Drag Tests Research Articles

Flow memory effects on the nonlinear hydrodynamic load of an ROV in translational maneuvering

This paper describes experimental and numerical investigations of the flow memory effect on the nonlinear hydrodynamic load response of a work-class remotely operated vehicle (ROV) under surge, sway, and heave impulse motions. The hysteresis loops of the dynamic drag coefficients during impulse motion tests are analyzed by comparing them with those obtained in steady drag tests. The areas of the loops and differences between the maximum and minimum dynamic and steady coefficients are used to quantify the flow memory effect. A novel unsteady hydrodynamic model for ROVs in translational maneuvering is established. This model considers the flow memory effect in terms of the unsteady hydrodynamic load response obtained from impulse motion response tests. The results given by the unsteady model are found to be in good agreement with those from CFD simulations. The unsteady hydrodynamic characteristics (including the asymmetric forces, force magnitude, and phase delay), motion amplitude, and frequency effect on the hydrodynamic forces of the ROV are analyzed by comparing the unsteady model results with those obtained from the steady model, revealing the rules governing the flow memory effect.

Evaluation of hydrodynamic coefficients and sensitivity analysis of a work-class remotely operated vehicle using planar motion mechanism tests

This paper presents a comprehensive analysis of the hydrodynamic forces and moments relating to the drag on an open-frame work-class remotely operated vehicle (ROV) AUTO-1000. We describe the results of planar motion mechanism experiments conducted with the aim of modeling and simplifying the mathematical maneuverability model for such an ROV. The scale of the model is 1:4. Various experiments are performed in a nonlinear wave channel. The flow speeds in the static drag tests range from ±0.2–±0.5 m/s and the angle in the drift tests is less than 10°. The motion frequencies of the dynamic tests range from 0.25 to 3.14 rad/s. The amplitude of the translation motions is 0.03 m and the largest angular amplitude in the rolling tests is 5°. The viscous and inertial hydrodynamic coefficients are estimated. Normalized sensitivity coefficients are used to investigate the sensitivity of both the viscous and inertial hydrodynamic coefficients considering the multi-degree-of-freedom motion and velocity effect. The drag, drift, and stationary random motions are used to examine the sensitivity. A comparison of the motion simulation results given by simplified and complete models shows that a threshold normalized sensitivity coefficient value of 0.01 is suitable for filtering the ROV coefficients.

Numerical Simulation of Bionic Underwater Vehicle Morphology Drag Optimisation and Flow Field Noise Analysis

The study of aquatic organisms’ ectomorphology is important to understanding the mechanisms of efficient swimming and drag reduction in fish. The drag reduction mechanism in fish remains unknown yet is needed for optimising the efficiency of bionic fish. It is thus crucial to conduct drag tests and analyses. In this paper, an optimal dolphin morphological model is constructed taking the beakless porpoise as the research object. A numerical simulation of the dolphin body model is carried out for different combinations of pitch angle and speed adopting computational fluid dynamics, and the flow field noise of the dolphin body model is solved for different speeds using the FW-H equation. When the dolphin model is oriented horizontally, the differential pressure drag accounts for approximately 20–25% of the total drag as airspeed increases. As both the pitch angle and airspeed increase, the differential pressure drag and friction drag decrease with increasing airspeed. Moreover, the acoustic energy is mainly concentrated at low frequencies for both the dolphin and Bluefin-21 models. The dolphin body model has better noise performance than the Bluefin-21 model at the same speed. The optimisation of the external morphology of the bionic underwater submarine and the analysis of the shape drag are thus important for revealing the drag reduction mechanism, reducing noise in the flow field and provide guidance for research on bionic fish.

Towards an accurate rolling resistance: Estimating intra-cycle load distribution between front and rear wheels during wheelchair propulsion from inertial sensors

ABSTRACT Accurate assessment of rolling resistance is important for wheelchair propulsion analyses. However, the commonly used drag and deceleration tests are reported to underestimate rolling resistance up to 6% due to the (neglected) influence of trunk motion. The first aim of this study was to investigate the accuracy of using trunk and wheelchair kinematics to predict the intra-cyclical load distribution, more particularly front wheel loading, during hand-rim wheelchair propulsion. Secondly, the study compared the accuracy of rolling resistance determined from the predicted load distribution with the accuracy of drag test-based rolling resistance. Twenty-five able-bodied participants performed hand-rim wheelchair propulsion on a large motor-driven treadmill. During the treadmill sessions, front wheel load was assessed with load pins to determine the load distribution between the front and rear wheels. Accordingly, a machine learning model was trained to predict front wheel load from kinematic data. Based on two inertial sensors (attached to the trunk and wheelchair) and the machine learning model, front wheel load was predicted with a mean absolute error (MAE) of 3.8% (or 1.8 kg). Rolling resistance determined from the predicted load distribution (MAE: 0.9%, mean error (ME): 0.1%) was more accurate than drag test-based rolling resistance (MAE: 2.5%, ME: −1.3%).

From theory to practice: Monitoring mechanical power output during wheelchair field and court sports using inertial measurement units

An important performance determinant in wheelchair sports is the power exchanged between the athlete-wheelchair combination and the environment, in short, mechanical power. Inertial measurement units (IMUs) might be used to estimate the exchanged mechanical power during wheelchair sports practice. However, to validly apply IMUs for mechanical power assessment in wheelchair sports, a well-founded and unambiguous theoretical framework is required that follows the dynamics of manual wheelchair propulsion. Therefore, this research has two goals. First, to present a theoretical framework that supports the use of IMUs to estimate power output via power balance equations. Second, to demonstrate the use of the IMU-based power estimates during wheelchair propulsion based on experimental data. Mechanical power during straight-line wheelchair propulsion on a treadmill was estimated using a wheel mounted IMU and was subsequently compared to optical motion capture data serving as a reference. IMU-based power was calculated from rolling resistance (estimated from drag tests) and change in kinetic energy (estimated using wheelchair velocity and wheelchair acceleration). The results reveal no significant difference between reference power values and the proposed IMU-based power (1.8% mean difference, N.S.). As the estimated rolling resistance shows a 0.9–1.7% underestimation, over time, IMU-based power will be slightly underestimated as well. To conclude, the theoretical framework and the resulting IMU model seems to provide acceptable estimates of mechanical power during straight-line wheelchair propulsion in wheelchair (sports) practice, and it is an important first step towards feasible power estimations in all wheelchair sports situations.

Pharmaco-toxicological effects of the novel tryptamine hallucinogen 5-MeO-MiPT on motor, sensorimotor, physiological, and cardiorespiratory parameters in mice—from a human poisoning case to the preclinical evidence

RationaleThe 5-methoxy-N-methyl-N-isopropyltryptamine (5-MeO-MiPT, known online as “Moxy”) is a new psychedelic tryptamine first identified on Italian national territory in 2014. Its hallucinogen effects are broadly well-known; however, only few information is available regarding its pharmaco-toxicological effects.ObjectivesFollowing the seizure of this new psychoactive substances by the Arm of Carabinieri and the occurrence of a human intoxication case, in the current study we had the aim to characterize the in vivo acute effects of systemic administration of 5-MeO-MiPT (0.01–30 mg/kg i.p.) on sensorimotor (visual, acoustic, and overall tactile) responses, thermoregulation, and stimulated motor activity (drag and accelerod test) in CD-1 male mice. We also evaluated variation on sensory gating (PPI, prepulse inhibition; 0.01–10 mg/kg i.p.) and on cardiorespiratory parameters (MouseOx and BP-2000; 30 mg/kg i.p.). Lastly, we investigated the in silico ADMET (absorption, distribution, metabolism, excretion, toxicity) profile of 5-MeO-MiPT compared to 5-methoxy-N,N-diisopropyltryptamine (5-MeO-DIPT) and N,N-dimethyltryptamine (DMT).ResultsThis study demonstrates that 5-MeO-MiPT dose-dependently inhibits sensorimotor and PPI responses and, at high doses, induces impairment of the stimulated motor activity and cardiorespiratory changes in mice. In silico prediction shows that the 5-MeO-MiPT toxicokinetic profile shares similarities with 5-MeO-DIPT and DMT and highlights a cytochrome risk associated with this compound.ConclusionsConsumption of 5-MeO-MiPT can affect the ability to perform activities and pose a risk to human health status, as the correspondence between the effects induced in mice and the symptoms occurred in the intoxication case suggests. However, our findings suggest that 5-MeO-MiPT should not be excluded from research in the psychiatric therapy field.

Trunk motion influences mechanical power estimates during wheelchair propulsion

In wheelchair sports, there is an increasing need to monitor mechanical power in the field. When rolling resistance is known, inertial measurement units (IMUs) can be used to determine mechanical power. However, upper body (i.e., trunk) motion affects the mass distribution between the small front and large rear wheels, thus affecting rolling resistance. Therefore, drag tests – which are commonly used to estimate rolling resistance – may not be valid. The aim of this study was to investigate the influence of trunk motion on mechanical power estimates in hand-rim wheelchair propulsion by comparing instantaneous resistance-based power loss with drag test-based power loss. Experiments were performed with no, moderate and full trunk motion during wheelchair propulsion. During these experiments, power loss was determined based on 1) the instantaneous rolling resistance and 2) based on the rolling resistance determined from drag tests (thus neglecting the effects of trunk motion). Results showed that power loss values of the two methods were similar when no trunk motion was present (mean difference [MD] of 0.6 ± 1.6 %). However, drag test-based power loss was underestimated up to −3.3 ± 2.3 % MD when the extent of trunk motion increased (r = 0.85). To conclude, during wheelchair propulsion with active trunk motion, neglecting the effects of trunk motion leads to an underestimated mechanical power of 1 to 6 % when it is estimated with drag test values. Depending on the required accuracy and the amount of trunk motion in the target group, the influence of trunk motion on power estimates should be corrected for.

Flow field identification and water resistance calculation method of underwater tracked vehicle based on artificial lateral line

In response to the issue of real-time measurement of water resistance of underwater vehicles, a method for identifying the flow field environment of tracked vehicles based on artificial lateral lines has been proposed. An artificial lateral line system is installed on the tracked vehicle and applied to underwater drag tests; In the drag tests, artificial lateral lines are used to collect flow mechanical signals and construct a flow field matrix, which includes information on flow velocities and flow angles; By mapping the flow field matrix into an image, a flow field environment image dataset is constructed, and combined with the ResNet18 residual network to identify the flow velocity and direction of the flow field; Based on the functional relationship between the flow angle, external dimensions, and viscous water resistance coefficient of the tracked vehicle, combined with the flow field identification results of artificial lateral line system, water resistance real-time calculation of the tracked vehicle model is achieved. The results of underwater drag tests on tracked vehicles show that the accuracy of flow field identification is greater than 86%, and the error of water resistance calculation is less than 10%.

Comprehensive evaluation of the pharmacological and toxicological effects of γ-valerolactone as compared to γ-hydroxybutyric acid: Insights from in vivo and in silico models

Γ-valerolactone (GVL), marketed online as “Tranquilli-G” and “excellent Valium”, is used as a legal substitute for γ-hydroxybutyric acid (GHB); however, until now, GVL has only been connected to one Drug-Facilitated Sexual Assault (DFSA) case. Moreover, the pharmaco-toxicological effects of GVL are poorly studied. The aim of this study was to investigate the 1) in vivo effects of gavage administration of GVL (100–3000 mg/kg) on neurological (myoclonia, convulsions), sensorimotor (visual, acoustic, and overall tactile) responses, righting reflex, thermoregulation, motor activity (bar, drag, and accelerod test) and cardiorespiratory changes (heart rate, breath rate, oxygen saturation, and pulse distension) in CD-1 male mice and the 2) in silico ADMET profile of GVL in comparison to GHB and the open active form γ-hydroxyvaleric acid (GHV). The present study demonstrates that GVL inhibits, in a dose-dependent manner, sensorimotor and motor responses and induces cardiorespiratory depression (at a dose of 3000 mg/kg) in mice. The determination of the ED50 in sensorimotor and motor responses revealed that GVL is about 4–5 times less potent than GHB. In silico prediction of ADMET profiles revealed toxicokinetic similarities between GHB and GHV, and differences with GVL. These results suggest that GVL could be used as a substitute for GHB and should be added to forensic toxicology screenings.

A comprehensive experimental investigation of total drag and wave height of ONR Tumblehome, including uncertainty analysis

A comprehensive hydrodynamic investigation of the 48.9 scale ONR Tumblehome (ONRT) form has been made by experiments carried out in Ata Nutku Ship Model Testing Laboratory of Istanbul Technical University (ITU-AN). Starting from the bare hull of ONRT hull, drag tests w/or w/o rudders, shafts and brackets, and the fully appended ONRT hull have sequentially been performed in the range of Froude number, 0.16≤Fr ≤ 0.36. The repeatability of drag tests of fully appended ONRT hull has been presented by uncertainty analysis between 0.10≤ Fr ≤ 0.42. The total drag (RTM) of ONRT form with the expanded uncertainty was estimated as 4.615 ± 1.098% N at Fr = 0.20, and 11.121 0.636% N at Fr = 0.30. At Fr = 0.20, it was concluded that the total drag (RTM) of fully appended model was 79.21% bare hull, 7.10% rudders, 8.78% shafts and brackets, and 4.91% bilge keels. The drag tests of fully appended ONRT performed at ITU-AN was also compared with those of carried out at IOWA-IIHR and OU-NAOE. New wave heights at two planes (namely, y/LWL = 0.1557 and y/LWL = 0.3623) of ONRT were also measured and presented at five different Fr numbers. These measurements were compared with those of CFD performed before. A very good agreement has been obtained.

A novel approach to directly measuring wheel and caster rolling resistance accurately predicts user-wheelchair system-level rolling resistance.

Clinical practice guidelines for preservation of upper extremity recommend minimizing wheelchair propulsion forces. Our ability to make quantitative recommendations about the effects of wheelchair configuration changes is limited by system-level tests to measure rolling resistance (RR). We developed a method that directly measures caster and propulsion wheel RR at a component-level. The study purpose is to assess accuracy and consistency of component-level estimates of system-level RR. The RR of N = 144 simulated unique wheelchair-user systems were estimated using our novel component-level method and compared to system-level RR measured by treadmill drag tests, representing combinations of caster types/diameters, rear wheel types/diameters, loads, and front-rear load distributions. Accuracy was assessed by Bland-Altman limits of agreement (LOA) and consistency by intraclass correlation (ICC). Overall ICC was 0.94, 95% CI [0.91-0.95]. Component-level estimates were systematically lower than system-level (-1.1N), with LOA +/-1.3N. RR force differences between methods were constant over the range of test conditions. Component-level estimates of wheelchair-user system RR are accurate and consistent when compared to a system-level test method, evidenced by small absolute LOA and high ICC. Combined with a prior study on precision, this study helps to establish validity for this RR test method.

Pharmaco-Toxicological Effects of Atypical Synthetic Cathinone Mephtetramine (MTTA) in Mice: Possible Reasons for Its Brief Appearance over NPSs Scene.

Over the last year, NPSs have been steadily on the rise in the illicit drug market. Among these, synthetic cathinones seem to become increasingly popular among young adults, mainly because of their ability to replicate the effects of traditional psychostimulant drugs, such as cocaine, MDMA and amphetamines. However, scarce data are available about the in vivo pharmaco-toxicology of these new substances. To this end, this study focused on evaluation of effects induced by repeated administration of mephtetramine (MTTA 0.1-30 mg/kg i.p.) in mice. This atypical cathinone highlighted a sensorial (inhibition of visual and acoustic reflexes) and transient physiological parameter (decrease in breath rate and temperature) change in mice. Regarding motor activity, both a dose-dependent increase (accelerod test) and biphasic effect (drag and mobility time test) have been shown. In addition, blood and urine samples have been analysed to enrich the experimental featuring of the present study with reference to evaluation of potential toxicity related to consumption of MTTA. The latter analysis has particularly revealed important changes in blood cells count and blood and urine physicochemical profile after repeated treatment with this atypical cathinone. Moreover, MTTA induced histological changes in heart, kidney and liver samples, emphasizing its potential toxicity.

Comparing rolling resistance of two treadmills and its influence on exercise testing in wheelchair athletics.

Standardized laboratory exercise testing is common in sport settings and rehabilitation. The advantages of laboratory-based compared to field testing include the use of calibrated equipment and the possibility of keeping environmental conditions within narrow limits, making test results highly comparable and reproducible. However, when using different equipment (e.g., treadmills), the results might deviate and impair comparability. The aim of this study was to compare the biomechanical properties (rolling resistance, speed, inclination) of two treadmills regularly used for exercise testing in elite wheelchair athletes. During the experiment, speed and inclination of two treadmills (same model and producer, different manufacturing year and belt material) were verified. Standardized drag tests were performed to assess rolling resistance. Power output conducted by the athlete during later exercise tests was calculated based on the results. Speed and inclination deviated only slightly from the values indicated by the producer. Rolling resistance caused by different belt material was mainly accountable for the differences in power output between the treadmills. In general, athletes had to deliver 10% more power output on one of the treadmills compared to the other. Concluding from these results: if different treadmills are used for testing, a proper validation is recommended to avoid misleading interpretations of test results.

Pouzdanost novokonstruisanih specifičnih testova za procenu profesionalne radne fizičke pripremljenosti vatrogasaca

The aim of this study was to determine the reliability of newly designed tests for assessing professional firefighters' physical fitness. A total of 15 healthy and physically active firefighters participated in this study. The following tests were performed: Modified Step Test (MStepT), Fire and Rescue Obstacle Course (VPol), Firefighting Equipment Carry Test (NVOpr, and Dummy Drag Test (VLut). The testing was carried out using a randomized method. There was a 10-minute break between the tests. After a week, retesting was conducted under the same conditions. The results of the regression analysis showed that the value of the adjusted coefficient of determination (adjR2 ) for all tests ranged from 0.90 (90.00%) to 0.98 (98.00%), from MStepT to NVOpr respectively, and the repeatability (reliability) of the tests in relation to the sample used in testing for all variables was highly statistically significant (p = 0.000). A moderate effect size (d = 0.748, 95% CI = 0.162 - 1.314) was found for the VPol variable, while the effect size was found small (d = 0.212 - 0.281) for the variables (MStepT, NVOpr, VLut). The findings demonstrated that the examined tests can be applied in the practice of professional firefighters for the purposes of testing physical fitness related to the job. Methodologically, it is acceptable to conduct tests for firefighters in complete PPE so that the test conditions and workload are similar to the situational conditions during intervention in the field.

Extended terramechanics model for machine–soil interaction: Representation of change in the ground shape and property via cellular automata

Terramechanics, as an interdisciplinary field, focuses on the interaction between the ground and vehicles. Terramechanics concepts can be used to realize the design of underbodies and pass-planning of off-road vehicles, among other applications. However, conventional semi-empirical terramechanics models cannot accurately evaluate the terrain surface deformation associated with the interaction between the solid object and ground. Therefore, this article proposes an extended terramechanics model, which incorporates the terrain surface deformation mechanism based on cellular automata. First, to examine the effectiveness of the proposed model to capture variations in the terrain surface deformation and draft force, an analysis of a vertical plate drag test was conducted based on the proposed model. Next, a single-wheel traveling analysis was performed. The experimentally obtained drawbar-pull and sinkage could be reasonably simulated, which cannot be easily realized using conventional methods.

Liquid Foaming Agent for Liquid Loading Reduction in Gas Producing Wells

The main objective of this research was to develop a liquid foaming agent for optimizing gas production in wells belonging to the Santa Rosa field in Área Mayor de Anaco, Venezuela. In this research, three liquid foaming agent formulations were developed with an anionic and amphoteric surfactants mixture, performing tests to evaluate foaming and lifetime on samples with different produced water/hydrocarbon condensate ratios. A liquid drag test was also carried out, explaining the liquid recovery performance after applying the developed formulations at different dosages and finally evaluated products results were compared with a commercial one. Formulation 1 obtained a higher liquid recovery compared to the other formulations, in addition, recovered liquid amount in dynamic drag tests decreased as the condensates composition increased in four samples evaluated. Formulation 1 and commercial product used as a reference did not have statistically significant differences.

Effect of Shear Flow on Drag Reducer Performance and Its Microscopic Working Mechanism

As the development of unconventional oil and gas resources goes deeper, the stimulation of reservoirs goes deeper year by year. Flow in longer wellbores poses a challenge to the stability of drag-reduction performance of fracturing fluid. However, at present we have limited understanding of the mechanism of drag-reduction damage caused by shear flow, especially the microscopic mechanism. Therefore, in this work, the variation pattern of drag reducer solution performance with shear rate has been analyzed by using a high precision loop flow drag test system. The test results show that there is a critical shear rate for the performance damage of the drag reducer solution, and high strength shear flow and cumulative shear flow time are the main factors leading to the performance degeneration of the drag reducer. Based on the nanometer granularity distributions, rheological properties and microscopic structures observed with a transmission electron microscope of drag reducer solutions subjected to shear flows of different velocities, it is confirmed that the damage to the microscopic structure of the solution is the main reason leading to its performance degeneration. The destruction of the microscopic structure causes the drag reducer solution to degrade in non-Newtonian characteristics, so it becomes poorer in its capability of reducing turbulent dissipation and drops in drag-reduction capability. This research can provide a reference for improving and optimizing drag-reduction capability of fracturing fluid.

Measurement technology in hypersonic wind tunnel

Integrated airframe/propulsion aerodynamic tests in a hypersonic wind tunnel are critical for developing an air-breathing hypersonic vehicle. Spurred by the shortcomings of traditional wind tunnel testing technology, this paper proposes a new aerodynamic testing technology called the balance-support integrated device (BSD). Additionally, we suggest a BSD optimization design method to improve BSD’s test performance. To reduce the impact of various interference signals on BSD‘s test accuracy, this study proposes an aerodynamic identification technology that effectively eliminates the influence of the model’s inertia force and the impact force generated by the joint BSD. We evaluate BSD’s performance by conducting several calibration tests, which reveal that the sensitivity of each BSD’s test channel is 2.3525 N/μV (drag test channel), 1.2691 N/μV (lift test channel), 9.7386 N.m/μV (pitching moment test channel). The test channel interference of lift to drag is less than 6.3 %, and drag to lift is less than 2.5 %, demonstrating that the wind tunnel force measurement system has an appealing sensitivity and less interference between the channels. Finally, we further challenge BSD’s test accuracy against the mature box balance technology on aerodynamic tests under Ma5.5, Ma6.0, and Ma6.5 conditions considering a 2-meter vehicle model in the Φ600mm pulse combustion wind tunnel. The test results highlight that the maximum test error of the lift test channel, drag test channel, and pitching moment Mz is 1.60 %, 6.45 %, and 4.99 %, respectively, proving that BSD can accurately measure the aerodynamic force during the test.

The Effect of External Power Output and Its Reliability on Propulsion Technique Variables in Wheelchair Users With Spinal Cord Injury.

The purpose of this study was to assess 1) how treadmill slope variance affected external power output (PO) and propulsion technique reliability; and 2) how PO is associated with propulsion technique. Eighteen individuals with spinal cord injury performed two wheelchair treadmill exercise blocks (0% and 1% treadmill slope, standardized velocity) twice on two separate days. PO, velocity, and 14 propulsion technique variables were measured. In a follow-up study, N = 29 performed wheelchair treadmill drag tests. Target and actual slope were documented and PO, intraclass correlation coefficients (ICC) and smallest detectable differences (SDD) were calculated. Within and between visits, the reliability study ICCs were perfect for velocity (1.0), weak for PO (0.33-0.46), and acceptable (>0.70) for five (0% slope) and 10 (1% slope) propulsion technique variables, resulting in SDDs of 35-196%. Measured PO explained 56-90% of the variance in key propulsion technique variables. In the follow-up, PO ICCs were weak (0.43) and SDDs high. Bias between target and actual slope appeared random. In conclusion, PO variability accounts for 50-90% of the variability in propulsion technique variables when speed and wheelchair set-up are held constant. Therefore, small differences in PO between interventions could mask the effect of the interventions on propulsion technique.

An Analysis of the Body Drag Test in Law Enforcement Recruits with Consideration to Current Population Demographics

An Analysis of the Body Drag Test in Law Enforcement Recruits with Consideration to Current Population Demographics