model scale using an unsteady Reynolds-averaged Navier–Stokes (URANS) solver and the Morison equation. This paper focused, first, on wake effects that need to be considered for the structural design of tripod configurations and, second, on the influence of these wake effects on wave-induced loads. For the Morison approach, flow velocities were gathered at incremental representative locations along the length of the cylinders, whereby the use of a central differencing approach obtained the associated flow accelerations. A first scenario dealt with a small- and a large-diameter cylinder, implemented individually at two immersion depths. A second scenario considered medium- and large-diameter cylinders arranged in a tripod configuration, where the upstream and downstream cylinders had the same diameter. For the single cylinder, impact loads obtained by both methods compared favorably to experimental measurements. For the tripod configuration, however, impact loads obtained by both methods differed due to the influence of wake effects. Thus, it was necessary to determine the influence of wake effects to assess the structural integrity of tripod configurations.

Homogeneous and heterogeneous reactions in the mixed convection flow of hybrid nanofluid over a slender cylinder

AbstractThis article is about the study of homogeneous and heterogeneous reactions in the mixed convection flow of hybrid nanofluid over a moving vertical slender cylinder. It is based on the considerations of unequal diffusivity of chemical species and the numerical solutions from the nonsimilar approach. This study has found applications in many chemically reacting processes, including the processes in the biochemical systems, combustion, and catalysis. Numerically approximate solutions to a set of equations, which govern the flow, temperature, and concentrations of the chemical species with prescribed boundary constraints, are obtained by utilizing the implicit finite‐difference scheme aided by the quasi‐linearization technique. The impacts of several relevant parameters on various profiles and gradients are discussed with the aid of graphs and tables. From the results, the skin friction coefficient and rate of heat transport are pronounced to be more for hybrid nanofluid than nanofluid. The strength of homogeneous reaction on species concentration is found to be fewer than the heterogeneous reaction. The streamwise coordinate (nonsimilar variable) is more favorable to the concentration of autocatalyst than to the reactant concentration.

A study of convective nanofluid flow over a rough slender cylinder under the influence of magnetic field and species diffusion

AbstractThe present work explores the analysis of magnetohydrodynamics nonlinear mixed conv ective nanofluid flow over a vertical slender cylinder in the presence of surface roughness. The application of the present study can be found in the process of coating wires. In fact, during such a process, thin wires in the slender cylinder need to be cooled, and also heat and mass transfer rates need to be controlled through nanofluid and liquid hydrogen to yield better results. By employing nonsimilar transformations, the partial differential equations governing the flow problem are reduced to dimensionless equations. Furthermore, the Quasilinearization technique and implicit finite difference scheme are used to solve the dimensionless governing equations. The novelty of the analysis is the impacts of surface roughness, diffusion of liquid hydrogen, and the presence of nonlinear mixed convective flow over a slender cylinder. The numerical results reveal that the energy transport strength and surface drag coefficient enhance with the roughness parameter values. The nanoparticle volume fraction profile reduces, while nanoparticle Sherwood number enhances with increasing values of velocity ratio parameter. The presence of nanoparticles in the conventional fluid diminishes the energy transfer value significantly for both smooth and rough surfaces. The velocity of the fluid enhances with increasing values of the mixed convection parameter. Due to surface roughness ( ≠ 0), sinusoidal variations of the drag are observed along the length of the cylinder in comparison to smooth surface case ( = 0). The friction between the fluid and the wall rises for a rough surface because pockets of fluid are formed in the cavities due to surface asperities.

Effect of heat radiating and generating second-grade mixed convection flow over a vertical slender cylinder with variable physical properties

The boundary-layer flow and heat transfer characteristics of an incompressible thermally radiating second-grade fluid on a linearly stretching permeable vertical slender hollow cylinder subject to viscous dissipation and convection heat exchange at the wall with the surroundings in conjunction with augmented far-field condition is studied. The free-stream or ambient velocity is considered to be linearly stretching while the prescribed surface temperature of the cylinde varies nonlinearly as the axial distance in the presence of elastic deformation and volumetric heat generation. The model incorporates the temperature dependent fluid properties as per dynamic viscosity and thermal conductivity while the viscoelastic or second-grade parameters are temperature-free. In virtue of appropriate transformation, the energy and momentum equations are reduced to nonlinear ordinary differential equations, and then solved numerically using forty-fifth order Runge-Kutta-Fehlberg (RKF45) integration scheme in tandem with shooting method. Analysis is carried out through simulated tables and codes generated graphs. This study reveals that the wall shear stress factor increases with the velocity ratio, mixed convection, curvature and suction parameters but reduces with the stretching parameter. Also the local heat transfer rate enhances with the Prandtl number, suction, curvature, velocity ratio and stretching parameters in contrast to that due to viscoelastic parameter.

Conjugate Heat and Mass Transfer on Steady MHD Mixed Convection Flow along a Vertical Slender Hollow Cylinder with Heat Generation and Chemical Reaction Effects

This paper studies the effects of heat generation and chemical reaction on the coupled conjugate heat and mass transfer by MHD laminar mixed convective flow along a vertical slender hollow cylinder. The governing boundary layer equations along with the boundary conditions are first cast into a dimensionless form by a non similar transformation and the resulting equations are then solved by the finite difference method using Matlab@ following the code bvp4c. Numerical results of the velocity, temperature and concentration for different values of the conjugate heat transfer parameter p, the magnetic parameter M, the heat generation Q, and the chemical reaction K are studied. The local skin friction, Nusselt number and Sherwood number are also analyzed and presented graphically. In the numerical ranges of the main parameters, it is found mainly that working with strong conjugate heat transfer or/and all others parameters affects negatively the Nusselt and Sherwood numbers. The same trend is revealed for the skin friction factor.

Experimental investigation of free connective heat transfer augmentation using transformer oil-Al2O3 nanofluid

There is a definite need to improve the heat transfer capability of the transformer oil as it plays a vital role in the life span of transformers. As the thermal conductivity of the transformer oil is very less compared to the conventional liquids and those liquids cannot be used as dielectric liquids as they do not possess electrical insulation properties. It is very much essential to improve the thermal conductivity of the transformer oil in any manner in order to augment the “heat transfer or thermal management performance” of the transformer oil. Dispersion of metallic or metallic oxide nanoparticles into the base fluid in a systematic way is a proven method to enhance the thermal properties for various practical heat transfer applications like forced convection, boiling, refrigeration, solar and electronic cooling. In this study, alumina nanoparticles are dispersed in transformer oil to synthesize stable, homogenous transformer oil – Al2O3 nanofluid and to investigate the free convection “coefficient of heat transfer performance” along a vertical slender cylinder submerged in the liquid. Experiments are conducted using the transformer oil - Al2O3 nanofluid at different particle loadings or fractions starting from 0.05 % to 0.6 %. It is learnt that the highest “coefficient of heat transfer performance” occurs at 0.1 Vol% among all the volume fractions. It has been acknowledged that the “coefficient of heat transfer” is got better up to 0.1 % particle loading and then decreased with additional accumulation of nanoparticles.

Erratum: “Wave-induced vortex generation around a slender vertical cylinder” [Phys. Fluids 32, 042105 (2020)

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Thermophoresis and Brownian Model of Pseudo-Plastic Nanofluid Flow over a Vertical Slender Cylinder

This study focuses on the industrial and engineering interest quantities, such as drag force and rate of transmission of heat, for pseudo-plastic nanofluid flow. The attributes of natural convection of the pseudo-plastic nanofluid flow model over a vertical slender cylinder are explored. The pseudo-plastic flow is studied under the influence of concentration of nanoparticles, rate of heat transmission, and drag force. For the first time, the pseudo-plastic nanofluid flow model has been implemented over a vertical slender cylinder which is not yet investigated. The acquired model is based on thermophoresis and Brownian motion mechanisms. The governing equations of pseudo-plastic nanofluid in cylindrical coordinates are modelled. The developed system of nonlinear equations is tackled by boundary layer assumptions and similarity transformations. Moreover, the solution of the acquired system exhibited by using a new powerful numerical technique. A comprehensive debate on drag force and transmission of heat under the influence of various emerging parameters is illustrated in the table. Furthermore, the effects of dimensionless parameters over the velocity profile, temperature profile, and concentration of nanoparticle profile have been exhibited graphically.

Wave-induced vortex generation around a slender vertical cylinder

Experimental results of wave-induced vortex generation around a slender, vertical cylinder are discussed. Coherent vortices appear in long waves (kR ∼ 0.1, where k is the wave number and R is the cylinder radius) during the timing of the secondary load cycle, a strongly nonlinear component of the wave force acting on the cylinder, which is also measured. However, the secondary load cycle is also present in moderately long wave cases (kR ∼ 0.3) where there is no vortex formation. The measurement of vortex generation is enabled by particle image velocimetry. The flow downstream the cylinder, in three horizontal planes at different depths, is measured. The vortex formation that occurs in the long waves is attached to the cylinder in the form of thin vortex tubes. These appear symmetrically at angles of 40°–45° off the wave propagation direction. In one weak long wave case, several very thin vortex tubes appear along the back side of the cylinder. Vortex diameters are 20% of the cylinder diameter in four cases and 50% of the cylinder diameter in one case. The measured vorticity emanates from the cylinder’s boundary layer and is an order of magnitude stronger than the vorticity caused by wave breaking. Wave breaking reduces the vortex strength. The fact that the secondary load cycle appears without and with flow separation effects indicates that the load cycle is a gravity wave phenomenon that scales with the Froude number but that flow separation effects also contribute to the magnitude of such suction forces.

Experimental study of plunging solitary waves impacting a vertical slender cylinder

Solitary waves can evolve into breakers in the nearshore area, generating strong destructive forces, especially for plunging breakers. In the present study, experiments are conducted to investigate plunging solitary waves propagating over a trapezoidal bar and to quantify their subsequent hydrodynamic forces on a cylinder. To do so, solitary waves are designed to break at varying phases and to strike the cylinder differently in space to examine their hydrodynamic forces. Furthermore, consideration of structural responses influencing measured forces for non-rigid structures provides the basis of an equation of motion that facilitates the extraction of hydrodynamic forces from measured forces. Additionally, the relation of cylinder's properties to surface elevations are evaluated and subsequently used to extract the hydrodynamic forces.The results show that the measured forces, extracted hydrodynamic forces, and dynamic amplification factors (DAF: ratio between the measured force and hydrodynamic force) achieve their highest values approximately at the same breaking phase, that is when the plunging jet has curled down, but prior to its impingement on the water surface, and this remains valid for different incident wave heights. Lastly, with an assumed asymmetrical triangular-pulse force, theoretical DAF is calculated and presents less than a 20% difference to the experimental DAF.

MHD mixed convective nanofluid flow about a vertical slender cylinder using overlapping multi-domain spectral collocation approach

This paper investigates the magnetohydrodynamic flow, heat and mass transfer characteristics in a silver water nanofluid about a vertical slender cylinder by considering diffusion-thermal, thermo-diffusion, chemical reaction and Hall effects. The nonlinear partial differential equations modelling the flow problem are non-dimensionalized and the overlapping multi-domain bivariate spectral quasilinearisation method is used to solve the dimensionless equations. The impact of flow parameters on the fluid properties and physical quantities of interest are determined. Amongst other findings, we found that increment in the nanoparticle volume fraction, Hall current and curvature parameter augments the skin friction coefficient and diminishes the heat transfer rate, while the introduction of chemical reaction, silver nanoparticles, Hall current and Soret effect into the system enhances the mass transfer rate. Also, the fluid properties amplifies in the curved surface than in the flat plate.

Nonlinear Mixed Convection Flow of Nanofluid Past a Moving Vertical Slender Cylinder

In this article, the nonlinear mixed convection flow of nanofluid past a slender cylinder, which is vertically moving with constant velocity, with viscous dissipation effects is examined. The governing equations of the flow are in the form of dimensional nonlinear partial differential equations (NPDEs), which are brought to non-dimensional form, along with the boundary conditions, by employing non-similar transformations. The resultant non-dimensional NPDEs are solved by adopting quasilinearization technique and implicit finite difference method. The numerical study focuses analysis of various non-dimensional parameters, such as Brownian diffusion Nb, nonlinear mixed convection $$\gamma$$, Richardson number Ri, Lewis number Le, Eckert number or viscous dissipation Ec, thermophoresis Nt, nanoparticle buoyancy ratio Nr, velocity ratio $$\varepsilon$$, on profiles as well as gradients in detail. The numerical results unveil that the increasing values of Ec increase temperature of the fluid. Further, wall gradients for energy transfer and also nanoparticle mass transfer are studied in the presence as well as in the absence of nonlinear mixed convection effects. At $$\xi = 1$$ as Nt increases from 0.05 to 0.15, the friction between the wall and the fluid increases by about 15.23% and 22.41% for Nb = 0.15 and Nb = 0.3, respectively.

Breaking Wave Interaction With a Group of Four Vertical Slender Cylinders in Two Square Arrangements

The main purpose of the study is to investigate the breaking wave interaction with a group of four circular cylinders. The physical process of wave breaking involves many parameters, and an accurate numerical modeling of breaking waves and the interaction with a structure remain a challenge. In the present study, the open-source computational fluid dynamics (CFD) model REEF3D is used to simulate the breaking wave interaction with multiple cylinders. The numerical model is based on the incompressible Reynolds-averaged Navier–Stokes (RANS) equations, the level set method for the free surface, and the k–ω model for turbulence. The numerical model is validated with experimental data of large-scale experiments for the free surface elevation and the breaking wave force on a single cylinder. A good agreement is obtained between the numerical results and experimental data. Two different configurations with four cylinders are examined: in-line square configuration and diamond square configuration. For both configurations, three different tank widths and four different spacings between the cylinders are investigated. The breaking wave forces on each cylinder in the group are computed for each case for the two configurations, and the results are compared with the breaking wave force on a single isolated cylinder. Furthermore, the study investigates the water surface elevations and the free surface flow features around the cylinders. For the closely spaced cylinders in a relatively narrower tank, the cylinders in both configurations experience the maximum forces lower than the maximum force on a single cylinder. But for the widely spaced cylinder in a relatively wider tank, the forces are higher and lower for the upstream cylinders and downstream cylinders, respectively, than the maximum force on a single isolated cylinder. The results of the present study show that the interference effects from the neighboring cylinders in a group strongly influence the kinematics around and the breaking wave forces on them.

Numerical Modeling of Breaking Wave Kinematics and Wave Impact Pressures on a Vertical Slender Cylinder

Wave loads from breaking waves on offshore wind turbine (OWT) substructures in shallow waters still remain uncertain. The interaction of breaking waves with structures is characterized by complex free surface deformations, instantaneous impact of the water mass against the structure, and consequently large wave forces on the structures. The main objective of the paper is to investigate wave impact pressures and kinematics during the interaction of breaking waves with a vertical cylinder using the open-source computational fluid dynamics (CFD) model REEF3D. The model is based on the Reynolds-averaged Navier–Stokes (RANS) equations coupled with the level set method and k–ω turbulence model. Three wave impact conditions are considered in this study. The numerically simulated free surface deformations around the cylinder during the breaking wave interaction are also presented for different wave impact conditions. For three wave impact conditions, the wave impact pressure and the horizontal and vertical components of the particle velocity are computed in front of the cylinder and analyzed. The pressure and velocity profile at their maximum values are also examined and discussed. In addition, the total force is calculated for three breaking conditions and they are correlated with the pressure and kinematics during the interaction.

Response of a slender cylindrical member under Breaking wave impact

A slender cylindrical member is the fundamental component of many coastal and offshore structures. It is essential to understand the action of breaking waves on structural members since, when these members are subjected to wave impact load, the structural damages and failures may be catastrophic. In the present study, an experimental investigation has been carried out to measure the response of the slender vertical cylinder subjected to breaking wave impact. Pressure measurements were made in order to estimate the total force acting on the structure. An empirical relation is established between total impact force and the wave steepness parameter which dictates the intensity of the breaking. Pressure rise time is an important parameter dictating the impact event. Simultaneous acceleration and strain measurements were made to evaluate the response of the cylinder. Deflection has been derived from structure acceleration. The deflection due to the moderate plunging differs by two order more than severe plunging events. Strain rate is another important consideration for the impact loading. The higher strain rate increases the resistance of the material. Under the breaking wave impact on the cylinder, the strain rate varies from2 to 10−4.

Flow visualization using heat lines for unsteady radiative hydromagnetic micropolar convection from a vertical slender hollow cylinder

The present study aims to investigate the thermal radiation heat transfer effect on unsteady magnetohydrodynamic flow of micropolar fluid over a uniformly heated vertical hollow cylinder using Bejan's heat function concept. The normalized conservation equations emerge as a system of time-dependent non-linear coupled partial differential equations. Under appropriate wall and free stream conditions these equations are solved with an efficient unconditionally stable implicit scheme of Crank-Nicolson type. Important thermo-physical parameters featured include the magnetic body force parameter (M), Grashof (free convection) parameter (Gr), Eringen micropolar material parameter (K), Prandtl number (Pr), conjugate heat transfer parameter (P) and radiative-conductive Rosseland parameter (N), are analyzed on the flow-field with ranges 0–3, 105–106, 0–1.2, 0.7–7.0, 0–0.5 and 0–15, respectively. The time-histories of average values of momentum and heat transport coefficients, as well as the steady-state flow variables are presented for selected values of these non-dimensional parameters. With elevation in magnetic parameter or radiation parameter, the time taken for the flow-field variables to attain the time-independent state increases. The dimensionless thermal radiative heat function values are closely correlated with the overall rate of heat transfer on the outer hot cylindrical wall. Bejan's heat flow visualization implies that the thermal radiative heat function contours are compact in the neighbourhood of leading edge of the boundary layer on the outer hot cylindrical wall. Increasing radiation or magnetic parameter values result in an increase in the deviation of heat lines from the hot wall. Also, the heat lines are observed to depart slightly away from the hot wall with greater values of vortex viscosity. Furthermore, the deviations of flow variables from the hot wall for a micropolar fluid are significant compared to the Newtonian fluid (vanishing micropolar vortex viscosity).

Wave-induced morphodynamics and sediment transport around a slender vertical cylinder

We study the dynamics of a sandy bed around a slender vertical cylinder forced by progressive, non-linear water waves. The seabed evolves continuously under the effects of the up-welling, down-welling and rolling events induced by vortical coherent structures. In turn, these are closely connected to the shape of the seabed, which is modified by the scouring and/or the deposition of the sand. Starting from a flat seabed, progressive waves induce a rapid and transient modification of the bottom morphology towards a dynamically stable equilibrium state, which is the focus of this work. The dynamical equilibrium state is a function of the wave period and is reached when the seabed morphology is not substantially altered. We describe such a state by an Eulerian in-phase analysis of the sand particle motion, inferred from Lagrangian data collected over a large number of wave passages. This analysis relies on the use of the defocusing digital PIV technique (DDPIV), for the first time applied to the specific flow of interest here. On the basis of the Eulerian analysis, the triggering of the key-events (up- and down-welling, rolling) over the wave phase is captured by identifying, through the Q > 0 criterion, the coherent flow structures responsible for the events. This analysis is coupled with the description of the sediment trajectories, analyzed in a Lagrangian manner and effectively assessing how and where the solid phase is transported during the key-events. Five main mobilization/transport mechanisms have been identified, three during the onshore flow and two during the offshore flow: (i) generation of a coherent structure reminiscent of a horseshoe vortex at the toe, (ii) intense scouring at the top of the flatbed region, (iii) vortex shedding in the wake during direct (onshore) flow, (iv) shear crossflow on the lee-side of the cylinder and (v) large vertical shearing in the flatbed region during the reverse (offshore) flow. At flow reversal, this shearing mechanism impacts on a significant area of sediments in the incoming region of the flow.