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A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Mechanical Engineering".

Deadline for manuscript submissions: closed (31 May 2022) | Viewed by 25793

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Dr. Jesús María Blanco

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Department of Energy Engineering, University of the Basque Country, Bilbao, Spain
Interests: thermal engineering; hydrodynamics; numerical modeling; fluid mechanics; numerical simulation; energy; computational fluid dynamics; turbomachinery; fluid structure interaction; industrial engineering
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Dear fluid mechanics community,

The comprehensive use of fluid mechanics has always been of key relevance for the development of human beings though numerous applications from the classical field of engineering, with its different sub-disciplines, to physics or even to medicine by modelling simple or complex flows, including Newtonian and non-Newtonian fluids. The progressive implementation of new techniques as computational fluid dynamics (CFD) has experienced a great increase over the last few decades as its use has become more feasible for most experts worldwide.

Generally speaking, the goal of turbulence modeling is to reproduce as accurately as possible these flow physics with a reasonable computational effort. In some cases, turbulence is modeled by the Reynolds Averaged Navier–Stokes (RANS) methods, where the ensemble averaging tends to remove the unsteady part. RANS models generally perform satisfactorily in less complex flows, whereas in more complex scenarios may result inappropriate.

A completely different approach is represented by the so-called large eddy simulation (LES) method, where the large-scale energy-containing eddies are solved directly, while the effects of smaller-scale eddies are simply modeled, resulting in models which are more expensive than RANS models in terms of computational cost.

As Guest Editor, I cordially invite you to present works that rigorously show new concepts, developments, and complete and comment on the state-of-the-art developments in the field, referring to the general phenomenon of fluid mechanics, covering aero/hydrodynamics, CFD, heat transfer and other related fields, to be published in this Special Issue, providing originality, usefulness, clarity, and well-founded conclusions.

Dr. Jesús María Blanco
Guest Editor

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Keywords

Aerodynamics
Artificial neuronal network
computational fluid dynamics (CFD)
cooling techniques
flow control
heat transfer
hydrodynamics
interaction fluid-structure
large eddy simulation (LES)
offshore applications
Reynolds Averaged Navier–Stokes (RANS) methods

Published Papers (12 papers)

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Editorial

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3 pages, 195 KiB

Open AccessEditorial

Special Issue on the Advances in Fluid Mechanics

by Jesús M. Blanco

Appl. Sci. 2023, 13(9), 5492; https://doi.org/10.3390/app13095492 - 28 Apr 2023

Viewed by 716

Abstract

The progressive implementation of computational fluid dynamics (CFD) has experienced a great increase over the last decades as its use has become more feasible worldwide [...] Full article

(This article belongs to the Special Issue The Advances in Fluid Mechanics)

Research

Jump to: Editorial

24 pages, 10932 KiB

Open AccessArticle

The Investigation of a New End Wall Contouring Method for Axial Compressors

by Xiangjun Li, Fuhao You, Qing Lu, Haoguang Zhang and Wuli Chu

Appl. Sci. 2022, 12(10), 4828; https://doi.org/10.3390/app12104828 - 10 May 2022

Cited by 1 | Viewed by 1294

Abstract

To further control corner separation in high-load axial compressors, this study proposes a new end wall contouring method. It defines multiple standard “surface units” with particular flow control effects and then applies a linear combination, finally forming the geometry of the end wall surface. Based on design experiences, three different end wall contouring cases are generated and calculated on a high-load compressor cascade in the first step. The results show that the new method achieves a clear and intuitive influence on the end wall geometry, with a proper number of design variables, and can effectively combine variables with the development of secondary flow. In the second step, the new method was applied to an axial compressor, with an improvement in the design variables. Although the end wall contouring only improved the efficiency of the compressor stage on the right part of its operating map, the experimental results of the flow field show that the corner separation and end wall loss are suppressed at multiple inflow conditions. The results thus verified the practical effect of the newly developed end wall contouring method. Full article

(This article belongs to the Special Issue The Advances in Fluid Mechanics)

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10 pages, 4259 KiB

Open AccessArticle

Numerical Simulation of Random Cavitation Suppression Based on Variable NACA Airfoils

by Weidong Shi, Zhouhao Shi, Zhanshan Xie, Qinghong Zhang, Yongfei Yang and Linwei Tan

Appl. Sci. 2021, 11(24), 11618; https://doi.org/10.3390/app112411618 - 7 Dec 2021

Cited by 3 | Viewed by 2093

Abstract

In order to suppress the cavitation of an airfoil under random operating conditions, a deformable covering was constructed in the cavitation prone area of the NACA0012 airfoil. By sensing the pressure difference between the inner and outer sides of the airfoil, the covering of the airfoil can be changed adaptively to meet the requirement of suppressing random cavitation of the airfoil. The simulation results show that the cavitation influence range of the airfoil with a shape memory alloy covering can be reduced by more than 70%, and the cavitation is well reduced and suppressed. Moreover, the backflow near the wall of the airfoil was reduced under random working conditions. When the maximum bulge deformation of the covering was between 3–6 mm, the airfoil produced a cavitation range only on the covering surface of the airfoil, and there was no cavitation erosion on other parts. This method with locally variable airfoil to suppress cavitation provides a good reference value for other hydraulic machinery to suppress cavitation. Full article

(This article belongs to the Special Issue The Advances in Fluid Mechanics)

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16 pages, 3669 KiB

Open AccessArticle

Numerical Modelling of a Floating Wind Turbine Semi-Submersible Platform

by Lander Galera-Calero, Jesús María Blanco and Gregorio Iglesias

Appl. Sci. 2021, 11(23), 11270; https://doi.org/10.3390/app112311270 - 28 Nov 2021

Cited by 6 | Viewed by 1654

Abstract

A detailed study is undertaken of the computational modelling of a sub-platform for floating offshore wind using the software Star-CCM+ with the application of the RANS approach. First, a mathematical introduction to the governing equations is carried out. Then, the computational grid is defined, and the grid-independence of the solution is verified. A time-dependent study is performed with the selected time-step. Finally, two examples of 3D decay tests in heave of the sub-platform without and with moorings are presented, accompanied by a damping factor study, with the aim of providing a better understanding of the hydrodynamic damping of the platform. Throughout the process, three degrees of freedom (DoFs) are locked due to the limitations imposed by the use of a symmetry plane; this implementation allowed us to reduce the computational cost of each simulation by 50%. Therefore, three DoFs (heave, surge and pitch) are considered. The coupling study, adding a mooring system in the decay tests and the regular wave tests, shows good agreement between the experimental and computational results. The first half-period of the simulations presents a greater discrepancy due to the fact that the damping of the platform is lower in the computational simulation. However, this does not imply that the hydrodynamic damping is underestimated but may be directly related to the lock of various DoFs associated with the hydrodynamic damping. Full article

(This article belongs to the Special Issue The Advances in Fluid Mechanics)

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14 pages, 3117 KiB

Open AccessArticle

Determination of the Reference Temperature for a Convective Heat Transfer Coefficient in a Heated Tube Bank

by Stanislav Kotšmíd and Zuzana Brodnianská

Appl. Sci. 2021, 11(22), 10564; https://doi.org/10.3390/app112210564 - 10 Nov 2021

Cited by 3 | Viewed by 2351

Abstract

The paper presents a theoretical analysis of heat transfer in a heated tube bank, based on the Nusselt number computation as one of the basic dimensionless criteria. To compute the Nusselt number based on the heat transfer coefficient, the reference temperature must be determined. Despite the value significance, the quantity has several different formulations, which leads to discrepancies in results. This paper investigates the heat transfer of the inline and staggered tube banks, made up of 20 rows, at a constant tube diameter and longitudinal and transverse pitch. Both laminar and turbulent flows up to Re = 10,000 are considered, and the effect of gravity is included as well. Several locations for the reference temperature are taken into consideration on the basis of the heretofore published research, and the results in terms of the overall Nusselt number are compared with those obtained by the experimental correlations. This paper provides the most suitable variant for a unique reference temperature, in terms of a constant value for all tube angles, and the Reynolds number ranges of 100–1000 and 1000–10,000 which are in good agreement with the most frequently used correlating equations. Full article

(This article belongs to the Special Issue The Advances in Fluid Mechanics)

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13 pages, 10588 KiB

Open AccessArticle

Influence of Blade Wrap Angle on the Hydrodynamic Radial Force of Single Blade Centrifugal Pump

by Linwei Tan, Yongfei Yang, Weidong Shi, Cheng Chen and Zhanshan Xie

Appl. Sci. 2021, 11(19), 9052; https://doi.org/10.3390/app11199052 - 28 Sep 2021

Cited by 7 | Viewed by 1520

Abstract

To investigate the effect of blade wrap angle on the hydrodynamic radial force of a single blade centrifugal pump, numerical simulation is conducted on the pumps with different blade wrap angles. The effect of the wrap angle on the external characteristics and the radial force of a single blade centrifugal pump was analyzed according to the simulation result. It is found that, with the increase of the blade wrap angle, the head and efficiency of the single blade centrifugal pump are improved, the H-Q curve becomes steeper, and the efficiency also increased gradually, while the high-efficiency area is narrowed. The blade wrap angle has a great effect on the radial force of the single blade centrifugal pump. When the blade wrap angle is less than 360°, the horizontal component of the radial force is negative and the value is reduced with the increase of the wrap angle of the blade. When the wrap angle is larger than 360°, the horizontal component of the radial force is positive and the value increases with the increase of the wrap angle. Under part-loading conditions, the radial force of the single blade pump is significantly reduced with the increase of the blade wrap angle. When the wrap angle is smaller than 360°, the radial force decreases with the flow rate increase. In the condition that the wrap angle is larger than 360°, the radial force increases with the flow rate increase. Full article

(This article belongs to the Special Issue The Advances in Fluid Mechanics)

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21 pages, 4253 KiB

Open AccessArticle

Compact Model of a Screen under Fan-Induced Swirl Conditions Using a Porous Media Approach

by Asier Bengoechea, Raúl Antón, Alejandro Rivas, Gorka S. Larraona and Juan Carlos Ramos

Appl. Sci. 2021, 11(5), 1999; https://doi.org/10.3390/app11051999 - 24 Feb 2021

Cited by 2 | Viewed by 1404

Abstract

A perforated plate in an electronic device is typically placed downstream of an axial fan (push cooling) in order to avoid electromagnetic interferences. Because of the swirling component in the flow approaching the screen, determining how the screen affects the flow pattern downstream of the screen is a challenge. It is important to understand this interaction, as the correct location of the electronic components will depend on the flow pattern (the components that dissipate more heat will be located where the maximum magnitude of the velocity is located). This work aims to present an approach of the flow pattern via a compact model based on three directional pressure loss coefficients. The values for the pressure loss coefficients are obtained through different correlations depending on the flow and geometric characteristics for the case that is being modeled. These correlations are obtained through an iterative process that compares different flow patterns obtained through different modeling strategies: the compact one that is presented in this paper and another detailed one, which was validated in previous works. Results show that if this compact model is used, an approximation of the flow pattern could be obtained with a huge decrease in the amount of time invested. Full article

(This article belongs to the Special Issue The Advances in Fluid Mechanics)

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13 pages, 3116 KiB

Open AccessArticle

Particle Image Velocimetry Measurements of the Flow-Diverting Effects of a New Generation of the eCLIPs Implant for the Treatment of Intracranial Bifurcation Aneurysms

by Sina G. Yazdi, Daniel Mercier, Renee Bernard, Adam Tynan and Donald R. Ricci

Appl. Sci. 2020, 10(23), 8639; https://doi.org/10.3390/app10238639 - 3 Dec 2020

Cited by 7 | Viewed by 2120

Abstract

Flow diverters (FDs) for the endovascular treatment of intracranial aneurysms are effective for sidewall aneurysms, but their use at a bifurcation is problematic because FDs only partially cover the aneurysm neck and impede flow into a daughter branch; they are thus not employed routinely in this anatomy. eCLIPs was developed as a non-tubular implant to completely cover the neck of an aneurysm and serve as a coil retention device necessary for the adequate treatment of wide-neck bifurcation aneurysms. eCLIPs has shown some flow diversion effects in bifurcation anatomy but not equal to those exhibited by clinically accepted flow diverters in sidewall anatomy. A new generation of eCLIPs implant, the eCLIPs bifurcation flow diverter (eBFD), with higher metal coverage, was developed to achieve a similar flow diversion as a Pipeline Embolization Device (PED), a prototypical FD. Particle image velocimetry was used to capture the fluid dynamics and velocity reduction within silicone aneurysm replicas. A circulatory mimicking loop was developed to circulate the flow through the silicone models. All generations of eCLIPs implants had some flow-diverting effect, with increasing metal coverage density of the implant proportionately increasing the flow diversion effect. The eBFD, with a metal density of 35%, showed greater flow diversion than PED, with 30% metal density, for bifurcation anatomy. The eBFD showed similar reduction of flow in a bifurcation anatomy to PED in a sidewall, both sufficient to permit early thrombosis of the aneurysm. Thus, the eBFD can potentially provide sufficient flow diversion for the treatment of bifurcation aneurysms to avoid adjunctive coiling. Full article

(This article belongs to the Special Issue The Advances in Fluid Mechanics)

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17 pages, 2572 KiB

Open AccessArticle

Thermal Accelerometer Simulation by the R‑Functions Method

by Mikhail Basarab, Alain Giani and Philippe Combette

Appl. Sci. 2020, 10(23), 8373; https://doi.org/10.3390/app10238373 - 25 Nov 2020

Cited by 6 | Viewed by 1524

Abstract

As well as many modern devices, thermal accelerometers (TAs) need a sophisticated mathematical simulation to find the ways for their performance optimization. In the paper, a novel approach for solving computational fluid dynamics (CFD) problems in the TA’s cavity is proposed (MQ-RFM), which is based on the combined use of Rvachev’s R-functions method (RFM) and the Galerkin technique with multiquadric (MQ) radial basis functions (RBFs). The semi-analytical RFM takes an intermediate position between traditional analytical approaches and numerical methods, such as the finite-element method (FEM), belonging to the family of the so-called meshless techniques which became popular in the last decades in solving various CFD problems in complex-shaped cavities. Mathematical simulation of TA by using the MQ-RFM was carried out with the purpose to simulate the temperature response of the device and to study and improve its performance. The results of numerical experiments were compared with well-known analytical and numerical benchmark solutions for the circular annulus geometry and it demonstrated the effectiveness of the MQ-RFM for solving the convective heat-transfer problem in the TA’s cavity. The use of solution structures allows one to take a relatively small number of expansion terms to achieve an appropriate accuracy of the approximate solution satisfying at the same time the given boundary conditions exactly. The application of the MQ-RFM gives the possibility to obtain semi-analytical solutions to the diffusion-convection problems and to identify the main thermal characteristics of the TA, that allows one to improve the device performance. Full article

(This article belongs to the Special Issue The Advances in Fluid Mechanics)

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17 pages, 3891 KiB

Open AccessArticle

Development of Driftwood Capture Trellis for Capturing Driftwood in Agricultural Drainage Ditches

by Youngseok Song and Moojong Park

Appl. Sci. 2020, 10(17), 5805; https://doi.org/10.3390/app10175805 - 21 Aug 2020

Cited by 2 | Viewed by 2109

Abstract

The flow of driftwood and soil into drainage from agricultural areas accelerates sedimentation and inflicts overflow damage after rainfall events due to insufficient discharge capacity, causing flooding on agricultural land. However, there have been few efforts to develop a driftwood capture trellis for agricultural drainage ditches, except for some suggested design criteria. In this study, we developed a driftwood capture trellis to capture driftwood in agricultural drainage ditches and evaluated its performance based on hydraulic characteristics. The facility was designed considering criteria for drainage and driftwood control barriers, as well as the properties of driftwood found near agricultural drainage ditches. Performance evaluation was conducted through hydraulic experiments. Driftwood capture trellises were installed in 400 mm drainage pipes and a total of 216 experimental runs were conducted: six runs each in six different velocity variations and six water depth variations. The results showed that the driftwood capture efficiency of the facility exceeded 60% at a velocity of 0.144 m³/s. Limited conditions for hydraulic experiments should be considered. The driftwood capture trellis for agricultural drainage ditches developed in this study could contribute to a reduction in overflow damage caused by driftwood sedimentation. Full article

(This article belongs to the Special Issue The Advances in Fluid Mechanics)

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11 pages, 1329 KiB

Open AccessArticle

Influence of the Ion Mass in the Radial to Orbital Transition in Weakly Collisional Low-Pressure Plasmas Using Cylindrical Langmuir Probes

by Guillermo Fernando Regodón, Juan Manuel Díaz-Cabrera, José Ignacio Fernández Palop and Jerónimo Ballesteros

Appl. Sci. 2020, 10(17), 5727; https://doi.org/10.3390/app10175727 - 19 Aug 2020

Cited by 5 | Viewed by 1869

Abstract

This paper presents an experimentally observed transition from the validity of the radial theories to the validity of the orbital theories that model the ion current collected by a cylindrical Langmuir probe immersed in low-pressure, low-temperature helium plasma when it is negatively biased [...] Read more.

Λ = λ_{+} / λ_{D}

. The study has been also conducted on argon and neon plasmas, which allows a comparison based on the mass of the ions, although no transition has been observed for these gases. As the radial or orbital behavior of the ions is essential to establish the validity of the different sheath theories, a theoretical analysis of such a transition not only as a function of the parameters

Λ

and

β = T_{+} / T_{e}

T_{+}

and

T_{e}

being the positive ion and electron temperature, respectively, but also as a function of the ion mass is provided. This study allows us to recognize the importance of the mass of the ion as the parameter that explains the transition in helium plasmas. Motivated by these theoretical arguments, a novel set of measurements has been performed to study the relationship between the

Λ

and

β

parameters in the transition that demonstrate that the effect of the ion mean free path cannot be completely ignored and also that its influence on the ion current collected by the probe is less important than the effect of the ion temperature. Full article

(This article belongs to the Special Issue The Advances in Fluid Mechanics)

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16 pages, 6798 KiB

Open AccessArticle

Performance and Modeling of a Two-Stage Light Gas Gun Driven by Gaseous Detonation

by Weiqi Tang, Qiu Wang, Bingchen Wei, Jiwei Li, Jinping Li, Jiahao Shang, Kun Zhang and Wei Zhao

Appl. Sci. 2020, 10(12), 4383; https://doi.org/10.3390/app10124383 - 25 Jun 2020

Cited by 8 | Viewed by 4852

Abstract

A two-stage light gas gun driven by gaseous detonation was newly constructed, which can make up for the disadvantages of the insufficient driving capability of high-pressure gas and the constraints of gunpowder. The performance of the gas gun was investigated through experiments and a quasi-one-dimensional modeling of it was also developed and described in detail. The model accounts for the friction and heat transfer to the tube wall for gases by adding a source term. An improved model has been established to consider the inertial loads in the piston or projectile and model the friction force with the tube wall. Besides, the effects of pump tube pressure on the performance of the gas gun are also investigated numerically. Simulations of the pressure histories in the pump tube and the piston and projectile velocities were conducted. A good agreement was observed between the computational predictions and experimental results. The results showed that the friction between the piston and wall had only small influence on the piston velocity. The proposed numerical approach is suitable for the development of two-stage light gas guns and tests of the operating conditions. Full article

(This article belongs to the Special Issue The Advances in Fluid Mechanics)

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