Security analysis of 3D-printed wind-energy concentration device in wind tunnel test

Abstract: Wind-energy concentration device model can be efficiently made by 3D (three-dimensional) printers, but its security must be tested. This research adopts a fluid-solid interaction (FSI) method to study the security of the 3D printed wind-energy concentration device model in wind tunnel tests. At first, by using the CAD (computer aided design) software, a solid field model of a wind-energy concentration device is created with a proportion of 1:4.5. Then the solid field model is imported into the finite element analysis software. Based on the size of the wind tunnel, a cubic area of 20 m × 3 m × 3 m (length × width × height) is established, and the concentration device model has the same axial line with the length direction. Then by the Boolean subtraction method, a geometric fluid field is built through subtracting the solid field area in the box area. The interface between the fluid field and the concentration device model is just fluid-solid interaction interface. And the fluid field is simulated and calculated with the help of the CFD (computational fluid dynamics) software. An SST k-ω turbulence model is adopted. In terms of the meshes, a non-uniform tetrahedron meshing is applied. Different numbers of meshes are meshed and the grid independence test is performed. This research takes air as the fluid medium. The temperature is 273.15 K and the pressure is 101325 Pa. The density, velocity, viscosity, thermal conductivity coefficient, constant-pressure specific heat capacity, mass flow rate, turbulent kinetic energy (k value) and specific dissipation rate (ω) are 1.293 kg/m3, 30 m/s, 1.72×10-5 kg/(m·s), 0.0244 W/(m·K), 1005 J/(kg·K), 349.11 kg/s, 1.3336 m2/s2 and 150.6047 s-1, respectively. This research adopts the mass flow inlet and pressure flow outlet. Surface roughness of the wind-energy concentration device model is set to 0.3 mm. When the component residual reaches 1.0×10-4 kg/s, the equation is thought to converge and the distribution of the wind speed in the fluid field is gained. The results show that the mean wind speed of 6 points on the mounting plane of wind turbine in the concentration device is 1.40 times the inlet wind velocity of the whole flow field, proximate to the average time of 1.40 in the actual measurement in the references. This shows that when applied in the wind tunnel with the size and design described in the paper, the simulative calculation based on the 1:4.5 design proportion of wind-energy concentration device model is correct. In the structural static module, the whole solid field is divided into tetrahedral meshes, each structural unit being 0.002 m. The stress cloud plot and the solid field deformation plot are gained after the distribution of wind pressure is loaded on the wind-energy concentration device model. The plots show that the maximum stress area lies on the outer edge of the diffusion pipe, with a maximum stress of 3.5385 MPa. This is far less than the tensile strength of 40.2 MPa and the bending strength of 67.8 MPa in the candidate DSM Somos Imagine 8 000 type photosensitive resin used in the 3D printing. And the maximum deformation is just 1.8675 mm. Therefore, this material satisfies the specifications of strength and resilience and can be adopted in the 3D printing of the wind-energy concentration device model used for the testing of flow field in the wind tunnel.