Fig.1

Sectional view of blade grid

Fig.2

System of “curvilinear blade grid and Cartesian background grid”

Fig.3

Method of parallel distance reduction with multi-starting points and diagram of its search path

Fig.4

Three-layer artificial boundary

Fig.5

High-accuracy interpolation method for variables interaction on overset grid

Fig.6

Schematic diagram of high-order Lagrangian interpolation dimension by dimension （show in two dimensions）

Table 1

Time consumed by interpolation in a time step

Fig.7

Comparison of grid block structures before and after averagely partition of overset grids

Fig.9

Overset grid system of NACA0021 airfoil

Fig.10

Comparison of computed and experimental time-averaged pressure coefficient distribution for NACA0021 airfoil

Table 2

Comparison of time-averaged lift coefficients and time-averaged drag coefficients for NACA0021 airfoil with experimental data

Fig.11

Comparison of computed and experimental unsteady normal force coefficients Cn and moments coefficients Cm over time for NACA0012 airfoil

Fig.12

Pressure coefficient distributions of NACA0012 airfoil at maximum angle of pitch （α=5.3°）

Table 3

Geometric parameters of four-blade rigid coaxial rotor in forward flight［23］

Fig.13

Blade grid of four-blade rigid coaxial rotor in forward flight

Fig.14

Schematic diagram of wake refinement region on background grid

Table 4

Averaged thrust coefficients of four-blade rigid coaxial rotor obtained with different methods

Fig.15

Variation of thrust coefficients CT and torque coefficients CQ with azimuthal angle ψ for four-blade rigid coaxial rotor at forward flight

Fig.16

Thrust coefficients of upper， lower rotor blade for four-blade rigid coaxial rotor over azimuthal angle

Fig.17

Schematic diagram of position of section line passing through rotating axis and along flow direction

Fig.18

Induced velocity on section line for four-blade rigid coaxial rotor in forward flight

Fig.19

Instantaneous Q-isosurface of coaxial rotor in forward flight calculated using different turbulence simulation methods （Q=0.001）

Table 5

Distribution of profile airfoil of X-2 Rigid Coaxial Rotor blade［27］

展向位置（r/R）	剖面翼型名称	剖面翼型外形
0.142	DBLN-526
0.331	DBLN-526
0.468	SC1012-R8
0.568	SC1012-R8
0.600	SSCA-09
1.000	SSCA-09

Fig.20

Geometry of X-2 Rigid blade Coaxial Rotor

Fig.21

Schematic diagram of grid and blade overset relationship for X-2 Rigid Coaxial Rotor

Fig.22

Variation of pitch angle θ of X-2 Rigid Coaxial Rotor blade in forward flight with azimuth ψ

Fig.23

Variation of thrust and torque coefficients of X-2 Rigid Coaxial Rotor blade in forward flight with azimuth

Fig.24

Schematic diagram for cross-section of spatial flow field （XoZ plane perpendicular to Y-axis）

Fig.25

Axial induction velocity distribution near rotor disk of X-2 Rigid Coaxial Rotor at forward flight

Fig.26

Pressure distribution of X-2 Rigid Coaxial Rotor blades on forward and retreating sides

Fig.27

Instantaneous Q-isosurface of X-2 Rigid Coaxial Rotor at forward flight （Q=0.001）

Fig.28

Blade-vortex-interaction of X-2 Rigid Coaxial Rotor at forward flight

Fig.29

Dynamic evolution of blade-vortex-interaction of X-2 Rigid Coaxial Rotor in forward flight