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Wake, Energy, and Heat 2021

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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "A: Sustainable Energy".

Deadline for manuscript submissions: closed (31 May 2022) | Viewed by 14739

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Prof. Dr. Md. Mahbub Alam

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Institute for Turbulence-Noise-Vibration Interaction and Control, Harbin Institute of Technology (Shenzhen), Shenzhen 518055, China
Interests: flow around bluff body; flow-induced vibration; wake; flow-induced load on structures; strouhal number; aerodynamics; hydrodynamics; turbulent flow; laminar flow; flow transition; airfoil aerodynamics; biological flow; flow control; heat transfer, renewable energy; wind energy; hydraulic energy; energy harnessing from flow-induced oscillating bodies
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Special Issue Information

Dear Colleagues,

I would like to extend a warm invitation to all colleagues who would like to submit their research papers to the Special Issue of Energies (ISSN 1996-1073; CODEN: ENERGA) on "Wake, Energy, and Heat." The Special Issue encompasses the advances in flow around bluff bodies, fluid-structure interactions, and wind/ocean energy in the fields of mechanical, civil, aerospace, ocean, chemical, energy, physics, and mathematics. Research articles, review articles, as well as short communications are welcomed. The research techniques can be experimental, theoretical, computational, or mixed. The paper should be academically excellent and have originality and novelty of applications, approaches, and fundamental outcomes.

Prof. Dr. Md. Mahbub Alam
Guest Editor

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Keywords

Flow around bluff body
Fluid-structure interactions
Wake
Heat transfer
Energy harvesting

Published Papers (6 papers)

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Research

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19 pages, 7763 KiB

Open AccessFeature PaperArticle

Wind Tunnel Experiments on Interaction between Two Closely Spaced Vertical-Axis Wind Turbines in Side-by-Side Arrangement

by Yoshifumi Jodai and Yutaka Hara

Energies 2021, 14(23), 7874; https://0-doi-org.brum.beds.ac.uk/10.3390/en14237874 - 24 Nov 2021

Cited by 5 | Viewed by 2707

Abstract

This study aimed to determine the optimal rotor spacing of two vertical-axis wind turbines, which are simulated by miniature models arranged side-by-side with a relatively low aspect ratio. Wind tunnel experiments with a pair of 3-D printed model rotors were conducted at a uniform velocity. A series of experiments were conducted involving both incremental adjustments to the rotor gaps, g, and the rotational direction of each rotor. Increases in the power and the related flow patterns were observed in all three arrangements: Co-Rotating (CO), Counter-Up (CU), and Counter-Down (CD). The maximum phase-synchronized rotational speed occurs at the narrowest gap in the CD arrangement. Meanwhile, local maxima arise in the CO and CU arrangements at g/D < 1, where D is the rotor diameter. From an engineering perspective, the optimal rotor spacing is g/D = 0.2 with the CO arrangement, using the same two rotors rotating in the same direction. Based on flow visualization using a smoke-wire method at a narrower gap opening of 0.2D, the wake width in the case of the CU arrangement was remarkably narrower than those obtained in the CO and CD arrangements. In the CU arrangement, a movement towards the center of the rotor pair of the nominal front-stagnation point of each rotor was confirmed via flow visualization. This finding explains a reduction tendency in the rotational speed of the rotors via a reduction in the lift in the CU arrangement. Full article

(This article belongs to the Special Issue Wake, Energy, and Heat 2021)

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26 pages, 7867 KiB

Open AccessArticle

Numerical Analysis of Mixed Convective Heat Transfer from a Square Cylinder Utilizing Nanofluids with Multi-Phase Modelling Approach

by Rajendra S. Rajpoot, Shanmugam. Dhinakaran and Md. Mahbub Alam

Energies 2021, 14(17), 5485; https://0-doi-org.brum.beds.ac.uk/10.3390/en14175485 - 02 Sep 2021

Cited by 2 | Viewed by 1865

Abstract

The present study deals with the numerical simulation of mixed convective heat transfer from an unconfined heated square cylinder using nanofluids (Al₂O_3-water) for Reynolds number (Re) 10–150, Richardson number (Ri) 0–1, and nanoparticles volume fractions (φ) 0–5%. Two-phase modelling approach (i.e., Eulerian-mixture model) is adopted to analyze the flow and heat transfer characteristics of nanofluids. A square cylinder with a constant temperature higher than that of the ambient is exposed to a uniform flow. The governing equations are discretized and solved by using a finite volume method employing the SIMPLE algorithm for pressure–velocity coupling. The thermo-physical properties of nanofluids are calculated from the theoretical models using a single-phase approach. The flow and heat transfer characteristics of nanofluids are studied for considered parameters and compared with those of the base fluid. The temperature field and flow structure around the square cylinder are visualized and compared for single and multi-phase approaches. The thermal performance under thermal buoyancy conditions for both steady and unsteady flow regimes is presented. Minor variations in flow and thermal characteristics are observed between the two approaches for the range of nanoparticle volume fractions considered. Variation in φ affects C_D when Reynolds number is varied from 10 to 50. Beyond Reynolds number 50, no significant change in C_D is observed with change in φ. The local and mean Nusselt numbers increase with Reynolds number, Richardson number, and nanoparticle volume fraction. For instance, the mean Nusselt number of nanofluids at Re = 100, φ = 5%, and Ri = 1 is approximately 12.4% higher than that of the base fluid. Overall, the thermal enhancement ratio increases with φ and decreases with Re regardless of Ri variation. Full article

(This article belongs to the Special Issue Wake, Energy, and Heat 2021)

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13 pages, 5038 KiB

Open AccessArticle

Effects of Mass and Damping on Flow-Induced Vibration of a Cylinder Interacting with the Wake of Another Cylinder at High Reduced Velocities

by Md. Mahbub Alam

Energies 2021, 14(16), 5148; https://0-doi-org.brum.beds.ac.uk/10.3390/en14165148 - 20 Aug 2021

Cited by 28 | Viewed by 2123

Abstract

Flow-induced vibration is a canonical issue in various engineering fields, leading to fatigue or immediate damage to structures. This paper numerically investigates flow-induced vibrations of a cylinder interacting with the wake of another cylinder at a Reynolds number Re = 150. It sheds light on the effects of mass ratio m^*, damping ratio, and mass-damping ratio m^*ζ on vibration amplitude ratio A/D at different reduced velocities Ur and cylinder spacing ratios L/D = 1.5 and 3.0. A couple of interesting observations are made. The m^* has a greater influence on A/D than ζ although both m^* and ζ cause reductions in A/D. The m^* effect on A/D is strong for m^* = 2–16 but weak for m^* > 16. As opposed to a single isolated cylinder case, the mass-damping m^*ζ is not found to be a unique parameter for a cylinder oscillating in a wake. The vortices in the wake decay rapidly at small ζ. Alternate reattachment of the gap shear layers on the wake cylinder fuels the vibration of the wake cylinder for L/D = 1.5 while the impingement and switch of the gap vortices do the same for L/D = 3.0. Full article

(This article belongs to the Special Issue Wake, Energy, and Heat 2021)

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10 pages, 70145 KiB

Open AccessArticle

Transition to Periodic Behaviour of Flow Past a Circular Cylinder under the Action of Fluidic Actuation in the Transitional Regime

by Wasim Sarwar, Fernando Mellibovsky, Md. Mahbub Alam and Farhan Zafar

Energies 2021, 14(16), 5069; https://0-doi-org.brum.beds.ac.uk/10.3390/en14165069 - 18 Aug 2021

Cited by 1 | Viewed by 1231

Abstract

This study focuses on the numerical investigation of the underlying mechanism of transition from chaotic to periodic dynamics of circular cylinder wake under the action of time-dependent fluidic actuation at the Reynolds number = 2000. The forcing is realized by blowing and suction [...] Read more.

\pm 90^{\circ}

on the top and bottom surfaces of the cylinder. The inverse period-doubling cascade is the underlying physical mechanism underpinning the wake transition from mild chaos to perfectly periodic dynamics in the spanwise-independent, time-dependent forcing at twice the natural vortex-shedding frequency. Full article

(This article belongs to the Special Issue Wake, Energy, and Heat 2021)

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23 pages, 34387 KiB

Open AccessArticle

The Steady Wake of a Wall-Mounted Rectangular Prism with a Large-Depth-Ratio at Low Reynolds Numbers

by Arash Zargar, Ali Tarokh and Arman Hemmati

Energies 2021, 14(12), 3579; https://0-doi-org.brum.beds.ac.uk/10.3390/en14123579 - 16 Jun 2021

Cited by 5 | Viewed by 2569

Abstract

The wakes of wall-mounted small (square) and large (long) depth-ratio rectangular prisms are numerically studied at Reynolds numbers of 50–250. The large depth-ratio significantly alters the dominance of lateral secondary flow (upwash and downwash) in the wake due to the reattachment of leading-edge separated flow on the surfaces of the prism. This changes the wake topology by varying the entrained flow in the wake region and changing the distribution of vorticity. Thus, the magnitude of vorticity significantly decreases by increasing the prism depth-ratio. Furthermore, the length of the recirculation region and the orientation of near wake flow structures are altered for the larger depth-ratio prism compared to the square prism. Drag and lift coefficients are also affected due to the change of pressure distributions on the rear face of the prism and surface friction force. This behavior is consistently observed for the entire range of Reynolds numbers considered here. The wake size is scaled with

R e^{1 / 2}

, whereas drag coefficient scaled with

R e^{- 0.3}

. Full article

(This article belongs to the Special Issue Wake, Energy, and Heat 2021)

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Review

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48 pages, 11931 KiB

Open AccessReview

Flow-Induced Vibrations of Single and Multiple Heated Circular Cylinders: A Review

by Ussama Ali, Md. Islam, Isam Janajreh, Yap Fatt and Md. Mahbub Alam

Energies 2021, 14(24), 8496; https://0-doi-org.brum.beds.ac.uk/10.3390/en14248496 - 16 Dec 2021

Cited by 39 | Viewed by 3027

Abstract

This study is an effort to encapsulate the fundamentals and major findings in the area of fluid-solid interaction, particularly the flow-induced vibrations (FIV). Periodic flow separation and vortex shedding stretching downstream induce dynamic fluid forces on the bluff body and results in oscillatory motion of the body. The motion is generally referred to as flow-induced vibrations. FIV is a dynamic phenomenon as the motion, or the vibration of the body is subjected to the continuously changing fluid forces. Sometimes FIV is modeled as forced vibrations to mimic the vibration response due to the fluid forces. FIV is a deep concern of engineers for the design of modern heat exchangers, particularly the shell-and-tube type, as it is the major cause for the tube failures. Effect of important parameters such as Reynolds number, spacing ratio, damping coefficient, mass ratio and reduced velocity on the vibration characteristics (such as Strouhal number, vortex shedding, vibration frequency and amplitude, etc.) is summarized. Flow over a bluff body with wakes developed has been studied widely in the past decades. Several review articles are available in the literature on the area of vortex shedding and FIV. None of them, however, discusses the cases of FIV with heat transfer. In particular systems, FIV is often coupled to heat transfer, e.g., in nuclear power plants, FIV causes wear and tear to heat exchangers, which can eventually lead to catastrophic failure. As the circular shape is the most common shape for tubes and pipes encountered in practice, this review will only focus on the FIV of circular cylinders. In this attempt, FIV of single and multiple cylinders in staggered arrangement, including tandem and side-by-side arrangement is summarized for heated and unheated cylinder(s) in the one- and two-degree of freedom. The review also synthesizes the effect of fouling on heat transfer and flow characteristics. Finally, research prospects for heated circular cylinders are also stated. Full article

(This article belongs to the Special Issue Wake, Energy, and Heat 2021)

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