measured speed
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Author(s):  
Thibault Ly ◽  
Kazim Koc ◽  
Lionel Meillard ◽  
Rainer Schnell

AbstractIn the present study, steady numerical simulations performed on the counter rotating turbo fan (CRTF) COBRA are compared with experimental data carried at the CIAM C-3A test-bench in Moscow. For this purpose, a systematic analysis of the measurement uncertainties was performed for the global aerodynamic performances of the CRTF, namely, the massflow, the total pressure ratio, the isentropic efficiency, as well as the torque ratio applied on both fan rows. Several numerical models are investigated to highlight their effects on the aforementioned predicted quantities. Differences in modeling consist in grid resolutions and the use of two turbulence models popular in the turbomachinery community. To match as much as possible the experiment running conditions, the performance map of the CRTF is simulated using the exact measured speed ratio and massflow. The comparisons show good estimations of the numerical simulation over the entire performance map. The main differences between the turbulence models occur at part-speed close to stall conditions. More surprisingly at aerodynamic design point, the importance of the turbulence modeling on the predicted torque ratio has been pointed out.


2021 ◽  
Vol 80 (1) ◽  
pp. 153-161
Author(s):  
Elissavet Terzi ◽  
Ariadni Skari ◽  
Stefanos Nikolaidis ◽  
Konstantinos Papadimitriou ◽  
Athanasios Kabasakalis ◽  
...  

Abstract Sprint interval training (SIT) sets are commonly used by coaches in the training routine of swimmers competing in short-distance events; however, data regarding their relevance to competitive events are scarce. The aim of this study was to examine whether performance variables differed or correlated between a 4 × 50-m maximal swimming set (with a work-to-rest ratio of 1:4) and the 100-m freestyle event. Eleven male and 16 female competitive swimmers aged 16.1 ± 1.1 years participated in the study. All swimmers trained at least six times a week and had training experience of more than 4 years. They completed the two freestyle tests on different days, in random and counterbalanced order. In each test, speed, blood lactate, stroke rate (SR), and stroke index (SI) were measured. Speed, blood lactate, and SR were higher at the 4 × 50 m compared to the 100 m and were positively correlated between tests (p < 0.001). The SI did not differ significantly, but was positively correlated between tests. Males were faster and had a higher SI than females, but genders did not differ in lactate. Since performance variables were better in the SIT set and correlated with those in the 100-m bout, we suggest that the 4 × 50-m set can be used to improve performance in the 100-m freestyle event. Moreover, this set can help coaches identify which swimmers will swim fastest in the event.


2021 ◽  
Vol 925 ◽  
Author(s):  
Jyun-An Chen ◽  
Touvia Miloh ◽  
Watchareeya Kaveevivitchai ◽  
Hsien-Hung Wei

Utilizing the joint singular natures of electric field and hydrodynamic flow around a sharp nanotip, we report new electrohydrodynamic Landau–Squire-type flows under the actions of alternating current (AC) electric fields, markedly different from the classical Landau–Squire flow generated by pump discharge using nanotubes or nanopores. Making use of the locally diverging electric field prevailing near the conical tip, we are able to generate a diversity of AC electrohydrodynamic flows with the signature of a 1/r point-force-like decay at distance r from the tip. Specifically, we find AC electrothermal jet and Faradaic streaming out of the tip at applied frequencies in the MHz and 102 Hz regimes, respectively. Yet at intermediate frequencies of 1–100 kHz, the jet flow can be reversed to an AC electro-osmotic impinging flow. The characteristics of these AC jet flows are very distinct from AC flows over planar electrodes. For the AC electrothermal jet, we observe experimentally that its speed varies with the driving voltage V as V3, in contrast to the common V4 dependence according to the classical theory reported by Ramos et al. (J. Phys. D: Appl. Phys, vol. 31, 1998, pp. 2338–2353). Additionally, the flow speed does not increase with the solution conductivity as commonly thought. These experimental findings can be rationalized by means of local Joule heating and double layer charging mechanisms in such a way that the nanotip actually becomes a local hotspot charged with heated tangential currents. The measured speed of the AC Faradaic streaming is found to vary as V3/2 logV, which can be interpreted by the local Faradaic leakage in balance with tangential conduction. These unusual flow characteristics signify that a conical electrode geometry may fundamentally alter the features of AC electrohydrodynamic flows. Such peculiar electrohydrodynamic flows may also provide new avenues for expediting molecular sensing or sample transport in prevalent electrochemical or microfluidic applications.


2021 ◽  
Vol 63 (6) ◽  
pp. 519-528
Author(s):  
Uğur Demir ◽  
Zeliha Kamış Kocabıçak

Abstract This paper presents the performance assessments for the traction motor of an electric racing kart, considering the different core materials. Firstly, the appropriate traction motor type is determined as a brushless direct current motor (BLDC) due to the superior features such as torque, efficiency, cooling performance and reliability. Thereafter the BLDC traction motor is optimized in Ansys RMXprt by using Taguchi’s design of experiment (DoE) method in order to meet the vehicle requirements. The BH curves are created for steel sheet (M19_24G), amorphous (2605SA1) and soft magnetic composite (SMC) (Somaloy 1000 3P) in Ansys Maxwell Environment, which are widely used as core materials in the literature. Then, the motor models are analyzed by the finite element method in Ansys Maxwell, and the core materials that can meet the minimum requirements in terms of magnetic flux density and saturation are verified. Finally, the dynamic vehicle model is set up in Ansys Simplorer in order to evaluate the motor performances. For that purpose, a reference speed profile is created by using the measured speed from the Gothenburg carting ring, and the battery consumption characteristic and reference speed tracking performance of the motor models with different cores are evaluated in the driving cycle.


2021 ◽  
Author(s):  
Musab ElDali

Due to the increase in complexity in aerospace systems, developing a diagnosis, prognosis and health monitoring (DPHM) framework is a challenge that must be considered to assure the safety of such systems. This thesis discusses this problem by proposing a novel growing neural network model to automate the process of DPHM for aerospace systems. The model optimizes the architecture of a recurrent neural network and was used to make Remaining Useful Lifetime (RUL) predictions for aircraft engines and detect failure for satellite attitude actuators (Reaction Wheels). It was tested on the CMAPSS and PHM08 aircraft engine datasets simulated by NASA, and it was able to make RUL predictions with root mean square errors as low as 14.31 engine cycles. Another application to test the proposed model was on the Kepler Spacecraft’s reaction wheels from which two have failed. The model detected the failure of the two failed reaction wheels by estimating a Health Index value which indicates the probability of failure of the reaction wheels using the residuals between the speed predictions made by the model and measured speed values. Failure was predicted using the model 105 days and 54 days before it occurred for reaction wheels two and four respectively. Prognostics were also applied on the Kepler Mission reaction wheels and RUL predictions were made with mean absolute errors ranging between 2-13 days depending on how close the reaction wheel is to failure. The proposed algorithm showed results in both applications that could regard it as a promising approach for DPHM models.


2021 ◽  
Author(s):  
Musab ElDali

Due to the increase in complexity in aerospace systems, developing a diagnosis, prognosis and health monitoring (DPHM) framework is a challenge that must be considered to assure the safety of such systems. This thesis discusses this problem by proposing a novel growing neural network model to automate the process of DPHM for aerospace systems. The model optimizes the architecture of a recurrent neural network and was used to make Remaining Useful Lifetime (RUL) predictions for aircraft engines and detect failure for satellite attitude actuators (Reaction Wheels). It was tested on the CMAPSS and PHM08 aircraft engine datasets simulated by NASA, and it was able to make RUL predictions with root mean square errors as low as 14.31 engine cycles. Another application to test the proposed model was on the Kepler Spacecraft’s reaction wheels from which two have failed. The model detected the failure of the two failed reaction wheels by estimating a Health Index value which indicates the probability of failure of the reaction wheels using the residuals between the speed predictions made by the model and measured speed values. Failure was predicted using the model 105 days and 54 days before it occurred for reaction wheels two and four respectively. Prognostics were also applied on the Kepler Mission reaction wheels and RUL predictions were made with mean absolute errors ranging between 2-13 days depending on how close the reaction wheel is to failure. The proposed algorithm showed results in both applications that could regard it as a promising approach for DPHM models.


2021 ◽  
Author(s):  
Kelsey E Schultz ◽  
Dominique C Denning ◽  
Vanessa Hufnagel ◽  
Nicole C Swann

Flexible, adaptive behavior is critically dependent on inhibitory control. For example, if you suddenly notice you are about to step on a tack and would prefer not to, the ability to halt your ongoing movement is critical. To address limitations in existing approaches for studying your ability to rapidly terminate your movement ('stopping'), we developed a novel stop task. This task requires termination of ongoing motor programs, provides a direct measure of SSRT, and allows for comparison of the same behavior (stopping) in conditions that elicit either prepared or reactive inhibitory control. Here, we present and evaluate our novel Continuous Movement Stop Task (CMST). We examined several versions of the task in a total of 49 participants. Our data reveal that the CMST is effectively able to dissociate stopping behavior between the planned and unplanned conditions. Additionally, within the subset of participants for which we measured speed, we found that participants initiated stopping (with respect to the stop signal) significantly earlier on planned stop compared to unplanned stop trials. Finally, participants took longer to arrive at full motor arrest (i.e. SSRT) following stop initiation on planned than on unplanned stop trials. This novel task design will enable a more precise quantification of stopping behavior and, in conjunction with neuroscientific methods, could provide more rigorous characterization of brain networks underlying stopping.


Author(s):  
V.V. Zavyalov ◽  
V.A. Agapov

Аннотация. Целью работы является обоснование метода повышения точности корреляционного лага на основе предварительной фильтрации сигналов на входе схемы слежения. Показаны проблемы, решаемые с помощью корреляционных лагов. Проведен анализ основных уравнений корреляционных методов измерения скорости и структурных схем вычислительных устройств корреляционных лагов, основанных на этих методах. Показано, что при измерении продольной скорости судна на выходе схемы слежения (измеренная скорость) коррелятора даже в установившемся режиме слежения сигнал не равен нулю, в отличие от метода корреляции для измерения модуля полной скорости судна. Предлагается фильтровать сигналы на входах вычитателя с последующим интегрированием выходного разностного сигнала. Для подтверждения работоспособности предложенного метода были разработаны схемы корреляторов. Измерители продольного измерителя скорости и модуля скорости на полной скорости судна. Получены динамические характеристики переходных процессов вычислительных устройств лагов, дисперсии входных и выходных сигналов схемы слежения. Представлены результаты теоретических расчетов относительных среднеквадратичных ошибок методов измерения продольной скорости и модуля абсолютной скорости, а также результаты, полученные в ходе моделирования, которые подтвердили эффективность предложенного метода.The aim of the work is to substantiate a method for increasing the ac-curacy of the correlation lag based on preliminary filtering of the signals at the input of the tracking circuit. The problems solved with the help of correlation lags are shown. The analysis of the basic equations of the correlation methods for measuring velocity and structural schemes of computing devices of the correlation lags based on these methods is carried out. It is shown that when measuring the ships longitudinal speed at the output of the tracking circuit (measured speed) of the correlator, even in the steady tracking mode, the signal is not equal to zero, in contrast to the correlation method for measuring the module of the ships full speed. It is proposed to filter the signals at the inputs of the subtractor with the sub-sequent integration of the output difference signal. To confirm the operability of the proposed method, the longitudinal velocity meter and meter for the module of the full speed were simulated. The dynamic characteristics of the transients computing devices of the correlation lags, the dispersions of the input and output signals of the tracking circuits are obtained. The results of theoretical calculations of the relative mean square errors of the methods for measuring the longitudinal velocity and module of the full velocity are presented, as well as the results obtained during the simulation, which confirmed the effectiveness of the proposed method.


2019 ◽  
Vol 50 (6) ◽  
pp. 670-685 ◽  
Author(s):  
G. Farries ◽  
K. F. Gough ◽  
A. C. Parnell ◽  
B. A. McGivney ◽  
C. L. McGivney ◽  
...  

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