Velocity Profile Data Research Articles

Numerical solution of nanofluids mixing processes in T-mixer equipped titled gate

AbstractIn this study, a numerical simulation technique is employed to predicate the temperature distribution and velocity profile data of cold and hot nanofluids within a T-mixer was studied. The mixing of nanofluid flow with Al2O3 nanoparticles of 50 nm flows at Φ = 0.4 vol.% in a T-shaped mixer. The present numerical problem has been solved using the COMSOL Multiphysics version 5.4. Six angle of inclination was studied (θ = 15, 30, 45, 60, 75, and 90°) of the gate and evaluated its effects on the temperatures and velocity contour in the T-junction. The study's findings indicated that the presence of a gate in a stationary, non-rotating flow regime has a noteworthy impact on the stationary vortex flow. Also, the mixing occurs more quickly at angles of 45 or 60°. Mixing at a 30° or 90° angle took longer.

TG Vascutrack: A User-Friendly and Open-Source Software for Automated Extraction of Arterial Diameter and Velocity Profile Data From Vascular Ultrasound Videos.

Existing automated software for vascular ultrasound data extraction lacks free, open-source options suitable for professionals without coding experience. These programs typically include signal-cleaning algorithms, resulting in processed output without access to raw data. To address these needs, we developed TG Vascutrack, an open-source and user-friendly software tailored for non-coder professionals. It features a graphical interface, multiple functionalities, and provides access to raw data. Comparative analysis against validated software and manual extraction revealed minimal biases and standard deviations in diameter and velocity measurements. TG Vascutrack offers a free, promising solution for non-coders needing automated vascular ultrasound data extraction.

Scaling of drag reduction and logarithmic profile in the turbulent boundary layer over micro-grated superhydrophobic surfaces

We developed a dedicated, high-resolution skin-friction balance in a water tunnel to measure turbulent drag reduction over micro-grate-patterned superhydrophobic (SHPO) surfaces at the Reynolds number ReL ranging from 4.1 × 105 to 6.9 × 105 and achieved a significant drag reduction of up to 46%. The correlation between drag reduction and surface topology was investigated. By considering air fraction, micro-grate gap, and meniscus curvature, an empirical scaling for drag reduction was proposed, which reconciles the widely scattered drag reduction data in the literature. This scaling law could provide a valuable guidance on future design of effective SHPO surfaces for real-world applications. The scaling of the logarithmic layer was also analyzed under the condition that the outer layer has not fully adapted to the SHPO wall manipulation, a common occurrence in experiments due to the limited length of fabricated SHPO surfaces. The slope of the logarithmic layer was found to increase with the drag reduction. Moreover, a theoretical expression describing the slope and up-shifting level of the logarithmic profile was proposed. These results are insightful, providing a new perspective for researchers to examine their velocity profile and drag reduction data in turbulent boundary layers.

Passive acoustic localization using dictionary learning

Ray-trace simulations are used to demonstrate the use of Dictionary Learning to improve passive localization of a source monitored with a vertical linear acoustic array. The learned dictionary, generated using historical sound velocity profile (SVP) data from a region of interest, is an over complete, sparse representation of the SVP training set. By minimizing an objective function that measures the differences between multipath reception intervals detected at a receiver for propagation through candidate and baseline SVP profiles, we show that an optimal SVP match to the “unknown” baseline can be reconstructed by an efficient dictionary search. Ray traces back-propagated through the reconstructed SVP according to beamformed receive angles computed with the baseline SVP are then found to well estimate the source position as the centroid of a cluster of multipath signal intersections. The accuracy for small unit-sparsity dictionaries of size up to 50 was evaluated on a randomly sampled, 30 SVP testing set obtained from an area close to that of the training set, demonstrating mean location errors less than 5% in both distance and depth. Five representative profiles spanning the range of observed sound speed variations were used to assess localization performance at source depths from 50 to 450 m and at source ranges from 2000 to 4500 m. Compared to using the average sound speed profile to estimate source position, using the learned dictionary produced a general performance increase in position accuracy.

Analysis of Nuclear Explosion Detection Capability of IMS Hydroacoustic Network

The Comprehensive Nuclear Test Ban Treaty (CTBT) organization has established a hydroacoustic network to ensure the effective detection of nuclear explosions in the vast ocean and in the atmosphere over it in order to effectively guarantee the implementation of the treaty. To assess its effectiveness, according to the reciprocity of underwater acoustic field, this study employs the hydrophone position as the central sound source and utilizes the parabolic equation, along with seabed topography and sound velocity profile data, to estimate the transmission loss. Background noise levels of station evaluation are conducted by using historical data so as to estimate the underwater nuclear explosion sound source level via a passive sonar equation. Utilizing the full ship shock trial (FSST) results of the “Ford” aircraft carrier on June 18, 2021, as a case study, the detection capability of the HA10 station for nuclear explosions is investigated. Subsequently, the network’s overall detection capability was evaluated using the source level at 20 Hz corresponding to a 1 kiloton nuclear explosion yield as a reference. Findings indicate the network’s proficiency in identifying long‐distance propagation signals, particularly those with high explosion source levels within the sound fixing and ranging (SOFAR) channel. The sensitivity analysis demonstrates the network’s ability to detect explosions smaller than 1 kg equivalent in close proximity to a station, and larger explosions exceeding 1 kg or 1 ton at greater distances. This evaluation underscores the network’s significance in detecting and monitoring underwater nuclear explosions across extensive oceanic regions.

VS30-based relationship for Chinese site classification

Classification of engineering sites is essential when considering site conditions for seismic fortification in seismic design codes. However, because of different site classification methods, it is difficult for Chinese seismological and engineering communities to share site metadata (e.g., site classes) and relevant results with international communities. This issue also prevents the Chinese communities from utilizing well-established models based on the time-averaged shear wave velocity for the top 30 m (VS30). This study aims to close the gap and develop a consistent VS30-based site classification method. We first assemble the shear wave velocity (VS) profile data from various sites in China, Japan, and California to study the statistical characteristics of VS30 and the equivalent shear wave velocity (VSe, time-averaged within soil layers for ≤ 20 m, which is used in Chinese site classification). We then investigate the efficiency of site classification by VS30 and VSe alone, respectively. We find that the single VSe parameter is insufficient to distinguish different Chinese site classes, especially for site classes III and IV (which consider soil layers deeper than 20 m). In contrast, the VS30 parameter can effectively differentiate Chinese site classes from I0 to IV. A new VS30-based site classification method for Chinese sites is then developed. The boundaries of VS30 for each Chinese site class are determined by maximizing the rate of correctness. Our new VS30-based classification facilitates the connection of Chinese site classes with well-developed VS30-based models and site data sharing between Chinese and international scientific communities.

The Application of Microtremor Exploration Technology in Thick Loess Area of Lanzhou

For the large thickness loess area in Lanzhou, engineering application research on excavated off-set loess using microtremor exploration technology. In this paper, by detecting the surface wave velocity structure of a single point, comparing the dispersion curve data of a single point with the borehole data, and comparing the surface wave velocity profile data with the engineering geological profile, the judgment basis of soil-rock interface and strong-medium interface is put forward. The stratigraphic structure of the loess area with large thickness is accurately divided; By analysing the relationship between the surface wave value of the borehole and the physical and mechanical indexes of the soil, the relationship curves of surface wave-porosity ratio, surface wave-density and surface wave-collapsibility coefficient are studied, and the fitting curves of each curve are obtained and the correlation is summarized. Through the research of this paper, it has certain guiding significance for the application of microtremor exploration in large thickness loess area.

Numerical Study of Flow Downstream a Step with a Cylinder Part 1: Validation of the Numerical Simulations

The backward-facing step flow (BFSF) is a classical problem in fluid mechanics, hydraulic engineering, and environmental hydraulics. The nature of this flow, consisting of separation and reattachment, makes it a problem worthy of investigation. In this study, divided into two parts, the effect of a cylinder placed downstream of the step on the 2D flow structure was investigated. In Part 1, the classical 2D BFSF was validated by using OpenFOAM. The BFSF characteristics (reattachment, recirculation zone, velocity profile, skin friction coefficient, and pressure coefficient) were validated for a step-height Reynolds number in the range from 75 to 9000, covering both laminar and turbulent flow. The numerical results at different Reynolds numbers of laminar flow and four RANS turbulence models (standard k-ε, RNG k-ε, standard k-ω, and SST k-ω) were found to be in good agreement with the literature data. In laminar flow, the average error between the numerical results and experimental data for velocity profiles and reattachment lengths and the skin friction coefficient were lower than 8.1, 18, and 20%, respectively. In turbulent flow, the standard k-ε was the most accurate model in predicting pressure coefficients, skin friction coefficient, and reattachment length with an average error lower than 20.5, 17.5, and 6%, respectively. In Part 2, the effect on the 2D flow structure of a cylinder placed at different horizontal and vertical locations downstream of the step was investigated.

Experimental Determination Of Parameters Of Flow Structure Of Filtration Currents Through Layers Of Adsorbent Granules In Ecological Mass Exchange Equipment

A new method of processing experimental data and identifying parameters of flow structure by gas phase under conditions of filtration currents through layers of adsorbent granules in ecological mass exchange equipment is presented. Experimental data of gas phase velocity profiles and procedure of conducting experimental studies are presented. Basic design dependencies are given for determining parameters of flow structure by gas phase, based on treatment of experimental dependencies of non-uniformity of fields of flows of filtration currents through layers of adsorbents. An example is given of constructing C- and F-response curves that allow you to recognize models of flow structures by a continuous gas phase and increase the accuracy of mathematical modeling of mass exchange environmental systems.

Image systems for regularised Stokeslets at walls and free surfaces

Flow around, and hydrodynamic forces on, moving objects can be determined for low Reynolds numbers by superposing elemental Stokeslets to enforce velocity boundary conditions. The method of regularised Stokeslets provides a computationally-practical approach, replacing a sum over singular point elements by one over finite distributed sources. Flow disturbances extend a considerable distance in low-Re flow (typically falling off in magnitude as the reciprocal of distance) and the presence and nature of a nearby boundary cause a profound change to forces on moving objects. Representing boundaries by additional Stokeslets requires significantly more computational resources, so it is common to represent single planar boundaries by the method of images.Here we formally state the image systems for regularised Stokeslets in the case of plane no-slip walls and free surfaces in a form that is independent of orientation and in canonical six-term forms (for velocity) and three-term forms (for pressure) that are convenient for computation. We validate our implementation using exact solutions (sphere moving in unbounded flow and parallel or perpendicular to slip or no-slip boundaries) and previous simulations (translating and rotating helical filament). We then present new comparisons with experimental data for velocity profiles and forces on objects translating (towed cube in a confined tank) and rotating (helical micro-robot). Our simulations illustrate competing physical effects near a boundary. For an object moving, or propelling fluid, toward or away from a boundary, whether slip or no-slip, an increase in thrust is required to redirect fluid through 90°; viscous drag on a no-slip boundary increases the resistance coefficient further. For an object moving parallel to a boundary, however, opposing effects with different range come into play: the absence of fluid above the boundary reduces the required overall thrust on the fluid over a wide range of gap sizes, but enhanced viscous drag near a no-slip wall exceeds this at small gap sizes.

Modeling of Bubbly Flow using a Combined Volume of Fluid and Discrete Bubble Model: Investigation on Interphase Forces

The gas-liquid two-phase flow with interfacial behaviors and bubble-liquid interactions is widely encountered in industrial processes such as that in gas-liquid reactors. The complicated phase structure makes it difficult to be modeled. The present work proposes a multi-scale mathematical model to simulate the bubbly flow in a square column. The volume of fluid (VOF) method is applied to treat the separated interface, and the discrete bubble model (DBM) is incorporated to handle the dynamics of dispersed bubbles. The hybrid model is validated against the benchmark experimental data to study the accuracy and suitability of the modeling framework for bubbly flows. And the influence of interphase forces on bubbly flow patterns and velocity profiles is investigated. It is found that the employment of both pressure gradient force and Ishii-Zuber drag model provides fairly good agreements with experimental data for velocity profiles.

Determination of Skin Friction Factor in Gravel Bed Rivers: Considering the Effect of Large-Scale Topographic Forms in Non-Uniform Flows

Determination of skin friction factor has been a controversial topic, particularly in gravel-bed rivers where total flow resistance is influenced by the existence of small-scale skin roughness and large-scale topographic forms. The accuracy of existing models predicting skin friction factors in conditions where small-scale skin roughness and large-scale topographic forms exist is very low. The objective of this study is to develop a modified model that improves the accuracy of the determination of skin friction factors in gravel-bed rivers. To this end, 100 velocity profile data obtained from eight gravel-bed rivers were utilized to develop an analytical method that considers the momentum thickness of the boundary layer and its deviation in large-scale topographic bedforms in a 1D force-balance model. The results show that the accuracy of the skin friction factors is enhanced when (1) the model is in the form of an exponential function of energy slope, and (2) the deviation of momentum thickness is considered in the model. The proposed model results in high accuracy of the predicted skin friction factors for energy slopes between 0.001 and 0.1, which exist in most gravel-bed rivers with different morphologies. Additionally, this study model was used to modify the classic Einstein–Strickler equation. The modified equation resulted in improved accuracy of the predicted skin friction factors in non-uniform flow conditions even when velocity profiles and energy slope were not available.

The effect of high‐fidelity flow models on electromagnetic flowmeter analysis

AbstractThe current research is unclear regarding the sensitivity of the output of a magnetic flowmeter analysis to the fidelity of the simulated flow field. This study evaluates the effects of higher fidelity models on magnetic flowmeter analysis. An eddy viscosity model, second‐moment closure model, and a Large‐Eddy simulation were compared to laboratory velocity profile data 0.67D downstream of a 1.58D elbow at a Reynolds number of 34,000. The Large‐Eddy simulation results matched the laboratory velocity profile data best. The authors conclude that the fidelity of the flow field model does cause differences in the analysis of the flowmeter voltage output.

Remote Sensing to Characterize River Floodplain Structure and Function

Advancing understanding of the complexities and expansive spatial scales of river ecology can be enhanced through the application of remote sensing. We obtained satellite (Quickbird) and airborne (LIDAR, hyperspectral, multispectral, and thermal) imagery data of an alluvial gravel-bed river floodplain in western Montana to quantify both riparian and aquatic habitats and processes. LIDAR data provided a detailed bare earth DEM and vegetation canopy DEM. We classified river hydraulics and aquatic habitats using a combination of the satellite multispectral, airborne hyperspectral, and LIDAR data coupled with spatially-explicit acoustic Doppler velocity profile data of water depth and velocity. Velocity, depth, and Froude classifications were aggregated into similar hydraulic zones of river habitat classes. Thermal imagery data were coupled with field measurements of temperature and radon gas tracer to identify patterns of water exchange between the alluvial aquifer and the surface. We found a high complexity of aquatic surface temperatures and radon tracer linked to groundwater discharge from the alluvial aquifer. Airborne hyperspectral data were used to identify “hot spots” of periphyton production, which coincided with the complex nature of groundwater–surface water exchange. Airborne hyperspectral data provided differentiation of vegetation patches by dominant species. When the hyperspectral data were coupled to LIDAR first return metrics, we were able to determine vegetation canopy height and relative vegetation patch age classes. The integration of these various remote sensing sources allowed us to characterize the distribution and abundance of floodplain aquatic and riparian species and model processes of change through space and time.

Velocity Optimization and Robust Energy Management of Connected Power-Split Hybrid Electric Vehicles

AbstractThis paper focuses on an eco-driving-based hierarchical robust energy management strategy for connected and automated hybrid electric vehicles in the presence of uncertainty. The proposed control strategy includes a velocity optimizer, which evaluates the optimal vehicle velocity, and a powertrain energy manager, which evaluates the optimal power split between the engine and the battery in a hierarchical framework. The velocity optimizer accounts for regenerative braking and minimizes the total driving power and friction braking over a short control horizon. The hierarchical powertrain energy manager employs a long- and short-term strategy where it first approximately solves its problem over a long time horizon (the whole trip time in this paper) using the traffic data obtained from vehicle-to-infrastructure (V2I) connectivity. This is followed by a short-term decision maker that utilizes the velocity optimizer and long-term solution, and solves the energy management problem over a relatively short time horizon using robust model predictive control (MPC) methods to factor in any uncertainty in the velocity profile due to uncertain traffic. We solve the long-term energy management problem using pseudo-spectral optimal control method, and the short-term problem using robust tube-based MPC method. Simulation results with standard driving cycle velocity profile and real-world traffic data show the competence of our proposed approach. Our proposed co-optimization approach with long- and short-term solution results in ≈12% more energy efficiency than a baseline co-optimization approach.

Simultaneous Measurement of Two-Phase Flow Parameters for Drift-Flux Model

The drift-flux model is widely used in study, calculation and design of two-phase flow. It is a highly efficient model that requires little computation resources. In the model, accurate calculation of the distribution parameter C0 and the drift velocity Vgj is a critically important factor. The calculation requires simultaneously measured data of phase velocity and void fraction distributions or profiles. By using currently widely used methods for two-phase flow measurement, satisfying the requirement is highly difficult. This paper presents novel results of simultaneous measurement of the phase velocity and void fraction profiles in a vertical round tube of 50 mm inner diameter. A combination measurement method has been developed. It comprises the multiwave Ultrasonic Velocity Profile (multiwave UVP) method and the Wire Mesh Tomography (WMT). Based on the measured data, C0 and Vgj have been calculated. They have been compared with those of the published experimental data and correlations. Analyses of the measured data have been carried out. For the first time, the analysis results reveal the variation of C0 and Vgj in the measured flow conditions. More importantly, the data obtained are also useful for the development and validation of the computational codes for two-phase flow.

Effect of SDS surfactant on gas-liquid flow and slug characteristics in slightly upward pipeline

A new pigging approach with SDS (Sodium dodecyl sulfate) surfactant was proposed for foam drainage in the gathering pipelines with wet gas production, especially for the pipeline section with a great pigging risk. For this purpose, the loop of gas-liquid two-phase flow with a 3 ° slightly upward pipeline was designed. The flow pattern characteristics of gas-liquid two-phase flow were collected by a high-speed camera, and the flow patterns with typical morphological structure were classified. Ultrasonic Doppler velocimeter and ultrasonic transducer were used to measure the velocity signal of the liquid phase near the pipe, and the slug frequency was calculated accurately according to the change of velocity profile data. The slug length was measured by the signal collected by pressure and differential pressure transmitter. The results show that with the addition of SDS surfactant, the flow pattern of gas-liquid two-phase flow is obviously improved, and the working condition of slug flow is suppressed. Besides, in the specific slug flow condition, the slug frequency decreases significantly and the slug length increases. It indicates that the addition of SDS surfactant is favorable to liquid discharge, and provide a reference value for the application of SDS surfactant in foam drainage in wet-gas gathering pipelines.

Assessment of Turbulence Models for Low Reynolds Number Flows and Their Computational Costs, Part 1: Staggered Tube Bank

Abstract This study investigates the accuracy of computational fluid dynamics (CFD) models to predict heat transfer in turbulent separated flows at low Reynolds numbers. This article will focus on flow in a staggered tube bank, while its companion articular will focus on a square prism (cylinder) in cross flow. Experimental data for both local heat transfer and velocity profiles are available for these cases and have been used extensively in the literature to evaluate various CFD methods. Six unsteady models were used and the results show that the unsteady shear stress transport (SST) model provided good overall accuracy relative to the mean Nusselt number for both cases. However, the SST model failed to accurately predict local variations. The partially averaged Navier–Stokes (PANS) variant of the SST model did show a marked improvement over the baseline SST model. The dynamic Smagorinsky large eddy simulation (LES) showed a much-improved fidelity to the local Nusselt number but unpredicted the actual values. The computational cost for the LES model was significant and it was found that the computationally expensive models with higher degrees of resolved turbulence did not necessarily return better results. Finally, the pressure drop results for the six models were scaled to predict the mean Nusselt number with the generalized Leveque method and were found to be very accurate. This method should prove useful to predict heat transfer performance with computationally less expensive cold flow results.

Use of Machine-Learning and Load-Velocity Profiling to Estimate 1-Repetition Maximums for Two Variations of the Bench-Press Exercise.

The purpose of the current study was to compare the ability of five different methods to estimate eccentric–concentric and concentric-only bench-press 1RM from load–velocity profile data. Smith machine bench-press tests were performed in an eccentric–concentric (n = 192) and a concentric-only manner (n = 176) while mean concentric velocity was registered using a linear position transducer. Load–velocity profiles were derived from incremental submaximal load (40–80% 1RM) tests. Five different methods were used to calculate 1RM using the slope, intercept, and velocity at 1RM (minimum velocity threshold—MVT) from the load–velocity profiles: calculation with individual MVT, calculation with group average MVT, multilinear regression without MVT, regularized regression without MVT, and an artificial neural network without MVT. Mean average errors for all methods ranged from 2.7 to 3.3 kg. Calculations with individual or group MVT resulted in significant overprediction of eccentric–concentric 1RM (individual MVT: difference = 0.76 kg, p = 0.020, d = 0.17; group MVT: difference = 0.72 kg, p = 0.023, d = 0.17). The multilinear and regularized regression both resulted in the lowest errors and highest correlations. The results demonstrated that bench-press 1RM can be accurately estimated from load–velocity data derived from submaximal loads and without MVT. In addition, results showed that multilinear regression can be used to estimate bench-press 1RM. Collectively, the findings and resulting equations should be helpful for strength and conditioning coaches as they would help estimating 1RM without MVT data.

Numerical and perturbative analysis on non-axisymmetric Homann stagnation-point flow of Maxwell fluid

In this paper, we examined the numerical and perturbative analysis of non-Newtonian fluid towards non-axisymmetric Homann stagnation-point flow. The Maxwell fluid model is applied to investigate the behavior of viscoelastic fluid for this particular geometry. The influence of Maxwell parameter {beta }_{1} and ratio gamma on different profiles are addressed in this analysis. The governed partial differential equations are reduced to ordinary differential equations with the help of similarity transformations. The numerical and perturbative outcomes of the resulting system of differential equations are obtained by applying the shooting technique. The solution is achieved for diverse values of relaxation time parameter {beta }_{1} and ratio gamma. The wall shear stress is compared to their large-gamma asymptotic behaviors and displacement thicknesses are also presented. The numerical data for velocity profiles are obtained in terms of plots. It is predicted through analysis that a gradual increase in relaxation time raises wall skin friction components. On the other hand, velocity decreases which constitutes to reduce the reverse flow. Meanwhile, displacement thicknesses in x and y direction decreases. However, three-dimensional displacement thickness increases due to more viscoelastic material like Maxwell fluid than viscous fluid.