Research On Performance Test Of ADV Based On Calibration Device For The Flow Velocity Of Towing Tank

Flow velocity is an important index for field observation of rivers and oceans.It is also the value of various indoor fluid experiments.In recent years,Acoustic Doppler Velocimeter(ADV)has been used in more and more applications depending on the advantages of high resolution,high sampling frequency,and measurable three-dimensional flow rate.The towing tank flow standard is the primary standard device of flow velocity.Its principle is using speed of towing vehicle,instead of flow velocity,as the the standard value to calibrate velocity meter.Therefore speed stability is one of the key factors for the accuracy of calibration results.Aiming at the problem that ADV operation and calibration methods are not standardized,a set of calibration device for towing tank is established,and the measurement performance of the device is experimentally studied.The main work of the paper includes:(1)According to the designed speed measurement system,hardware and software of the device is designed,the selection and calibration of the hardware equipments is completed,the application of upper computer is programed.Through the test and analysis of the speed,the synthetic uncertainty of the device is 0.43% according to the speed measuring mode triggered by the photoelectric trigger.(2)Towing speed is usually measured by using a tachometer which has systematic bias due to static calibration without considering dynamic characteristics.The encoder coefficients should be various under different speeds,due to the tachometer wheel used in low speed under the indicated value is low.(3)The time averaged velocity measurement capability of MicroADV is calibrated by using the towing flume flow rate device.The flow velocity indication error at different speeds is tested,and the influence of signal intensity and sampling frequency on its speed measurement ability is analyzed.The results show that the accuracy of MicroADV time averaged flow velocity can meet the accuracy requirement.The signal intensity has a significant effect on the accuracy of MicroADV when sampling at high frequency.When the sampling frequency is greater than 10 Hz,the probability of the time averaged velocity exceeds 1% of the declared index is increased.At the same time,the background velocity and the settlement of tracer particles are analyzed by theoretical calculation and experimental verification during the test.