Test Section Research Articles

Design of a Wind Tunnel Nozzle Section Trolley Control System Based on Backstepping Method

Abstract To accommodate different types of supersonic wind tunnel tests, frequent replacements of nozzle sections and test sections are required, involving multiple complex technical processes. To optimize operational procedures and improve efficiency, a control system for the wind tunnel nozzle section trolley based on the backstepping method was designed. The system uses radio frequency identification (RFID) signals for station positioning and intelligently adjusts the speed and direction of the control motor, thus driving the trolley to move back and forth automatically. Through the simulation of the motor motion control model, the system effectively reduces random disturbances in the motion system caused by load changes, achieves precise positioning of wind tunnel plugins and nozzle assemblies, enhances system operating accuracy, reduces production cycle times, and realizes a one-button positioning function for all components, playing a significant role in improving wind tunnel test efficiency and operational quality.

Investigation of Grewia mollis Gum as Biopolymer Drag Reducing Agent

The hydraulic fracturing treatment relies heavy on fracturing fluid. Finding inexpensive polymer that lowers the pressure gradient in turbulent flow systems during hydraulic fracturing is crucial for the development of shale gas. Most researches focused on investigating the effects of polymers such as partially hydrolysed polyacrylamide, polyethylene oxide, guar gum, xanthan gum and synergies of mixtures as friction reducing polymers. The use of Grewia Mollis mucilage as the natural polymer as a potential friction reducer in slickwater fracturing treatment was the main focus of this study. The sample of Grewia gum was obtained and the mucilage was extracted from the inner stem bark by maceration in water at ambient temperature. The mucilage was the oven-dried at a temperature of 50 oC. Atomic Absorption spectrophotometer (AAS) and Fourier Transform Infrared (FT-IR) were employed to identify the elemental composition and the functional groups of the plant. The FT-IR spectrum exhibited typical peaks and bands characteristics of polysaccharide, while the ASS result shows the presence of minute quantity (0.219 mg/100 g) of lead (Pb) in the plant may show contamination (toxicity). The rheological measurements of the mucilage plotted on the shear viscosity graph exhibit shear-thinning or pseudo-plastic behaviour. Formulated slickwater fracturing fluid at various concentrations ranging from 200 to 500 ppm, were run in a constructed closed flow loop of 0.01905 m diameter of galvanised steel pipe, test section length of 2 m and entrance length of 2 m. Drag reduction was measured at flow rates (2.3, 2.8, 3.2, 3.6 and 4.0) m3/hour at different concentrations (200 to 500) ppm. Percentage friction reduction of 37% was achieved at Reynolds number of 74269 by addition of 200 ppm of the fluid while 56% was achieved at Reynolds number 74269 by addition of 500 ppm. This indicates that Grewia mollis mucilage exhibit drag reducing potential and can be applied in slickwater hydraulic fracturing application.

Research on shock wave driving technology of methane explosion

In order to improve the driving ability of the explosion wave simulation equipment, reduce the erosion effect of condensed explosives on the explosion wave simulation equipment, improve the safety of the test process, and make better use of the meteorological detonation driving method, it is necessary to optimize the source of the shock wave load in the driving section. Based on the finite volume method of FLACS, a methane detonation driving model corresponding to the test is established to explore the feasibility of using methane as an explosion source to test the structure against explosion shock wave. A methane detonation drive test was carried out to verify the accuracy of the numerical model. Finally, an engineering model for attenuation of shock wave overpressure peak value in pipeline is established by dimensional analysis, and the model coefficient is determined by numerical simulation and test data. The results show that the blast pressure is the highest when the methane volume ratio reaches 9.5 vol% in the methane-air mixture. Simply increasing oxygen content has little effect on the peak overpressure and positive pressure duration of shock wave. In the pure oxygen environment, the detonation effect can be achieved when the volume ratio of methane to oxygen is 1:2, and the incident pressure of the shock wave is proportional to the volume of the gas cloud. When the gas cloud volume is constant, a reasonable selection of methane-oxygen mixture ratio can achieve a better detonation effect, which can effectively increase the peak overpressure of the shock wave in the test section. The research results can provide technical reference for the development of new explosion wave simulation equipment.

Hydrodynamic Analysis of Pipelines Transporting Capsule for Onshore Applications

Abstract— Rapid depletion of energy resources hasimmensely affected the cargo transportation industry.Efforts have been made to develop newer economic andenvironmental friendly modes for this purpose. Bulk solidscan be transported for long distances effectively in pipelines.Raw materials can be stored in spherical containers(commonly known as capsules) transported through thepipeline. For economical and efficient design of anytransportation mode, both the local flow characteristics andthe global performance parameters need to be investigated.Published literature is severely limited in establishing theeffects of local flow features on system characteristics ofHydraulic Capsule Pipelines (HCPs). The present study focuses on using a well-validatedComputational Fluid Dynamics (CFD) based solver tosimulate the unsteady turbulent flow of a sphericalcapsule as a simplified case in HCPs for onshoreapplications. A novel numerical model has beenemployed in the present study with the aid of thedynamic mesh technique for calculating the pressureand the velocity variations within such pipelines. Thenumerical model comprises a straight test section. Thenumerical model for capsule flow yields realisticresults for the global flow parameters as compared tothe experimental data from the test rig developed inthe present study. The influence of the carrying fluid(water) on the capsule has been verified by estimatingthe shear forces and the friction coefficient. Inaddition, novel models have been developed forpredicting the wet friction coefficient considering thestart-up effect in such systems.

Motion Analysis of a Single Capsule in a Horizontal Hydraulic Pipeline

A Computational Fluid Dynamics (CFD) based solver is used to numerically analyze the motion of a single spherical capsule in a horizontal hydraulic pipeline. A novel numerical model is employed with the aid of the dynamic mesh technique for calculating the pressure and the velocity of the moving capsule. The numerical model comprises a 2m long straight test section of 50mm diameter. The results from the numerical model were close to those from the experimental data from the test rig developed in the study. The capsule is assumed to be a point mass rigid body and the coaxial-annular-flow model around the capsule is used to derive the boundary conditions for water flow at the capsule discontinuity region. The results are compared with experimental work done.

Flow boiling heat transfer characteristics and mechanism analysis of high-pressure water in parallel twin narrow rectangular channels

Experimental investigations on the flow boiling heat transfer characteristics of high-pressure water are carried out in parallel twin narrow rectangular channels. An integrated structure was utilized to define the geometry of the test section in this study. The cross-sectional size of a single channel measures 60 × 2 mm, with an effective heating and flow length of 1450 mm. Experiments encompass a range of pressures 10–16 MPa, mass flux 500–1500 kg m−2·s−1 and heat flux 100–300 kW m−2. First, the heat transfer characteristics in the parallel twin channels are determined. Results show the heat transfer and flow distribution between the twin channels are generally balanced, with only a slight fluctuation observed near the saturation point. Besides, for one narrow rectangular channel, the boiling heat transfer coefficient is found to be essentially affected by the system parameters. The increases in mass flux, heat flux, and pressure will all exert the promotion of boiling enhancement. Among these factors, pressure and heat flux have a relatively more pronounced impact. In addition, heat transfer mechanisms in narrow rectangular channel with a large aspect ratio under high-pressure conditions are analyzed in detail. The transverse buoyancy effect has been identified as a significant factor in the regions of single-phase forced convection and partial subcooled boiling. Once the heat transfer reaches the stage dominated by nucleate boiling, the bubble nucleation and motion behaviors constitute the primary factors of heat transfer enhancement, under the coupling effects of channel structure and high-pressure conditions.

Relationship between deflection basin parameters and backcalculated pavement layer moduli

In the case analysed, a glass fibre mesh was applied under the asphalt layer during a rehabilitation treatment. Because only one lane was reinforced, the test section can be used to observe the influence of glass fibre mesh on the relationship between the selected deflection basin parameters (RoC, BLI, MLI, and LLI) and back-calculated pavement layer moduli. The FWD measures were used to determine the bowl of deflection indicators and to back-calculate the layer’s moduli. The values of DBP-s allowed confirmation of the technical condition of pavement construction. The first measures were carried out in 2019 and repeated in 2021; the results were then compared and analysed. Influence was observed on the relationship between the deflection basin and moduli, especially for the base course and subgrade. The reinforced lane showed a better coefficient of determination between DBPs and moduli in 2019, but in 2021 relationships were observed only for LLI and subgrade moduli. The unreinforced lane, however, showed the mentioned relationships in both 2019 and 2021. Because of a relatively small number of measurement points, the presented analyses and observations should be considered as preliminary. Presented results and relationships are another step into developing an alternative approach to determining the initial pavement moduli i.e. to use as a seed moduli.

Analysis of the Application of Static Load Test in Bridge Bearing Capacity Testing

This article uses real engineering projects as examples to analyze how static load test technology is applied in testing the bridge-bearing capacity. The analysis covers aspects such as testing section layout, test load and efficiency coefficient, loading plan, evaluation optimization, test result modification, and result evaluation. The aim is to support the accurate detection and evaluation of bridge-bearing capacity.

Experimental Investigations of Heat Transfer in Simultaneously Developing Transitional Regime of Mixed Convection Flows in a Vertical Tube

Abstract The study of flow behavior in the simultaneously developing transitional regime of mixed convection flows is rare. It has been believed that the transitional regime will give a good compromise between pressure drop and heat transfer compared to laminar and turbulent flow regime. In this experimental study, the friction factor (f) and Nusselt number (Nu) characteristics for buoyancy-assisted and opposed flows of water in concurrently developing transitional regime of mixed convection through a vertical tube are studied. Experiments were done for Reynolds numbers (Re) varying from 500 to 15,000, Grashof numbers (Gr) from 1.25 × 104 to 5 × 106, Prandtl numbers (Pr) from 3 to 7, and Richardson numbers (Ri) from 0 to 0.1 subjected to uniform heat flux boundary conditions. A flow visualization provision after the test section which confirms an early transition in buoyancy-opposing flow (Rec = 2264) compared to buoyancy-aiding flow (Rec = 2468) at a fixed Ri of 0.1. Further, with the increase in Ri from 0 to 0.1, the average f decreases, and the average Nu increases in both aiding and opposing flows. It confirms that the onset of transition gets delayed with the increase of heat flux supplied in both the flows. Based on the present outcomes, an efficient heat exchanging device can be operated either to delay or advance the transition in a vertical pipe flow for optimum heat transfer.

How to select candidates for an undergraduate degree in psychology? Combining high-school GPA and admission test score

AbstractThe current study investigated whether the grade point average (GPA) of high school courses and the score on the test for admission to a bachelor’s degree in Psychology—assessing logical reasoning, reading comprehension, and general knowledge—can predict student academic success (AS) and to what extent. Archival data from 5147 candidates (82.4% female) collected over six years (2010–2016) were used. For 2559 of these, indicators of AS (graduation marks, average weighted marks, completion of the degree on time, and dropout) were also available. A series of hierarchical regressions were performed, in which the high school GPA was included as the first predictor, and the scores of the three sections of the admission test were included as the second set of predictors. Findings indicated high school GPA as the best predictor of AS. However, admission test scores predicted a portion of AS that the high school GPA was not able to account for. This result indicates that the administration of the admission test, which evaluates logical reasoning, reading comprehension, and general knowledge, can add relevant information to the high school GPA, thus increasing the efficacy in the selection of candidates, who can have the best chance to earn a bachelor’s degree in psychology.

Validation of a Hybrid Domain Overlapping Coupling Between SAM and CFD Against the TALL-3D Transients

The system thermal-hydraulic (STH) code SAM has been coupled to the computational fluid dynamics (CFD) code Simcenter STARCCM+ utilizing a hybrid domain overlapping coupling method in space and an explicit coupling in time. The coupling aims to extend the STH code’s applicability to scenarios where local momentum and energy transfers are important yet difficult for STH standalone models to capture, such as three-dimensional (3D) mixing and thermal stratification. The coupling method’s numerical stability was previously verified against multiple test cases including two closed-loop configurations, and it was validated against a double T-junction experiment with 3D scalar mixing. In the present work, the method is validated against the TALL-3D STH/CFD coupling benchmark facility. TALL-3D is a liquid-metal facility with a large, pool-type enclosure (test section) that exhibits 3D flow effects to be modeled by a CFD code. The rest of the system exhibits approximately one-dimensional behavior that is well predicted by a STH code. First, a STAR-CCM+ CFD model of the 3D test section is validated against experimental temperature data. Then a SAM-STARCCM+ coupled model is validated against six different TALL-3D steady states and includes SAM standalone results for comparison. Last, the coupled model is validated against two TALL-3D transients: one exhibiting flow reversal in the test section and one exhibiting nonlinear, limit cycle oscillations (LCOs). For the first transient, the SAM-STARCCM+ coupled model properly predicts an increase in the test section’s inlet temperature during flow reversal, and this increase is not predicted by the SAM standalone model. The coupled model also better predicts initial flow recovery and subsequent oscillations as the system approaches a final natural circulation state. For the second transient, no true final steady state is observed due to LCOs. Neither the SAM-STARCCM+ coupled model nor the SAM standalone model can perfectly capture the experiment’s changing oscillation frequency during the transient. Nevertheless, the coupled model does reproduce the general oscillatory feedback observed. This is a significant achievement because the present coupling only uses an explicit coupling in time, as opposed to a tighter, semi-implicit coupling. In comparison, STH/CFD coupling efforts previously performed by other authors required a semi-implicit coupling to obtain similar results to this work. The strengths of the novel coupling scheme validated in the present paper lie in the superior convergence characteristics and the much simpler, nonintrusive implementation.

In-situ pressure differential-accelerated mechanical fatigue testing and modeling of a reinforced fuel cell membrane

Modern polymer electrolyte fuel cells typically use reinforced membranes for improved mechanical durability. Due to costly experimentation, however, the fatigue properties of these membranes remain poorly understood. In this work, we employ the G'Sell-Jonas constitutive material model to investigate the mechanical fatigue response of a reinforced membrane under various environmental conditions in accelerated in-situ test settings. For fatigue evaluation, we utilize a novel pressure differential-accelerated mechanical stress test (ΔP-AMST) of shorter duration (<1 week) than previous AMSTs. The S–N curves constructed from experimental results at variable ΔP and temperature demonstrate inverse linear relationship between logarithmic fatigue lifetime and nominal stress, with greatly enhanced (∼10x) lifetime at reduced temperature. According to the results, a finite element-based fatigue model is developed and validated, which considers the impacts of hygrothermal fluctuations and strain rates. The model shows peak tensile stress during the dry phase at the center of the test section, which is consistent with the expected scenario for in-situ fuel cell membrane fatigue. Through this novel accelerated test and its modeling, it becomes possible to assess the fatigue lifetime of reinforced membranes under variable temperatures, humidity swings, pressure differentials, and swelling properties, in much shorter time than with standard protocols.

A Novel Method for Full-Section Assessment of High-Speed Railway Subgrade Compaction Quality Based on ML-Interval Prediction Theory.

The high-speed railway subgrade compaction quality is controlled by the compaction degree (K), with the maximum dry density (ρdmax) serving as a crucial indicator for its calculation. The current mechanisms and methods for determining the ρdmax still suffer from uncertainties, inefficiencies, and lack of intelligence. These deficiencies can lead to insufficient assessments for the high-speed railway subgrade compaction quality, further impacting the operational safety of high-speed railways. In this paper, a novel method for full-section assessment of high-speed railway subgrade compaction quality based on ML-interval prediction theory is proposed. Firstly, based on indoor vibration compaction tests, a method for determining the ρdmax based on the dynamic stiffness Krb turning point is proposed. Secondly, the Pso-OptimalML-Adaboost (POA) model for predicting ρdmax is determined based on three typical machine learning (ML) algorithms, which are back propagation neural network (BPNN), support vector regression (SVR), and random forest (RF). Thirdly, the interval prediction theory is introduced to quantify the uncertainty in ρdmax prediction. Finally, based on the Bootstrap-POA-ANN interval prediction model and spatial interpolation algorithms, the interval distribution of ρdmax across the full-section can be determined, and a model for full-section assessment of compaction quality is developed based on the compaction standard (95%). Moreover, the proposed method is applied to determine the optimal compaction thicknesses (H0), within the station subgrade test section in the southwest region. The results indicate that: (1) The PSO-BPNN-AdaBoost model performs better in the accuracy and error metrics, which is selected as the POA model for predicting ρdmax. (2) The Bootstrap-POA-ANN interval prediction model for ρdmax can construct clear and reliable prediction intervals. (3) The model for full-section assessment of compaction quality can provide the full-section distribution interval for K. Comparing the H0 of 50~60 cm and 60~70 cm, the compaction quality is better with the H0 of 40~50 cm. The research findings can provide effective techniques for assessing the compaction quality of high-speed railway subgrades.

Colour pervious concrete pavements applied to bikeway track: mechanical, hydraulic and functional performances

ABSTRACT Pervious concrete pavement test sections employing coloured permeable concrete were constructed as an experimental bicycle lane. For two of the sections, coloured concrete was used with pigment addition consisting of Fe2O3 (red) and Cr2O2 (green). The impacts on the resistance and stiffness of the concretes when using these pigments were analysed in relation to the reference concrete (grey). Alterations in plasticiser dosage during mixing were readily observed with the red concrete. The flexural strength increased substantially in the case of the red coloured concrete, as well as the modulus of elasticity of the material. Initial infiltration rates decreased with the use of coloured pigments, especially for red concrete, with expressive drops in permeability. Simultaneously, the resistance to friction given by the British Pendulum Number was reduced due to the use of red or green pigments. The consequences of using red pigment with a very high grains specific surface are discussed, since they are advantageous in the case of mechanical responses eventually inferior in terms of hydraulic and functional aspects.

Implementation of Text Mining to Detect Emotions of Fuel Price Increase Using BERT-LSTM Method

Fuel is essential in everyday life to be used as a means of transportation, which generally uses fuel oil. In early April 2022, there was an issue that caused an uproar in Indonesian society: rising fuel prices. Based on the problems described, this research uses emotion classification with the BERT and LSTM methods using social media data, such as YouTube, to classify types of emotions based on community responses to government decisions. The highest results were obtained when oversampling was used, with an accuracy of 95%, while without oversampling, the accuracy was only 47%. In the experiments that have been carried out, it turns out that using the oversampling method and the BERT method for emotion classification will cause a reduction in accuracy for the test section.

Dynamic response of a wind turbine wake subjected to surge and heave step motions under different inflow conditions

The development of floating offshore wind turbines poses new challenges since the floating platform introduces complex dynamics in the wind turbine wake. These wake dynamics are intricately tied to the advection velocity, referring to the velocity of the downstream propagation of the air flow, and used in the context of wind farm modelling. The present article investigates the far-wake dynamic response of a wind turbine model subjected to heave (up-down translation) and surge (fore-aft translation) step motions under two distinct inflow conditions. Wind tunnel experiments were conducted with hot-wires in a realistic turbulent inflow and a low shear and no ground effect inflow, achieved by varying the hub height of the wind turbine model in the atmospheric boundary layer developed in the test section. The results show that the dynamic response of the wake under the low shear and no ground effect inflow conditions aligns with a second-order system with the presence of undershoots and overshoots. In contrast, under realistic conditions, it appears like a first-order system with undershoots and overshoots less evident in most cases. Despite these variations the determined advection velocity remains roughly the same and consistent with the literature for both heave and surge step motions, regardless of the inflow conditions.

Application of BPNN algorithm in thermal-hydraulic analysis of unwrapped LFR core

Due to the complex structure of the LFR fuel rod bundle, refined CFD simulation consumes significant computing resources and time, making it difficult to meet the immediate needs of engineering design and research. This paper introduces a method that integrates the sub-channel level thermal-hydraulic analysis code CorTAF-LBE with the BPNN algorithm to analyze the thermal-hydraulic phenomena within the LFR core. The method has been validated by refined simulation results of the THEADES test section, which indicate that the error is within an acceptable range. The feasibility of its application in LFR fuel assemblies was also evaluated. The flow characteristics and temperature distribution in unwrapped LFR rod bundles are investigated. Due to differences in fuel distribution and flow area, the temperature in the central channel is much higher than that in the side and trapezoidal channels. Three accident conditions, including inlet blockage, center blockage, and outlet blockage, were simulated. The corresponding peak temperatures of the fuel cladding were 670 K, 767 K, and 860 K, respectively, representing an increase of approximately 170 K compared to the nominal conditions. The analysis results effectively demonstrate the 3D temperature distribution of the fluid in the rod bundles, which is significant for reactor design and safety analysis of LFRs.

Using 5TE Sensors for Monitoring Moisture Conditions in Green Parks.

The ground surface and subsurface of green parks in arid and desert areas may be subjected to desiccation as a result of weather and hot temperatures. It is not wise to wait until plants are turning pale and yellow before watering is resumed. Given the scarcity of water in typical desert zones, we recommend full control of irrigation water. This study presents a method of recycling irrigation water using 5TE sensors, employing time-domain reflectometry (TDR) technology. A trial test section was constructed along the coast of the eastern province of Saudi Arabia. Water recycling involves using clay-sand liners placed below the top agricultural soils to intercept excess water and direct it towards a collection tank, and then it is pumped out to a major water supply tank. The main properties of soils and clay-sand liners normally taken into account include moisture content, density, and hydraulic conductivity. An assessment of geotechnical properties of clay-sand mixtures containing 20% clay content was conducted. The profiles of moisture and temperature changes were monitored using 5TE sensors and data loggers. The 5TE sensors provided continuous measurements at varying temperatures and watering cycles. Twenty-nine watering cycles were conducted over a six-month period. An additional section was considered with a liner consisting of the same clay but enhanced with bentonite as one-third of the clay content. The volumetric water content was found to vary from 0.150 to 0.565 following changing weather and direct watering cycles. The results indicated that the use of a TDR instrumentation is a cost-effective and time-saving technique to construct a system for saving irrigation water.

Low-Cost Portable Road Smoothness Testing Method Based on Pseudo-Vibration Velocity Range

Road smoothness not only directly affects the safety and comfort of vehicle travel but also relates to the efficiency and cost-effectiveness of road maintenance. Traditional road smoothness detection methods usually require professional equipment and personnel, leading to high costs and cumbersome operations. Therefore, finding a low-cost, simple, and accurate method for detecting road smoothness is of great significance. This study uses vehicle-mounted acceleration sensors to detect road smoothness, establishing a correlation between driving vibration acceleration data and the international roughness index (IRI). For this research, a driving vibration acceleration data acquisition device was developed, and the driving acceleration data from the test sections were denoised and their feature values extracted. The pseudo-vibration velocity range was used as the characteristic index representing the road surface smoothness IRI value. Testing with different vehicle types showed that the method is applicable to both sedans and SUV models, yielding a relative error of 8.9% for the sedan smoothness test model and 6.7% for the SUV smoothness test model. This study contributes to conducting large-scale road smoothness detection at a low cost, improving the efficiency of road maintenance and operations.

Influence of the contraction section configuration and deflector layout density on the wind-snow flow characteristics inside the ice snow wind tunnel for railway vehicles

The significant accumulation of snow and ice in the bogie region severely compromises operational quality and poses a safety hazard to high-speed trains. To enhance testing capabilities for assessing ice and snow accumulation within bogie regions, this study conducts numerical investigations into the influence of contraction section configuration and deflector layout density on wind-snow flow quality within an ice and snow wind tunnel. The predictive accuracy of the numerical method is comprehensively validated against wind-snow wind tunnel tests, involving a comparison of airflow velocity in the test section and snow accumulation thickness on the channel's floor. The results demonstrate that the coupled numerical method of Improved Delayed Detached Eddy Simulation (IDDES) and Discrete Phase Model (DPM) is a reliable tool for analyzing wind-snow flow characteristics within an ice and snow wind tunnel. Furthermore, compared to the vickers curve and bicubic curve, quintic curves applied to the contraction section consistently compress and accelerate airflow. This contributes to a more uniform flow characterized by lower stream-wise fluctuation levels, pitch angles, and yaw angles in the test section, thereby significantly enhancing the overall flow quality of wind and snow. Thus, the quintic curves or smoother curves are recommended for the design of the contraction section in ice and snow wind tunnels. Moreover, increasing the deflector number leads to a noticeable improvement in flow quality inside the test section, while resulting in increased snow accretion on the windward surfaces of deflectors. Hence, a medium-level deflector density is suggested for designing ice and snow wind tunnels to achieve a better balance between flow quality and the additional snow accretion inside the channel.