Figure 1.
Aircraft geometry model divided into triangle elements.
Figure 1.
Aircraft geometry model divided into triangle elements.
Figure 2.
Schematic diagram of rotating element and rotation axis.
Figure 2.
Schematic diagram of rotating element and rotation axis.
Figure 3.
Comparison of sound pressure between the calculated result and experimental data of an experimental rotor.
Figure 3.
Comparison of sound pressure between the calculated result and experimental data of an experimental rotor.
Figure 4.
Comparison of dynamic RCS between the calculated result and FEKO result of a tilt-rotor model.
Figure 4.
Comparison of dynamic RCS between the calculated result and FEKO result of a tilt-rotor model.
Figure 5.
Three views of geometry model of coaxial tilt-rotor aircraft.
Figure 5.
Three views of geometry model of coaxial tilt-rotor aircraft.
Figure 6.
Schematic diagram and model elements of CSM for coaxial rotor: (a) Compass angle ≤ 90°, (b) Compass angle > 90°.
Figure 6.
Schematic diagram and model elements of CSM for coaxial rotor: (a) Compass angle ≤ 90°, (b) Compass angle > 90°.
Figure 7.
The relationship between situation “left scissors angle = 0°, right scissors angle = 20°” (a) and situation “left scissors angle = 90°, right scissors angle = 110°” (b).
Figure 7.
The relationship between situation “left scissors angle = 0°, right scissors angle = 20°” (a) and situation “left scissors angle = 90°, right scissors angle = 110°” (b).
Figure 8.
Schematic diagram of simulation in helicopter mode.
Figure 8.
Schematic diagram of simulation in helicopter mode.
Figure 9.
Schematic diagram of simulation in fixed-wing mode.
Figure 9.
Schematic diagram of simulation in fixed-wing mode.
Figure 10.
Carpet diagrams of noise SPL in helicopter mode at an azimuth angle = 0° with the scissors angle difference = (a) 0°, (b) 30°, (c) 60°, (d) 90°.
Figure 10.
Carpet diagrams of noise SPL in helicopter mode at an azimuth angle = 0° with the scissors angle difference = (a) 0°, (b) 30°, (c) 60°, (d) 90°.
Figure 11.
Carpet diagrams of noise SPL in helicopter mode at an azimuth angle = 90° with a scissors angle difference = (a) 0°, (b) 30°, (c) 60°, (d) 90°.
Figure 11.
Carpet diagrams of noise SPL in helicopter mode at an azimuth angle = 90° with a scissors angle difference = (a) 0°, (b) 30°, (c) 60°, (d) 90°.
Figure 12.
Carpet diagrams of noise SPL in helicopter mode at an azimuth angle = 180° with a scissors angle difference = (a) 0°, (b) 30°, (c) 60°, (d) 90°.
Figure 12.
Carpet diagrams of noise SPL in helicopter mode at an azimuth angle = 180° with a scissors angle difference = (a) 0°, (b) 30°, (c) 60°, (d) 90°.
Figure 13.
Carpet diagrams of noise SPL in fixed-wing mode at an azimuth angle = 0° with scissors angle difference = (a) 0°, (b) 30°, (c) 60°, (d) 90°.
Figure 13.
Carpet diagrams of noise SPL in fixed-wing mode at an azimuth angle = 0° with scissors angle difference = (a) 0°, (b) 30°, (c) 60°, (d) 90°.
Figure 14.
Carpet diagrams of noise SPL in fixed-wing mode at an azimuth angle = 90° with scissors angle difference = (a) 0°, (b) 30°, (c) 60°, (d) 90°.
Figure 14.
Carpet diagrams of noise SPL in fixed-wing mode at an azimuth angle = 90° with scissors angle difference = (a) 0°, (b) 30°, (c) 60°, (d) 90°.
Figure 15.
Carpet diagrams of noise SPL in fixed-wing mode at an azimuth angle = 180° with scissors angle difference = (a) 0°, (b) 30°, (c) 60°, (d) 90°.
Figure 15.
Carpet diagrams of noise SPL in fixed-wing mode at an azimuth angle = 180° with scissors angle difference = (a) 0°, (b) 30°, (c) 60°, (d) 90°.
Figure 16.
Carpet diagrams of average RCS in helicopter mode at an azimuth angle = 0° with scissors angle difference = (a) 0°, (b) 30°, (c) 60°, (d) 90°.
Figure 16.
Carpet diagrams of average RCS in helicopter mode at an azimuth angle = 0° with scissors angle difference = (a) 0°, (b) 30°, (c) 60°, (d) 90°.
Figure 17.
Carpet diagrams of average RCS in helicopter mode at an azimuth angle = 90° with scissors angle difference = (a) 0°, (b) 30°, (c) 60°, (d) 90°.
Figure 17.
Carpet diagrams of average RCS in helicopter mode at an azimuth angle = 90° with scissors angle difference = (a) 0°, (b) 30°, (c) 60°, (d) 90°.
Figure 18.
Carpet diagrams of average RCS in helicopter mode at an azimuth angle = 180° with scissors angle difference = (a) 0°, (b) 30°, (c) 60°, (d) 90°.
Figure 18.
Carpet diagrams of average RCS in helicopter mode at an azimuth angle = 180° with scissors angle difference = (a) 0°, (b) 30°, (c) 60°, (d) 90°.
Figure 19.
Carpet diagrams of average RCS in fixed-wing mode at an azimuth angle = 0° with scissors angle difference = (a) 0°, (b) 30°, (c) 60°, (d) 90°.
Figure 19.
Carpet diagrams of average RCS in fixed-wing mode at an azimuth angle = 0° with scissors angle difference = (a) 0°, (b) 30°, (c) 60°, (d) 90°.
Figure 20.
Carpet diagrams of average RCS in fixed-wing mode at an azimuth angle = 90° with scissors angle difference = (a) 0°, (b) 30°, (c) 60°, (d) 90°.
Figure 20.
Carpet diagrams of average RCS in fixed-wing mode at an azimuth angle = 90° with scissors angle difference = (a) 0°, (b) 30°, (c) 60°, (d) 90°.
Figure 21.
Carpet diagrams of average RCS in fixed-wing mode at an azimuth angle = 180° with scissors angle difference = (a) 0°, (b) 30°, (c) 60°, (d) 90°.
Figure 21.
Carpet diagrams of average RCS in fixed-wing mode at an azimuth angle = 180° with scissors angle difference = (a) 0°, (b) 30°, (c) 60°, (d) 90°.
Figure 22.
View of a coaxial tilt-rotor aircraft with PPC1.
Figure 22.
View of a coaxial tilt-rotor aircraft with PPC1.
Figure 23.
View of a coaxial tilt-rotor aircraft with PPC2.
Figure 23.
View of a coaxial tilt-rotor aircraft with PPC2.
Figure 24.
View of a coaxial tilt-rotor aircraft with PPC3.
Figure 24.
View of a coaxial tilt-rotor aircraft with PPC3.
Table 1.
Sizes of mesh generations of different parts of aircraft model.
Table 1.
Sizes of mesh generations of different parts of aircraft model.
Part | Mesh Size/mm |
---|
Fuselage | 0.5 |
Tail | 0.1 |
Wings | 0.1 |
Rotor nacelles | 0.1 |
Rotor shafts | 0.1 |
Blades | 0.05 |
Table 2.
Numerical values of the geometry parameters of the coaxial tilt-rotor aircraft model.
Table 2.
Numerical values of the geometry parameters of the coaxial tilt-rotor aircraft model.
Parameter | Value | Parameter | Value |
---|
| 5.2 m | | 17 m |
| 2 m | | 12 m |
| 13.6 m | | 5.3 m |
Table 3.
Various parameters of the 12 simulation cases considered in this paper.
Table 3.
Various parameters of the 12 simulation cases considered in this paper.
Case | Azimuth Angle/° | Flight Mode | Calculation |
---|
1 | 0 | Helicopter | Noise |
2 | 90 | Helicopter | Noise |
3 | 180 | Helicopter | Noise |
4 | 0 | Fixed-wing | Noise |
5 | 90 | Fixed-wing | Noise |
6 | 180 | Fixed-wing | Noise |
7 | 0 | Helicopter | Dynamic RCS |
8 | 90 | Helicopter | Dynamic RCS |
9 | 180 | Helicopter | Dynamic RCS |
10 | 0 | Fixed-wing | Dynamic RCS |
11 | 90 | Fixed-wing | Dynamic RCS |
12 | 180 | Fixed-wing | Dynamic RCS |
Table 4.
Fixed parameters of 12 simulation cases considered in this paper.
Table 4.
Fixed parameters of 12 simulation cases considered in this paper.
Elevation Angle/° | Distance between Observer and Aircraft/m | Speed in Helicopter Mode/(km/h) | Speed in Fixed-Wing Mode/(km/h) |
---|
45 | 1000 | 0 | 500 |
Table 5.
Maximum and minimum SPL values at an azimuth angle = 0° in helicopter mode.
Table 5.
Maximum and minimum SPL values at an azimuth angle = 0° in helicopter mode.
Scissors Angle Difference/° | Maximum Value/dB | Minimum Value/dB |
---|
0 | 56.5 | 46.1 |
30 | 53.6 | 45.2 |
60 | 56.5 | 46.1 |
90 | 53.6 | 45.2 |
Table 6.
Maximum and minimum SPL values at an azimuth angle = 90° in helicopter mode.
Table 6.
Maximum and minimum SPL values at an azimuth angle = 90° in helicopter mode.
Scissors Angle Difference/° | Maximum Value/dB | Minimum Value/dB |
---|
0 | 56.4 | 46.8 |
30 | 53.5 | 49.2 |
60 | 56.4 | 46.8 |
90 | 53.5 | 49.2 |
Table 7.
Maximum and minimum SPL values at an azimuth angle = 180° in helicopter mode.
Table 7.
Maximum and minimum SPL values at an azimuth angle = 180° in helicopter mode.
Scissors Angle Difference/° | Maximum Value/dB | Minimum Value/dB |
---|
0 | 56.5 | 46.3 |
30 | 53.6 | 45.1 |
60 | 56.5 | 46.3 |
90 | 53.6 | 45.1 |
Table 8.
Maximum and minimum SPL values at an azimuth angle = 0° in fixed-wing mode.
Table 8.
Maximum and minimum SPL values at an azimuth angle = 0° in fixed-wing mode.
Scissors Angle Difference/° | Maximum Value/dB | Minimum Value/dB |
---|
0 | 74.0 | 67.6 |
30 | 71.1 | 65.1 |
60 | 74.0 | 67.6 |
90 | 71.1 | 65.1 |
Table 9.
Maximum and minimum SPL values at an azimuth angle = 90° in fixed-wing mode.
Table 9.
Maximum and minimum SPL values at an azimuth angle = 90° in fixed-wing mode.
Scissors Angle Difference/° | Maximum Value/dB | Minimum Value/dB |
---|
0 | 72.5 | 64.6 |
30 | 69.5 | 63.9 |
60 | 72.5 | 64.6 |
90 | 69.5 | 63.9 |
Table 10.
Maximum and minimum SPL values at an azimuth angle = 180° in fixed-wing mode.
Table 10.
Maximum and minimum SPL values at an azimuth angle = 180° in fixed-wing mode.
Scissors Angle Difference/° | Maximum Value/dB | Minimum Value/dB |
---|
0 | 68.2 | 55.4 |
30 | 65.3 | 58.5 |
60 | 68.2 | 55.4 |
90 | 65.3 | 58.5 |
Table 11.
Maximum and minimum average RCS values at an azimuth angle = 0° in helicopter mode.
Table 11.
Maximum and minimum average RCS values at an azimuth angle = 0° in helicopter mode.
Scissors Angle Difference/° | Maximum Value/dBsm | Minimum Value/dBsm |
---|
0 | 7.8 | 6.3 |
30 | 7.6 | 6.6 |
60 | 7.8 | 6.3 |
90 | 7.6 | 6.6 |
Table 12.
Highest and lowest average RCS values at an azimuth angle = 90° in helicopter mode.
Table 12.
Highest and lowest average RCS values at an azimuth angle = 90° in helicopter mode.
Scissors Angle Difference/° | Maximum Value/dBsm | Minimum Value/dBsm |
---|
0 | 25.6259 | 25.5916 |
30 | 25.6154 | 25.5873 |
60 | 25.6251 | 25.5898 |
90 | 25.6176 | 25.5849 |
Table 13.
Highest and lowest average RCS values at an azimuth angle = 180° in helicopter mode.
Table 13.
Highest and lowest average RCS values at an azimuth angle = 180° in helicopter mode.
Scissors Angle Difference/° | Maximum Value/dBsm | Minimum Value/dBsm |
---|
0 | 5.2 | 3.9 |
30 | 5.1 | 3.8 |
60 | 5.2 | 4.0 |
90 | 5.2 | 3.9 |
Table 14.
Maximum and minimum average RCS values in fixed-wing mode at an azimuth angle = 0°.
Table 14.
Maximum and minimum average RCS values in fixed-wing mode at an azimuth angle = 0°.
Scissors Angle Difference/° | Maximum Value/dBsm | Minimum Value/dBsm |
---|
0 | 5.0 | 3.2 |
30 | 4.5 | 3.3 |
60 | 5.0 | 3.2 |
90 | 4.5 | 3.3 |
Table 15.
Highest and lowest average RCS values at an azimuth angle = 90° in fixed-wing mode.
Table 15.
Highest and lowest average RCS values at an azimuth angle = 90° in fixed-wing mode.
Scissors Angle Difference/° | Maximum Value/dBsm | Minimum Value/dBsm |
---|
0 | 29.5128 | 29.4957 |
30 | 25.5128 | 25.4964 |
60 | 29.5128 | 29.4957 |
90 | 25.5128 | 25.4964 |
Table 16.
Highest and lowest average RCS values at an azimuth angle = 180° in fixed-wing mode.
Table 16.
Highest and lowest average RCS values at an azimuth angle = 180° in fixed-wing mode.
Scissors Angle Difference/° | Maximum Value/dBsm | Minimum Value/dBsm |
---|
0 | 3.8 | 2.0 |
30 | 3.4 | 2.1 |
60 | 3.8 | 2.0 |
90 | 3.4 | 2.1 |
Table 17.
Noise SPL and average RCS values with CSM phase parameters of Equations (43)–(46).
Table 17.
Noise SPL and average RCS values with CSM phase parameters of Equations (43)–(46).
| Helicopter Mode | Fixed-Wing Mode |
---|
Noise SPL/dB | Average RCS/dBsm | Noise SPL/dB | Average RCS/dBsm |
---|
Azimuth angle = 0° | 49.1 | 6.7 | 69.5 | 3.4 |
Azimuth angle = 90° | 49.1 | 25.6 | 64.9 | 29.5 |
Azimuth angle = 180° | 49.1 | 4.0 | 58.1 | 2.8 |
Table 18.
Noise SPL and average RCS values with CSM phase parameters of Equations (47)–(50).
Table 18.
Noise SPL and average RCS values with CSM phase parameters of Equations (47)–(50).
| Helicopter Mode | Fixed-Wing Mode |
---|
Noise SPL/dB | Average RCS/dBsm | Noise SPL/dB | Average RCS/dBsm |
---|
Azimuth angle = 0° | 45.1 | 6.7 | 65.1 | 4.0 |
Azimuth angle = 90° | 53.5 | 25.6 | 68.9 | 29.5 |
Azimuth angle = 180° | 45.1 | 4.7 | 58.6 | 2.8 |
Table 19.
Noise SPL and average RCS values with CSM phase parameters of Equations (51)–(54).
Table 19.
Noise SPL and average RCS values with CSM phase parameters of Equations (51)–(54).
| Helicopter Mode | Fixed-Wing Mode |
---|
Noise SPL/dB | Average RCS/dBsm | Noise SPL/dB | Average RCS/dBsm |
---|
Azimuth angle = 0° | 53.4 | 7.2 | 71.0 | 4.1 |
Azimuth angle = 90° | 41.3 | 25.6 | 64.2 | 29.5 |
Azimuth angle = 180° | 53.4 | 4.7 | 65.3 | 2.8 |
Table 20.
Noise SPL and average RCS values with PPC1.
Table 20.
Noise SPL and average RCS values with PPC1.
| Helicopter Mode | Fixed-Wing Mode |
---|
Noise SPL/dB | Average RCS/dBsm | Noise SPL/dB | Average RCS/dBsm |
---|
Azimuth angle = 0° | 49.1 | 6.7 | 69.5 | 3.4 |
Azimuth angle = 90° | 49.1 | 25.6 | 64.9 | 29.5 |
Azimuth angle = 180° | 49.1 | 4.0 | 58.1 | 2.8 |
Table 21.
Noise SPL and average RCS values with PPC2.
Table 21.
Noise SPL and average RCS values with PPC2.
| Helicopter Mode | Fixed-Wing Mode |
---|
Noise SPL/dB | Average RCS/dBsm | Noise SPL/dB | Average RCS/dBsm |
---|
Azimuth angle = 0° | 45.1 | 6.7 | 65.1 | 4.0 |
Azimuth angle = 90° | 53.5 | 25.6 | 68.9 | 29.5 |
Azimuth angle = 180° | 45.1 | 4.5 | 58.6 | 2.8 |
Table 22.
Noise SPL and average RCS values with PPC3.
Table 22.
Noise SPL and average RCS values with PPC3.
| Helicopter Mode | Fixed-Wing Mode |
---|
Noise SPL/dB | Average RCS/dBsm | Noise SPL/dB | Average RCS/dBsm |
---|
Azimuth angle = 0° | 53.4 | 7.2 | 71.0 | 4.1 |
Azimuth angle = 90° | 41.3 | 25.6 | 64.2 | 29.5 |
Azimuth angle = 180° | 53.4 | 4.7 | 65.3 | 2.8 |
Table 23.
Reduction values of noise SPL and average RCS of PPC1, PPC2 and PPC3.
Table 23.
Reduction values of noise SPL and average RCS of PPC1, PPC2 and PPC3.
| Helicopter Mode | Fixed-Wing Mode |
---|
Noise Reduction/dB | RCS Reduction/dBsm | Noise Reduction/dB | RCS Reduction/dBsm |
---|
Azimuth angle = 0° | PPC1: 7.4 | PPC1: 1.1 | PPC1: 4.5 | PPC1: 1.6 |
PPC2: 11.4 | PPC2: 1.1 | PPC2: 8.9 | PPC2: 1 |
PPC3: 3.1 | PPC3: 0.6 | PPC3: 3 | PPC3: 0.9 |
Azimuth angle = 90° | PPC1: 7.3 | PPC1: 0 | PPC1: 7.6 | PPC1: 0 |
PPC2: 2.9 | PPC2: 0 | PPC2: 3.6 | PPC2: 0 |
PPC3: 15.1 | PPC3: 0 | PPC3: 8.3 | PPC3: 0 |
Azimuth angle = 180° | PPC1: 7.4 | PPC1: 1.2 | PPC1: 10.1 | PPC1: 1 |
PPC2: 11.4 | PPC2: 0.7 | PPC2: 9.6 | PPC2: 1 |
PPC3: 3.1 | PPC3: 0.5 | PPC3: 2.9 | PPC3: 1 |