Role Of Computational Fluid Dynamics Research Articles

Computational Fluid Dynamics Prediction of External Thermal Loads on Film-Cooled Gas Turbine Vanes: A Validation of Reynolds-Averaged Navier–Stokes Transition Models and Scale-Resolving Simulations for the VKI LS-94 Test Case

Given the increasing role of computational fluid dynamics (CFD) simulations in the aerothermal design of gas turbine vanes and blades, their rigorous validation is becoming more and more important. This article exploits an experimental database obtained by the von Karman Institute (VKI) for Fluid Dynamics for the LS-94 test case. This represents a film-cooled transonic turbine vane, investigated in a five-vane linear cascade configuration under engine-like conditions in terms of the Reynolds number and Mach number. The experimental characterization included inlet freestream turbulence measured with hot-wire anemometry, aerodynamic performance assessed with a three-hole pressure probe in the downstream section, and vane convective heat transfer coefficient distribution determined with thin-film thermometers. The test matrix included cases without any film-cooling injection, pressure-side injection, and suction-side injection. The CFD simulations were carried out in Ansys Fluent, considering the impact of mesh sizing and steady-state Reynolds-Averaged Navier-Stokes (RANS) transition modelling, as well as more accurate transient scale-resolving simulations. This work provides insight into the advantages and drawbacks of such approaches for gas turbine hot-gas path designers.

From past to future: The role of computational fluid dynamics in advancing nuclear safety in Spain and Portugal

This document explores the role of CFD in nuclear safety studies, with a particular focus on advancements in Spain and Portugal. The field of nuclear safety has increasingly included CFD models to address complex safety–critical phenomena, given their ability to capture three-dimensional behavior with high resolution. While traditional one-dimensional codes remain very valuable, they often rely on conservative approximations, making 3D CFD approaches indispensable for accurate predictions across various nuclear scenarios. In the context of Spain and Portugal, this document shows the contribution to CFD applications for nuclear safety research. The topics covered include code development and validation, combustion studies, simulations of nuclear spent casks, fuel assembly analyses, and investigations into containment safety issues. These advances have mainly contributed to improving the predicting capabilities of CFD models for applications in various safety–critical domains. In addition to detailing the achievements and contributions in the field of CFD in Spain and Portugal, readers will find a comprehensive overview of the current challenges and future perspectives of CFD within the domain of nuclear fission technology.

The transformative role of Computational Fluid Dynamics (CFD) in chemical engineering

Chemical engineering is a discipline intrinsically linked to fluid behavior. From reaction kinetics to reactor design, understanding how fluids flow, mix, and transfer heat is paramount. Traditionally, this relied heavily on experimentation, a time-consuming and resource-intensive process. The emergence of Computational Fluid Dynamics (CFD) has revolutionized the field, offering a powerful in-silico approach to analyze fluid dynamics in chemical engineering processes. This review paper explores the transformative role of CFD, examining its impact on various aspects of chemical engineering, including reactor design, optimization, process intensification, scale-up, and safety analysis. The paper also discusses the challenges associated with CFD simulations, ongoing advancements in the field, and potential future directions.

Recent advancements of CFD and heat transfer studies in pyrolysis: A review

There is a pressing need to process the solid waste by using pyrolysis technology due to its uniqueness to produce various solid, liquid and gaseous products. However, further understanding of pyrolysis process is needed. Most importantly, the role of computational fluid dynamics (CFD) in pyrolysis is to be thoroughly investigated. In recent times, there has been significant progress in the research works aligned with evaluating the role of CFD in biomass pyrolysis. Hence, the current review manuscript focusses the current state of the art in the application of CFD tools to multi-scale biomass pyrolysis systems. Modeling of fluid and heat transport in conventional pyrolysis reactors, microwave-assisted pyrolysis reactors, and solar-assisted pyrolysis reactors for the conversion of biomass have been critically analyzed. The theoretical basis and the practical applicability of the CFD models to efficiently emulate and predict the overall complexity of pyrolysis process for the multi-scale and multi-phase nature of biomass have been discussed. However, the validity and accuracy of the CFD models needs to be enhanced. In the future directions, the steps for expanding the applicability of these theoretical and computational models have been outlined. This review would provide detailed understanding of CFD role in pyrolysis process conducted in various reactor systems.

Role of Computational Fluid Dynamics in the Design of Aerospace Configurations

Computational Fluid Dynamics (CFD), a mature discipline now, can contribute considerably to the design, analysis and development of engineering systems involving fluid flows. Visualization of flow-field, surface load distribution and various aerodynamic forces and moments are the criteria for basic design of aerospace configurations. CFD complements experimental and theoretical fluid dynamics by providing an alternative and cost effective means to simulate real flow phenomena. The main advantage lies in its ability to cut down the number of wind-tunnel tests leading to reduction in the design cycle time and design cost. After a brief introduction to CFD, the role played by the modern CFD tools developed at the Computational and Theoretical Fluid Dynamics Division of National Aerospace Laboratories, Bangalore in the design and analysis of Aerospace configurations will be discussed here.

Numerical Study of Wind-Tunnel Wall Effects on Lift and Drag Characteristics of NACA 0012 Airfoil

Possible interference effects of the wind tunnel walls play an important role especially for measurements in closed-wall test sections. In this study, a numerical analysis of two-dimensional subsonic flow over a NACA 0012 airfoil at different computational domain heights, angles of attack from 0o to 10o, and operating Reynolds number of 6×106 is presented. The work highlights the role of computational fluid dynamics (CFD) in the investigation of wind tunnel wall effect on lift curve slope correction factor (Ka). The flow solution is obtained using Ansys Fluent software by solving the steady-state continuity and momentum governing equations combined with turbulence model k-v shear stress transport (SST-K?). The numerical results are validated by comparing with the available experimental measurements. Calculations show that the lift curve slope correction results are very close to the published data.

Numerical Modeling of Subcooled Flow Boiling and Heat Transfer Enhancement: Validation and Applicability to Fusion Reactor Target Design

Abstract Boiling flows are an extremely efficient mechanism for the transfer of ultrahigh heat fluxes and used in numerous industrial applications. In this paper, the accuracy of computational fluid dynamics in predicting the temperature distributions and heat transfer performance is examined within a nuclear fusion reactor divertor. The aim is to establish the role of computational fluid dynamics (CFD) within the design of complicated high heat flux components using a semi-mechanistic approach to flow boiling that is independent of geometry and flow conditions. An Eulerian–Eulerian two-fluid method is developed and a conjugate heat transfer model is validated against the existing experimental data where available. Overall, a satisfactory accuracy is achieved in the prediction of several important quantities. Temperature distribution throughout the divertor is found to be highly accurate and aligns with the physical testing across two expected operating regimes. Additionally, the system heat transfer coefficients and coolant temperatures are close to the assumptions already established within the literature. Heat transfer enhancement is a critical component of the divertor design, and a twisted-tape insert appears to be necessary for the system to withstand ultrahigh heat fluxes encountered within the fusion reactor. The results show that the inclusion of a twisted tape improved the heat transfer coefficient of the system by almost 45% allowing the divertor to withstand the required heat fluxes of 10 MW/m2 and 20 MW/m2.

Computational fluid dynamics as a risk assessment tool for aneurysm rupture.

The authors reviewed the clinical role of computational fluid dynamics (CFD) in assessing the risk of intracranial aneurysm rupture. A literature review was performed to identify reports on CFD assessment of aneurysms using PubMed. The usefulness of various hemodynamic parameters, such as wall shear stress (WSS) and the Oscillatory Shear Index (OSI), and their role in aneurysm rupture risk analysis, were analyzed. The authors identified a total of 258 published articles evaluating rupture risk, growth, and endovascular device assessment. Of these 258 articles, 113 matching for CFD and hemodynamic parameters that contribute to the risk of rupture (such as WSS and OSI) were identified. However, due to a lack of standardized methodology, controversy remains on each parameter's role. Although controversy continues to exist on which risk factors contribute to predict aneurysm rupture, CFD can provide additional parameters to assess this rupture risk. This technology can contribute to clinical decision-making or evaluation of efficacy for endovascular methods and devices.

A novel non-reflecting boundary condition for fluid dynamics solved by smoothed particle hydrodynamics

Non-reflecting boundary conditions (NRBCs) play an important role in computational fluid dynamics (CFD). A novel NRBC based on the method of characteristics using timeline interpolations is proposed for fluid dynamics solved by smoothed particle hydrodynamics (SPH). It is performed by four layers of particles whose pressures and velocities are obtained through the Lagrange interpolation in the time domain which is derived from the propagation of characteristic waves between particles. The proposed NRBC can allow outward travelling pressure and velocity messages to pass through the boundary without obvious reflection. That is, with the implementation of the NRBC, the solution in a finite computational domain of interest is close to that in an infinite domain. Several numerical tests show that this NRBC is robust and applicable for a broad variety of hydrodynamics ranging from low to high speed.

Role of computational fluid dynamics in thoracic aortic diseases research: technical superiority and application prospect

Computational fluid dynamics (CFD) technology has the potential to simulate normal or pathologic aortic blood flow changes of mechanical properties and flow field, thereby helping researchers understand and reveal the occurrence, development and prognosis of aortic disease. In aortic diseases research, the initial conditions of CFD numerical simulation has experienced a developed process from idealization (forward engineering), rigid vessel wall, uniform cross-sections, laminar flow and stable blood flow towards personalization (reverse engineering), elastic vessel wall (fluid-solid coupling technique), cone-shaped diminishing cross-sections, turbulent flow, pulsatile blood flow. In this review, the research status, the technical superiority and application prospect of CFD technology were discussed with examples in following three major application areas: (1) dynamics characteristic and mechanical properties in normal thoracic aorta; (2) occurrence, advance and disruptive risk predicting in thoracic aortic aneurysm; (3) therapeutic effect and aneurysmal dilatation simulation in thoracic aortic dissection. For the future, the CFD technology may profoundly put an influence on the awareness to aortic diseases and treatment strategies.

The role of computational fluid dynamics in understanding shipwreck site formation processes

Studies indicate that physical processes commonly dominate the initial stages of wreck site formation. Detailed knowledge and understanding of hydro- and sediment- dynamics are therefore imperative for studies dealing with site formation and in-situ preservation. In this investigation, the results of computational fluid dynamic modelling over a shipwreck site are presented, using a high-resolution surface derived from multi-beam echo-sounder data and boundary conditions constrained by field measurements (sediment samples and flow measurements). Simulation of the 3-dimensional flow velocity field around the wreck site, and secondary products derived from the computational model, confirm that flow velocity and turbulence are both amplified by the presence of the wreck, causing changes in the morphology of the flow regime. Flow contraction, the formation of lee-wake vortices behind the structure (accompanied by vortex shedding) and increased turbulence are all observed. Shear-stress and TKE amplification three to four times greater than ambient values are recorded downstream of the wreck structure. Benefits of this approach for studies of site-formation and in-situ conservation include the inexpensive, open-source, and desk-based nature of the investigation.

Experimental investigation of in-vessel mixing phenomena in a VVER-1000 scaled test facility during unsteady asymmetric transients

In-vessel turbulent mixing phenomena affect the time and space distribution of coolant properties (e.g., boron concentration and temperature) at the core inlet which impacts consequently the neutron kinetics response. For reactor safety evaluation purposes and to characterize these phenomena it is necessary to set and validate appropriate numerical modelling tools to improve the current conservative predictions. With such purpose, an experimental campaign was carried out by OKB Gidropress, in the framework of the European Commission Project “TACIS R2.02/02 – Development of safety analysis capabilities for VVER-1000 transients involving spatial variations of coolant properties (temperature or boron concentration) at core inlet”. The experiments were conducted on a scaled facility representing the primary system of a VVER-1000 including a detailed model of the Reactor Pressure Vessel with its internals. The simulated transients involved perturbations of coolant properties distribution providing a wide validation matrix. The main achievements of the set of experiments featuring transient asymmetric pump behaviour are presented in this paper. The potential of the obtained experimental database for the validation of thermal fluid dynamics numerical simulation tools is also discussed and the role of computational fluid dynamics in supporting the experimental data analysis is highlighted.

Extending the role of computational fluid dynamics in screw machines

Previous publications show that computational fluid dynamics (CFD) can be readily used for the flow prediction and analysis of screw compressors. Several case studies are presented in this article to show the scope and applicability of such methods. These include solid–fluid interaction in screw compressors, prediction of flow generated noise in screw machines, cavitation modelling in gear pumps, and flow in multiphase pumps for oil and gas industry. Numerical grids for all these cases were generated by the authors using an in-house grid generator, while the CFD calculations were performed with a variety of commercially available CFD codes. In order to validate the accuracy of the CFD calculations, an extended test programme was carried out using laser Doppler velocimetry to measure the mean and fluctuating velocity distribution in screw compressor flow domains. The measurement results are then compared with the CFD simulations. The results confirm the viability of the developed techniques. It is shown in this publication that the flexibility of the developed method creates further opportunities for a broader use of CFD for analysis of twin screw machines in a range of new applications.

English

The role of computational fluid dynamics (CFD) in the design of fighter aircraft, transport aircraft, launch vehicle and missiles in India is explained. Indigenous developments of grid generators, 3-D Euler and NavierStokes solvers using state-of-the-art numerical techniques and physical models have been described. Applications of these indigenous softwares for the prediction of various complex aerodynamic flows over a wide range of Mach number, angle of attacks, are presented. Emergence of CFD methods as an efficient tool for aerospace vehicle design is highlighted.

English

The study reviews the role of computational fluid dynamics (CFD) in aerodynamic shape optimisation, and discusses some of the efficient design methodologies. The article in the first part, numerical schemes required for high-fidelity aerodynamic flow analysis are discussed. To accurately resolve high-speed flow physics, high-fidelity shock-stable schemes as well as intelligent limiting strategy mimicking multi-dimensional flow physics are essential. Exploiting these numerical schemes, some applications for 3-D internal/external flow analyses were carried out with various grid systems which enable the treatment of complex geometries. In the second part, depending on the number of design variables and the way to obtain sensitivities or design points, several global and local optimisation methods for aerodynamic shape optimisation are discussed. To avoid the problem that solutions of gradient-based optimisation method (GBOM), are often trapped in local optimum, remedy by combining GBOM with global optimum strategy, such as surrogate models and genetic algorithm (GA) has been examined. As an efficient grid deformation tool, grid deformation technique using NURBS function is discussed. Lastly, some 3-D examples for aerodynamic shape optimisation works based on the proposed design methodology are presented. Defence Science Journal, 2010, 60(6), pp.628-638 , DOI:http://dx.doi.org/10.14429/dsj.60.581

CFD simulation of smooth and T-abrupt exits in circulating fluidized bed risers

Gas–solid flow in circulating fluidized bed (CFB) risers depends not only on operating conditions but also on exit configurations. Few studies investigated the effects of exit configurations on flow structure using computational fluid dynamics (CFD). This paper provides a 2D two-fluid model to simulate a cold bench-scale square cross-section riser with smooth and T-abrupt exits. The drag force between the gas and solid phases plays an important role in CFD. Since the drag force model based on homogeneous two-phase flow, such as the Wen-Yu correlation, could not capture the heterogeneous structures in gas–solid flow, the structure-dependent energy-minimization multi-scale (EMMS) drag force model (Wang, Ge, & Li, 2008), applicable for Geldart B particles (sand), was integrated into the two-fluid model. The calculated axial solids hold-up profiles were respectively exponential curve for smooth exit and C-shaped curve for T-abrupt exit, both consistent with experimental data. This study once again proves the key role of drag force in CFD simulation and also shows the validity of CFD simulation (two-fluid model) to describe exit effects on gas–solid flow in CFB risers.

English

High-speed turbines are used in upper stage liquid engines of launch vehicles and the most common ones include LH2 and LOX turbines used in the cryogenic stages. The main constraints in the design of turbine system for a liquid engine are thermal loads, mass flow and pressure drops in various systems ahead of the turbine inlet. The temperature of the combustion products/gases reaching the turbine blades must be well below the melting point of the turbine blade material and the mass flow rate must be sufficient to generate the required power. Turbine can be started in two ways, by generating gases using a solid propellant-based spinner motor, and using compressed gases stored in gas bottles. The first method involves design challenges but requires less space and weight. On the other hand, second method is simple but requires more space. Because of the space and weight constraints associated with the upper stages, first method is preferred and discussed in this paper. It consists of a solid propellant-based spinner motor with a convergent-divergent nozzle, a guiding duct connecting nozzle exit, and the turbine inlet manifold in the form of a torroid with nozzle block having 39 guiding nozzles. The combustion products generated by the spinner motor are guided to the manifold through the guiding duct. Inlet manifold acts as a reservoir and supplies hot gases uniformly to the turbine through 39 nozzles. This study addresses the role of computational fluid dynamics in the design of turbine startup system using unstructured cell-centered AUSM+-UP-based finite volume solver with the twoequation turbulence model. The flow and the thermal characteristics of the solid motor with a convergentdivergent nozzle were studied to evaluate the gas temperature, operating pressure, and flow velocities. The guiding duct along with the inlet manifold was analysed separately to find the drop in temperature and pressure within the system. From the simulation results, the mass flow through each guiding nozzle, and hence, energy available could be evaluated to ensure proper functioning of the turbine. Defence Science Journal, 2009, 59(3), pp.215-229 , DOI:http://dx.doi.org/10.14429/dsj.59.1515

Lattice Boltzmann methods on the ClearSpeed Advance™ accelerator board

Numerical analysts and programmers are currently facing a conceptual change in processor technology. Multicore concepts, coprocessors and accelerators are becoming a vital part in scientific computing. The new hardware techno- logies lead to new paradigms and require adapted methodologies and techniques in numerical simulation. These developments play an important role in computational fluid dynamics (CFD) where many highly CPU-time demanding problems arise. In this paper, we propose a parallel lattice Boltzmann method (LBM) in the context of a coprocessor technology, the ClearSpeed Advance™ accelerator board. Implementations of LBMs on parallel architectures benefit from localities of the necessary interactions and the regular structure of the underlying meshes. The considered board supports high-level parallelism and double precision conforming to the IEEE 754 standard. However, the solution process relies on a huge amount of data which needs to propagate along the mesh. This prototypical fact shows up the bottleneck of internal communication bandwidth and indicates the limits of this type of small-scale parallel systems.

The Role of Computational Fluid Dynamics in the Management of Unruptured Intracranial Aneurysms: A Clinicians' View

Objective. The importance of hemodynamics in the etiopathogenesis of intracranial aneurysms (IAs) is widely accepted. Computational fluid dynamics (CFD) is being used increasingly for hemodynamic predictions. However, alogn with the continuing development and validation of these tools, it is imperative to collect the opinion of the clinicians. Methods. A workshop on CFD was conducted during the European Society of Minimally Invasive Neurological Therapy (ESMINT) Teaching Course, Lisbon, Portugal. 36 delegates, mostly clinicians, performed supervised CFD analysis for an IA, using the @neuFuse software developed within the European project @neurIST. Feedback on the workshop was collected and analyzed. The performance was assessed on a scale of 1 to 4 and, compared with experts' performance. Results. Current dilemmas in the management of unruptured IAs remained the most important motivating factor to attend the workshop and majority of participants showed interest in participating in a multicentric trial. The participants achieved an average score of 2.52 (range 0–4) which was 63% (range 0–100%) of an expert user. Conclusions. Although participants showed a manifest interest in CFD, there was a clear lack of awareness concerning the role of hemodynamics in the etiopathogenesis of IAs and the use of CFD in this context. More efforts therefore are required to enhance understanding of the clinicians in the subject.

Computational hemodynamics in the human aorta: A computational fluid dynamics study of three cases with patient-specific geometries and inflow rates

To demonstrate the potential role of computational fluid dynamics (CFD) in therapeutic decision making for treatment of vascular pathologies of the human aorta. CFD simulations with patient specific geometries and patient-specific inflow boundary conditions obtained with magnetic resonance imaging were performed in three cases: 1) mobile thrombus in the aortic arch in a patient with ischemic stroke 2) acute type II B aortic dissection 3) abdominal aortic aneurysm repaired with an endoluminal graft. Blood flow pathlines, wall shear stresses (WSS), dynamic pressures, blood velocities and flow particle resident times were calculated. Aortic thrombus was indicated as possible source of emboli by flowlines and elevated WSS (8% higher than average WSS at aortic wall) in case 1. This was not identified on conventional imaging. In case 2, the false lumen of the dissection showed elevated pressures and high blood velocities at systole but low pressures and stagnant flow at other times (blood velocity < 0.02 m/s and WSS < 0.1 Pa). Flow disturbances at the reentrance zone of blood from the false lumen were recognized. For case 3, elevated WSS at the landing zone of the endoluminal graft and at the right iliac section together with disturbed flow patterns and increased flow particle resident times were noted. Focal stenoses coincided with the flow disturbances. Measured velocity patterns were qualitatively in agreement with velocity patterns calculated with CFD. CFD simulations provide additional information of the hemodynamics in the diseased human aorta and may have potential in aiding the therapeutic decision making process.