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Wind Tunnels and Experimental Fluid Dynamics Research Part 18

Tham khảo tài liệu 'wind tunnels and experimental fluid dynamics research part 18', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 668 Wind Tunnels and Experimental Fluid Dynamics Research Lengthwise pressure centre coefficient is shown in figure 11. Fig. 11. Lengthwise pressure centre coefficient Front axial force coefficient is shown in figure 12. Fig. 12. Front axial force coefficient 2.5.3 CFD results There are four kinds of grid. The first step is to value which kind of grid is more suitable for this dome CFD simulation. The drag comparison table is shown in table 2. Compared with the wind tunnel experiments result the structire grid is more suitable for this kind of simulation. Then using the structure grid more CFD simulations have been done. And we can get the precision of CFD simulation. The comparison table is shown in table 3. Wind Tunnel Experiments for Supersonic Optical-electrical Seeker s Dome Design 669 Speed Ma 0.6 0.95 1.5 2 2.6 Structure grid 12.915 109.535 486.925 950.299 1625.430 Un-structure grid 26.973 138.798 509.046 969.552 1704.025 Mix grid 30.069 158.682 508.339 978.657 1708.466 Polyhedra grid 17.373 111.899 501.365 970.484 1672.004 Table 2. Drag comparison table CFD Wind tunnel error 0.4Ma 4 Drag 74.6 70.5 5 Lift 289.9 272.3 6 Pressure centre 1306 1418 7.8 0.6Ma 6 Drag 169.3 149.4 13 Lift 1016.6 982.9 3.5 Pressure centre 1362 1448 6 0.8Ma 8 Drag 308.1 272.7 13.2 Lift 2643.2 2569.1 2.9 Pressure centre 1526 1457 4.5 1.1Ma 4 Drag 1367.9 1164.5 17 Lift 2815.4 2640.7 6 Pressure centre 1561 1408 10 1.5Ma 0 Drag 2619.4 2289.3 14 Lift -43 0 - Pressure centre 1182 1294 9 2Ma 2 Drag 4349.9 4154.2 3.8 Lift 2198.3 2594.6 15 Pressure centre 1528 1434 6.5 2.5Ma 5 Drag 6374.3 6260.2 0.98 Lift 8220.2 8462.9 2.9 Pressure centre 1497 1462 2.4 3Ma 10 Drag 8372.5 8591.5 2.5 Lift 23255.2 23469.4 0.9 Pressure centre 1529 1471 3.9 Table 3. CFD and wind tunnel experiments comparison table The biggest error is the drag value at Mach 1.1 attack angle 4 and the best CFD simulation is the lift value at Mach 3 attack angle 10 . The average drag error is 8.685 the average lift value is 5.314 and