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was surface tension. These factors were related to the lamella thickness and the
critical spreading velocity, which complemented each other. The non-monotonic
threshold velocity for various impact angles supported this hypothesis. On the 0°
target, the forward lamella was thickest, and the gas boundary layer contributed
additionally to the aerodynamic force, therefore the threshold velocity was the lowest.
As this effect vanished with the increasing target angle, the threshold velocity
rose sharply. Further increase of the impact angle enhanced the spreading velocity,
but meanwhile reduced the lamella thickness, leading to firstly a decrease of the
threshold velocity from 20° to 35° of the impact angle, and a subsequent steep increase.
With impact angles greater than 35°, the threshold velocity became almost
constant indicating that the increase of the spreading velocity and the reduction of
the lamella thickness complemented each other exactly.
The velocity of the liquid jets of asymmetric splash was for the first time reported.
It was found out that the velocity of the liquid jets had higher magnitudes than the
impact velocity, and it increased as the impact angle increased, i.e. while approaching
the normal impact. Neglecting the kinetic losses because of the short time scale,
the velocity of the liquid jets was the velocity of the secondary droplets.
The dynamic spreading radii were measured for the oblique impact, highlighting
the asymmetric spreading of the lamella in the presence of a tangent velocity.
The mass-loss was measured for the drop impact on the 0° target, in which case
the secondary droplet was singular. It was found out that higher Re and We promoted
mass-loss. The scaling parameter, K = We 1/2 Re 1/4 , collapsed the data on
one curve. Although empirical, this parameter reflected the physics partially.
6.6. Conclusion 185