Design, Modeling and Simulation of a Liquid Jet Gyroscope Based on Electrochemical Transducers

We propose a novel liquid jet gyroscope based on electrochemical transducers, which uses electrolyte as the jet medium, and two electrochemical transducers placed symmetrically as the velocity measuring unit. The gyroscope includes a fluid pump to generate a jet flow, which flows into the jet chamber. Then, it is diverged into the shunt channels, pumped into reflux channels and merged by a fluid pump. The velocities of shunt flows are measured by two electrochemical transducers. The feasibility of the method was demonstrated in theory, and a 2D finite element model was built to simulate the dynamics of the liquid jet gyroscope. Simulation results confirm the effectiveness of the gyroscope, which has higher sensitivity in the near DC frequency band.

INFLUENCE OF THE MEASURING TOOLS ON THE FLOW CHARACTERISTICS IN VORTEX CHAMBER PUMP

Problem. Perturbation of the flow by measuring instruments forces researchers to choose optical research methods. But these methods significantly increase the cost of experimental research, due to the high cost of optical-type measuring equipment. On the other hand, using contact methods for measuring the flow velocity, such as Pitot tubes, hot-wire anemometers, the researcher must be sure that the measurement results can really be compared with the calculations results and the equipment influence on the flow parameters is minimal. The aim of this work is to study the measuring tool influence on the flow characteristics in the swirl chamber pump, as well as to compare the results obtained due to the measurements with the parameters of the undisturbed flow. The research methodology consisted of two stages: 1) modeling the flow in the model pump; 2) comparison of flow characteristics, as well as the values of velocity and pressure at the points of installation of the measuring tool. Results. Although the total velocity at the measuring point is practically independent of the measuring tool, the tangential component of the velocity is significantly reduced. It indicates that there is a significant error in velocity measuring. For a more accurate rotational velocity component measurement, it is necessary to orient the instrument perpendicular to the measured component. Scientific novelty. Installing the measuring tool in the end cover of the swirl chamber reduces the flow rate sucked by the pump through the lower axial channel. The size of the tool has practically no effect on the energy characteristics of the swirl chamber pump. Practical value. To ensure measurement accuracy, the ratio of the swirl chamber dimensions and the tool should be ensured in the way that the relative diameter of the tool does not exceed 0.25 of the swirl chamber neck diameter.

Validation of Velocity Measuring Devices in Velocity Based Strength Training

To control and monitor strength training with a barbell various systems are on the consumer market. They provide the user with information regarding velocity, acceleration and trajectory of the barbell. Some systems additionally calculate the 1-repetition-maximum (1RM) of exercises and use it to suggest individual intensities for future training. Three systems were tested: GymAware, PUSH Band 2.0 and Vmaxpro. The GymAware system bases on linear position transducers, PUSH Band 2.0 and Vmaxpro base on inertial measurement units. The aim of this paper was to determine the accuracy of the three systems with regard to the determination of the average velocity of each repetition of three barbell strength exercises (squat, barbell rowing, deadlift). The velocity data of the three systems were compared to a Vicon system using linear regression analyses and Bland-Altman-diagrams. In the linear regression analyses the smallest coefficient of determination (R2.) in each exercise can be observed for PUSH Band 2.0. In the Bland-Altman diagrams the mean value of the differences in the average velocities is near zero for all systems and all exercises. PUSH Band 2.0 has the largest differences between the Limits of Agreement. For GymAware and Vmaxpro these differences are comparable.

A Flow-Measuring Algorithm of Arc-Bottomed Open Channels through Multiple Characteristic Sensing Points of the Flow-Velocity Sensor in Agricultural Irrigation Areas

Precise flow measurement in the open channel is a key prerequisite to implementation of modern agricultural efficient water use. The channel with an arc-bottomed shape is the most common channel type in irrigation area at present. The paper has verified the log-law is along the normal line rather than along the vertical line in arc-bottom channel. By conducting the velocity distribution log-law, this paper derives the expression of the multiple characteristic sensing points location of the flow-velocity sensor in the channel section, which is along the normal line. Based on this, a new algorithm to estimate the discharge of the arc-bottomed channel flow is proposed. We have also developed the experiment of the arc-bottomed channels (including semicircular channels, arc-bottom trapezoidal channels and U-shaped channels) and utilize the data to verify the method. The results indicate that the sensing locations expression of the flow velocity measuring sensor such as acoustic doppler velocimetry and propeller is suitable for improving discharge estimation’s accuracy of the arc-bottomed channels. This method could be extensively used in estimating discharge of irrigation and drainage channels in agricultural water conservancy projects. It will enhance the efficiency and accuracy of water resources management departments in irrigation areas, which also meet the strategic requirements of agricultural sustainable development.

Perception of bar velocity in resistance training: Accuracy levels within and between exercises

Velocity-based training is a method used to monitor resistance-training programs based on repetition velocities measured with tracking devices. Since velocity measuring devices can be expensive and impractical, trainee’s perception of velocity (POV) may be used as a possible substitute. Here, 20 resistance-trained males first completed 1RM tests in the bench-press and squat. Then, in three counterbalanced sessions, participants completed four sets of eight repetitions in both exercises using 60%1RM (two-sessions) or 70%1RM. Starting from the second repetition, participants reported their POV of each repetition as a percentage of the first repetition. Accuracy was calculated as the difference between POV and actual-velocity measured with a linear-encoder. Two key findings emerged. First, the absolute error in both exercises was ~5.8 percentage-points in the second repetition, and it increased to 13.2 and 16.7 percentage-points by the eighth repetition, in the bench-press and squat, respectively. Second, participants were 4.2 times more likely to underestimate velocity in the squat. Given the gradual increments in the absolute error, POV may be better suited for sets of fewer repetitions (e.g., 4-5) and wider velocity-loss threshold ranges (e.g., 5-10%). Given the systematic underestimation error in the squat, a correction factor may increase POV accuracy in this exercise.

Research on Target Deviation Measurement of Projectile Based on Shadow Imaging Method in Laser Screen Velocity Measuring System

In the laser screen velocity measuring (LSVM) system, there is a deviation in the consistency of the optoelectronic response between the start light screen and the stop light screen. When the projectile passes through the light screen, the projectile’s over-target position, at which the timing pulse of the LSVM system is triggered, deviates from the actual position of the light screen (i.e., the target deviation). Therefore, it brings errors to the measurement of the projectile’s velocity, which has become a bottleneck, affecting the construction of a higher precision optoelectronic velocity measuring system. To solve this problem, this paper proposes a method based on high-speed shadow imaging to measure the projectile’s target deviation, ΔS, when the LSVM system triggers the timing pulse. The infrared pulse laser is collimated by the combination of the aspherical lens to form a parallel laser source that is used as the light source of the system. When the projectile passes through the light screen, the projectile’s over-target signal is processed by the specially designed trigger circuit. It uses the rising and falling edges of this signal to trigger the camera and pulsed laser source, respectively, to ensure that the projectile’s over-target image is adequately exposed. By capturing the images of the light screen of the LSVM system and the over-target projectile separately, this method of image edge detection was used to calculate the target deviation, and this value was used to correct the target distance of the LSVM to improve the accuracy of the measurement of the projectile’s velocity.