Simulation Of 3D Flow Field Research Articles

Numerical Simulation of 3D Flow Field and Flow-Induced Noise Characteristics in a T-Shaped Reducing Tee Junction

The so-called T-shaped reducing tees are typically used to divide, change and control (to a certain extent) the flow direction in pipe networks. In this study, the Ffowcs Williams–Hawkings (FW-H) equation and the Large Eddy Simulation (LES) methods are used to simulate the flow-induced noise related to T-shaped reducing tees under different inlet flow velocities and for different pipe diameter ratios. The results show that the maximum flow velocity, average flow velocity, and vorticity in the branch pipe increase gradually as the related diameter decreases. Strong vorticity and secondary flows are also observed in the branch pipe, and the associated violent pressure fluctuations are found to be the main sources of flow-induced noise. In particular, as the pipe diameter ratio decreases from 1 to 0.45, the Total Sound Pressure Level (TSPL) increases by 6.8, 6.26, and 7.43 dB for values of the inlet flow velocity of 1, 2, and 3 m/s, respectively. The distribution characteristics of the flow-induced noise in the frequency domain follow similar trends for different pipe diameter ratios.

Performance prediction of a horizontal axis wind turbine using BEM and CFD methods

In this study, a combination of CFD (Computational Fluid Dynamics) and BEM (Blade Element Momentum Method) methods are used to simulate the flow field around a wind turbine rotor with horizontal axis. The main objectives are to predict the aerodynamic performances such as forces and torque imposed on the rotor blades which are essential to its structure or design. This approach requires much less computing time and memory than three-dimensional simulation flow around the wind turbine rotor with simple CFD method. The flow is assumed unsteady, incompressible and fully turbulent. This work consists of two parts: -The Calculation of aerodynamic coefficients by the CFD method, using Ansys / Fluent software. -The Simulation of 3D flow field through the rotor of the wind turbine using the BEM method. The obtained results are in good agreement with the experimental measurements.

Investigation of the Effects of Airfoil-probes on the Aerodynamic Performance of an Axial Compressor

In order to investigate the effects of the airfoil-probes on the aerodynamic performance of an axial compressor, a numerical simulation of 3D flow field is performed in a 1.5-stage axial compressor with airfoil-probes installed at the stator leading-edge (LE). The airfoil-probes have a negative influence on the compressor aerodynamic performance at all operating points. A stream-wise vortex is induced by the airfoil-probe along both sides of the blade. At the mid-operating point, the vortex is notable along the pressure side and is relatively small along the suction side (SS). At the near-stall point, the vortex is slightly suppressed in the pressure surface (PS), but becomes remarkable in the suction side. A small local-separation is induced by the interactions between the vortex and the end-wall boundary layer in the corner region near the hub. That the positive pitch angle of the airfoil-probe at 6.5% span is about 15° plays an important role in the vortex evolution near the hub, which causes the fact that the airfoil-probe near the hub has the largest effects among the four airfoil-probes. In order to get a further understanding of the vortex evolution in the stator in the numerical simulation, a flow visualization experiment in a water tunnel is performed. The flow visualization results give a deep insight into the evolution of the vortex induced by the airfoil-probe.

Dynamic Simulation of 3D Flow Field of Train Damper

Hydraulic damper is an important component of the travel unit of train,its damping characteristics are fulfilled by a group of damper valves of special structure.In order to optimize the whole runner structure of hydraulic damper cylinder and analyze the influence of local flow field on the damping characteristics when the key damper valve is in different open positions,it is necessary to use fluid dynamic 3D simulation calculation method to estimate its characteristics.Aiming at the structure and parameters of vertical damper used on a train of typical structure,a corresponding mathematical model and physical model are built.Alternating flow fields in valve body and in inner and outer cylinders under various typical vibration conditions are simulated by using CFX adaptive dynamic grid technology,then velocity fields,pressure fields and streamline distributions of corresponding runners are obtained.By further using visualized analysis method based on 3D flow field,the fluid flow condition of every key runner is reflected clearly and roundly.The obtained working curve of damper agrees with the practical standard characteristic curve,thus proving the feasibility of the analytical models and the effectiveness of the simulation method,which provides theory basis for analyzing the damper energy dissipation process from the mechanism,and also provides a quick and effective way for structure optimization design of runner.