Research on Propeller Modeling and Fluid-Solid Coupling Analysis

CFD simulation of an agitated gas-fluidized bed: Effects of particle–particle restitution coefficient on the hydrodynamics

Benchmark and parametric study of a passive flow controller (fluidic device) for the development of optimal designs using a CFD code

Based on the MSFR (Molten Salt Fast Reactor) reactor concept presented within the framework of the EVOL (Evaluation and Viability of Liquid Fuel Fast Reactor System, EU FP7) international research project preliminary three-dimensional thermal-hydraulic analyses and the discussion of scaled experimental modelling will be presented. The MSFR concept is a single region, homogeneous liquid fuelled fast reactor. The reactor concept uses fluoride-based molten salts with fissile uranium and/or thorium and other heavy nuclei content with the purpose of applying the thorium cycle and the burn-up of transuranic elements. The concept has a single region cylindrical core with sixteen radial inlet and outlet nozzles located at the bottom and top of the core. The external circuit (internal heat exchanger, pump, pipes) is broken up into sixteen identical modules distributed around the core. Purpose of the three-dimensional computational fluid dynamics (CFD) calculations is to study the possibility of experimental investigation of the fluid flow in the core of the proposed MSFR concept using a scaled model and Particle Image Velocimetry (PIV) flow measurement technique. First the main properties of the proposed MSFR concept are introduced, and the information on other experimental thermal-hydraulic modelling of different reactors, including MSRE (Molten Salt Reactor Experiment) are summarised. With a scaled plexiglas MSFR model it would be possible to carry out flow field measurements under laboratory conditions using PIV method. Possible way of scaling are presented and a series of preliminary CFD calculations are discussed. Possibilities and limitations of such scaling and segmenting of a model and the use of water as substitute fluid for the experimental mock-up will be discussed. Objectives of such a measurement series would be validation, benchmarking of CFD calculations and codes, application of CFD modelling experience in the detailed thermal-hydraulic design of the MSFR concept, possible measurements for the study of specific problems or phenomena, for example refinement of inlet geometry, effects of internal structures, coolant mixing.

Distributed-parallel CFD computation for all fuel assemblies in PWR core

This paper presents the results of wind loads computational fluid dynamics (CFD) calculations performed on the topside structures of a typical GustoMSC designed self-propelled wind turbine installation jack-up. To investigate the effect of geometrical simplifications on the overall wind loads acting on the jack-up, the CFD calculations were performed for the detailed as well as simplified topside structures. An atmospheric boundary layer profile was applied. The full range of heading angles was considered. The CFD results were validated through comparison with the wind tunnel tests which were carried out at the German-Dutch wind tunnels (DNW) in Marknesse, The Netherlands. Moreover, a comparison is presented between the simplified and detailed topside structures at model-scale as well as at full-scale. Based on the results of the CFD calculations at model-scale and full-scale, this paper discusses the scale effects of the wind loads acting on a self-propelled wind turbine installation jack-up. Furthermore, the effects of topside simplifications on the wind loads and advantages of the applied approach are highlighted.

In the concrete cask, the canister is sealed with lids by welding, and has high sealing performance. But considering long-term storage, there is a concern about loss of the sealing performance due to stress corrosion cracking (SCC). In the concrete cask, unlike the metal cask, it is not mandatory to constantly monitor helium pressure between the lids. However, it is useful from the viewpoint of improving safety during the long-term storage to install a helium leak detector in the canister inside the concrete cask. Currently, we are developing the leak detector utilizing the phenomenon that the surface temperature of the canister changes when helium leaks out of the canister. As part of developing the leak detector of the canister, leak tests were performed using a small canister model as a pressurized vessel and a 1/4.5 scale cask model of the actual cask including the canister. This leak detector utilized the phenomenon that canister bottom temperature (TB) increases and canister lid temperature (TT) decreases when the internal pressure of the canister decreases. In computational fluid dynamics (CFD) calculation, focused on this phenomenon, the influence of the internal pressure and physical properties of internal gas in the canister were examined by calculating conditions of three kinds of pressure and two types of gas (air and helium). The main purpose of the CFD calculation was to confirm the results of the experiment, and we grasped the phenomenon occurring in the canister and elucidated its mechanism. For the CFD calculation, a commercial CFD software, STAR-CCM+® (ver.12.06.010) by Siemens PLM Software Company, was used. A CAD file used for the calculation simulated also the shape inside the canister (e.g. basket, fuel rods). A polyhedral mesh was used for a calculation mesh. In the small canister model, a mesh of its ambient air was not generated, and heat transfer between the canister surface and the ambient air was calculated from a heat transfer correlation equation. On the other hand, in the 1 / 4.5 scale cask model, the mesh of its ambient air was generated, so that the heat transfer on the surface of the canister was calculated according to the actual heat transfer phenomenon. The internal gas and the ambient air of the canister were ideal gas, and buoyancy due to density change was taken into consideration. A realizable k-epsilon model was used for a turbulence model, and a DO model was used for a radiation model.

In the framework of the European research project LEMCOTEC, a section was devoted to the further optimization of the recuperation system of the Intercooled Recuperated Aero engine (IRA engine) concept, of MTU Aero Engines AG. This concept is based on an advanced thermodynamic cycle combining both intercooling and recuperation. The present work is focused only on the recuperation process. This is carried out through a system of heat exchangers mounted inside the hot-gas exhaust nozzle, providing fuel economy and reduced pollutant emissions. The optimization of the recuperation system was performed using computational fluid dynamics (CFD) computations, experimental measurements and thermodynamic cycle analysis for a wide range of engine operating conditions. A customized numerical tool was developed based on an advanced porosity model approach. The heat exchangers were modeled as porous media of predefined heat transfer and pressure loss behaviour and could also incorporate major and critical heat exchanger design decisions in the CFD computations. The optimization resulted in two completely new innovative heat exchanger concepts, named as CORN (COnical Recuperative Nozzle) and STARTREC (STraight AnnulaR Thermal RECuperator), which provided significant benefits in terms of fuel consumption, pollutants emission and weight reduction compared to more conventional heat exchanger designs, thus proving that further optimization potential for this technology exists.

Numerical study on the hull–propeller interaction of autonomous underwater vehicle

ABSTRACTDetailed insight into the hydrodynamics of aeration tanks is of crucial importance for improvements in treatment efficiency, optimization of the process design and energy-efficient operation. These factors have triggered increasing interest in the use of Computational Fluid Dynamics (CFD) to evaluate performance of wastewater treatment systems. Whilst factors such as incorrect input assumptions, poor model choice and excessive simplifications have been recognized as potential sources of output errors, there remains a need to identify the most robust strategy to faithfully simulate aeration tank performance. Therefore, the focus of this work was to undertake rigorous transient simulations of the hydrodynamics and oxygen mass transfer in a lab-scale aeration tank in order to work towards the development of robust modeling guidelines for activated sludge systems. Unlike most previous CFD analyses of aeration systems, the work reported here employed the shear stress transport (SST) turbulence model to account for the turbulent interactions between the phases inducing bubble breakup and/or coalescence, and as a consequence, promoting the formation of bubbles of different sizes and shapes. The results obtained were compared with those arising from an analysis using the standard () model – and assuming fixed bubble diameter- the most common CFD modeling framework used within the wastewater modeling community. Model validation was achieved using acoustic Doppler velocimetry and particle image velocimetry techniques, and experimentally derived oxygen mass transfer data. Limitations of both turbulence models used and modeling assumptions concerning bubbly flow are discussed. The benefits of the SST turbulence model are demonstrated, but the need to balance the increased computational expense of this approach compared to the model and, indeed, bubble flow modeling are recognized. Thus, this paper presents the first rigorous analysis of turbulence model and bubble flow generation models together for activated sludge system optimization.Abbreviations: ADV: Acoustic Doppler velocimetry; AS: Activated sludge; ASM1: Activated Sludge Model No. 1; BOD: Biochemical oxygen demand; CCD: Charge-coupled device; CFD: Computational fluid dynamics; COD: Chemical oxygen demand; CPU: Central processing unit; DO: Dissolved oxygen; GCI: Grid convergence index; HPC: High performance computing; IAC: Interfacial area concentration; MRF: Multiple reference frame; MLSS: Mixed liquor suspended solids; PBM: Population balance models; PIV: Particle image velocimetry; PST: Phase-space thresholding; RAM: Random access memory; RANS: Reynolds-averaged Navier-Stokes; SNR: Signal-to-noise-ratio; SST: Shear stress transport

CFD Simulations of Abnormal Flow in Horizontal Pipes for Offshore Hydrocarbon Transport

Analyzing grid independency and numerical viscosity of computational fluid dynamics for indoor environment applications

Numerical investigation of water forced convection inside a copper metal foam tube: Genetic algorithm (GA) based fuzzy inference system (GAFIS) contribution with CFD modeling

A systematic method was developed for ice-class propeller modeling, performance estimation, strength and integrity evaluation and optimization. To estimate the impact of sea ice on the propeller structure, URI3 rules, established by the International Association of Classification Societies in 2007, were applied for ice loading calculations. An R-class propeller (a type of ice-class propeller) was utilized for subsequent investigations. The propeller modeling was simplified based on a conventional method, which expedited the model building process. The propeller performance was simulated using the computational fluid dynamics (CFD) method. The simulation results were validated by comparison with experimental data. Furthermore, the hydrodynamic pressure was transferred into a finite element analysis (FEA) module for strength assessment of ice-class propellers. According to URI3 rules, the ice loading was estimated based on different polar classes and working cases. Then, the FEA method was utilized to evaluate the propeller strength. The validation showed that the simulation results accorded with recent research results. Finally, an improved optimization method was developed to save the propeller constituent materials. The optimized propeller example had a minimum safety factor of 1.55, satisfying the safety factor requirement of ≥1.5, and reduced the design volume to 88.2% of the original.

This study aims to investigate the icing behavior of unmanned aerial vehicles (UAVs) propellers under different operating conditions. Unlike previous work, a systematic analysis of droplet impingement, heat transfer characteristics, and ice accretion distribution on the blade surface is conducted, revealing the spatial distribution characteristics of propeller icing from multiple perspectives. The propeller flow field is solved using the Reynolds-averaged Navier–Stokes (RANS) equations coupled with the Multiple Reference Frame (MRF) model, the droplet motion and collection are predicted by an Eulerian multiphase approach, and the icing process is modeled using the shear-stress transport-based shallow water film method (SWIM). The results show that higher rotational speeds and larger droplet diameters significantly increase ice accumulation, with more complex ice shapes forming particularly at the blade tip. In contrast, higher temperatures reduce the overall icing amount but alter the spatial distribution of ice. The blade tip region exhibits stronger transport capacity for unfrozen water, leading to faster ice accretion. These findings provide useful guidance for designing more effective anti-icing strategies for UAV propellers.

Aeroacoustic noise produced by high speed face milling cutters is a serious environmental concern. This paper develops a modeling approach to investigate the aeroacoustic noise generation and propagation by the idling face milling cutters. The approach consists of two parts: (1) an aerodynamic model for evaluating the flow fields based on the Navier–Stokes (N–S) equation and (2) an aeroacoustic model for predicting the acoustic noise by using the Ffowcs Williams and Hawkings (FW–H) equation. Both the steady mode with the multiple reference frames (MRF) model and the unsteady mode with the sliding mesh technique by introducing steady flow variables as its initial fields are simulated. The cutter gullet regions and the insert rake face regions are found to be the primary contributors in noise generation through spectral analysis of noise sources. The acoustic noise in face milling is significantly affected by the cutter diameter and the number of cutter teeth. The noise directivity is found in vertical plane, and the irregular tooth spacing can spread the maximum sound power at the rotating frequency to higher frequencies. In addition, experiments are conducted to measure the acoustic noise from two high speed milling cutters. It is found that the experimental results are generally in good agreement with the simulations.