bluuebunny/crossref_metadata_2025 huggingface dataset:
Mode Transition Of A Flexible Film Motion In The Circular Cylinder Wake
Authors: Duan Fan , Wang Jinjun
Published: July 2024

The fluid-structure interaction between a flexible film and the wake of a circular cylinder is an abstract of a series of natural phenomena like flag flapping and fish swimming. Diverse patterns of both solid deformation and fluid dynamics arise in this coupling system as the nondimensional parameters are varied. In our recent experiments, we find that beyond the extensively studied periodic coupling process, irregular processes also emerge in this system under specific conditions. However, due to the complexity inherent in the irregular coupling processes, no in-depth investigation into this topic is available yet. In this work, we delve into the irregular aperiodic flutter of a flexible film behind a circular cylinder in the uniform flow as well as the related irregular evolution of flow structures. Two representative cases of film streamwise length (L/D) pertinent to the irregular process, specifically L/D=3 and L/D=4, have been investigated experimentally in the wind tunnel with time-resolved synchronized measurements of both film deformation and flow field. Continuous wavelet transform and virtual dye visualization are employed to extract the time-frequency characteristics of film motion and Lagrangian coherent structures in the flow fields during the film’s irregular flutter, respectively. It is determined that the irregular flutter is aperiodic in terms of the overall view, but it also encompasses transient quasi-periodic stages as its motion modes alter. Hence, we term this irregular flutter as the “hybrid flutter” state. In the quasi-periodic stages of the hybrid flutter, the large-scale vortex structures are periodically formed on the surfaces of the film and evolve in the wake as a Kármán vortex street. The periodic formation of large-scale vortices exerts periodic alternating force on the film, which, therefore, leads to the quasi-periodic flutter of the film with the second-order mode. By comparison, the aperiodic stage entails the significant extension of the separated shear layers in such a way that the whole film is enveloped by the shear layers; then, large-scale vortices are formed downstream of the film’s trailing edge. In this scenario, no periodic force is acted on the film; as a result, the film flutters aperiodically with the first-order mode.
Spatiotemporal Filter Velocimetry With Arbitrary-Shaped Measurement Region For Accurate Measurement In The Vicinity Of A Boundary
Authors: Hosokawa Shigeo
Published: July 2024

Viscous stress at a boundary or an interface is a source of drag acting on a body or a fluid particle and therefore its measurement is of great importance for understanding the motion of the body or the fluid particle. In this study, spatiotemporal filter velocimetry (SFV: Hosokawa & Tomiyama, 2012) is extended to arbitrary quadrilateral measurement areas fitted to an interface shape for accurate measurement of flow about a deformed drop, and it is applied to flows about single drops of glycerol-water solution falling in stagnant silicon oil under clean and contaminated conditions. Figure 1 shows the trajectories of tracer particles and the measured velocity distributions. No separation is observed for the spherical and ellipsoidal drops. On the other hand, the stagnant region is observed in the dimple region of the tail of the cap drop. These results clearly indicate that the flow about the deformed drop is successfully measured by SFV with arbitrary quadrilateral measurement areas. Figure 2 shows the trajectories of tracer particles and the measured velocity distributions of single ellipsoidal drops in clean and contaminated systems. Triton X-100 was used as the surfactant and its concentration C in the drop ranges from 0.0 to 0.1 mol/m3 . The drop tail becomes flat and then slightly dimpled shape, and the internal circulation becomes weak as C increases. The internal circulation remains even at the high surfactant concentration condition under which the internal circulation in single spherical drop is fully damped (Hosokawa et al., 2017). We also evaluate interfacial velocity, interfacial shear stresses, the Marangoni stress and surfactant concentration at the interface from measured velocity distributions in the vicinity of the interface. As a result, we confirmed that SFV enables us to measure velocity distribution about a single deformed drop and enables us to evaluate interfacial velocity, interfacial shear stresses, the Marangoni stress and surfactant concentration at the interface.
Depth from Defocus Technique For High Number Density Particle Images
Authors: Xu Rixin , Huang Zuojie , Gong Wenchao , Zhou Wu , Tropea Cameron
Published: July 2024

The Depth from Defocus (DFD) imaging technique is used to measure the size and number concentration of particles in dispersed two-phase flows, but until now it has primarily been applied to low concentration particle images. This study explores how the technique can be extended to handle overlapping images caused by neighboring particles, significantly broadening the application scope of the DFD technique and enabling measurements at higher particle number/volume concentrations. The processing algorithms are experimentally validated using a dedicated apparatus that can systematically vary particle size, shape, and degree of image overlap. Additionally, this study explores the use of Convolutional Neural Networks (CNN) for this task, comparing these results with those obtained using conventional analyses in terms of accuracy, tolerable concentration limits, and computational speed. This approach
requires a large teaching dataset of images, which is only practical and feasible if the dataset can be synthetically generated. An image generation procedure for out-of-focus neighboring spherical particles, resulting in a known blurred image overlap, is therefore first developed. This procedure is validated using laboratory images with known particle size distribution, position, and image overlap before creating the teaching dataset. The trained processing scheme is then applied to both synthetic datasets and experimental data, allowing the evaluation of the technique’s limits in
terms of image overlap and tolerable volume concentration, as a function of particle size distribution.
LIF Thermometry With A sCMOS Color Camera And Multiple Dyes
Authors: Mucignat Claudio , Rösgen Thomas , Lunati Ivan
Published: July 2024

We propose a method to perform accurate temperature measurements by means of Laser Induced Fluorescence (LIF). We use a sCMOS color camera and a 2-dye solution based on RuPhen, excited in the blue part of the visible spectrum. By changing the relative concentration of the dyes we can manipulate the color channels temperature sensitivity, which allows us to apply a laser power correction which is robust and less affected by image noise compared to convectional ratiometric approaches. Another advantage is that the overall temperature sensitivity is only partially reduces compared to the one of RuPhen, which is not the case if a ratiometric approach is chosen. The method is demonstrated on a bench-top setup, where temperatures can be precisely controlled. An error analysis shows that an accuracy better than 0.5 ◦ C is possible. The correction method can be applied to other measurement techniques, such as Pressure Sensitive Paints (PSPs).
Extension Of Spatial Filtering Technique Using Kalman Filters For Real-Time Pipe Flow Profile Measurements
Authors: Otto Jonas , Steinmetz Tino , Schaeper Martin , Damaschke Nils
Published: July 2024

Spatial filtering is used for real-time velocity measurement due to its computational efficiency. However, this method can be noisy in real measurement environments, requiring the averaging of a substantial number of measurements to achieve reliable results, which compromises temporal resolution. This study proposes enhancing the spatial filtering algorithm by implementing Kalman filtering for pipe flow profile measurements. Kalman filtering is expected to mitigate the noise issue more effectively than traditional methods like low-pass filtering while maintaining or improving the temporal resolution of measurements.
Fluorescence Lifetime Measurement For Studying Evaporation Of Bi-Component Droplet
Authors: Wang Minghao , Stiti Mehdi , Castanet Guillaume
Published: July 2024

Sprays are essential in engineering applications like evaporators and combustion chambers. Predicting the evaporation of multi-component liquid droplets is complex due to changing composition and properties. Measuring droplet composition is challenging, with limited non-intrusive methods available. Raman spectroscopy faces hurdles like weak signals and interference. Intensity based Laser-Induced Fluorescence (LIF) requires optical models to interpret data due to varying droplet size and position. Fluorescent dyes in liquid mixtures are sensitive to temperature, complicating measurements. Fluorescence lifetime measurements offer a promising alternative, being an absolute quantity less affected by reabsorption. This study develops a novel method using fluorescence lifetime to analyze droplet composition, leveraging Time-Correlated Single Photon Counting (TCSPC) for precise measurements. Factors such as dye concentration, solvent polarity, and temperature sensitivity are investigated. Calibration curves for ethanol-water mixtures correlate fluorescence lifetime with volume fraction. Experimental setups use TCSPC and femtosecond lasers for dye excitation. Results show that fluorescence lifetime decreases linearly with solvent polarity and is influenced by temperature and dye concentration. High dye concentrations cause self-quenching, altering temperature sensitivity. The method was applied to study the evaporation of ethanol-water droplets under acoustic levitation. Findings indicate that evaporation rates slow as the water fraction increases, with initial measurements showing higher water content due to partial evaporation. This research introduces a novel technique for droplet compositional analysis using fluorescence lifetime, providing insights into optimizing measurement accuracy and advancing understanding in engineering and related fields.
Single-Frame Lagrangian Tracking Of 3-D Acoustic Streaming Flows Using Digital Defocusing Micro Particle Streak Velocimetry
Authors: Tien Wei Hsin , Lin Zi-Ling
Published: July 2024

In this study, a single-frame particle streak velocimetry technique is applied to the classic DDPIV(Digital Defocusing Particle Image Velocimetry) concept to achieve a single-frame 3-D Lagrangian tracking of particles in microscopic flows. The shortcoming of images suffering low signal to noise ratio due to pinholes can be avoided. With the streak resolving algorithm, it allows extended exposure time when streak images are taken, and the single-frame approach also eliminates the need for high-cost and complicated synchronization hardware for double-pulse frame-straddling light sources. For each long-exposure, color-coded images received from each pinhole equipped with red, green or blue color filters, the streak-resolving algorithm is applied first to find each streak on the separate color channel, followed by an one-time triplet-matching process to group the red, green and blue streak projections. From the streak triplets, 3-D reconstruction can be done on all the resolved points on the streak, and trajectory fitting can then be applied to resolve the tracer particle trajectories in the field of view with temporal history. This procedure was applied for visualizing a microscale 3-D acoustic streaming flow pattern induced by a longitudinal spine-shaped fin oscillating at 12kHz. The height of the channel is 1mm with the spine of 0.3mm height and a 30 。 tip angle. Resolved flow fields show that the particle streak images can be resolved with the same level of accuracy to the particle tracking method, while the throughput of velocity vectors can be significantly higher due to multiple velocity vectors can be resolved from each streak triplet. The methodology has the potential to be applied to various applications that can capture long-exposure images and possible to resolve higher-order information such as acceleration and forces applied on the particles or the flow.
Fourier light-field microscope for micro tomo-PTV in a cross-junction microfluidic channel
Authors: Fort Charles , Solomon Halen , Capanna Roberto , Wang Sheng , Li Zhenyu , Bardet Philippe M.
Published: July 2024

This paper presents a novel approach for comprehensive flow analysis within microfluidic systems by integrating particle tracking velocimetry (PTV) and shake-the-box (STB) techniques with plenoptic imaging. By combining the strengths of PTV and STB, which offer particle trajectory tracking and high-resolution particle position determination, respectively, our method enables accurate and detailed flow characterization. Leveraging Fourier light-field microscopy, a recent development of plenoptic imaging (or integral microscopy), we eliminate the need for multiple imagers and achieve high-resolution three-dimensional flow measurements using a single high-speed camera. The diffraction-limited resolution is on the order of 2 um in 3D, with the lateral and depth resolution within 25% of each other. This is an unprecedented depth resolution for a 3D velocimeter. Particle positions can in fact be resolved to less than the imaging wavelength. We demonstrate the effectiveness of this approach by capturing and analyzing a complex flow within a microfluidic device with a cross-junction channel. This measurement technique will provide valuable insights for optimizing microfluidic device design and performance as well as wall-bounded flows.
Event Based Cameras: A Comparative Study For Fluid Event Detection
Authors: Court Alecsandra , Bruecker Christoph
Published: July 2024

A feasibility study using an event-based camera for the detection of plane-wise motion of a 2D array of bio-inspired sensing pillars to detect generated flow events. EBCs show potential for future applications where PIV may have been classically used. They have the benefit of only generating data when an event happens and with comparatively cheaper setups, they hold great potential for flow monitoring. EBCs collect pixel x and y locations, as well as pixel contrast change data at each time there is an event and can be trained on regions of interest. Comparative experiments were carried out in the labs at City, University of London, to investigate the feasibility of using EBCs for the detection of generated large flow structures in both air and water. The disturbances were produced by a gust generator, an upstream cylinder and an air gun for a variety of controlled situations, such as disturbances caused by gusts, crossflows and wake downstream oscillations. Some results were also compared to known PIV results from our lab to see how EBCs can detect a known flow structure over the sensing pillars. The results presented demonstrate the capability of the pillars and EBC to detect large flow structures. These initial results show promise for future applications of flow monitoring, such as real-time flow monitoring via a machine learning algorithm that is trained to detect certain flow patterns over the sensing pillars. This would be an intermediate step into a fully automated flow control loop.
Enhancing Accuracy In 3D Defocusing Particle Tracking Using 3D-Printed Ramp
Authors: Chen Zhengwei , Tao Baoxuan , Wereley Steven T.
Published: July 2024

Three-dimensional defocusing particle tracking velocimetry (3D DPTV) is an emerging tool for investigating fluid motion within microfluidic devices, where observation is typically limited to a single direction. This technique enables the reconstruction of 3D flow fields by analyzing the defocused particle images. The accuracy of 3D DPTV significantly relies on the collection of a proper calibration image stack containing particle images with precisely known defocus distances. One major challenge is to insert a microscale calibration target inside the microfluidic devices due to the small length scales of microfluidic devices. While the alternative approaches such as using tilted glass slides or conducting z-scans of particles fixed at the bottom wall, face several limitations. Here, we present the application of a two-photon polymerization (2PP) based method to manufacture a microscale reference ramp as the calibration target. We demonstrate the fabrication of a precise reference ramp structure that spans the desired calibration range to enhance accuracy in 3D defocusing particle tracking. We experimentally and computationally compare the result with the commonly employed methods to obtain the calibration image stack. The performance of the 2PP-based calibration ramps is compared with the z-scanning method using the General Particle tracking (GPTV). The results demonstrate that the z-scanning method underestimates the defocused distances compared to the ground truth provided by the ramp approach, with the error increasing as the defocused distance grows. The integration of microscale calibration targets using 2PP fabrication method offers a significant advancement in the reliability and accuracy of 3D DPTV measurements in microfluidic systems. By enabling precise, device-specific calibration, this approach can enhance the fidelity of flow field reconstructions, benefiting a wide range of microfluidic applications that rely on detailed velocity field information.
Aerodynamic and acoustic investigations of rotor-rotor wake interaction
Authors: Gregorio Fabrizio De , Rossignol Karl-Stephane , Ceglia Giuseppe , Yin Jianping
Published: July 2024

The paper presents part of the experimental activities carried out in the GARTEUR Action Group RC/AG-26 to study the acoustic and aerodynamic characteristics of small rotor configurations, including the influence of the rotor-rotor interactions. Two rotors, equipped with two-bladed propellers of a diameter of D=330.2 mm, were operated at two rotating speeds of 8025 RPM and 10120 RPM and arranged in different configurations. Isolated rotor and two different coaxial configurations in hover conditions were assessed. The aerodynamic loads and the rotor slipstream characterisation, in terms of flow field velocity, tip vortex characterization as well as acoustics emissions, were performed using a six-component load cell, Particle Image Velocimetry and microphone measurements. The isolated pusher rotor presented better aerodynamic performance with respect to the puller one. The coaxial configurations result in a loss of thrust and an increase in torque compared to the isolated rotors. The upper rotor is barely affected by the presence of the lower one, while the lower rotor experiences a thrust loss ranging from 17 to 19%. The configuration with the larger rotor distance experiences greater performance loss. The mean velocity fields of the isolated rotors are measured and compared with the coaxial configurations for assessing the roto-rotor interaction, the results support the aerodynamic behaviour. The isolated rotor slipstream characterisation was carried out by phase-locked measurements covering the full rotor azimuth angle range from 0° to 350° with an increment of 30°. Tip vortex paths are followed up to a vortex age of 3.5 rotor revolutions. The 3D reconstruction of the tip vortices is conducted to gain insight into the slipstream behaviour and enhance the occurring vortex roll-up during the second revolution. The tip vortex jitter is investigated and the anisotropic distribution is confirmed along the slipstream. Furthermore, the noise emission intensifies in magnitude for the coaxial configuration with increasing relative gap between the rotors. The turbulent kinetic energy and the meandering of the blade tip vortices support the findings of the acoustics results.
Galerkin Model For Time Super-Sampling Of PIV Measurements
Authors: Hu Qihong Lorena Li , García-Caspueñas Patricia , Ianiro Andrea , Discetti Stefano
Published: July 2024

We propose a data-driven method for increasing the time resolution of snapshot Particle Image Velocimetry. The flow dynamics are reconstructed by integrating in time an empirical Galerkin model based on Proper Orthogonal Decomposition modes of the flow field, as developed by Noack et al. (2005). The main objective is to obtain a time-resolved description of the flow dynamics of an experimental non-time-resolved dataset. The proposed methodology is assessed both with numerical and experimental data of a wake and a jet flow. The results we obtained indicate that the method can effectively reconstruct the flow dynamics over a duration spanning several flow characteristic times.
Implementation Of Optical Diagnostics For Study Of A Non-Canonical Hypersonic Geometry
Authors: Beresh Steven , Pandey Anshuman , Richardson Daniel , Carter Douglas , Saltzman Ashley , Casper Katya
Published: July 2024

The study of shock/boundary-layer interactions on a non-canonical hypersonic geometry involves physical complexities not found on the canonical investigations that dominate the literature. The present case examines a cone-slice-ramp, which combines an upstream asymmetric flow expansion with a downstream three-dimensional compression ramp. Optical diagnostics of the off-body flowfield are a necessary complement to surface instrumentation including high-frequency pressure sensors and Temperature Sensitive Paint (TSP). Focused Laser Differential Interferometry (FLDI) measured the flowfield distribution of second-mode instability waves responsible for transition. Filtered Rayleigh Scattering (FRS) was used for flow visualization of the separation region and unsteady shear layer. Velocimetry through the separation shear layer was provided by Femtosecond Laser Electronic Excitation Tagging (FLEET) whereas Coherent Anti-Stokes Raman Scattering (CARS) measured the thermal profiles through multiple flow features generated by the interaction. These flowfield diagnostics detail the alterations in the shock/boundary-layer interaction as the flow state moves from laminar to transitional to turbulent conditions, revealing behaviors absent from canonical flows.
Volumetric Measurement Of The Acoustically Induced Fluid Flow In A Micro Chamber With A Two-Dimensional Standing Surface Acoustic Wave Field
Authors: Sachs Sebastian , Deng Zhichao , Schmidt Hagen , König Jörg , Cierpka Christian
Published: July 2024

The non-invasive, contactless and label-free trapping and patterning of individual cells with acoustic tweezers is a key technology to reliably analyze single cells and cell-cell interactions in biological applications. By using two-dimensional standing surface acoustic waves (2DsSAW), the precise manipulation of the cells in a micro chamber is primarily governed by the acoustic radiation force, which acts directly on the cells due to scattering effects of the acoustic waves. However, a fluid flow of three-dimensional nature is concurrently induced acoustically, which additionally influences the cell pattern by Stokes' drag. In this study, we shed light on the complex acoustically induced fluid flow forming in an acoustic tweezer by 3D3C velocity measurements using the astigmatism particle tracking velocimetry (APTV). Vortex structures above the antinodes of the 2DsSAW field were revealed. The fluid flow converge and diverge in the vicinity of the chamber bottom and ceiling, respectively. Hence, the fluid flow influences the stable trapping locations of cells or particles in different ways depending on their height position, which might explain the recently reported formation of various particle patterns at different height levels. Moreover, the experimental findings are used to validate a three-dimensional numerical model. The numerical model provides deep insights into the underlying acoustic fields responsible for the formation of the fluid flow and acoustic radiation force. By combining the experimental and numerical results, a profound understanding of the physical mechanisms for cell or particle trapping and patterning is established.
Exploring Electrohydrodynamic Flows Inside Leaky Dielectric Drops: A Laser Velocimetry Approach
Authors: Karp Joel R. , Lefebvre Franck , Godard Gilles , Idlahcen Said , Lecordier Bertrand , Shadloo Mostafa S.
Published: July 2024

A novel experimental methodology based on laser velocimetry for the investigation of electrohydrodynamic (EHD) flows inside a neutrally buoyant leaky dielectric drop of 2.25 mm of radius is proposed. Utilizing fluorescent particles, 2D and 3D Lagrangian Particle Tracking (LPT) measurements of the EHD flows inside an initially spherical drop under a constant electric field are reported. Two leaky dielectric fluids, namely Silicone and Castor oils, were used as either the drop or the medium phases, depending on the case investigated, thus covering oblate and prolate drops both with small and larger deformations. 2D measurements of the trajectories and velocities of the tracer particles in a Lagrangian referential enabled a direct comparison with the leaky dielectric model (LDM), a well-stablished theory covering drops with smaller deformations, showing a good agreement with our measurements. The symmetry inside a drop with increased deformation is investigated from an analysis of the mean 3D velocity field, whose measurements converge to the two-dimensional analysis at the plane of symmetry of the drop, suggesting symmetrical flow structures inside the drop.
Flow Measurements Above A DBD Plasma Actuator Array By Means Of Defocusing PTV
Authors: Pasch Saskia , Lange Heinrich Lionel , Leister Robin , Kriegseis Jochen
Published: July 2024

Lagrangian defocusing particle tracking velocimetry (DPTV) measurements are conducted in a thin, wall-parallel volume above a plasma actuator array that is applied to mimic the effect of wall oscillations by inducing alternating, wall-parallel forcing in opposite directions into the air above the actuator surface. The aim of the experiments is to capture the plasma-induced flow structures in otherwise quiescent air in order to increase the understanding of different actuation parameters. For this purpose, high-speed particle image velocimetry equipment with one camera is used in a DPTV setup, where the out-of-plane particle coordinate is obtained through the diameter of a defocused particle image. On this basis, an approach for continuous particle tracking in several consecutive frames is presented, allowing to derive three component, three dimensional velocity and acceleration data. Light reflections that occur on the adjacent actuator surface give raise to particular challenges concerning the measurement uncertainty estimation as well as the calibration procedure for the evaluation of the wall-normal coordinate of tracer particles. To overcome the latter, a calibration approach is presented for which solid particles are applied to the actuator surface and their particle image diameter is captured at different camera positions in a separate measurement. The estimation of in-plane and out-of-plane displacement measurement uncertainties is conducted following a newly-developed procedure where the deviation of particle displacements from a straight track is evaluated for measurements in quasi-quiescent air. The obtained results show the suitability of DPTV measurement technique for the practical application of the characterization of flow structures above a plasma actuator array. The measurement accuracy is found to be limited due to the available illumination, which depends on the used components. The measured flow fields together with optical and electrical measurement data allow for a further analysis of the present forcing strategy. Particularly, by recording phase-resolved, three-dimensional flow velocity and acceleration fields in the vicinity of the wall, the spatio-temporal occurrence and homogeneity of the near-wall forcing effects can be analyzed in future investigations.
Reconstruction Of The Shape Of Irregular Rough Particles From Their Interferometric Images Using A Convolutional Neural Network
Authors: Abad Alexis , Poux A , Boulet Alexis , Brunel Marc
Published: July 2024

We have developed a convolutional neural network (CNN) to reconstruct the shape of irregular rough particles from their interferometric images. The CNN is based on a UNET architecture with residual block modules. The database has been constructed using the experimental patterns generated by perfectly known pseudo-particles programmed on a Digital Micromirror Device (DMD) and under laser illumination. The CNN has been trained on a basis of 18000 experimental interferometric images using the AUSTRAL super computer (at CRIANN in Normandy). The CNN is tested in the case of centrosymmetric (stick, cross, dendrite) and non-centrosymmetric (like T, Y or L) particles. The size and the 3D orientation of the programmed particles are random. The different shapes are reconstructed by the CNN with good accuracy. Using three angles of view, the 3D reconstruction of particles from three reconstructed faces can be further done.
Large-Scale Measurements Using Robotic Volumetric LPT With Shake-The-Box Inside A Vehicle Cabin: Influence Of Different Fan Speeds On The Flow Topology
Authors: Gericke Timo , Alfaro Juan Camilo Londono , Hüttig Steffen
Published: July 2024

In this work, the flow topology inside a passenger car cabin for different fan speeds of the heat, ventilation and air conditioning (HVAC) system is investigated using robotic volumetric Lagrangian Particle Tracking (LPT). The coaxial volumetric velocimeter (CVV), also called MiniShaker, in combination with a robotic arm enables the measurement of the complete passenger's side. In total 37 CVV perspectives (sub-volumes) were measured. At each position 3000 double frame images were recorded. The interior was painted black and the mannequin was wrapped with black aluminum foil in order to keep reflections at a low level. Experimental results for three different fan speeds using helium-filled soap bubbles (HFSB) as tracers and Shake-the-Box (StB) algorithm for the three-dimensional LPT data analyses show that the flow topology changes significantly with increasing fan speeds. At higher fan speeds the flow fields show the highest complexity with four vortices.
On-Site Characterization of Automotive Diffuser Aerodynamics by 3D LPT
Authors: Battegazzore Andrea , Guerra Adrian Grille , Sciacchitano Andrea
Published: July 2024

This investigation proposes a novel LPT facility featuring Helium-Filled Soap Bubbles flow tracers, LED illumination and two high-speed cameras to characterize the dominating flow patterns within automotive underbodies. A remote control (RC) car model, fitted with custom-made floor and diffusers, traverses a region of seeded air following the Ring of Fire methodology. Underground-placed cameras view the car through a transparent panel, providing unparalleled optical access to the underbody of the car. The on-site measurement setup and the interaction between car model and ground enhance the realism and fidelity of the experiments, while potentially reducing testing costs associated with wind tunnel operation. The setup is shown to be a valid alternative to conventional testing approaches to capture flow separation, 3D flow evolution and differences in the flow field between the four tested configurations, whereby the diffuser angle was varied in the range between 5° and 20°. The 15° diffuser led to the largest velocity and pressure peaks under the car, whereas the 10° diffuser produced the most downforce thanks to the diffuser “pumping” effect, leading to a large region of low pressure under the vehicle. Notably, the 20° diffuser featured the most prominent flow separation at the diffuser’s leading edge, heavily affecting its ability to sustain low pressures under the car. The results show that the wide tyres have a major impact on the underbody flow, because their large wakes induce mass flow leakage through the sides of the car, thus disrupting the mechanism of downforce generation and impairing the generation of streamwise vortices.
Time-Resolved Imaging Of Wavy Interface In The Primary Atomisation Region Of An Air Assist Atomiser Using An Event-Based Camera
Authors: Rajamanickam Kuppuraj , Hardalupas Yannis
Published: July 2024

The current work discusses the demonstration of a low-cost event-based camera for time-resolved imaging (10000 frames/sec) of a primary atomization zone in canonical air-assist atomizers. Experiments have been conducted simultaneously with traditional high-speed and event-based cameras, enabling us to quantitatively assess the potential of event-based cameras in spray imaging applications. Three atomization breakup regimes are considered: columnar, bag, and multimode. Dynamic Mode Decomposition (DMD) is implemented over the instantaneous data sets acquired from both cameras to assess their performance in extracting turbulence statistics. The obtained DMD modes from both cameras are similar, highlighting the potential of low-cost event-based cameras in extracting coherent structures and their spectral contents. Finally, the limitations (e.g., event saturation) of event-based cameras in the context of primary atomization are also discussed.
Characterization Of Cryogenic Sloshing Via Image Velocimetry, Free Surface Tracking And Data Assimilation
Authors: Marques Pedro Afonso , Simonini Alessia , Delsipée Mathieu , Mendez Miguel Alfonso
Published: July 2024

Cryogenic fuels such as liquid hydrogen (LH_2 ) and liquified natural gas (LNG) are promising energy carriers for the future. Their thermal management is significantly challenged by the liquid sloshing induced by external acceleration because sloshing strongly impacts the evaporation rate and, thus, the reservoir’s pressure control. This work presents a unique experimental characterization of liquid sloshing in cryogenic conditions combining interface tracking, image velocimetry and physics-constrained data assimilation. The experiments were conducted in a reduced-scale cryogenic tank partly filled with liquid nitrogen undergoing lateral harmonic sloshing. A combination of floating and neutrally buoyant seeding particles was used to simultaneously carry out interface tracking using a moving-window Radon transform and image velocimetry using Particle Tracking Velocimetry (PTV). The data assimilation was carried out using constrained radial basis function (RBF) regression, imposing kinematic boundary conditions at the walls and interface. The assimilation allows for unprecedented super-resolution of the velocity field.
REVIEW: AN EXPERIMENTAL STUDY ON EFFECT OF NANO MATERIALS ON STRENGTH OF CONCRETE AND PLANE STRESS ANALYSIS USING ANSYS SOFTWARE
Authors: Malim Umera F ,   Department of Civil Engineering, Ashokrao Mane Group of Institutions Vathar Tarf Vadgaon, Dist.-  Kolhapur, Maharashtra, India, Chavan-Patil Prof. G. N ,   Department of Civil Engineering, Ashokrao Mane Group of Institutions Vathar Tarf Vadgaon, Dist.-  Kolhapur, Maharashtra, India
Published: July 2024

These days, making efficient and cost-effective use of resources has taken precedence. The main ingredient in concrete, cement has been under criticism in recent years for the quantity of CO2 released during production. Although cement has better mechanical properties, it hasn't been able to live up to the expectations in terms of durability. Owing to cement's shortcomings, scientists started looking into additives that would enhance concrete's qualities while also making it stronger and lighter. Fly ash, silica fume, and other micro particles were added to cementitious materials to improve their compactness, strength, and durability. These additives were also selected because they are eco-friendly by products of industrial waste that may be handled ethically. Fly ash has significant disadvantages because it is not good for initial strength increase and setting time. Because silica fume affects cementitious material performance, researchers have recently become interested in combining it with ceramic waste and rice husk ash. A more effective way to utilize rice husk ash, a by-product of rice cultivation, would be to replace 10% to 15% of cement. Studies have shown improvements in the durability performance of recycled ceramic waste concrete and rice husk ash concrete. There are issues since the RHA production process is quite time-consuming. With the discovery of nano-particles (NP) smaller than 100 nm, researchers have advanced the field of nanotechnology to new levels. The mechanical properties of many materials, including polymers and cementitious materials, can be enhanced by NP. NP is also helpful in the fields of food, engineering, and medicine. This led researchers to investigate the effects of nano-silica (NS) on concrete in further detail. Nano materials can improve the compressive strength and ductility of concrete. In this project an effort will be made to increase the compressive strength of concrete using Nano materials and waste product like GGBS. Also plane stress analysis of concrete cubes and cylinders is to be done using Ansys Software to find deformation, principal stresses and shear stresses. Keywords: Nano –Silica, Nano Titanium dioxide, Ansys, GGBS, Compressive strength
Design Things in Ethnographic Police Research
Authors: Marriott Thomas
Published: July 2024

Design Things in Ethnographic Police Research

How, and in what ways, can design practice contribute to observational research on policing? This article outlines the potential for design research methods, and more specifically, “design Things”, to be used in ethnographic policing research. The article outlines some of design practices’ unique epistemic qualities, describes what design Things are and suggests they might relate to ethnographic policing research. Reflecting on doctoral research into police use of body-worn video cameras, the article discusses how design Things have successfully been used to introduce specific questions, matters of concern and elicit speculations from research participants. As well as highlighting the possibilities of this novel methodology for policing research, the challenges and ethical considerations are also considered.
Anteseden Pengelolaan Keuangan Desa
Authors: Debora Freti Gracia  , Loggar Bhilawa
Published: July 2024

The public has the right to know information, transparency and accountability of regional financial management so that the presentation of financial reports can be accessed by various parties. Therefore, the purpose of this study was to determine whether transparency, accountability, community participation and the role of village officials have a positive effect on village financial management. The method used in this research is a quantitative method whose data comes from primary data in the form of questionnaires. The sample in this study were 380 people in Trawas District. The sampling technique used in this study used purposive sampling technique. The independent variables in this study are transparency (X1), accountability (X2), community participation (X3), and the role of village officials (X4). The dependent variable in this study is village financial management (Y). The data analysis that the authors use in this quantitative research uses statistics using IBM SPSS software version 25 The results of this study are the village financial management of Trawas Regency is positively and significantly influenced by transparency, accountability, community participation, and the role of village officials.
Evaluasi Tim Renang Kota Mojokerto Dalam Mengikuti Kejuaraan Daerah Renang Jawa Timur Tahun 2023
Authors: Muhammad Zailul Rizky  , Mokhamad Nur Bawono
Published: July 2024

Sport is a physical activity needed by humans which has many purposes, such as maintaining body health, maintaining mental health (refreshing), achieving achievements, building character and other people (Wijaya, 2018). According to Kurt et al., (2023) swimming is a sport that can be used as a means of talent search, achievement, recreation, education, rehabilitation and self-preservation. Coaches, facilities and infrastructure, training programs, athlete development, government support and parents are some of the components that contribute to good performance. Sports achievements can be achieved through professional and quality sports training. In the sport of swimming, there are several events, namely events representing clubs, events representing regions at the provincial level, events representing regions at the national level, and events representing international national levels. The process of improving actions or techniques that have been carried out is known as evaluation. This research is motivated by the fact that there is still no research on the Mojokerto City swimming team in participating in the 2023 East Java Regional Swimming Championship. This research aims to cycle the Mojokerto City swimming team in participating in the 2023 East Java Regional Swimming Championship. The use of the SWOT method is important in analyzing and determining points earned. This method focuses on evaluating the Mojokerto City swimming team in participating in the 2023 Regional Swimming Championships which is expected to contribute to achievements for the City of Mojokerto in the future. To explain the evaluation results, the methodology used is qualitative descriptive research. The source of information comes from licensed swimming coaches. Data collection methods include interviews and documentation. Research findings include, (1) strengths include: the Mojokerto City swimming team is in young athletes and young coaches. If young athletes are coached properly, they will develop, while young coaches who are full of ideas, if given space or a platform, can express their aspirations. (2) Weaknesses include: no management questions, no atlhletes selection, no impressive Training Center (TC), no space or forum for young coaches to express their aspirations. (3) Opportunities include: the Mojokerto City swimming team has good opportunities for the future because this team is dominated by young athletes and young coaches. (4) Threats include: if the existing management is not immediately improved, the young athletes and young coaches, the Mojokerto City swimming team is threatened with not being able to get maximum results in future events.
METHOD OF VORT IN PRACTICE OF DENTISTRY
Authors: Nigora Narziyeva ,   Samarkand State Medical University, Uzbekistan, Kobilovna Burxonova Zarafruz ,   Samarkand State Medical University, Uzbekistan
Published: July 2024

The challenge facing reconstructive dentistry today is how to achieve excellent aesthetic results while preserving the biological structures involved as much as possible. Today, clinicians and dental technicians have materials and procedures at their disposal that make it possible to recreate aesthetics and function in a simpler and more predictable way.
SOCIO-PSYCHOLOGICAL CLASSIFICATION OF THE FORMATION OF HOPE FOR NEAR FUTURE SUCCESS IN PEOPLE
Authors: Kozimov Sayfullokh ,   Andijan State Pedagogical Institute, Faculty Of Pedagogy 3rd Level Student Of Pedagogy And Psychology, Uzbekistan
Published: July 2024

This article describes the socio-psychological classification of the formation of a sense of hope for the near future success in people. A sense of hope is considered an important motivational factor in achieving one's goals. The article analyzes the origin, development and ways of strengthening the feeling of hope, as well as the role of the social environment in this process.
Intrinsically Motivated Multi-Goal Reinforcement Learning Using Robotics Environment Integrated with OpenAI Gym
Authors: Balasubramanian Sivasubramanian
Published: July 2024

Sparse reward is one of the most challenging problems in reinforcement learning (RL). Hindsight Experience Replay (HER) attempts to address this issue by converting a failed experience to a successful one by relabelling the goals. In open-ended and changing environments, agents face a wide range of potential tasks that might not come with associated reward functions. Such autonomous learning agents must set their own tasks and build their own curriculum through an intrinsically motivated exploration. Because some tasks might prove easy and some impossible, agents must actively select which task to practice at any given moment, to maximize their overall mastery on the set of learnable tasks. The purpose of this technical report is two-fold. First, it introduces a suite of challenging continuous control tasks (integrated with OpenAI Gym) based on currently existing robotics hardware. The tasks include pushing, sliding and pick & place with a Fetch robotic arm as well as in-hand object manipulation with a Shadow Dexterous Hand. All tasks have sparse binary rewards and follow a Multi-Goal Reinforcement Learning (RL) framework in which an agent is told what to do using an additional input.
The second part of the paper presents a set of concrete research ideas for improving RL algorithms, most of which are related to Multi-Goal RL and Hindsight Experience Replay. The Fetch environments are based on the 7-DoF Fetch robotics arm,2 which has a two-ﬁngered parallel gripper. Agents focus on achievable tasks first and focus back on tasks that are being forgotten. Experiments conducted in a new multi-task multi-goal robotic environment show that our algorithm benefits from these two ideas and demonstrate properties of robustness to distracting tasks, forgetting and changes in body properties
Importance Of Using Generative AI In Education: Dawn of a New Era
Authors: Rajendran Rajashree Manjulalayam
Published: July 2024

The teaching methodology has witnessed a paradigm shift by incorporating advanced technologies. The modern world offers a whole new insight into the mental well-being of students. This transformation has opened new doors that are eye-opening for the human mind.
The invention of artificial intelligence (AI) in the modern world has helped solve and detect problems. Among all these developments, one has shifted the standard of the educational world. It has taken over the old methods and techniques the students did not previously appreciate. This technology, the Generative Artificial Intelligence (GAI), has altered the orthodox educational approaches. It has provided a potential benefit for delivering knowledge in the best direction, enabling students to understand and implement it in their lives.
Therefore, this paper significantly focuses on the impact of Generative Artificial Intelligence (GAI) technology in providing protection and assistance in the education system. It has contributed value and principles to the revolution of the modern education system. The data declared in the paper was taken from effective sources and proved to favor the study.