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The flow that crosses the arrangement of four circular cylinders will form a certain flow pattern according to the geometry of the body contour, the distance between the cylinders, and the flow orientation (α), and generated aerodynamic forces, such as lift force, drag force, as well as induced vibration on the body. The force coefficients on four circular cylinders in an equispaced arrangement with a staggered configuration located near a plane wall were calculated through the pressure distributions measurement. The pressure distributions on each cylinder surface and the plane wall were measured for various gap ratio values of G/D= 0.0 and 0.2 (G, the gap between cylinder to the plane wall; D, diameter) and L/D= 2.7 (L, gap spacing between cylinders) in a uniform flow at a Reynolds Number of 1.743 x 10 4 . The results show that the drag and lift coefficients on the cylinders depend on the gap ratio value of G/D. The drag coefficient decreases, when the amount of G/D increases, especially on the upstream cylinders. The lift coefficient on the upper-downstream cylinders has a significant value more than other cylinders at a small spacing ratio.

We are introducing the Carrier-Domain Method (CDM) for high-resolution computation of time-periodic long-wake flows, with cost-effectives that makes the computations practical. The CDM is closely related to the Multidomain Method, which was introduced 24 years ago, originally intended also for cost-effective computation of long-wake flows and later extended in scope to cover additional classes of flow problems. In the CDM, the computational domain moves in the free-stream direction, with a velocity that preserves the outflow nature of the downstream computational boundary. As the computational domain is moving, the velocity at the inflow plane is extracted from the velocity computed earlier when the plane’s current position was covered by the moving domain. The inflow data needed at an instant is extracted from one or more instants going back in time as many periods. Computing the long-wake flow with a high-resolution moving mesh that has a reasonable length would certainly be far more cost-effective than computing it with a fixed mesh that covers the entire length of the wake. We are also introducing a CDM version where the computational domain moves in a discrete fashion rather than a continuous fashion. To demonstrate how the CDM works, we compute, with the version where the computational domain moves in a continuous fashion, the 2D flow past a circular cylinder at Reynolds number 100. At this Reynolds number, the flow has an easily discernible vortex shedding frequency and widely published lift and drag coefficients and Strouhal number. The wake flow is computed up to 350 diameters downstream of the cylinder, far enough to see the secondary vortex street. The computations are performed with the Space–Time Variational Multiscale method and isogeometric discretization; the basis functions are quadratic NURBS in space and linear in time. The results show the power of the CDM in high-resolution computation of time-periodic long-wake flows.

In the current work, slip and radial magnetic field effects are taken into consideration as they relate to a comparison examination regarding two-dimensional heat transfer caused on the basis of the free convective flow of a Casson (non-Newtonian) fluid in electro-conductive and non-Darcy porous medium of a horizontal circular cylinder. The formulation has been created, and the boundary layer equations are then transformed using similarity transformations into a self-similar form. Using the Keller box method (KBM), a nonlinear boundary value that is simplified issue is numerically resolved, the momentum and temperature equations, higher-order partial differential equation to first-order partial differential equation. Graphs are used to show the numerical solutions for Nusselt number, skin friction coefficient, velocity profile, and temperature profile. With graphs and tables, the impact of key variables, rate of heat transfer, and skin irritation are measured. The flow of the fluid is the most interesting aspect of the analysis; the outcome shows that Casson fluid velocity fields are reduced by an increase in magnetic number and nonuniform heat source/sink, radiation parameter, and when it comes to magnetic number variation. Increase in magnetic body force parameter ( H ) values results in decreases in the component of velocity. Skin friction coefficient and Nusselt number rise at high Newtonian slip (SF), non-Darcy parameter (Da), and Prandtl number (Pr) values.

Based on overset grid method, the problems about flow past circular cylinder were numerically studied, which include the flow around a single circular cylinder at Reynolds number Re=100 and Reynolds number Re=200, the flow past two tandem circular cylinders at Reynolds number Re=200 and dimensionless distance g * =4, and the flow around a lateral oscillating circular cylinder at Reynolds number Re=200. Overset grid method is effective in dealing with the problems of flow over multi-body and flow with moving boundaries. This grid method couple overlapping regions in an arbitrary manner through flow field information updating over acceptor cells in one region suing its donor cells in another region. The computed drag coefficient and lift coefficients of the circular cylinder, vortical structure in the flow wake and vortex shedding P+S mode are agreed well with the results in previous experiment investigations and numerical simulations.

Unsteady simulations of the flow around two cylinders arranged in tandem are carried out using Scale-Adaptive Simulation (SAS) turbulence model for high subcritical Reynolds number (Re=2×〖10〗^5). Three-dimensional simulations are performed for different center-to-center distances between the cylinders (L/D varies 1.1 to 7, where D is cylinder diameter). The effects of the gaps between the cylinders are analyzed through the values of mean and fluctuating force coefficients, Strouhal number, pressure distribution, as well as through the wake flow structures behind both cylinders. The results are compared with published experimental data by different authors. The obtained results reveal good general agreement with the experimental data. Besides, to explore the effects of the interference, two tandem cylinders test are compared with a single cylinder case. The results show that this simple configuration (tandem) can strongly influence the flow pattern and forces on the cylinders. A critical nondimensional distance is obtained at L/D=3 at which two different flow patterns are identified, one pattern momentarily similar to the reattachment regime and another pattern similar to the co-shedding regime.

Purpose The purpose of this paper is to numerically analyze the stagnation point flow of Cu-Al2O3/water hybrid nanofluid with mixed convection past a flat plate and circular cylinder. Design/methodology/approach The similarity equations that reduced from the boundary layer and energy equations are solved using the bvp4c solver. The duality of solutions is observed within the specific range of the control parameters, namely, mixed convection parameter λ, curvature parameter γ and nanoparticles volumetric concentration ϕ1 for alumina, while for copper ϕ2. The stability analysis is also designed to justify the particular solutions’ stability. Additionally, the idea to obtain the solution for large value of λ and γ is also presented in this paper. Findings Two solutions exist in opposing and assisting flows up to a critical value λc where λc lies in the opposing region. An upsurge of the curvature parameter tends to extend the critical value (delay the separation process), whilst increase the heat transfer performance of the working fluid. Meanwhile, the application of hybrid Cu-Al2O3/water nanofluid also can decelerate the separation of laminar boundary layer flow and produce higher heat transfer rate than the Cu–water nanofluid and pure water. Originality/value The results are new and original. This study benefits to the other researchers, specifically in the observation of the fluid flow characteristics and heat transfer rate of the hybrid nanofluid. Also, this paper features with the mathematical formulation for the solution with large values of λ and γ.

Purpose This paper aims to investigate magnetic impacts on bioconvection flow within a porous annulus between an outer cylinder and five inner cylinders. The annulus is filled by oxytactic microorganisms and nano-encapsulated phase change materials. Design/methodology/approach The modified ISPH method based on the time-fractional derivative is applied to solve the regulating equations in Lagrangian dimensionless forms. The pertinent factors are bioconvection Rayleigh number Rab (1–100), circular cylinder’s radius Rc (0.1–0.3), fractional time derivative α (0.95–1), Darcy parameter Da (10−5–10−2), nanoparticle parameter ϕ (0–0.1), Hartmann number Ha (0–50), Lewis number Le (1–20), Peclet number Pe (0.1–0.75), s (0.1–0.9), number of cylinders NCylinders (1–4), Rayleigh number Ra (103–106) and fusion temperature θf (0.005–0.9). Findings The simulations revealed that there is a strong enhancement in the velocity field according to an increase in Rab. The intensity and location of the phase zone change in response to changes in θf. The time-fractional derivative a acting on a nanofluid velocity and flow characteristics in an annulus. The number of embedded cylinders NCylinders is playing a significant role in the cooling processes and as NCylinders increases from 1 to 4, the velocity field’s maximum reduces by almost 33.3%. Originality/value The novelty of this study is examining the impacts of the magnetic field and the presence of several numbers of embedded cylinders on bioconvection flow within a porous annulus between an outer cylinder and five inner cylinders.

Purpose This study aims to numerically explore the heat transfer characteristics in turbulent two-degree-of-freedom vortex-induced vibrations (VIVs) of three elastically mounted circular cylinders. Design/methodology/approach The cylinders are at the vertices of an isosceles triangle with a base and height that are the same. The finite volume technique is used to calculate the Reynolds-averaged governing equations, whereas the structural dynamics equations are solved using the explicit integration method. Simulations are performed for three different configurations, constant mass ratio and natural frequency, as well as distinct reduced velocity values. Findings As a numerical challenge, the super upper branch observed in the experiment is well-captured by the current numerical simulations. According to the computation findings, the vortex-shedding around the cylinders increases flow mixing and turbulence, hence enhancing heat transfer. At most reduced velocities, the Nusselt number of downstream cylinders is greater than that of upstream cylinders due to the impact of wake-induced vibration, and the maximum heat transfer improvement of these cylinders is 21% (at Ur = 16), 23% (at Ur = 5) and 20% (at Ur = 15) in the first, second and third configurations, respectively. Originality/value The main novelty of this study is inspecting the thermal behavior and turbulent flow–induced vibration of three circular cylinders in the triangular arrangement.

Purpose The purpose of this study is to apply an incompressible smoothed particle hydrodynamics (ISPH) method to simulate the Magnetohydrodynamic (MHD) free convection flow of a nanofluid in a porous cavity containing rotating hexagonal and two circular cylinders under the impacts of Soret and Dufour numbers. Design/methodology/approach The inner shapes are rotating around a cavity center by a uniform circular motion at angular rate ω. An inner hexagonal shape has higher temperature Th and concentration Ch than the inner two circular cylinders in which the temperature is Tc and concentration is Cc. The performed numerical simulations are presented in terms of the streamlines, isotherms and isoconcentration as well as the profiles of average Nusselt and Sherwood numbers. Findings The results indicated that the uniform motions of inner shapes are changing the characteristics of the fluid flow, temperature and concentration inside a cavity. An augmentation on a Hartman parameter slows down the flow speed and an inclination angle of a magnetic field raises the flow speed. A rise in the Soret number accompanied by a reduction in the Dufour number lead to a growth in the concentration distribution in a cavity. Originality/value ISPH method is used to simulate the double-diffusive convection of novel rotating shapes in a porous cavity. The inner novel shapes are rotating hexagonal and two circular cylinders.

The vortex shedding is one of the main reasons for vibration in cylindrical bodies. Accordingly, by controlling the vortex shedding, the vortex-induced vibration (VIV) can be controlled in these objects. Correcting the shape of objects through installing trip wires, installing screw plates, and creating holes on the object can reduce these vibrations. For this purpose, in the present study, the effects of installing four trip wires with different diameters on the vortex pattern, mean and fluctuation velocities, characteristics of the wake such as defect velocity and half width are numerically investigated in variable stations ( X / D  = 1.06, 1.54, 2.02, 5, 7, 10) at different inlet velocities 2.85, 10 and 20 m/s. The diameter of the circular cylinder was 20 mm, and the diameter of the installed trip wires was 0.25, 0.5, 0.75, 1, and 1.5 mm. The disturbance trip wires were installed at positions θ  =  ± 40 and ± 140. The results showed that the vortex pattern is sensitive to the installation of trip wires. By decreasing the diameter of the trip wires, the length of the shear layer decreases. In the area near the model (rotating area), the half width increases for a smooth cylinder. The velocity defect parameter is decreased by increasing the Reynolds number and decreasing the diameter of the trip wires.