Jet apparatus and method of evaluating jet

A method of evaluating a jet, comprising;

• generating the jet from an injection reference position of a nozzle;
• measuring an impact force distribution based on an impact force per unit area of the jet when the jet collides with a plurality of impact force detectors;
• extracting, by an evaluation value extraction unit, a peak impact force and a center coordinate, the peak impact force being a maximum impact force in the impact force distribution, the center coordinate being a position where the peak impact force is detected with respect to a measurement reference position;
• calculating, by an evaluation value extraction unit, an approximation function for approximating the impact force on a straight line passing through the center coordinate;
• calculating, by an evaluation value extraction unit, the center coordinate, a displacement that is an absolute value of the center coordinate, and the peak impact force based on the approximation function;
• comparing, by an evaluation unit, the peak impact force with a minimum peak impact force that is a minimum value of the peak impact force;
• comparing, by the evaluation unit, the displacement with a maximum displacement that is a maximum value of the displacement;
• and
• determining, by the evaluation unit, that the nozzle is adaptive when the peak impact force is equal to or greater than the minimum peak impact force, and the displacement is equal to smaller than the maximum displacement.