CFD simulations of a performance-scaled wind turbine

Ye, Maokun,Chen, Hamn-Ching,Koop, Arjen Techno-Press 2022 Ocean systems engineering Vol.12 No.2

In the present study, we focus on the CFD simulations for the performance and the rotor-generated wake of a model-scale wind turbine which was designed for wave tank experiments. The CFD simulations with fully resolved rotor geometry are performed using MARIN's community-based open-source CFD code ReFRESCO. The absolute formulation method (AFM) is leveraged to model the rotating wind turbine. The k - ω SST turbulence model is adopted in the incompressible Reynolds Averaged Navier-Stokes (RANS) simulations. First, the thrust and torque coefficients, C_T and C_P, are calculated at different Tip Speed Ratios (TSR), and the results are compared against the experimental data and previous numerical results. The pressure distribution of the turbine blades at the 70% span is obtained and compared to the results obtained by other tools. Then, a verification study aiming at quantifying the discretization uncertainty of the turbine performance with respect to the grid resolution in the wake region is performed. Last, the rotor-generated wake at the TSR of 7 is presented and discussed.

CFD Numerical Simulation of Wind Field and Vehicle Aerodynamic Characteristics on Truss Bridge Deck under Crosswind

Mingjin Zhang,Jinxiang Zhang,Junting Long,Yongle Li,Yulin Zou,Dianguo Yin 대한토목학회 2022 KSCE Journal of Civil Engineering Vol.26 No.12

Due to the complexity and changeability of the wind field in deep-cut gorges, the vehicles on the bridge deck are easily affected by a strong crosswind. Thus, to accurately evaluate the wind field characteristics of a suspension bridge deck, the wind profiles of wind speed and angle of attack (AoA) and the vehicle aerodynamic parameters were investigated by the CFD. The results show that the shape of wind speed profile is mainly controlled by the AoA but less affected by the Reynolds number. The main girder's shielding effect can accelerate the local wind field, and the closer to the windward lane, the less the interference; thus, a suitable location of measuring points to represent the incoming flow is found. Furthermore, the equivalent wind speed based on the equivalent side force is generally larger than the value based on the rolling moment, and the responding value is greatly affected by the AoA. In addition, the vortex is a time-dependent phenomenon, the averaged flow field produced less force in the wake, but the high local wind speed variations may affect the traffic unfavorably. The results provide an essential reference significance for studying the local wind field characteristics of the bridge deck.

Numerical simulation and investigation of jet impingement cooling heat transfer for the rotor blade

Peiravi, Amin,Bozorg, Mohsen Agha Seyyed Mirza,Mostofizadeh, Alireza Techno-Press 2020 Advances in aircraft and spacecraft science Vol.7 No.6

Investigation of leading edge impingement cooling for first stage rotor blades in an aero-engine turbine, its effect on rotor temperature and trailing edge wake loss have been undertaken in this study. The rotor is modeled with the nozzle for attaining a more accurate simulation. The rotor blade is hollowed in order for the coolant to move inside. Also, plenum with the 15 jet nozzles are placed in it. The plenum is fed by compressed fresh air at the rotor hub. Engine operational and real condition is exerted as boundary condition. Rotor is inspected in two states: in existence of cooling technique and non-cooling state. Three-dimensional compressible and steady solutions of RANS equations with SST K-ω turbulent model has been performed for this numerical simulation. The results show that leading edge is one of the most critical regions because of stagnation formation in those areas. Another high temperature region is rotor blade tip for existence of tip leakage in this area and jet impingement cooling can effectively cover these regions. The rotation impact of the jet velocity from hub to tip caused a tendency in coolant streamlines to move toward the rotor blade tip. In addition, by discharging used coolant air from the trailing edge and ejecting it to the turbines main flow by means of the slot in trailing edge, which could reduce the trailing edge wake loss and a total decrease in the blade cooling loss penalty.

The internal flow field simulation of the cyclone separator of different structures

Chen Xin,Liu Jin(유진),Erfan Zal Nezhad 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12

In view of the increasingly serious problems of oily waste water treatment, this paper encompasse d development structure parametric and operating condition of defiling hydrocyclone by CFD simulation. The large eddy simulation was used to calculate the hydrocyclones of different structures. The main aim was to study the effects of different structure sizes and operating conditions on the performances of hydrocyclone. The results showed that in the straight pipe hydrocyclone and taper pipe hydrocyclone, the pressure and flowing radius were positively correlated. The pressure decreased with the reducing of the flowing radius, and the pressure reaches the lowest point at the central axis part. If tangential speed increased, the centrifugal force would be strengthened which can help oil drop move to the center part. Therefore, the separation efficiency was improved. On the contrary, the separation efficiency would decrease. However, it was not true that the bigger the tangential speed was, the better it was. If the tangential speed was too fast, the shear stress borne by the oil drop would increase which may cause the oil drop breakage and would aggravate the oil drop emulsification. This was not benefit to improve the separation efficiency. The oil and water separation effect of the taper pipe hydrocyclone was better than that of straight pipe hydrocyclone.

Study on Drilling Ground Collapse Induced by Groundwater Flow and Prevention Based on a Coupled CFD-DEM Method

Hao-tong Zhou,Chang-qing Liu,Gui-he Wang,Kai Kang,Yu-hong Liu 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.5

Given the hazards caused by drilling ground collapse (DGC) due to groundwater flow in the processes of geotechnical engineering investigation, a coupled computational fluid dynamics and discrete element method (CFD-DEM) method is adopted to numerically simulate the development of hazards. An improved coupling program is employed to realize the two-way coupling between open-source CFD code OpenFOAM and commercial DEM software PFC3D. The coupling program allows complex meshes generated by ANSYS ICEM to be imported into PFC3D. The feasibility and accuracy of the CFD-DEM method are first verified by simulating a single spherical particle settling in hydrostatic water and the formation of the repose angle of sandpiles. Then, this method is adopted to investigate the patterns of stratum deformation and foundation loss, typical particle flow processes, and characteristics of drilling rig toppling. Finally, measures for prevention of DGC induced by groundwater flow are discussed in detail. Two typical strata, including a water-rich sand stratum and a water-rich sand-clay compound stratum, are considered. The research results show that for the water-rich sand stratum, DGC induces a “bowl”-shaped settlement trough, and the maximum value of ground surface settlement is proportional to the foundation loss rate. For the water-rich sand-clay compound stratum, a “jar”-shaped settlement trough is created. Four typical particle flow processes are involved in DGC. The drilling rig topples toward the center of the settlement trough. The maximum displacement appears at the top of the tower and has an approximate linear correlation with the groundwater flow velocity. The measures and methods of DGC prevention are also summarized in detail. The results of this research provide a reference for hazard prevention and delicacy control of DGC induced by groundwater flow.

Comparison of Numerical Simulation and Experiment of Designed Vortex Type Micro hydro Water Turbine

Ema Amalia,Hendarko,Muhammad N Hamzah,Faridl A Maulana,Farhan H Budisatrio,Muhammad Rafie,Mochammad A Moelyadi 한국유체기계학회 2022 International journal of fluid machinery and syste Vol.15 No.3

Vortex type's micro hydro water turbine is a new technology for harvesting energy from water which the performance is still providing more c hallenge . After h aving designed the vortex type water turbine in previous work, a laboratory scale experimental apparatus is built to prove the design and to val idate numerical simulations of the turbine The important design parameters such as torque, powe r, and efficiency are considered. It is found that the CFD results gives higher t orque , power, and efficiency compared to experiments results with a similar tren d This is due to no feature in the used CFD software in evaluating mechanical friction that ha ppened in experim ents device , for more specific in torque meter used Head of CFD for discharge of 2.7 L/s and 2.8 L/s are 0.06 m and 0.06 m while from experimen t is 0.07 m and 0.072 respectively. A NSYS has been used for CFD simulation.

친수성/소수성 수평 표면상에서의 액적이송에 관한 새로운 개념

명현국(Hyon Kook Myong) 대한기계학회 2014 大韓機械學會論文集B Vol.38 No.3

유체이송 기술은 최근 마이크로 유체시스템 개발에서 핵심문제로 인식되고 있다. 본 논문에서는 외부동력을 사용하지 않고 액적을 이송시킬 수 있는 새로운 개념을 제안하고, 수치해석을 통해 증명하였다. 제안된 장치는 표면을 단순하게 친수성과 소수성 표면의 복합표면으로 구성하는 것이다. 새로운 개념을 입증하기 위한 수치해석은 보존적인 압력기반 유한체적방법에 기초한 비정렬 셀 중심 방법 및 VOF 방법에 체적포착법인 CICSAM을 채용하고 있는 자체개발 코드(PowerCFD)를 사용하였다. 연구결과 본 연구에서 제안된 개념이 마이크로 유체시스템에서 액적이송에 대해 우수한 성능을 나타내는 것으로 확인되었다. A fluid transport technique is a key issue for the development of microfluidic systems. In this paper, a new concept for transporting a droplet without external power sources is proposed and verified numerically. The proposed device is a heterogeneous surface which has both hydrophilic and hydrophobic horizontal surfaces. The numerical simulation to demonstrate the new concept is conducted by an in-house solution code (PowerCFD) which employs an unstructured cell-centered method based on a conservative pressure-based finite-volume method with interface capturing method (CICSAM) in a volume of fluid (VOF) scheme for phase interface capturing. It is found that the proposed concept for droplet transport shows superior performance for droplet transport in microfluidic systems.

Numerical Investigation of Jet Interaction for Missile with Continuous Type Side Jet Thruster

Kyoung Tai Kang,Eunseok Lee,Soogab Lee 한국항공우주학회 2015 International Journal of Aeronautical and Space Sc Vol.16 No.2

A continuous type side jet controller which has four nozzles with thrust control devices was considered. It is deployed to a missile for high maneuverability and fast controllability in the terminal guidance phase. However, it causes more complex aerodynamic jet interactions between the side jet and the supersonic free stream than does the conventional impulse type side jet with a small single thruster. In this paper, a numerical investigation of the jet interference effects for the missile equipped with a continuous type side jet thruster is presented. A three-dimensional flow field was simulated by using a commercial unstructured-based CFD solver. The numerical simulation method was validated through comparison with wind tunnel test results for the single jet. The method of defining jet direction for this type of side jet control to minimize simulation cases was also introduced. Flow fields investigation and jet interaction effects for various flow conditions, jet pressure ratios and defined jet direction conditions were performed. From the numerical simulation for the continuous type side jet, extensive aerodynamic interference data were obtained to construct an aerodynamic coefficients database for precise missile control.

전산 풍공학을 이용한 돔구조물의 풍압계수 산정

정재용(Chung Jae-Yong),이승창(Lee Seung-Chang),오정근(Oh Jung-Keun) 대한건축학회 2007 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.27 No.1

Recent advancement of CFD (Computational Fluid Dynamics) technique makes it possible to predict the wind flows around a building and a structure under the wind-induced conditions very close to the actual state. Therefore the practical use of CFD even for wind-resistant design becomes almost realized now. Due to the trend of applicability of CFD, the computed wind-induced pressure distribution on hemispherical domes is estimated. Pressure coefficients, referenced to freestream static pressure, were investigated for domes with height to diameter ratios of 1, 1/2, and 1/3. The results of numerical simulation were compared with tthe experimental data. Based on the results of the numerical simulation obtained in a good agreement with the experimental data. The numerical simulations are used to predict the pressure coefficients on the surfaces of the structure and to evaluate the wind environment. This paper suggests the applicability of the numerical simulation in the field of wind engineering.

Application of numerical simulation to determine ability of air used in MQL method to clean grinding wheel active surface during sharpening of hob cutters

Wojciech Stachurski,Jacek Sawicki,Krzysztof Krupanek,Krzysztof Nadolny 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.4

This article presents the results of experiments concerning a computational fluid dynamics (CFD)/numerical analysis of the flow of air in the grinding zone during the sharpening of the face surface of hob cutters while using the MQL method. The carrying out of a simulation allows one to determine the influence of various settings of the angle of the spray nozzle on the amount of air directly reaching the zone of contact of the grinding wheel with the workpiece, as well as the grinding wheel active surface (GWAS). In the numerical analysis, the ‘SST k-ω ’ model available in the Ansys CFX program was used, and to which the Kato and Lander’s modification was applied. With the aim of verifying the results obtained from the basis of the numerical simulations, experimental testing was conducted. As a verification parameter, the percentage rate of grinding wheel clogging was used. The measurement of clogging was conducted by the optical method taking microscopic images of the grinding wheel active surface (GWAS) and then analysing it which the use of digital processing and image analysis. As a result of the numerical simulations, it was confirmed that the greatest effectiveness in delivering air to the contact zone of the grinding wheel with the workpiece being machined was achieved by setting the nozzle at the lowest of the angles tested (90°). At the same time, the greatest efficiency in delivering air to the grinding wheel active surface was achieved by setting the nozzle at the largest of the angles tested (90°). The experimental tests allowed one to state that the change in the inclination of the spray nozzle does not significantly influence the effectiveness of chip removal from the surface of the intergranular spaces of the grinding wheel. By setting the nozzle at a 90° angle, wall shear stresses τ w have a decisive influence on cleaning the GWAS, while at an angle of 30° the cleaning function is taken on by air being delivered directly into the contact zone of the grinding wheel with the face surface of the hob cutter being sharpened. A comparison of the percentage rates of grinding wheel clogging obtained from using the flood method (WET), as well as the MQL method, indicates the insufficient cleaning ability of the MQL method. A solution to this problem may be the application of additional cleaning nozzles employing streams of compressed air (CA) or cold compressed air (CCA).