Flow Kinetic Energy Research Articles

Kiosk 4R-TB-04 - Relationship Between Left Ventricular Blood Flow Kinetic Energy with Intramyocardial Hemorrhage in Patients with Acute St-segment-elevation

Kiosk 4R-TB-04 - Relationship Between Left Ventricular Blood Flow Kinetic Energy with Intramyocardial Hemorrhage in Patients with Acute St-segment-elevation

Evaluation of the overset method applied to an active lift turbine

In the current context of energy transition, the development and improvement of energy recovery systems is essential. These system are numerous and some of them use turbines to convert flow kinetic energy into electricity. For a long time, vertical-axis turbines were considered less efficient than horizontal-axis ones. However, they are still better suited to urban areas. Thus, they are now being studied again and new turbine concepts are emerging that can works differently from today’s turbines. The entire dynamics of these new-generation turbines can be completely different from those of conventional turbines. The active lift turbine, for example, changes the trajectory of the blades (by varying the turbine radius) to convert the normal forces applying on them into torque. This particularity hinders the use of conventional rotation methods for turbines (Arbitrary Mesh Interface (AMI), Rotating Frame of Reference (RFR), …) in Computational Fluid Dynamics (CFD) and an innovative method such as overset could be an alternative. The purpose of this work is to evaluate the overset method for these new-generation turbines modelling. It enables the motion of a structure in its environment to be controlled at will. Various modelling parameters are being tested. The impact of the mesh size (mesh convergence), the turbulence modelling approach (RANS/LES) and the interpolation method between the background mesh and the overset mesh (Cell Volume Weight/Inverse distances) are evaluated and compared. The overset method is first validated on a conventional turbine (Darrieus turbine). The results obtained for the conventional turbine are close to those expected, with a relative error (numerical/experimental) between 3% and 8% depending of the Tip Speed Ratio (TSR) with an averaged error around 7%. Then overset method is extended to an active lift turbine to assess the potential of this new technology. The overset method proves its worth for this type of problem, which cannot be solved by conventional CFD methods of setting structures into motion. It provides control over blade motion without loss of information. Overall, this study demonstrates the interest and applicability of the overset method to the Active Lift Turbine or other kind of turbines that have a specific motion.

QCD Equation of State of Dense Nuclear Matter from a Bayesian Analysis of Heavy-Ion Collision Data.

Bayesian methods are used to constrain the density dependence of the QCD equation of state (EOS) for dense nuclear matter using the data of mean transverse kinetic energy and elliptic flow of protons from heavy ion collisions (HICs), in the beam energy range sqrt[s_{NN}]=2-10 GeV. The analysis yields tight constraints on the density dependent EOS up to 4 times the nuclear saturation density. The extracted EOS yields good agreement with other observables measured in HIC experiments and constraints from astrophysical observations both of which were not used in the inference. The sensitivity of inference to the choice of observables is also discussed.

The numerical modelling of the ejector pump working process with variable geometry of the flow channel

The range of application of the ejector pumps for industry is extensive. The ejector pumps are used for gas, liquid and the multicomponent or multiphase mixtures transport. The stream-flow devices (pumps, compressors) has several advantages, for example: simple design, schema without moving parts, high reliability. Possibility of working with multiphase mixtures for ejectors determines their usage in the oil and gas mining systems as part of pumping stations for oil and gas pipe transport. Hydrodynamic of the stream-flow devices, which are used for oil and gas pipe transport, was researched good over a span of last years. This allows create optimal design of flow channel for ejectors. However, in the real life, in the working process of pumping station, is the flow unstable with the random occurrence of the gas and liquid slugs. Известно, что при перекачке газов длина камеры смешения должна быть значительно больше, чем при перекачке жидкости. In this way, creating design of ejectors for both effective gas and oil transport is very difficult problem. It is known that a length of the ejectors mixing section should be longer by gas transport than by liquid transport. In this paper was presented variant of the ejector’s flow channel with variable geometry, which was designed as the moving conical body in diffuser section. In this configuration, the annular conical channel between conical body and inner surface of diffuser is propagation of the mixing section and allows to effective mixing of components in ejectors with the short cylindrical mixing section actually. The diffuser’s function - converting kinetic energy of flow to pressure energy - holds because the surface area of annular channel increases in flow direction. The move of conical body in diffuser allows to control of the fluid transport efficiency. Researches are made as numerical flow simulation with CFD STAR-CCM+. This gives the possibility to the detail research all mixing processes with the analysis of the velocity, pressure and volume of fraction fields and flow.

Abstract 12854: Early and Late Features of Intracardiac Flow in Repaired Tetralogy of Fallot (rTOF) Patients Using Doppler Velocity Reconstruction (DoVeR)

Background: Intracardiac flow analysis has implicated flow energy loss (FEL), kinetic energy (KE) and vortex strength (VS) as markers of ventricular dysfunction in repaired Tetralogy of Fallot (TOF); no studies have investigated early vs. late intracardiac flow conditions after repair. We utilized novel echocardiography (echo) based Doppler Velocity Reconstruction (DoVeR) to determine FEL, KE and VS in pre-operative TOF vs early post-repair (<1 month) and late post-repair (>10 years). Methods: This was a single-center retrospective cross-sectional study on TOF patients with pre- and post-operative surveillance transthoracic echo. Apical 4 chamber color Doppler views were collected. The streamfunction-vorticity formulation was used to reconstruct left ventricular (LV) blood velocity fields by DoVeR. Velocity flow fields were evaluated for peak FEL, KE and VS. The FEL was also normalized against KE to account for physiologic variations. Data were compared via one-way ANOVA. Results: Echo studies from 14 pre-operative (1.7±0.5 months), 14 early-post repair (3.6±2.3 months) and 15 late-post repair (16.5±6.6 years) TOF patients were included. There was significant variation in FEL, KE, VS, and normalized FEL across timepoints (all p<0.05) (Figure B). In general, when compared to pre-operative TOF, the early post-repair cohort had lower FEL/KE/VS corresponding to reduction in ventricular volume load; however late post-repair cohort had higher FEL/KE/VS, suggestive of effects from long-term interventricular interactions. Conclusion: The LV intracardiac flow in TOF changes early after initial repair and late after repair. DoVeR could potentially be used to serially evaluate TOF patients.

Abstract 14833: Association of RV Hemodynamics From 4D Flow CMR With RV Restrictive Physiology From Pediatric to Adult Repaired Tetralogy of Fallot

Introduction: Right ventricular restrictive physiology (RVRP) is common after repair of Tetralogy of Fallot (rTOF), especially with residual pulmonary regurgitation. Four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) quantitates biventricular blood flow components and kinetic energy (KE) parameters, but their association with RVRP is unclear. We aimed to study 4D flow CMR parameters in adult and pediatric rTOF patients vs healthy controls and associations of 4D flow parameters with RVRP in rTOF. Methods: 103 rTOF patients (40 pediatric, 63 adult; age 24±17 years; 53M:50F) and 171 healthy controls (14 pediatric, 157 adult; age 40±15 years; 97M:74F) were prospectively recruited from centers in Singapore (2) and China (1) to undergo 4D flow CMR on multi-vendor scanners. LV and RV flow components—direct flow, retained inflow, delayed ejection flow and residual volume—and KE parameters (normalized to end-diastolic volume, KEi EDV )—global, peak systolic, average systolic, average diastolic, peak E-wave and peak A-wave—were analyzed. KE discordance was calculated as the ratio of RV and LV average systolic KEi EDV . Results: See Table. RVRP was identified in 70 patients (68%). rTOF with RVRP exhibited higher median RV stroke volume index, RV ejection fraction, RV direct flow, RV peak E-wave and E-wave/A-wave, and lower RV residual volume compared to rTOF without RVRP (all P<0.05). Using binary multivariable logistic regression analysis—and after adjustment for age, pulmonary regurtitation, LV and RV ejection fraction, RV direct flow was found to be independently associated with RVRP in rTOF (P<0.001). Conclusion: Patients with RVRP had higher RV direct flow, RVEF and RV peak E-wave energy, indicating the potential compensatory adaptations in patients with RVRP.

A hydraulic energy flow within the moving Earth

We consider the Earth moving through empty space at 30 km s−1 (in the Sun’s frame of reference). Associated with this motion is a convective flow of kinetic and internal energy. Since there is high pressure inside the Earth, and since the Earth is moving, there is yet another ‘hydraulic’ energy flow. This latter is what this article is about. Although this energy flow is huge, it is not addressed in the textbooks. The reason is that for the explanation one needs a concept which is not introduced in traditional presentations of classical gravitation: the gravitomagnetic field. The corresponding theory, gravitoelectromagnetism, was formulated in 1893 by Heaviside in analogy to Maxwell’s theory of electromagnetism. We discuss the question of what are the sources and sinks of this hydraulic, non-convective energy flow. To answer the question, we need to study the energy flow density distribution within the gravitational field. In doing so, we will make some interesting observations. The energy flow within the field is twice as large as it should be to transfer the field energy from one side of the Earth to the other. The excess flow goes back through the matter of the Earth. Since our readers may not be familiar with Heaviside’s theory, we first treat the electromagnetic analogue of our problem and then translate the results to the gravitational situation.

Particle transport-driven flow dynamics and heat transfer modulation in solar photovoltaic modules: Implications on soiling

Wind-swept debris and excessive heating reduce solar photovoltaic efficiency and accelerate panel degradation. For many solar plants in open environments, particle deposition is well-understood to exacerbate efficiency losses by blocking useable light and insulating panel surfaces. However, little is known about particle behavior in multi-panel systems, where complex wakes dominate and alter trajectories. This study examines debris-laden flow within a scaled array of two model solar panels, observing convective cooling and focusing on turbulent inter-panel flow dynamics. Convection is compared between the first and second panels (P1 and P2) for a single inflow velocity at four particle concentrations (ϕv), including a neutrally buoyant particle (i.e. tracer) case and three water droplet cases. Tracers and ϕv>0 concentrations show increased convective heat transfer for P2 compared to P1, while inertial particle presence and increased concentration reduces this improvement from +170% to +90%. Particle image velocimetry surrounding P2 reveals dampened inter-panel wake features for particle-laden flow compared to the tracer case, where diminished mean flow and mean kinetic energy breakdown are observed for the particles due to their inertia. Together, the reduction in comparative convection and dampened wake effects accompanying inertial particle concentration motivates further studies on coupled array physics in debris-filled flow.

Investigation of a Near-Field Cylinder Wake in the Subsonic, Transonic, and Supersonic Regimes

The near wake of a circular cylinder in a high-Reynolds-number regime is investigated using the particle image velocimetry technique for an inflow Mach number spanning 0.3 to 2. The mean flow and turbulent kinetic energy field for different Mach number cases are presented. Furthermore, the influence of the Reynolds and Mach number effects is examined based on the mean separation point along the cylinder surface, which is extracted from complementary schlieren visualization measurements, and the literature. The wake width for the supersonic inflow case is found to be an order of magnitude smaller physically than the subsonic case with an identical cylinder diameter. Additionally, the swirl strength criterion is used to identify the eddies present within the wake, and the eddy size and convection velocity are characterized based on the spatiotemporal correlations. The result suggests that the mean wake features for the subsonic and supersonic cases are very different. Moreover, the interaction of eddies generated at the cylinder’s top and bottom shear layers leads to the large-scale features present in the wake, and the differing paths followed by the eddies between the subsonic and supersonic cases are responsible for the variation in the observed wake width.

The Effect of Spatial Velocity Gradients on Block-Matching Accuracy for Ultrasound Velocimetry

Block matching serves as the foundation for ultrasound velocimetry techniques such as blood speckle tracking and echo-particle image velocimetry. Any spatial velocity gradients (SVGs) inside a block-matching pair will result in tracking error, due to both the finite block size and the ultrasound point-spread-function. We assess, using an in silico sinusoidal flow phantom, the effect of SVG magnitude and beam-to-flow angle on block-matching bias and precision. Secondarily we assess the effect that SVGs have on velocimetry bias when using angled plane-wave compounding. The magnitude and angle of SVGs were varied by adjusting the wavelength and direction of a sinusoidal flow profile. Scatterers displaced by this flow profile were used for simulating ultrasound radio frequency data at discrete time points. After beamforming, the 2-D flow field was estimated using block matching. Two imaging sequences were tested, a single plane-wave and a three-angled plane-wave. Smaller sinusoidal flow wavelengths resulted in increased bias and reduced precision, revealing an inverse relationship between sinusoidal flow wavelength and tracking error, with median errors ranging from 69%-90% for the smallest flow wavelengths (highest SVGs) down to 3%-5% for the largest (lowest SVGs). The SVG angle was also important, in which lateral SVGs (with axially oriented flows) resulted in significant speckle decorrelation and high tracking errors in regions with high SVGs. Conversely, axial SVGs (laterally oriented flow) experienced higher bias in the peak velocity regions of the flow profile. Coherent compounding resulted in higher velocity errors than using a single transmission for lateral SVGs but not for axial SVGs. The highest SVGs that could be measured with ≤10% error was when the sinusoidal flow wavelength was less than 20 times the ultrasound pulse wavelength. The clinical significance is that the high SVGs present in high kinetic energy flows, such as severe carotid stenosis and aortic regurgitation, will limit the ability to accurately quantify the velocities in these flow structures.

Iterated stochastic integrals and random velocity fluctuations

Iterated stochastic integrals of nonrandom integrands are constructed in the two-dimensional case. They are applied to the velocity fluctuations in a two-dimensional flow and mean kinetic energy of the velocity fluctuations is discussed.

Energetics of Cardiac Blood Flow in Hypertrophic Cardiomyopathy through Individualized Computational Modeling.

Hypertrophic cardiomyopathy (HCM) is a congenital heart disease characterized by thickening of the heart's left ventricle (LV) wall that can lead to cardiac dysfunction and heart failure. Ventricular wall thickening affects the motion of cardiac walls and blood flow within the heart. Because abnormal cardiac blood flow in turn could lead to detrimental remodeling of heart walls, aberrant ventricular flow patterns could exacerbate HCM progression. How blood flow patterns are affected by hypertrophy and inter-patient variability is not known. To address this gap in knowledge, we present here strategies to generate personalized computational fluid dynamics (CFD) models of the heart LV from patient cardiac magnetic resonance (cMR) images. We performed simulations of CFD LV models from three cases (one normal, two HCM). CFD computations solved for blood flow velocities, from which flow patterns and the energetics of flow within the LV were quantified. We found that, compared to a normal heart, HCM hearts exhibit anomalous flow patterns and a mismatch in the timing of energy transfer from the LV wall to blood flow, as well as changes in kinetic energy flow patterns. While our results are preliminary, our presented methodology holds promise for in-depth analysis of HCM patient hemodynamics in clinical practice.

Blood Flow Energy Identifies Coronary Lesions Culprit of Future Myocardial Infarction

The present study establishes a link between blood flow energy transformations in coronary atherosclerotic lesions and clinical outcomes. The predictive capacity for future myocardial infarction (MI) was compared with that of established quantitative coronary angiography (QCA)-derived predictors. Angiography-based computational fluid dynamics (CFD) simulations were performed on 80 human coronary lesions culprit of MI within 5 years and 108 non-culprit lesions for future MI. Blood flow energy transformations were assessed in the converging flow segment of the lesion as ratios of kinetic and rotational energy values (KER and RER, respectively) at the QCA-identified minimum lumen area and proximal lesion sections. The anatomical and functional lesion severity were evaluated with QCA to derive percentage area stenosis (%AS), vessel fractional flow reserve (vFFR), and translesional vFFR (ΔvFFR). Wall shear stress profiles were investigated in terms of topological shear variation index (TSVI). KER and RER predicted MI at 5 years (AUC = 0.73, 95% CI 0.65–0.80, and AUC = 0.76, 95% CI 0.70–0.83, respectively; p < 0.0001 for both). The predictive capacity for future MI of KER and RER was significantly stronger than vFFR (p = 0.0391 and p = 0.0045, respectively). RER predictive capacity was significantly stronger than %AS and ΔvFFR (p = 0.0041 and p = 0.0059, respectively). The predictive capacity for future MI of KER and RER did not differ significantly from TSVI. Blood flow kinetic and rotational energy transformations were significant predictors for MI at 5 years (p < 0.0001). The findings of this study support the hypothesis of a biomechanical contribution to the process of plaque destabilization/rupture leading to MI.

Turbulent Lorentz heat flow visualization in radiative boundary layer regime

Modern nuclear energy systems often employ the magneto-hydrodynamic and feature radiative heat transfer. Motivated by studying the near-wall transport phenomena in such applications, the present article examines the simultaneous influence of thermal radiative flux and magneto-hydrodynamics on two-dimensional electrically conducting natural convective turbulent heat transfer about a vertical surface under a transverse static magnetic field using the low Reynolds number kinetic energy and dissipation (k – ε) model. An optimized Crank–Nicolson finite difference method is applied to solve the nonlinear and coupled system of Reynolds-averaged boundary layer equations. Numerical computations are conducted to visualize the streamlines and heatlines in laminar and turbulent regimes via mathematical stream and heat functions based on the Bejan approach. A detailed parametric study of the effects of the magnetic field, radiative flux, and turbulent Reynolds number on flow average velocity, temperature, kinetic energy, and dissipation rate is conducted. The simulations reveal that an increase in the magnetic field intensity reduces the average velocity and dissipation rate, whereas an increase in thermal radiation decreases the time mean temperature. The study also includes contour plots of turbulence energy and dissipation rate, along with skin friction coefficient and Nusselt number. The obtained numerical outcomes are compared to previous literature, and a good agreement is found.

Development and numerical investigation of Mach probe model in a hypersonic, low-temperature flowing plasma

This study conducted a numerical simulation around a Mach probe under hypersonic low-temperature plasma. The Mach probe has three ion collection planes: front, side, and back. Under a hypersonic flowing plasma, the front and side planes are practical ion collection areas, and the backplane collects no ion flux. The collected ion current density on the front plane is almost identical to that of the mainstream ion flux. By contrast, the ion current collected on the side plane is affected by the concentration of the electric field at the probe edge. As this edge effect has a different influence on the front and side planes, the ion current density ratio of the side to the front planes is dominated by a non-dimensional parameter—the ratio of electrostatic to kinetic flow energy. Based on this non-dimensional parameter, the calculated ion current density ratio can be fitted using a simple mathematical formula. Therefore, the proposed Mach probe model with non-dimensional parameters extends the conventional Mach probe model validated in sub-to-supersonic high-temperature plasma to hypersonic low-temperature flowing plasma, which is commonly observed in electric propulsions.

Effects of surfactants on bubble-induced turbulence

We use experiments to explore the effect of surfactants on bubble-induced turbulence (BIT) at different scales, considering how the bubbles affect the flow kinetic energy, anisotropy and extreme events. To this end, high-resolution particle shadow velocimetry measurements are carried out in a bubble column in which the flow is generated by bubble swarms rising in water for two different bubble diameters (3 and 4 mm) and moderate gas volume fractions (0.5 %–1.3 %). We use tap water as the base liquid and add 1-Pentanol as an additional surfactant with varying bulk concentration, leading to different bubble shapes and surface boundary conditions. The results reveal that with increasing surfactant concentration, the BIT generated increases in strength, even though bubbles of a given size rise more slowly with surfactants. We also find that the level of anisotropy in the flow is enhanced with increasing surfactant concentration for bubbles of the same size, and that for the same surfactant concentration, smaller bubbles generate stronger anisotropy in the flow. Concerning the intermittency quantified by the normalized probability density functions of the fluid velocity increments, our results indicate that extreme values in the velocity increments become more probable with decreasing surfactant concentration for cases with smaller bubbles and low gas void fraction, while the effect of the surfactant is much weaker for cases with larger bubble and higher void fractions.

Turbulent wave-balance exchanges in the ocean

Oceanic flows are turbulent and multi-scale in nature, and are composed of fast internal waves and slowly evolving balanced eddies. Contrary to conventional wisdom in physical oceanography, the past two decades ofin situ, satellite altimeter and realistically forced global scale ocean model outputs have revealed that internal gravity waves can have comparable or higher energy levels than geostrophically balanced flows at 10–100 km scales in different parts of the world’s oceans. These relatively recent findings have fuelled a wide range of research activities aimed at understanding how fast internal gravity waves interact with slowly evolving balanced flows, particularly with the goal of deducing whether internal waves can form an energy sink for oceanic balanced flows. In this paper, we comprehensively review theoretical, numerical and observational investigations undertaken to study internal wave-balance flow exchanges. Theoretical calculations, inspired by different wave-balance regimes seen in observational and global ocean model outputs, are used to point out that internal waves can affect balanced flow dynamics. The theoretical results are followed up by a detailed discussion of numerical results on wave-balance interactions in a broad set of parameter regimes. The numerical results reveal how different kinds of waves exchange energy with balance flow, affect energy flux across scales of balanced flow and facilitate the generation of small-scale dissipative balanced flow structures. The numerical simulation results and global internal wave energy and balanced energy maps are used to conjecture that out of the 0.8 TW of power going to balanced flow kinetic energy in the ocean, at least 0.1 TW could be dissipated by internal gravity waves. We therefore hypothesize that internal waves can form a non-negligible energy sink for balanced flow in the world’s oceans.

Secondary Flow in Rotating Ducts

A simulation study is performed on laminar flow of an incompressible viscous fluid through rotating ducts. The ducts considered were rectangular straight, rectangular curved and circular curved. Simulations were carried out at two Reynolds numbers, three rotation numbers and five radii of curvature. Secondary flow is induced due to the rotation as well as the curvature of the duct independently, and this can be observed by the presence of double vortex in the bend region and in the downstream region of the rotating duct. Secondary flow creates unwanted losses in the flow. In the present study, the variation of the losses is estimated by plotting the secondary flow kinetic energy and the total pressure loss coefficient for different radii of curvature and rotation speeds. It was observed that both the coefficients increase rapidly in the curved region. The total pressure loss coefficient keeps increasing along the length, while the secondary kinetic energy coefficient decreases after peaking in the curved portion and converges to a constant value. This flow phenomenon, especially in turbines and rotating coolant channels are of practical interest in such applications as heat exchangers, rotors of electrical machinery, cooling channels of gas turbine rotor blades. Therefore it is important to understand the underlying physics, which could help in the design of turbomachines and in optimizing heat transfer rate in the relevant applications.

Process planning for hybrid manufacturing using additive friction stir deposition

Additive friction stir deposition (AFSD) provides a solid-state approach to metal deposition that does not rely on local melting and solidification, but rather on kinetic energy and plastic flow. In this study, AFSD is combined with structured light scanning, turning, and milling to produce metal components while considering the unique requirements imposed by the hybrid manufacturing process sequences. Two demonstrations are presented which include: 1) a cylindrical build plate selection to enable coordinate system transfer between deposition and turning of a hollow cone; and 2) intermittent deposition-machining operations with structured light scanning to fabricate a two-sided hexagon-cylinder geometry.

The influence of different runner widths on the performance of micro Pelton turbine

Pelton turbine can not only utilize the high head hydraulic resources but also recover the flow kinetic energy in the pipeline. It is more and more widely used. Thus, the research on improving the efficiency and performance of Pelton turbine is important. In this paper, Boltzmann method is used to study the influence of different runner widths on the performance of a micro Pelton turbine. And two micro Pelton turbines with runner widths of 25mm and 20mm are taken as the research object. Then turbine efficiency is calculated and the internal flow characteristics of micro Pelton turbine are analyzed. The results show that the runner width has obvious influence on the efficiency. When the runner width decreases from 25mm to 20mm, the turbine efficiency decreases by 1.16%. Besides, the turbulence area in the runner decreases, and the velocity decreases. But the turbulence intensity and vorticity in the runner is enhanced, which causes more serious hydraulic loss.