Fluids

Editorial

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5 pages, 173 KiB

Open AccessEditorial

Flow-Based Optimization of Products or Devices

by Nils T. Basse

Fluids 2020, 5(2), 56; https://doi.org/10.3390/fluids5020056 - 22 Apr 2020

Viewed by 1560

Abstract

Flow-based optimization of products and devices is an immature field compared to corresponding topology optimization based on solid mechanics [...] Full article

(This article belongs to the Special Issue Flow-Based Optimization of Products or Devices)

Research

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24 pages, 6098 KiB

Open AccessArticle

Cloud-Based CAD Parametrization for Design Space Exploration and Design Optimization in Numerical Simulations

by Joel Guerrero, Luca Mantelli and Sahrish B. Naqvi

Fluids 2020, 5(1), 36; https://doi.org/10.3390/fluids5010036 - 18 Mar 2020

Cited by 8 | Viewed by 3672

Abstract

In this manuscript, an automated framework dedicated to design space exploration and design optimization studies is presented. The framework integrates a set of numerical simulation, computer-aided design, numerical optimization, and data analytics tools using scripting capabilities. The tools used are open-source and freeware, [...] Read more.

In this manuscript, an automated framework dedicated to design space exploration and design optimization studies is presented. The framework integrates a set of numerical simulation, computer-aided design, numerical optimization, and data analytics tools using scripting capabilities. The tools used are open-source and freeware, and can be deployed on any platform. The main feature of the proposed methodology is the use of a cloud-based parametrical computer-aided design application, which allows the user to change any parametric variable defined in the solid model. We demonstrate the capabilities and flexibility of the framework using computational fluid dynamics applications; however, the same workflow can be used with any numerical simulation tool (e.g., a structural solver or a spread-sheet) that is able to interact via a command-line interface or using scripting languages. We conduct design space exploration and design optimization studies using quantitative and qualitative metrics, and, to reduce the high computing times and computational resources intrinsic to these kinds of studies, concurrent simulations and surrogate-based optimization are used. Full article

(This article belongs to the Special Issue Flow-Based Optimization of Products or Devices)

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21 pages, 332 KiB

Open AccessFeature PaperArticle

Derivation of the Adjoint Drift Flux Equations for Multiphase Flow

by Shenan Grossberg, Daniel S. Jarman and Gavin R. Tabor

Fluids 2020, 5(1), 31; https://doi.org/10.3390/fluids5010031 - 11 Mar 2020

Cited by 2 | Viewed by 2193

Abstract

The continuous adjoint approach is a technique for calculating the sensitivity of a flow to changes in input parameters, most commonly changes of geometry. Here we present for the first time the mathematical derivation of the adjoint system for multiphase flow modeled by [...] Read more.

The continuous adjoint approach is a technique for calculating the sensitivity of a flow to changes in input parameters, most commonly changes of geometry. Here we present for the first time the mathematical derivation of the adjoint system for multiphase flow modeled by the commonly used drift flux equations, together with the adjoint boundary conditions necessary to solve a generic multiphase flow problem. The objective function is defined for such a system, and specific examples derived for commonly used settling velocity formulations such as the Takacs and Dahl models. We also discuss the use of these equations for a complete optimisation process. Full article

(This article belongs to the Special Issue Flow-Based Optimization of Products or Devices)

17 pages, 3652 KiB

Open AccessArticle

Experimental Investigation of Finite Aspect Ratio Cylindrical Bodies for Accelerated Wind Applications

by Michael Parker and Douglas Bohl

Fluids 2020, 5(1), 25; https://doi.org/10.3390/fluids5010025 - 17 Feb 2020

Cited by 1 | Viewed by 2368

Abstract

The placement of a cylindrical body in a flow alters the velocity and pressure fields resulting in a local increase in the flow speed near the body. This interaction is of interest as wind turbine rotor blades could be placed in the area [...] Read more.

The placement of a cylindrical body in a flow alters the velocity and pressure fields resulting in a local increase in the flow speed near the body. This interaction is of interest as wind turbine rotor blades could be placed in the area of increased wind speed to enhance energy harvesting. In this work the aerodynamic performance of two short aspect ratio (AR = 0.93) cylindrical bodies was evaluated for potential use in “accelerated wind” applications. The first cylinder was smooth with a constant diameter. The diameter of the second cylinder varied periodically along the span forming channels, or corrugations, where wind turbine blades could be placed. Experiments were performed for Reynolds numbers ranging from 1 × 10⁵ to 9 × 10⁵. Pressure distributions showed that the smooth cylinder had lower minimum pressure coefficients and delayed separation compared to the corrugated cylinder. Velocity profiles showed that the corrugated cylinder had lower peak speeds, a less uniform profile, and lower kinetic energy flux when compared to the smooth cylinder. It was concluded that the smooth cylinder had significantly better potential performance in accelerated wind applications than the corrugated cylinder. Full article

(This article belongs to the Special Issue Flow-Based Optimization of Products or Devices)

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19 pages, 11916 KiB

Open AccessArticle

Valve Geometry and Flow Optimization through an Automated DOE Approach

by Micaela Olivetti, Federico Giulio Monterosso, Gianluca Marinaro, Emma Frosina and Pietro Mazzei

Fluids 2020, 5(1), 17; https://doi.org/10.3390/fluids5010017 - 30 Jan 2020

Cited by 5 | Viewed by 3612

Abstract

The objective of this paper is to show how a completely virtual optimization approach is useful to design new geometries in order to improve the performance of industrial components, like valves. The standard approach for optimization of an industrial component, as a valve, [...] Read more.

The objective of this paper is to show how a completely virtual optimization approach is useful to design new geometries in order to improve the performance of industrial components, like valves. The standard approach for optimization of an industrial component, as a valve, is mainly performed with trials and errors and is based on the experience and knowledge of the engineer involved in the study. Unfortunately, this approach is time consuming and often not affordable for the industrial time-to-market. The introduction of computational fluid dynamic (CFD) tools significantly helped reducing time to market; on the other hand, the process to identify the best configuration still depends on the personal sensitivity of the engineer. Here a more general, faster and reliable approach is described, which uses a CFD code directly linked to an optimization tool. CAESES^® associated with SimericsMP+^® allows us to easily study many different geometrical variants and work out a design of experiments (DOE) sequence that gives evidence of the most impactful aspects of a design. Moreover, the result can be further optimized to obtain the best possible solution in terms of the constraints defined. Full article

(This article belongs to the Special Issue Flow-Based Optimization of Products or Devices)

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16 pages, 4343 KiB

Open AccessArticle

Shape Optimization of a Two-Fluid Mixing Device Using Continuous Adjoint

by Pavlos Alexias and Kyriakos C. Giannakoglou

Fluids 2020, 5(1), 11; https://doi.org/10.3390/fluids5010011 - 08 Jan 2020

Cited by 6 | Viewed by 3087

Abstract

In this paper, the continuous adjoint method is used for the optimization of a static mixing device. The CFD model used is suitable for the flow simulation of the two miscible fluids that enter the device. The formulation of the adjoint equations, which [...] Read more.

In this paper, the continuous adjoint method is used for the optimization of a static mixing device. The CFD model used is suitable for the flow simulation of the two miscible fluids that enter the device. The formulation of the adjoint equations, which allow the computation of the sensitivity derivatives is briefly demonstrated. A detailed analysis of the geometry parameterization is presented and a set of different parameterization scenarios are investigated. In detail, two different parameterizations are combined into a two-stage optimization algorithm which targets maximum mixture uniformity at the exit of the mixer and minimum total pressure losses. All parameterizations are in conformity with specific manufacturability constraints of the final shape. The non-dominated front of optimal solutions is obtained by using the weighted sum of the two objective functions and executing a set of optimization runs. The effectiveness of the proposed synthetic parameterization schemes is assessed and discussed in detail. Finally, a reduced length mixer is optimized to study the impact of the length of the tube on the device’s performance. Full article

(This article belongs to the Special Issue Flow-Based Optimization of Products or Devices)

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22 pages, 7175 KiB

Open AccessArticle

Numerical Investigation of Air-Side Heat Transfer and Pressure Drop Characteristics of a New Triangular Finned Microchannel Evaporator with Water Drainage Slits

by Brice Rogie, Wiebke Brix Markussen, Jens Honore Walther and Martin Ryhl Kærn

Fluids 2019, 4(4), 205; https://doi.org/10.3390/fluids4040205 - 11 Dec 2019

Cited by 4 | Viewed by 4073

Abstract

The present study investigated a new microchannel profile design encompassing condensate drainage slits for improved moisture removal with use of triangular shaped plain fins. Heat transfer and pressure drop correlations were developed using computational fluid dynamics (CFD) and defined in terms of Colburn [...] Read more.

The present study investigated a new microchannel profile design encompassing condensate drainage slits for improved moisture removal with use of triangular shaped plain fins. Heat transfer and pressure drop correlations were developed using computational fluid dynamics (CFD) and defined in terms of Colburn j-factor and Fanning f-factor. The microchannels were square 2.00 × 2.00 mm and placed with 4.50 mm longitudinal tube pitch. The transverse tube pitch and the triangular fin pitch were varied from 9.00 to 21.00 mm and 2.50 to 10.00 mm, respectively. Frontal velocity ranged from 1.47 to 4.40 m·s⁻¹. The chosen evaporator geometry corresponds to evaporators for industrial refrigeration systems with long frosting periods. Furthermore, the CFD simulations covered the complete thermal entrance and developed regions, and made it possible to extract virtually infinite longitudinal heat transfer and pressure drop characteristics. The developed Colburn j-factor and Fanning f-factor correlations are able to predict the numerical results with 3.41% and 3.95% deviation, respectively. Full article

(This article belongs to the Special Issue Flow-Based Optimization of Products or Devices)

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20 pages, 15622 KiB

Open AccessArticle

Computational Optimization of Adaptive Hybrid Darrieus Turbine: Part 1

by Palanisamy Mohan Kumar, Mohan Ram Surya, Krishnamoorthi Sivalingam, Teik-Cheng Lim, Seeram Ramakrishna and He Wei

Fluids 2019, 4(2), 90; https://doi.org/10.3390/fluids4020090 - 17 May 2019

Cited by 11 | Viewed by 4206

Abstract

Darrieus-type Vertical Axis Wind Turbines (VAWT) are promising for small scale decentralized power generation because of their unique advantages such as simple design, insensitive to wind direction, reliability, and ease of maintenance. Despite these positive aspects, poor self-starting capability and low efficiency in [...] Read more.

Darrieus-type Vertical Axis Wind Turbines (VAWT) are promising for small scale decentralized power generation because of their unique advantages such as simple design, insensitive to wind direction, reliability, and ease of maintenance. Despite these positive aspects, poor self-starting capability and low efficiency in weak and unsteady winds deteriorate further development. Adaptive Hybrid Darrieus Turbine (AHDT) was proposed by the author in the past study as a potential solution to enhance low wind speed characteristics. The objective of the current research is to optimize the parameters of AHDT. AHDT integrates a dynamically varying Savonius rotor with a Darrieus rotor. A fully detailed 2D numerical study employing Reynold-Averaged Navier Stokes (RANS) is carried out to investigate the impact of the Darrieus rotor diameter (D_R) on the Savonius rotor (D_T) with regard to hybrid turbine performance. The power coefficient of the Darrieus rotor is evaluated when the Savonius rotor is in the closed condition (cylinder) of various diameters. The influence of Reynolds number (Re) on the torque coefficient is examined. Power loss of 58.3% and 25% is reported for D_R/D_T ratio of 1.5 and 2 respectively for AHDT with solidity 0.5 at 9 m/s. The flow interaction between the Savonius rotor in closed configuration reveals the formation of von Karman vortices that interact with Darrieus blades resulting in flow detachment. An optimum diametrical ratio (D_R/D_T) of 3 is found to yield the maximum power coefficient of the Darrieus rotor. Full article

(This article belongs to the Special Issue Flow-Based Optimization of Products or Devices)

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Review

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32 pages, 3066 KiB

Open AccessFeature PaperEditor’s ChoiceReview

A Review of Topology Optimisation for Fluid-Based Problems

by Joe Alexandersen and Casper Schousboe Andreasen

Fluids 2020, 5(1), 29; https://doi.org/10.3390/fluids5010029 - 04 Mar 2020

Cited by 141 | Viewed by 14511

Abstract

This review paper provides an overview of the literature for topology optimisation of fluid-based problems, starting with the seminal works on the subject and ending with a snapshot of the state of the art of this rapidly developing field. “Fluid-based problems” are defined [...] Read more.

This review paper provides an overview of the literature for topology optimisation of fluid-based problems, starting with the seminal works on the subject and ending with a snapshot of the state of the art of this rapidly developing field. “Fluid-based problems” are defined as problems where at least one governing equation for fluid flow is solved and the fluid–solid interface is optimised. In addition to fluid flow, any number of additional physics can be solved, such as species transport, heat transfer and mechanics. The review covers 186 papers from 2003 up to and including January 2020, which are sorted into five main groups: pure fluid flow; species transport; conjugate heat transfer; fluid–structure interaction; microstructure and porous media. Each paper is very briefly introduced in chronological order of publication. A quantititive analysis is presented with statistics covering the development of the field and presenting the distribution over subgroups. Recommendations for focus areas of future research are made based on the extensive literature review, the quantitative analysis, as well as the authors’ personal experience and opinions. Since the vast majority of papers treat steady-state laminar pure fluid flow, with no recent major advancements, it is recommended that future research focuses on more complex problems, e.g., transient and turbulent flow. Full article

(This article belongs to the Special Issue Flow-Based Optimization of Products or Devices)

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