A laboratory investigation was conducted to quantify the influence of background rotation on nearly zero-mean turbulence generated within an off-axis mounted isotropic box. High-resolution particle image velocimetry measurements were performed at the box center under varying rotation rates to examine the onset and development of anisotropy. In the absence of rotation, the turbulence exhibits nearly isotropic behavior, with radial and azimuthal velocity fluctuations closely matched and energy spectra consistent with Kolmogorov scaling. As the inverse turbulent Rossby number, Ro(epsilon)(-1), increases, spectral anisotropy becomes increasingly pronounced, and the range of scales over which the radial and azimuthal spectra diverge broadens. The lower bound of this anisotropic range follows the scaling (kappa(L)-kappa(DI))eta = Ro(epsilon)(-1)/40, indicating a progressive influence of the Coriolis effects. A generalized Taylor transformation applied to spatial and temporal spectra yields characteristic convection velocities U-r* and U-theta*, which exceed the local rms fluctuations and scale as U-r* similar to 3 u(r)' and U-theta* similar to 2 u(theta)'. Direction-specific turbulent rotation numbers exhibit a linear dependence on Ro(epsilon)(-1), linking integral-scale rotational dynamics to small-scale anisotropy. The results provide experimental support for theoretical predictions of energy redistribution, quasi-two-dimensionalization, and wave-eddy interaction in rotating turbulence. The empirical scalings may offer compact constraints for turbulence closures in noninertial frames and establish a basis for future studies of scalar transport and dispersion in geophysical and astrophysical flows.

An experimental investigation was conducted to explore the interplay of turbulence and noninertial effects introduced by off-axis rotation on isotropic-turbulence dynamics using tomographic particle image velocimetry. A cubic box, generating isotropic turbulence with the aid of eight mixers positioned at each corner, rotated with a turntable, was subjected to different rotational speeds. Particular focus was placed on the changes in distinct turbulence quantities, including the Kolmogorov, Taylor, and integral scales, as well as changes in the velocity spectra. An inspection within a central subregion featuring isotropic flow with nearly zero mean flow revealed distinct rotation-induced anisotropic effects. The analysis of the longitudinal and transverse autocorrelation functions indicated rotation-induced changes predominantly at larger scales. The compensated spectral counterparts demonstrated a scale-dependent response to rotation, where energy distribution exhibited minor changes at smaller scales and significant alterations at larger scales, affecting the extent of the inertial subrange. The inverse-turbulent Rossby number Ro_{ε}^{-1}=2Ω〈k〉/ε, where Ω represents the rotational speed, 〈k〉 is the turbulence kinetic energy, and ε denotes the energy-dissipation rate, demonstrated a monotonic relationship between rotational speed and various turbulence characteristics. As the Ro_{ε}^{-1} value increases, there is an increase in turbulence levels and the dissipation rate, while the Kolmogorov microscale, Taylor microscales, and integral scales decrease. Also, changes in the tangential direction were more significant than those in the vertical axis of rotation.

Turbulent flows in rotational systems are crucial to both large-scale phenomena, such as atmospheric and oceanic currents, and small-scale applications like flows in turbomachinery. While previous experimental studies have mostly focused on the rotational effect on mean flow, there is a lack of understanding of the interplay of turbulence directly with rotation. Previous numerical studies mostly adopted turbulence models, with modifications, developed based on knowledge of turbulence in inertial coordinates. There is a lack of turbulence models specially developed for non-inertial coordinates where Navier-Stokes (NS) equations do not directly apply. In this study, the turbulent kinematic energy (TKE) transport equations in cylindrical noninertial coordinates are derived to accommodate the analysis for off-axis rotation conditions, revealing a Coriolis transport mechanism to explain the TKE transport between tangential and radial directions. Experimental measurements of isotropic turbulence under the different off-axis rotation conditions acquired by Particle Image Velocimetry (PIV) are used to evaluate the Coriolis transport. As the level of rotational effect increases, the difference between TKE components in tangential and radial directions increases. Meanwhile, the Coriolis transport may reach up to 30% of the dissipation rate, indicating that it plays a significant role in the energy transfer mechanism of turbulent flow under off-axis rotational conditions.

Pulsed cold spray (PCS) is a type of cold spray metal coating technique that incorporates cyclical compressed gas pulses to control the gas-powder for improved surface deposition. In recent years, PCS has garnered great attention owing to its unique pulsed nature in the domains of dense coatings, metal matrix composite coatings, cellular metallic structures, etc. However, research on the PCS to uncover process-structure-property relationships of this emerging deposition technique is limited. To this end, this study thoroughly investigates PCS to gain a deeper understanding of this coating technique. First, a PCS system incorporating a converging-diverging (CD) nozzle is designed and prototyped. Next, two-phase flow (i.e., gas + powder) within the PCS is modeled using computational fluid dynamics (CFD). The modeling results are then experimentally validated using particle image velocimetry (PIV), followed by a case study on surface deposition. The results show that the optimal powder injection window occurs when the gas inlet pressure is at least 99 % of the set inlet pressure, achieving a steady-state gas flow for 100 ms. CFD modeling showed that Mach diamonds formed at the nozzle exit by 30 ms, though powder velocity does not reach steady-state until 50 ms. Numerical modeling captured the average particle with an error of approximate to 8 % as compared to the PIV measurements. Furthermore, surface deposition experiments showed that the PCS can create dense coatings with remarkably less porosity (i.e., 1.73-fold) as compared to the traditional CS. Overall, this study unravels the intricacies of designing and modeling of a PCS system with a CD nozzle, complemented by surface deposition experiments.

Impinging jet atomizers are essential in engineering applications, where two liquid jets collide to form a sheet that breaks into droplets, completing the atomization process. The sheet's properties-size, thickness, velocity, and shape-are influenced by factors like impingement angle, jet velocity, and liquid properties. Since sheet formation occurs before droplet generation, modeling the sheet is critical for understanding the downstream atomization. This research investigates the sheet's velocity using experimental and theoretical approaches. Particle tracking velocimetry (PTV), combined with shadowgraph imaging, is used to measure sheet velocity. Small seeding particles are introduced into the liquid while their motion is tracked across frames to calculate velocity. However, when particle size matches the sheet thickness, a 'particle-induced lens effect' distorts conventional imaging due to fluid wrapping around the particles. This effect is leveraged to achieve an extended field of view, enhancing measurement accuracy. Experimental results, obtained for Reynolds numbers ranging from 362 to 430, show significant deviations from existing theoretical predictions of sheet velocity. To address this, a revised theoretical model is proposed, incorporating air friction effects. Based on boundary layer theory in cylindrical coordinates, the model uses unique boundary conditions and a similarity variable to simplify and solve the governing equations numerically. The revised model predicts air boundary layer profiles and velocity distributions as functions of distance and azimuthal angle. The initial jet velocity profile, modeled as a free jet transitioning from Poiseuille flow, is also estimated. The revised model aligns more closely with experimental observations, identifying key parameters that influence sheet behavior. This study advances the understanding of impinging sheet dynamics, offering insights for improving atomization performance in practical applications.

INTRODUCTION:The primary purpose of this study was to examine the relationship between phonation quotient (PQ) obtained using a low-cost vortex whistle system (VWS) vs phonatory airflow (PA) in sustained voicing calculated using a clinical-standard pneumotach-based system (the Phonatory Aerodynamic System [PAS]). PQ values obtained using the VWS were also compared with PQ values obtained using a "gold" standard pneumotach-based Koko Sx1000 spirometer. METHODOLOGY:Participants were 91 vocally healthy young adults (61 females and 30 males) between the ages of 18 and 30 years. Measures of vital capacity (VC) were obtained using the VWS and Koko Sx1000 spirometer, and measures of maximum phonation time (MPT) and PA during sustained phonation were obtained from the Maximum Sustained Phonation protocol on the PAS. PQs were calculated via PQ = VC (L)/MPT (s). RESULTS:Correlations of r = 0.828 and r = 0.791 were observed between PA and PQKoko and PQVWS, respectively, with no significant difference between the two correlations. Stronger correlations between both PQKoko and PQVWS and PA were observed in males vs females. Linear regressions to predict PA from either PQKoko or PQVWS resulted in residual standard errors of 0.037 L/s (37 mL/s) and 0.040 L/s (40 mL/s), respectively. PQVWS and PQKoko were highly correlated (r = 0.961). CONCLUSION:These results confirm prior research demonstrating that PQ may be used as a reasonable substitute for PA, with error values within previously reported expected ranges of intrasubject variability. In addition, a low-cost VWS can provide similarly accurate measures of PQ vs those computed using VC estimates from a "gold standard" pneumotach-based spirometer. PQ estimates of airflow via a VWS show great promise as a low-cost method that can promote the use of respiratory measures of capacity and flow to the voice assessment protocols of speech-language pathologists.

Compliance mismatch between native arteries and prosthetic grafts contribute to complications such as neointimal hyperplasia and pseudoaneurysms, leading to reduced graft patency. Three-dimensional (3D) printing offers a promising solution by flexibly customizing mechanical properties using elastic polymers. This study investigates whether 3D-printed polymeric grafts can better replicate native arterial compliance compared with commercial prosthetic grafts. We conducted compliance tests on human aortoiliac arteries, polytetrafluoroethylene (PTFE) grafts, Dacron grafts, and 3D-printed arteries with BioMed Elastic Resin within a mock circulation loop. All samples shared controlled geometry and were tested under the same physiological flow conditions. Pressure waveforms and key hemodynamic parameters were recorded and analyzed. The 3D-printed graft demonstrated a compliance of 0.49 cm3/mmHg, more closely matching the human artery than PTFE (0.38 cm3/mmHg) and Dacron (0.45 cm3/mmHg). Its mean arterial pressure (82 ± 0.6 mmHg) and peak pressure (40 ± 0.7 mmHg) in the flow loop also aligned more closely with the native artery compared with conventional grafts. Standard prosthetic graft materials have remained relatively static, whereas there has been immense advancement in new polymer technology. These polymers can match the compliance of native vessels, theoretically reducing complications associated with traditional grafts, and future work should investigate their biocompatibility, durability, and clinical feasibility.

Cardiovascular diseases remain the leading cause of morbidity and mortality worldwide, underscoring the need for continuous innovation in diagnostics and treatment. Mock circulation loops (MCLs) systems have recently emerged as new research platforms capable of replicating the hemodynamics of the human cardiovascular system. This review explores the expanding applications of MCLs to cardiovascular diseases beyond their traditional role in testing ventricular assist devices and heart failure management. We focus on their versatility in simulating various cardiovascular conditions, particularly arterial diseases such as atherosclerosis, stenosis, and aneurysms. This review traces the evolution of MCLs and their integration with computational simulations and real-time data acquisition systems. MCLs provide detailed insights into hemodynamic responses under diverse conditions, enhancing the precision and safety of cardiovascular interventions. This comprehensive review emphasizes the critical role of MCLs in advancing cardiovascular research, refining clinical interventions, and improving patient outcomes.

The steel industry, as one of the most fundamental industrial sectors, may no longer represent the forefront of technological innovation. However, it remains a crucial area of research due to its role as an upstream supplier for nearly all other industries. The vast scale of steel production ensures that even minor efficiency improvements can lead to significant economic benefits. Additionally, given the industry's high energy consumption, any advancements in energy efficiency can have a substantial impact on global carbon emissions, making the pursuit of innovation in this field both economically and environmentally essential.

We introduce electropulsing-assisted laser shock imprinting (EPLSI), a transformative approach for bulk metal nanotexturing that combines ultrafast laser shocks with pulsed currents. Overcoming conventional lithography limits, EPLSI enables high-resolution 3D patterning of bulk metals using soft molds, achieving previously unattainable formability. Electropulsing doubles nano-feature aspect ratios and quadruples multi-step patterning efficiency by activating electroplasticity at ultrahigh strain rates (103–106 s−1). Microstructural analyses demonstrate how pulsed currents reduce dislocation density while promoting twinning and stacking faults, enabling hierarchical nanostructuring. Multiplex EPLSI produces biomimetic surfaces with enhanced hydrophobicity and large-area uniformity on copper and aluminum alloys. This technique bridges the gap between scalable manufacturing and precision nanofabrication, offering new opportunities for functional surfaces in plasmonics, catalysis, and biomedical devices. By elucidating the interplay between electropulsing and defect dynamics during ultrafast deformation, we establish a foundation for next-generation metal nanostructuring technologies that combine nanoscale precision with industrial-scale throughput.

Turbulent flows in rotational systems are fundamental to a wide range of natural and engineering phenomena, from large-scale phenomena like atmospheric and oceanic currents to small-scale applications such as flow around rotating blades in turbomachinery. While previous studies have primarily focused on rotational effects on mean flows and turbulent boundary layers, there is a lack of direct understanding of non-inertial effects on the dynamics of turbulence. In this study, an experimental investigation is conducted to explore the off-axis rotational effect on the dynamics of isotropic turbulence and energy transfer mechanisms using Particle Image Velocimetry (PIV). The study focuses on rotation-induced anisotropy, analyzing first-order statistics and velocity spectra in tangential and radial directions. The turbulent Rossby number, RO is an element of-1 = 2 Omega < k >/is an element of, where Omega, < k >, and is an element of denote rotation speed, turbulent kinetic energy (TKE), and dissipation rate, respectively, is defined to quantify the Coriolis effect induced by rotation. As RO is an element of-1 increases, turbulent intensity and TKE rise, with more pronounced changes in the tangential direction than in the radial direction.

Compliance mismatch between native arteries and prosthetic grafts contribute to complications such as neointimal hyperplasia and pseudoaneurysms, leading to reduced graft patency. Three-dimensional (3D) printing offers a promising solution by flexibly customizing mechanical properties using elastic polymers. This study investigates whether 3D-printed polymeric grafts can better replicate native arterial compliance compared with commercial prosthetic grafts. We conducted compliance tests on human aortoiliac arteries, polytetrafluoroethylene (PTFE) grafts, Dacron grafts, and 3D-printed arteries with BioMed Elastic Resin within a mock circulation loop. All samples shared controlled geometry and were tested under the same physiological flow conditions. Pressure waveforms and key hemodynamic parameters were recorded and analyzed. The 3D-printed graft demonstrated a compliance of 0.49 cm3/mmHg, more closely matching the human artery than PTFE (0.38 cm3/mmHg) and Dacron (0.45 cm3/mmHg). Its mean arterial pressure (82 ± 0.6 mmHg) and peak pressure (40 ± 0.7 mmHg) in the flow loop also aligned more closely with the native artery compared with conventional grafts. Standard prosthetic graft materials have remained relatively static, whereas there has been immense advancement in new polymer technology. These polymers can match the compliance of native vessels, theoretically reducing complications associated with traditional grafts, and future work should investigate their biocompatibility, durability, and clinical feasibility.

A cost-effective dual-color scanning PIV system is developed, experimentally demonstrated, and validated. The scanning PIV system has two CW DPSS lasers of different wavelengths (green: 532 nm and blue: 473 nm), which sweep through the region of interest to provide illumination. The illuminated region is captured by a conventional DSLR camera. Two different color lasers produce two illuminations, which are captured on a single frame. The single-frame color recording causes the phenomenon of color crosstalk, which is the leakage of light to neighboring pixels on the imaging sensor. Due to the color crosstalk, some unwanted particle images are observed in different color channels, referred to as ghost particles. This leads to inaccurate velocity measurements, and to mitigate the color crosstalk from images, a correction algorithm is proposed in this study. The captured images are corrected using the color crosstalk correction algorithm and processed further to obtain the velocity field. The scanning PIV system is tested by measuring the flow field downstream of a moving circular cylinder, and validated by measuring steady vortex flow generated using a magnetic stirrer. The applicability of the proposed scanning PIV system is also discussed.

The low/zero head river current energy converter represents an attractive way of producing electricity for rural areas with nearby rivers and a shift towards reliable no-dam technology. This work presents a new design of a low/zero head river current energy converter. Different from the traditional fixed-pitch turbines that operate at angles of attack that either prevent power extraction or stall the blade during a portion of their revolution, the horizontally deployed pitch adjustable turbine (cycloidal cross-flow turbine) features varying blade pitch throughout each revolution to maximize the energy harvest. The optimal hydrodynamic design of this concept is explored by adopting an optimization routine for determining the pitching scheme and running hydrodynamic analysis via CFD in a domain with two sets of sliding interfaces. Simulations of both a one-section turbine and a three-section turbine yield similar averaged values of power coefficient of about 0.49, significantly higher than other turbine designs. The three-section turbine produces less oscillatory load transmitted to the turbine structure and benefits from enlarging the turbine lifespan in long-term operations. For the current three-section design, an optimal Tip-Speed Ratio is recommended as the design condition. Increased turbulence level of the river current results in decreased turbine efficiency.

The water propulsion system offers advantages such as high performance, low toxicity, low manufacturing costs, and ease of integration with other propulsion systems. The microwave ignition technology provides benefits including high ignition energy, faster combustion speeds, and better control. This study develops a water electrolysis chemical propulsion system based on microwave ignition technology, combining the strengths of both water electrolysis propulsion and microwave ignition. It addresses the needs for high thrust and specific impulse while eliminating the catalytic bed design to avoid issues related to catalyst lifespan. The propulsion system we designed consists of a water storage module, a water electrolysis module, a gas supply module, and an ignition module. The thruster utilizing the microwave ignition method has been developed. This study conducts experimental research using this propulsion system at various hydrogen and oxygen mixture ratios. The high-speed camera, spectrometer, and pressure sensors were used to capture images of the flame and quantify information. The results indicate that the combustion of hydrogen and oxygen using the microwave ignition method excites the hydrogen and oxygen atoms to higher energy levels, resulting in different flame colors during the ignition phase due to plasma effects. In the stable combustion phase, the flame at the nozzle exit appears as a bright white conical inner region. As the mixture ratio increases, both the brightness of the flame inner and outer regions intensify, and the length of the outer region significantly increases, accompanied by a noticeable pale blue color. The mixture ratio decreased from 1083 to 694, representing a 36% reduction. More intense combustion was observed, leading to a 6.7% increase in combustion pressure. The spectral intensity increased by 1525.6%, and the velocity at the nozzle exit increased by 3.16%. Furthermore, spectral data reveal the presence of O2, H2, and H2O molecules in the combustion flame. This study is the first to integrate microwave ignition technology with a water electrolysis propulsion system, establishing the first physical prototype of a microwave ignition-based water electrolysis chemical propulsion system. It validates the feasibility of combining microwave ignition with water electrolysis chemical propulsion technology, exploring a reliable new approach to microwave water propulsion technology. Future work will focus on further optimizing and modularizing the system.

ABSTRACT Monitoring the casting rate of the molten iron released from the blast furnace in real-time is essential for maintaining the efficiency of the smelting process. This research is dedicated to developing an image-based method to estimate iron casting rate. The live video of the iron jet is recorded and processed with the image processing algorithm to extract both the velocity and the size of the jet, which are then used to estimate the casting rate. After the validation in the laboratory, this method shall be integrated into the monitoring system of the blast furnace used by the industrial company.

Understanding the flow-induced sound represents a serious problem in many engineering applications. A wide variety of aeroacoustics problems are solved by CFD-CAA simulations, in which the time step typically cannot be too small due to the limited computational resources. This situation results in an identified aliasing error in spectral analysis. Therefore, an anti-aliasing operation prior to sampling is necessary to remove such aliasing errors from acoustic source terms. In the present study, an anti-aliasing filter in a time-domain, compact filter scheme, was designed based on the compact finite difference formulation. This filter was applied on the Navier-Stokes solver directly, prior to sampling for CAA analysis. A case of cavity flow was simulated to validate the mitigation strategy. The result shows that the artificial spectral peak induced by the aliasing error is removed while not affecting other signature peaks. The anti-aliasing filter was applied to more complicated cases with signature peaks in predicting the acoustic field of a vortex whistle. The acoustic field around the vortex whistle with constant inlet flow rates and variable flow rates was simulated and the aliasing peak was successfully removed. Although the peak magnitudes are decreased slightly by the filter, the signature frequencies are not changed. Therefore, the simulation with anti-aliasing operation can predict acoustic features without introducing the aliasing error, even if the time step is not sufficiently small, and thus reduce the simulation time significantly.

Efficient ventilation systems play a crucial role in reducing occupants' exposure to indoor contaminants, including particles potentially carrying viruses like SARS-CoV-2. Displacement ventilation systems have demonstrated their effectiveness in improving indoor air quality during cooling modes. However, traditional displacement ventilation systems often struggle to achieve satisfactory distribution of contaminant concentrations during heating modes. To address this issue, this study focused on enhancing the ventilation performance of a dual-coil displacement-induction unit. Through a combination of experimental measurements and computational fluid dynamic (CFD) techniques, the study examined airflow and contaminant concentration distributions in an environmental chamber conditioned by these units. The results demonstrated good agreement between measured and simulated data, validating the CFD model. Further evaluation in a 25-occupant classroom under cold outdoor conditions showed that the dual-coil unit could achieve satisfactory ventilation performance in heating modes with proper design, comparable to traditional displacement ventilation in cooling modes. Additionally, the unit's versatility allows it to accommodate a wide range of air conditioning applications, from heating to cooling, making it a promising solution for displacement ventilation in various environments.