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In this paper, we develop a new physical model which involves a Taylor vortex around a rotating cylinder. The scattering of sound waves from this new model is investigated by solving the linearized Euler equations under the polar coordinate system in the time domain. We use the enhanced optimized scheme for numerical simulations. Numerical results show that scattering causes a change in the spatial distribution of sound energy as the sound wave passes through a rotating cylinder. The directionality of the scattered field varies significantly with the length ratio of the acoustic wavelength to the radius of the rotating cylinder and the vortex intensity. The influences of the ratio and the strength on the directivities and intensities of scattered fields are analyzed. It is shown that the intensity of the scattering cross-section increases with the strength of the vortex. The pressure of the scattered sound fields has a phase shift induced by the couple scattering from the cylinder and the vortex.

Numerical simulations are carried out to investigate the vortex-induced vibrations of a two-degree-of-freedom (2DOF) near-wall rotating cylinder. Considering the effects of gap ratio, reduced velocity and rotational rate, the amplitude response, wake variations and fluid forces are analyzed, with the Reynolds number of 200 and the mass ratio set to 1.6. The correlative mechanism in the wake–hydrodynamics–vibration is revealed. The results show that the influence of the wall dominates the vortex-induced vibration of the cylinder. The effect of the wall on the vibration weakens as the gap ratio increases, and the effect of the wall on the vibration is negligible when H/D > 1.1. The forward rotation of the cylinder enhances the wall effect, while the backward rotation presents the reverse effect. The vortex-induced vibration of the cylinder is suppressed when 0 < α < 1, and the amplitude range is concentrated at Vr ∈ (3, 5). The wake mode can be divided into five modes, and the wake modes are clarified under different rotation rates and reduced velocities.

Purpose This study aims to investigate magnetohydrodynamic (MHD) conjugate pure mixed convection considering interior heat production and resistive heating inside a square closed/open cavity featuring a rotating cylinder for aiding (clockwise) and opposing (counterclockwise) flow configurations. Moreover, the impacts of altering cylinder size and conductivity on the system’s overall performance to determine optimum conditions are examined in this investigation. Design/methodology/approach The closed chamber is differentially heated by keeping high and low temperatures at the vertical boundaries. In contrast, the open cavity has a heated left wall and an open right boundary. The Galerkin finite element method is used to solve the Navier–Stokes and the thermal energy equations, which construct the present study’s mathematical framework. Numerical simulations are conducted for the specified ranges of several controlling parameters: Reynolds (31.62 ≤ Re ≤ 1000), Grashof (103 ≤ Gr ≤ 106) and Hartmann numbers (0 ≤ Ha ≤ 31.62), and volumetric heat generation coefficient (Δ = 0, 3). Findings When Gr, Re and Ha simultaneously increase, the average Nusselt number along the warmed boundary rises accordingly. Conversely, interior heat production lowers heat transmission within the computational domain, which is also monitored regarding mean fluid temperature, overall entropy production and thermal performance criterion. Finally, the open cavity confirms better thermal performance than the closed cavity. Originality/value Comprehending the impacts of the magnetic field, Joule heating, internal heat generation and enclosed or open boundary on pure MHD combined free-forced convective flow offers valuable understandings of temperature fluctuations, velocity propagations, heat transport and irretrievable energy loss in numerous engineering applications.

Control of flow past a circular cylinder using a rotating control rod is investigated by conducting two-dimensional numerical simulations with a Reynolds number of 200, a rod-to-cylinder diameter ratio of 0.2, a gap ratio of 0.2, position angles of the control rod between 0° and 180°, and rotation rates between −7 and 7. The rotation rate is positive if the cylinder rotates in the anticlockwise direction. The aim of this paper is to discover the effects of the position angle and the rotation rate on flow control. If the rod is placed at the side (position angle = 90°) or nearly to the side of the cylinder (position angle = 45° and 135°), the rotating rod affects the flow in three ways, depending on its rotation rate: (1) strong negative rotation of the rod weakens the negative free shear layers and reduces the lift; (2) flow through the gap interferes with vortex shedding when the rotation rate is small in either direction; and (3) strong positive rotation of the rod enhances the negative free shear layers and increases the lift coefficient. Placing a rotation rod immediately in front of or behind the cylinder (position angle = 0° or 180°) causes a reduction in the lift coefficient for all rotation rates.

To investigate the suppression method for vortex-induced vibrations (VIV) of two-degree-of-freedom (2-DOF) rotating cylinders with dual splitter plates, numerical simulations are conducted at a Reynolds number of 200, a mass ratio of 2.6, and rotation ratio of 2. The effects of the gap distance and the width of splitter plates on the vibration response, hydrodynamic coefficients, and flow wakes of rotating cylinders are examined. The numerical results show the existence of distinct suppression mechanisms between low gap distances (G/D = 0.25–0.5) and high gap distances (G/D = 0.75–2.0). Furthermore, the width (W/D) is considered as a critical factor in suppression effectiveness. The distributions of wake patterns under different gap distance and width are analyzed, and six wake patterns are observed. Finally, lift and drag coefficients are examined, revealing their distinct sensitivities to G/D and W/D. The optimal gap distance and width parameters of dual splitter plates for rotating cylinders suppression are determined. Marine drilling is persistently subjected to VIV, which critically compromise structural stability. The findings of this study deliver engineering value for marine riser VIV suppression.

The vertical axis turbine used in the maritime energy sector must rotate and deal with turbulent flows in order to generate electricity. Structural failures and operational problems like corrosion can occur and lower turbine efficiency. Thus, additional surface protection through coatings is required for metal corrosion prevention. In these studies, the effects of turbulent flow on polyamine epoxy and fluoropolymer marine coatings were examined using electrochemical impedance spectroscopy (EIS). To simulate the flow effect, a rotating cylinder electrode (RCE) sample was placed in an aqueous solution containing 3.5 wt% sodium chloride, along with additional treatments of neutral salt spray to speed up the aging process. The fluoropolymer coating exhibits the best coating properties and provides robust corrosion protection with an impedance value of 8.7 Ω·cm 2 . However, the results also show that turbulent flow, at a maximum speed of 5400 rpm, has an impact on coating corrosion resistance and reduces the protective properties of coatings of polyamine epoxy by up to 19% and fluoropolymer by up to 33%.

A three-dimensional flow of a viscous heat-conducting gas in a rapidly rotating straight circular cylinder in the presence of axial temperature gradients is studied. At the initial stage, gas-dynamic and thermal boundary layers on a rotating extended disk are considered. When taking into account the temperature change in density, the Dorodnitsyn transformation is used, which makes it possible to reduce the solution of the problem to the integration of a system of ordinary differential equations. Taking into account inertial effects, an approximate analytical solution of the problem is obtained in the case of small values of the Prandtl number, when the thermal boundary layer thickness exceeds the thickness of the hydrodynamic layer. The result of the calculation for an extended disk is used to estimate the intensity of the axial circulation flow in a rotating cylinder of finite dimensions. The influence of the intensity of temperature perturbation on the radial profile of circulation in a rotor is studied.

This study describes thermal transmission features across a gravity-driven bioconvection flow of the viscoplastic-type Casson nanofluid caused by a vertically rotating cylinder under gyrotactic microorganisms. The research further quantifies the impact of nonlinear thermal radiations, heat source/sink and convective interface on the temperature and heat transmission rate of a nanofluid rotating on a cylindrical surface. The Buongiorno two-phase model characterizing Brownian diffusion and thermophoretic properties is utilized to examine the nanoparticle’s effect on the Casson nanofluid. A system of strongly nonlinear PDEs is converted into a system of ODEs by using the appropriate variables. The MATLAB technique is used to build a numerical solution for nonlinear flow equations. The influences of various parameters on the volumetric concentration of nanoparticles, velocities, thermal fields, and microorganism profiles are examined. The finding indicates that an upsurge in the bioconvection Lewis parameter causes declines in the microorganism profile. The thermal and solutal distribution of species increases with an increase in thermophoresis parameter estimations. Significant thermal transport is acquired with greater radiation impacts. The microorganism’s distribution is improved with a larger Peclet number.

A numerical simulation approach is substantiated and verified for predicting the Taylor-Couette flow with an impermeable outer stationary cylinder and porous rotating inner one. An imposed throughflow is considered, supplied via one end of the annular gap and leaving the domain through another gap end (retentate) and from inside of the rotating cylinder (permeate). The flow is typical for dynamic filtration by rotating cylindrical filters. In contrast to known publications, the rotating porous cylinder is included into the computational domain and the liquid flow inside of it is fully resolved. The influence of the permeate-retentate ratio and permeability of the rotating inner cylinder onto the centrifugal stability boundary and supercritical flow details is discussed. It is found that filtration velocity becomes distributed not uniformly along the porous cylinder when its hydraulic resistance  is less than a definite value. After some critical threshold, the flow structure drastically changes, and spiral vortices appears, which crosses the porous rotating cylinder back and forth several times, providing multiple flow recirculation through the porous cylinder. The results obtained create the basis for the development of dynamic rotational filters for various applications.

Purpose The purpose of this study is to use the incompressible smoothed particle hydrodynamics method to examine the influences of a magnetic field on the double-diffusive convection caused by a rotating circular cylinder with paddles within a square cavity filled by a nanofluid. Design/methodology/approach The cavity is saturated by two wavy layers of non-Darcy porous media with a variable amplitude parameter. The embedded circular cylinder with paddles carrying T_h and C_h is rotating around the cavity center by a uniform circular velocity. Findings The lineaments of nanofluid velocity and convective flow, as well as the mean of Nusselt and Sherwood numbers, are represented below the variations on the frequency parameter, amplitude parameter of the wavy porous layers, Darcy parameter, nanoparticles parameter, Hartmann number and Ryleigh number. The performed simulations showed the role of paddles mounted on circular cylinders for enhancing the transmission of heat and mass within a cavity. The wavy porous layers at the lower Darcy parameter are playing as a blockage for the nanofluid flow within the porous area. Increasing the concentration of the nanoparticles to 6% reduces the maximum flow speed by 8.97% and maximum streamlines |ψ|max by 10.76%. Increasing Hartmann number to 100 reduces the maximum flow speed by 65.83% and |ψ|max by 75.54%. Originality/value The novelty of this work is to examine the effects of an inclined magnetic field and rotating novel shape of a circular cylinder with paddles on the transmission of heat/mass in the interior of a nanofluid-filled cavity saturated by undulating porous medium layers.