T	Surface tension
σ	Surface tension coefficient
Lb	Total length of boundary
∆P	Additional pressure
R 1	Radius of curvature
R 2	Radius of curvature
P	Comprehensive pressure on gas-liquid interface
Pa	Atmospheric pressure
Pd	Dynamic pressure generated by gas jet
PS	Hydrostatic pressure
p 0	Gas pressure in the nozzle
T 0	Gas temperature in the nozzle
ρ 0	Gas density in the nozzle
p 1	Gas pressure at the nozzle outlet
T 1	Gas temperature at the nozzle outlet
ρ 1	Gas density at the nozzle outlet
Tg	Temperature of jetted gas
ρg	Density of jetted gas
H	Distance between nozzle outlet and liquid level
h 0	Keyhole depth
R	Radius of curvature at the depth h on the keyhole wall
n	Normal of a point on the keyhole wall D Outlet diameter of the nozzle
vg	Velocity of the gas in the jet prior to the collision with the surface of the liquid
ρL	Density of liquid
σL	Surface tension coefficient of liquid
Rkh	Radius of curvature of the liquid surface at the keyhole depth h0
Pw	Comprehensive pressure in keyhole in laser welding
Pv	Vapor pressure of the material
v	Movement speed
V	Gas velocity at the nozzle outlet
q	Gas flow rate
θ	Angle
vh	Moving speed of keyhole
vd	Drilling speed of keyhole
FH	The resultant force directions of the surface tension in the transverse direction
FL	The resultant force directions of the surface tension in longitudinal direction