Comparison of flow structures in the wake region of a square cylinder or a U shape cylinder

Bahrami, Arian; Hacisevki, Hasan

doi:10.1016/j.oceaneng.2019.106211

Cited by 7 publications

(2 citation statements)

References 21 publications

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“…The passive control method changed the shape of the bluff body or added other microstructures. The passive control method is simpler and less expensive ( Koide et al, 2006 ; Kim and Kim, 2012 ; Bahrami and Hacışevki, 2019 ).…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation and Deep Neural Network Revealed Drag Reduction of Microstructured Three-Dimensional Square Cylinders at High Reynolds Numbers

Wang

2022

Front. Bioeng. Biotechnol.

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Square cylinders are widely used in various fields. For example, they are common structures in fishways. The flow around square cylinders has been a common problem in various fields. However, reducing the flow drag of the square cylinder is a problem that remains unexplored. Many previous studies have reported the drag reduction of 2D square cylinders, which failed to reflect the drag of real structures. Also, some studies focus on the drag force of the inner wall of the square cylinder modified by the microstructure. Achieving drag reduction by microstructuring the surface of the 3D square cylinder is a challenging problem. This study applied a 3D numerical simulation and deep neural network to study the drag reduction performance of the square cylinder under different patch sizes. We studied the drag reduction performance of protrusion and pit-patched square cylinders and tried to find the rule between drag reduction performance and patch configuration. The results show that the square cylinder has better drag reduction performance in some cases. However, its drag reduction performance is greatly affected by the protrusion structure. Also, too large protrusions will increase the drag force of the structure. When the surface protrusion accounts for 10% of the total area of the square cylinder, the drag reduction performance is the best (22.1%). The pit patch structure demonstrated an insignificant drag reduction performance and even increased the drag in most cases. The DNN prediction model demonstrated the robustness of the numerical simulation data.

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Section: Introductionmentioning

confidence: 99%

Numerical Simulation and Deep Neural Network Revealed Drag Reduction of Microstructured Three-Dimensional Square Cylinders at High Reynolds Numbers

Wang

2022

Front. Bioeng. Biotechnol.

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“…They observed 86, 92 and 90% reduction for drag coefficient, root-mean-square value of lift coefficient (C Lrms ) and drag coefficient (C Drms ), respectively. In the literature one can find more different types of passive flow control devices used for square cylinders [34][35][36].…”

Section: Introductionmentioning

confidence: 99%

Numerical study of reduction of fluid forces acting on a square cylinder using a control plate

Zia-ul-Islam

Shams-ul-Islam

Zhou

et al. 2021

J Braz. Soc. Mech. Sci. Eng.

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A numerical study on the effects of control plate on the fluid force reduction on a square cylinder has been carried out using lattice Boltzmann method where a configuration of a square cylinder with upstream control plate is studied. In the present computations we have studied the important flow characteristics for 0.1 ≤ l/w ≤ 1 and 1 ≤ g/D ≤ 10. The effects of the l/w and g/D on force reduction, flow separation and vortex shedding frequency have been studied with Reynolds number focused on 150. Vorticity structures, vortex shedding frequency and fluctuating forces and time-mean are presented and discussed. It was found that considerable change in the wake structure and fluid forces depending on the values of l/w and g/D. The numerical results show that there exists an optimum position where the force coefficients acting on the main square cylinder attains their minimum values. At the optimum position, the mean drag coefficient is reduced by 139.3%. Four different flow regimes were identified in this study at different g/D for selected range of l/w. The negative values of drag coefficient for the main square cylinder are also found for different combinations of l/w and g/D.

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Aerodynamics of smooth and rough square-section prisms at incidence in very high Reynolds-number cross-flows

Hinsberg

2021

Exp Fluids

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The aerodynamics of smooth and slightly rough prisms with square cross-sections and sharp edges is investigated through wind tunnel experiments. Mean and fluctuating forces, the mean pitch moment, Strouhal numbers, the mean surface pressures and the mean wake profiles in the mid-span cross-section of the prism are recorded simultaneously for Reynolds numbers between 1$$\times$$ × 10$$^{5}$$ 5 $$\le$$ ≤ Re$$_{D}$$ D $$\le$$ ≤ 1$$\times$$ × 10$$^{7}$$ 7 . For the smooth prism with $$k_s$$ k s /D = 4$$\times$$ × 10$$^{-5}$$ - 5 , tests were performed at three angles of incidence, i.e. $$\alpha$$ α = 0$$^{\circ }$$ ∘ , −22.5$$^{\circ }$$ ∘ and −45$$^{\circ }$$ ∘ , whereas only both “symmetric” angles were studied for its slightly rough counterpart with $$k_s$$ k s /D = 1$$\times$$ × 10$$^{-3}$$ - 3 . First-time experimental proof is given that, within the accuracy of the data, no significant variation with Reynolds number occurs for all mean and fluctuating aerodynamic coefficients of smooth square prisms up to Reynolds numbers as high as $$\mathcal {O}$$ O (10$$^{7}$$ 7 ). This Reynolds-number independent behaviour applies to the Strouhal number and the wake profile as well. In contrast to what is known from square prisms with rounded edges and circular cylinders, an increase in surface roughness height by a factor 25 on the current sharp-edged square prism does not lead to any notable effects on the surface boundary layer and thus on the prism’s aerodynamics. For both prisms, distinct changes in the aerostatics between the various angles of incidence are seen to take place though. Graphic abstract

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Comparison of flow structures in the wake region of a square cylinder or a U shape cylinder

Cited by 7 publications

References 21 publications

Numerical Simulation and Deep Neural Network Revealed Drag Reduction of Microstructured Three-Dimensional Square Cylinders at High Reynolds Numbers

Numerical Simulation and Deep Neural Network Revealed Drag Reduction of Microstructured Three-Dimensional Square Cylinders at High Reynolds Numbers

Numerical study of reduction of fluid forces acting on a square cylinder using a control plate

Aerodynamics of smooth and rough square-section prisms at incidence in very high Reynolds-number cross-flows

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