scholarly journals Numerical Study of the Unsteady Aerodynamic Performance of Two Maglev Trains Passing Each Other in Open Air Using Different Turbulence Models

2021 ◽  
Vol 11 (24) ◽  
pp. 11894
Author(s):  
Xianli Li ◽  
Siniša Krajnovic ◽  
Dan Zhou
Keyword(s):  
Numerical Study ◽  
Turbulence Models ◽  
Simulation Method ◽  
Aerodynamic Performance ◽  
Transient Pressure ◽  
Near Wake ◽  
Strong Change ◽  
Maximum Value ◽  
The Difference ◽  
Drag And Lift

The strong change in the flow fields around two maglev trains (MTs) passing each other in open air may affect their manoeuvrability and passengers’ comfort. In this study, we evaluated the aerodynamic performance of two MTs passing each other via shear stress transport (SST) k–ω model and improved delayed detached eddy simulations based on the Spalart–Allmaras model (SA−IDDES) and the SST k–ω model (SST−IDDES). The accuracy of the numerical simulation method was verified using experimental data acquired from a moving model test. The results showed that the difference in the amplitude of the transient pressure obtained with the different turbulence models was less than 5%. The wake vortex structures on the intersection side were found to interact, and their intensity consequently decreased. The SST−IDDES model produced smaller-scale vortices than the SA−IDDES model, particularly in the near-wake region. There were large differences in the drag and lift forces obtained using the different turbulence models. Among them, the lift force of the tail car was more sensitive to the turbulence model, and its maximum value obtained with the SST−IDDES model was 11% larger than that obtained with the SA−IDDES model.

Yawed Effect on Wind Turbine Near Wake

2014 ◽  
Author(s):  
Yuntian Ge ◽  
Xiuling Wang
Keyword(s):  
Wind Turbine ◽  
Flow Pattern ◽  
Wind Turbines ◽  
Air Flow ◽  
Aerodynamic Performance ◽  
Wake Flow ◽  
Near Wake ◽  
Rotation Plane ◽  
The Difference ◽  
Ansys Workbench

Wind turbines rotation was motivated by the force of wind. In reality, wind doesn’t moving vertically to the wind turbine rotation plane, but in random directions instead. Therefore, the yawed effect has to be taken into consideration when study wind turbine aerodynamic performance. The purpose of this study is to compare the difference between the wind turbine near wake flow with yawed effect and without yawed effect aerodynamically. The research uses CFD technology to simulate the rotation movement and air flow pattern, which is completed in software Ansys Workbench.

Numerical Study of the Roughness Influence on NACA 63-430 Profile Aerodynamic Performance

2016 ◽  
Vol 10 (4) ◽  
pp. 231
Author(s):  
Abdekarim Tebbal ◽  
Fethi Saidi ◽  
Boualem Noureddine ◽  
Bachir Imine ◽  
Benameur Hamoudi
Keyword(s):  
Numerical Study ◽  
Aerodynamic Performance

CFD study of aerodynamic performance of non-pneumatic tyre with hexagonal spokes

2021 ◽  
pp. 095440702110131
Author(s):  
Daksh Bhatia ◽  
Praneeth KR ◽  
Babu Rao Ponangi ◽  
Meghana Athadkar ◽  
Carine V Dsouza
Keyword(s):  
Comparative Study ◽  
Lift Coefficient ◽  
Aerodynamic Performance ◽  
Practical Implementation ◽  
Air Velocity ◽  
Aerodynamic Forces ◽  
Steering Angle ◽  
Camber Angle ◽  
Drag And Lift ◽  
Yaw Angle

Non-pneumatic tyres (NPT) provide a greater advantage over the pneumatic type owing to their construct which increases the reliability of the tyre operation and effectively reduces maintenance involved. Analysing the aerodynamic forces acting on a NPT becomes a crucial factor in understanding it’s suitability for practical implementation. In the present work, the aerodynamic performance of a NPT using CFD tool – SimScale® is studied. This work includes a comparative study of a pneumatic tyre, a NPT with wedge spokes and a NPT with hexagonal spokes (NPT-HS). The effect of air velocity, steering (yaw) angle and camber angle on the aerodynamic performance of the NPT-HS is evaluated using CFD. By increasing the steering angle from 0° to 15°, the lift coefficient decreases by 37% approximately at all velocities. Whereas drag coefficient initially decreases by 21% till 7.5° steering angle and then starts increasing. Increasing camber angle from 0° to 1.5°, both drag and lift coefficients goes on decreasing by approximately 7% and 27% respectively.

scholarly journals Equivalent Scalar Stress Formulation Taking into Account Non-Resolved Turbulent Scales

2021 ◽  
Author(s):  
Lucas Konnigk ◽  
Benjamin Torner ◽  
Martin Bruschewski ◽  
Sven Grundmann ◽  
Frank-Hendrik Wurm
Keyword(s):  
Mechanical Stress ◽  
Turbulence Models ◽  
Turbulent Channel Flow ◽  
Simulation Method ◽  
Blood Damage ◽  
Stress Calculation ◽  
High Risk Factors ◽  
Cardiovascular Engineering ◽  
Scalar Stress ◽  
Definition Of

Abstract Purpose Cardiovascular engineering includes flows with fluid-dynamical stresses as a parameter of interest. Mechanical stresses are high-risk factors for blood damage and can be assessed by computational fluid dynamics. By now, it is not described how to calculate an adequate scalar stress out of turbulent flow regimes when the whole share of turbulence is not resolved by the simulation method and how this impacts the stress calculation. Methods We conducted direct numerical simulations (DNS) of test cases (a turbulent channel flow and the FDA nozzle) in order to access all scales of flow movement. After validation of both DNS with literature und experimental data using magnetic resonance imaging, the mechanical stress is calculated as a baseline. Afterwards, same flows are calculated using state-of-the-art turbulence models. The stresses are computed for every result using our definition of an equivalent scalar stress, which includes the influence from respective turbulence model, by using the parameter dissipation. Afterwards, the results are compared with the baseline data. Results The results show a good agreement regarding the computed stress. Even when no turbulence is resolved by the simulation method, the results agree well with DNS data. When the influence of non-resolved motion is neglected in the stress calculation, it is underpredicted in all cases. Conclusion With the used scalar stress formulation, it is possible to include information about the turbulence of the flow into the mechanical stress calculation even when the used simulation method does not resolve any turbulence.

A numerical study on combined baffles quick-separation device

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Ehsan Dehdarinejad ◽  
Morteza Bayareh ◽  
Mahmud Ashrafizaadeh
Keyword(s):  
Turbulent Flows ◽  
Separation Efficiency ◽  
Numerical Study ◽  
Turbulence Models ◽  
Complete Separation ◽  
Solid Particles ◽  
Flow Rates ◽  
Separation Device ◽  
Coupling Technique ◽  
Laminar And Turbulent Flows

Abstract The transfer of particles in laminar and turbulent flows has many applications in combustion systems, biological, environmental, nanotechnology. In the present study, a Combined Baffles Quick-Separation Device (CBQSD) is simulated numerically using the Eulerian-Lagrangian method and different turbulence models of RNG k-ε, k-ω, and RSM for 1–140 μm particles. A two-way coupling technique is employed to solve the particles’ flow. The effect of inlet flow velocity, the diameter of the splitter plane, and solid particles’ flow rate on the separation efficiency of the device is examined. The results demonstrate that the RSM turbulence model provides more appropriate results compared to RNG k-ε and k-ω models. Four thousand two hundred particles with the size distribution of 1–140 µm enter the device and 3820 particles are trapped and 380 particles leave the device. The efficiency for particles with a diameter greater than 28 µm is 100%. The complete separation of 22–28 μm particles occurs for flow rates of 10–23.5 g/s, respectively. The results reveal that the separation efficiency increases by increasing the inlet velocity, the device diameter, and the diameter of the particles.

scholarly journals Characterization of aerodynamic performance of ducted wind turbines: A numerical study

Wind Energy ◽  
2019 ◽  
Vol 22 (12) ◽  
pp. 1655-1666 ◽  
Author(s):  
Vinit V. Dighe ◽  
Gael Oliveira ◽  
Francesco Avallone ◽  
Gerard J. W. Bussel
Keyword(s):  
Wind Turbines ◽  
Numerical Study ◽  
Aerodynamic Performance

Magnetocrystalline Anisotropy and Twinning Stress of 10M and 2M Martensites in Ni-Mn-Ga System

2006 ◽  
Vol 512 ◽  
pp. 195-200 ◽  
Author(s):  
Nariaki Okamoto ◽  
Takashi Fukuda ◽  
Tomoyuki Kakeshita ◽  
Tetsuya Takeuchi
Keyword(s):  
Magnetic Field ◽  
Shear Stress ◽  
Magnetocrystalline Anisotropy ◽  
Anisotropy Constant ◽  
The Other ◽  
Magnetic Shear ◽  
Maximum Value ◽  
Twinning Plane ◽  
Twinning Shear ◽  
The Difference

Ni2MnGa alloy with 10M martensite exhibits rearrangement of martensite variants (RMV) by magnetic field, but Ni2.14Mn0.92Ga0.94 with 2M martensite does not. In order to explain the difference, we measured uniaxial magnetocrystalline anisotropy constant Ku and the stress required for twinning plane movement τreq in these alloys. Concerning the former alloy, the maximum value of magnetic shear stress acting across twinning plane τmag, which is evaluated as |Ku| divided by twinning shear, becomes larger than τr eq. On the other hand, concerning the latter alloy, the maximum of τmag is only one-tenth of τreq at any temperature examined. Obviously, the relation, τmag> τr eq, is satisfied when RMV occurs by magnetic field and vice versa. In this martensite, the large twinning shear of 2M martensite is responsible for small τmag and large τreq.

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