This study was the function of discharge control system by personal computer and the mathematical simulation of water height control by automatic gate in hydraulic transient.
Here that computer was connected with electromagnetic flow meter and frepuency converter of motor of pump, with 30 l/s as maximum discharge.
At first, the function and deviation from the desired line was examined against very severe hydraulic conditions as sin curve that had very little mean discharge and relatively large amplitude and very short period.
Then it was very effective to make the deviation little to adjust the valve opening ratio suitably small, and this deviation mostly owed to the time lag from the desrred one.
The time lag and amplitude of input curve had to be reformed as multiplied by function K(⊿t, T, β) to the desired curve, here β as feed back ratio in ⊿t and T as period of sin curve.
Secondly the simulation by digital computer of hydraulic experiment to maintain the water height in hydraulic transient condition as linear increase or decrease of discharge as 2 l/s from 10 l/s in 5 mimutes.
At the experiment, the water height control was done by sensor and relay circuit in control box, which had the adjustments of time lags between the touch of sensor (1 meter up stream side from the gate) and starting of actioh of up and down of the gate which suited at the down points of the channel.
In the experiment, the surface tension caused some lag between the sensor and gate action, especially by the water ripple on the surface wave in the dischargeincrease.
Then discrete digital simulation by TSLW scheme with ⊿t (0.5 sec), ⊿x (1 meter) showed sufficient approximation of the real action of the automatic gate and water height in the channel.