Influence of the Curvature Correction on Turbulence Models for the Prediction of the Aerodynamic Coefficients of the S809 Airfoil

Using the appropriate procedure, Computational Fluid Dynamics allows predicting many things in several fields, and especially in the field of renewable energies, which has become a promising research axis. The present study aims at highlighting the influence of the curvature correction on turbulence models for the prediction of the aerodynamic coefficients of the S809 airfoil using the Computational Fluid Dynamics code ANSYS Fluent 17.2. Three turbulence models are used: Spalart-Allmaras, Shear Stress Transport k-ω and Transition SST. Experimental results of the 1.8 m × 1.25 m low-turbulence wind tunnel at the Delft University of Technology are used in this work for comparison with the numerical results for a Reynolds number of 106. The results show that the use of the curvature correction improves the prediction of the aerodynamic coefficients for all the turbulence models used. A comparison of the three models is also made using curvature correction since it gave better results. The Transition SST model is the one that gives the best results for the lift coefficient, followed by the Shear Stress Transport kω model, and finally the Spalart-Allmaras model. For the drag coefficient, Transition SST model is the best, followed by the Spalart-Allmaras model, and finally the Shear Stress Transport kω model.

Pengaruh Jumlah Sudu 8, 12, 16 dan 20 terhadap Performa Hidro-Turbin Cross-Flow dengan sudut 15° Menggunakan Metode Computational Fluids Dynamics

<p>Energi listrik merupakan kebutuhan primer dalam kehidupan sehari-hari. Perkembangan teknologi mengakibatkan meningkatnya kebutuhan energi listrik setiap tahunnya. Energi baru terbarukan memasok kebutuhan energi listrik nasional sebesar 14%. Di sisi lain, pemerintah mengharapkan komposisi energi baru terbarukan sebesar 23% hingga 31% pada tahun 2050. Hal ini menunjukan bahwa energi baru terbarukan masih memiliki gap yang cukup tinggi. Penelitian ini merupakan salah satu upaya dalam pengembangan energi baru terbarukan, terutama pada pembangkit listrik mikro-pico hidro. Penelitian ini dilakukan menggunakan metode <em>Computational Fluid Dynamics</em> menggunakan Aplikasi Ansys dengan CFX <em>Solver</em>. Penelitian dilakukan untuk mengetahui pengaruh jumlah sudu pada hidro-turbin <em>cross-flow</em> terhadap performa <em>Coefficient of Power</em>. Peneltian dilakukan pada rotor dengan dimensi diameter 80 mm, panjang 130 mm dan sudut sudu 15°. Variasi jumlah sudu dilakukan pada jumlah sudu 8, 12, 16, dan 20. Simulasi dilakukan pada <em>steady state,</em> dan menggunakan tipe turbulen <em>Shear Stress Transport</em>. Turbin <em>cross-flow</em> beroperasi pada kecepatan air 3m/s dengan kecepatan sudut pada interval 50 sampai 350 RPM. Hasil menunjukan <em>Coefficient of Power Maximum</em> yang dihasilkan untuk sudu 8,12, 16 dan 20 adalah 10,8%; 14,1%; 16,8% dan 20,1%. Dari hasil tersebut menunjukan performa maksimal dihasilkan oleh hidro-turbin tipe <em>cross-flow</em> dengan jumlah sudu rotor 20.</p>

Calibration of CFD grid for simulating the impeller clearance flow and axial hydraulic force of centrifugal pump

The axial hydraulic force of centrifugal pump is an important parameter affecting pump performance. The force mainly includes the force inside impeller and in clearance. Due to the special structural characteristics of the clearance, the influence of grid discretization method on the calculation of axial force in the clearance is not fully understood. Therefore, based on the Reynolds-averaged method with shear stress transport turbulence model, an orthogonal experiment was designed to compare the correlation coefficient of velocity and pressure distribution between shear stress transport model and large eddy simulation models. A more suitable grid discretization strategy was found by artificial neural network for grid calibration. When the strategy is applied to the entire centrifugal pump, the prediction of axial force has high accuracy. The range analysis shows that the grid node number in the wall-wall direction has the greatest impact on velocity distribution. When the mesh parameters are in a certain range, it can compromise between the simulation accuracy and computational resource. The Reynolds-averaged model based simulation is proved accurate in capturing the complex velocity and pressure field inside clearance. The entire pump model is also used for the verification after the calibration of grid. The typical axial force law can be found under different flow rate conditions. This study provides a significant guidance in determining the grid scheme for accurate prediction of centrifugal pump’s axial force. It makes the computational fluid dynamics simulation feasible in the initial design of centrifugal pump which specifically considers the axial force problem.

ANALISA PERFORMA HIDRO-TURBIN CROSS-FLOW DENGAN SUDUT DIAMETER RUNNER 10° DAN JUMLAH SUDU 8, 16, DAN 24 MENGGUNAKAN METODE CFD

Hidro turbin adalah salah satu komponen utama pada pembangkit listrik tenaga air. Penelitian terhadap turbin air memiliki peran penting dalam pengembangan renewable energy yang bersumber dari tenaga hidro. Dimana Indonesia memiliki potensi sumber energi hidro yang sangat besar. Hidro-turbin memiliki beberapa jenis yaitu turbin Sumbu Horizontal, Turbin Sumbu vertical dan turbin Cross-Flow. Penelitian ini dilakukan pada turbin air tipe Cross-Flow, dan dilakukan dengan metode Computational Fluid Dynamics (CFD). Simulasi dilakukan secara tiga dimensi dan menggunakan perangkat lunak Ansys Student 2021 dengan solver CFX. Turbin cross-flow menggunakan runner dengan sudut 10°, dengan variasi jumlah sudu 8, 16, dan 24. Penelitian ini bertujuan untuk mengetahui performa turbin Cross-flow dan mengetahui pengaruh jumlah sudu pada performa tersebut. Turbin Cross-flow beroperasi pada kecepatan fluida 3m/s dan angular velocity 50-250 rpm. Simulasi menggunakan tipe turbulensi Shear Stress Transport dalam kondisi tunak, Hasil menunjukan turbin cross-flow dengan sudut runner 10o dan jumlah sudu 24 memiliki performa terbaik bila dibandingkan dengan jumlah sudu 8 dan 16.

Analysis and research on vehicle wading performance

With the inclusion of the effects from wheels rotation, vehicle wading phenomenon was simulated using computational fluid dynamics tools and compared with road wading test. The new method utilizing the volume of fluid model to simulate the two-phase (water and air) flow when vehicle wades, Reynolds-Averaging Navier–Stokes simulation with both Realizable and shear stress transport turbulent models were conducted and the results indicated that the essential features of vehicle wading phenomenon were captured accurately. A relatively better correlation is achieved between computational fluid dynamics analysis and road test when shear stress transport turbulent model was utilized compared to using Realizable turbulent model. With the addition of the wheel rotation effects in vehicle wading simulation, the potential risks of water intrusion into the critical chassis and electronic components can be early detected and the frequent late design changes can be avoided. The new approach adopted in this study with VOF model and RANS simulation with SST turbulent model has shown that the benefits of shorter vehicle development cycles and parts warranty cost reduction. Thus, the results from computational fluid dynamics simulation with wheel rotation effects included can serve as the design guidance for any future vehicle wading developments.