Mean Flow Velocity Research Articles

Observation of Relationship between Surface Flow Velocity and Mean Velocity

Surface velocity measurement using electromagnetic waves is common in flood season discharge surveys in Korea. In order to expand the relatively safe non-contact discharge survey, this study investigated the reliability of the coefficient that converts surface velocity to mean velocity in rivers and waterways. Surface and mean velocity were investigated for agricultural reservoir spillways, gravel rivers, and irrigation canals, and the volumetric capacity of agricultural reservoirs was confirmed. As a result of the investigation, the mean velocity conversion coefficients according to the riverbed slope or riverbed material were very diverse, such as 0.61, 0.90, 0.52, and 0.88. The above result makes it clear that each investigation point has a unique conversion coefficient according to the characteristics of the bed material. In other words, accurate discharge investigation is possible by knowing the unique conversion factor to each point. The importance of water management due to climate change is increasing day by day. Accurate flow rate for rivers and waterways will be used as an essential factor for quantitative water resource management in the future.

Correction factor for determining mean velocity of shallow flow on rough surfaces under varying inundation conditions using dye tracer method

AbstractAccurate estimation of mean flow velocity is crucial for hydraulics and soil erosion studies. A correction factor (α) is required to convert flow surface velocity to mean velocity when using the dye tracer method. However, the determination of an appropriate α value is challenging and little information is available about how α varies with progressive inundation conditions, especially for rough surfaces with protruding roughness elements (e.g., stones). Therefore, laboratory experiments were conducted in a flume with sandpaper (SD) and stones (ST) surfaces to investigate the impact of roughness elements on the correction factor with varying inundation conditions. The results showed that using a single α value is inappropriate for rough surfaces. The correction factor was positively correlated with the Reynolds number and is controlled by flow regimes as well. Moreover, the impacts of inundation conditions as well as protruding roughness elements should be taken into account for determining α. Correction factor varied non‐monotonically with inundation ratio, depending on the progressive inundation status of protruding roughness elements. The developed equations introducing the inundation ratio performed well in predicting α, with R2 = 0.86 and NSE = 0.91. The results contribute to our understanding of measuring mean flow velocity using the dye tracer method.

Corrugated pipes conveying fluid: Vibration and instability analysis

The global flexibility and local rigidity of corrugated pipes have made them a good candidate in many engineering applications such as aerospace, oil and gas industries, heat and cooling systems, compact heat exchangers, etc. In this study, dynamic responses of corrugated clamped-clamped pipes conveying fluid are investigated. The governing equations of the system are derived by using the Hamiltonian principle based on the Euler-Bernoulli beam hypothesis. Non-uniformity of the flow velocity profile is considered in the formulation for both laminar and turbulent fluid flow. So, the flow-profile-modification factor for laminar flow and space-dependent mean velocity for turbulent flow are proposed. For spatial discretization of these equations, the finite element method is used. The effects of several parameters including fluid velocity, the corrugation length, as well as corrugation amplitude on the stability of the pipe system are examined. Natural frequencies of the pipe in hydrostatic flow conditions and critical flow velocities are determined for a vast range of parameters. Numerical results show that the stability of the system is significantly affected by the corrugation length and amplitude.

Effects of traditional Chinese exercise on vascular function in patients with Alzheimer's disease: A protocol for systematic review and network meta-analysis of randomized controlled trials.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder with an insidious onset, usually characterized by memory impairment, visual-spatial skill impairment, executive dysfunction and personality behavioral changes. Studies have confirmed that vascular dysfunction may precede AD pathological changes and can present as vascular malformations, atherosclerosis, and impaired self-regulation, and can affect oxidative stress and amyloidosis. Therefore, it is important to improve or prevent vascular dysfunction in AD patients. Regular exercise can effectively inhibit the production of reactive oxygen species during the occurrence of AD and can improve the reduction of cerebral blood flow due to AD. Previous studies have shown that exercise can achieve superior clinical results in improving vascular function in AD patients. Therefore, we hypothesize that traditional Chinese exercises (TCEs) may have a good clinical effect in improving vascular function in patients with AD. We will search "PubMed," "the Cochrane Library," "Embase," "Web of Science," "CINAHL," "ProQuest Dissertations and Theses," and "ProQuest-Health & Medical Collection," "CNKI," "SinoMed," "VIP," and "Wanfang Data" to find randomized controlled trials of the effects of TCEs on AD vascular function from the creation of the database to the present, including at least 1 indicator in carotid intima-media thickness (cIMT), middle cerebral artery mean flow velocity (MFV), blood indicators [Heme Oxidase-1 (HO-1), angiopoietin I (Ang I), vascular endothelial growth factor (VEGF), brain-derived neurotrophic factor, matrix metalloproteinase-9 (MMP-9)], and arterial stiffness [(Ankle Brachial Index (ABI), pulse wave velocity (PWV)]. For the included literature, Excel 2019 will be used for data extraction and collection. For the indicators that can be netted for network meta-analysis, Surface Under the Cumulative Ranking for each exercise modality will be calculated with the help of Stata 16.0 and rank, where the higher the SUCRA score, the higher the ranking. For the indicators that cannot be netted, Review Manager 5.4 will be used for meta-analysis will be performed to evaluate the improvement effect of TCEs on AD patients. This meta-analysis will further determine the efficacy and safety of TCEs on vascular function in AD patients. In this study, randomized controlled trials of the effects of TCEs on vascular function in AD patients will be selected to provide evidence-based medical evidence for promoting the application of TCEs by observing the order of advantages and disadvantages of various exercise modalities through network meta-analysis.

The predictive value of deep learning-based cardiac ultrasound flow imaging for hypertrophic cardiomyopathy complicating arrhythmias

ObjectiveTo investigate the predictive value of deep learning-based cardiac ultrasound flow imaging for hypertrophic cardiomyopathy (HCM) complicated by arrhythmias.MethodsThe clinical data of 158 patients with hypertrophic cardiomyopathy were retrospectively collected from July 2019 to December 2021, and additionally divided into training group 106 cases, validation group 26 cases and test group 26 cases according to the ratio of 4:1:1, and divided into concurrent and non-concurrent groups according to whether they were complicated by arrhythmia or not, respectively. General data of patients (age, gender, BMI, systolic blood pressure, diastolic blood pressure, HR) were collected, a deep learning model for cardiac ultrasound flow imaging was established, and image data, LVEF, LAVI, E/e', vortex area change rate, circulation intensity change rate, mean blood flow velocity, and mean EL value were extracted.ResultsThe differences in general data (age, gender, BMI, systolic blood pressure, diastolic blood pressure, HR) between the three groups were not statistically significant, P > 0.05. The differences in age, gender, BMI, systolic blood pressure, diastolic blood pressure, HR between the patients in the concurrent and non-concurrent groups in the training group were not statistically significant, P > 0.05.ConclusionsDeep learning-based cardiac ultrasound flow imaging can identify cardiac ultrasound images more accurately and has a high predictive value for arrhythmias complicating hypertrophic cardiomyopathy, and vortex area change rate, circulation intensity change rate, mean flow velocity, mean EL, LAVI, and E/e' are all risk factors for arrhythmias complicating hypertrophic cardiomyopathy.

Wake flow field of a wall-mounted pipe with spoiler on a rough channel bed

This research work focuses on the wake flow region of a cylinder with a spoiler on a rough bed under steady flow conditions. The acoustic Doppler velocimetry was used for the measurement of three-dimensional velocity data for two Reynolds numbers in a fully developed turbulent flow around the cylinder with a spoiler. The mean flow velocities, second-order turbulence structures, and conditional statistics were investigated in the wake region of the spoilered cylinder. The flow was separated from the spoiler with the formation of two shear layers between free surface flow and recirculating flow. It is observed that the flow is reattaching to the bed at 11D irrespective of the Reynolds number. Downstream of the cylinder, the mean velocity distributions are asymmetric due to the wall–wake effect, and the point of inflection is observed for each velocity profile at z = 0.40ẟ. The turbulence intensities, Reynolds stresses, and TKE are highly enhanced in the wake region of the cylinder as compared to their respective upstream values for both runs. The turbulence intensities, Reynolds normal stresses, Reynolds shear stresses, and turbulent kinetic energy are attaining peaks at z = 0.4 ẟ for all the streamwise locations, and the peaks are found to be highest at x = 10D. The quadrant analysis results indicate that the sweeps are dominating bursting events in the inner and intermediate layers, while ejections are dominating in the outer layer of the wake region. As the hole size, H increases ejections stress fraction rises as compared to that of the sweeps in the wake region for z = 0.2–0.7 h.

Sediment transport capacity equation for soils from the Loess Plateau and northeast China

Sediment transport capacity (Tc) is a relevant component in physical-process-based soil erosion models. At present, the sediment transport capacity prediction model for soils with a low median grain diameter is not fully understood. In this study, the Tc values of three different soils (median grain diameter d50 = 0.015, 0.040, and 0.095 mm) were investigated by conducting indoor experiments at unit flow discharges of 0.19 – 1.89 × 10-3 m2·s−1 and slopes of 0.07–0.21. In addition, data describing the overland flow sediment transport capacity of black soil (d50 = 0.01 mm) were obtained from Yu et al. (2018). First, the performance of seven shear stress, unit stream power, stream power, and mean flow velocity concept-based Tc equations were evaluated based on the measurements. The results confirmed that none of the existing formulas performed well over the entire experimental range. Tc equations derived using soils with a large particle size generally underestimate the Tc of soils containing small particles. The Zhang equation, when calibrated based on the data in this study, can predict overland flow Tc with a PoP of 66 % (PoP refers to the percentage of predictions in which the discrepancy ratio falls between 0.5 and 2.0, whilst the discrepancy ratio is the ratio of the predicted and measured Tc). Based on the general flow parameter concept, a more accurate Tc equation was developed for the four types of soils, which was characterized by a PoP of 83 %. When these equations are beyond the scope of their development conditions, they should be verified further.

Characterization of interfacial waves in stratified turbulent gas-liquid pipe flow using Particle Image Velocimetry and controlled disturbances

The work reports an experimental investigation on stratified gas-liquid pipe flow characteristics in the presence of controlled interfacial waves. Studies of this flow regime with controlled interfacial waves are scarce in the literature. Here, the disturbances are excited at the liquid interface by an oscillating paddle. The waves are synchronized with image acquisitions, enabling the utilization of phase-locked measurements and ensemble averaging techniques. Off-axis Particle Image Velocimetry (PIV) and Shadowgraph techniques were applied to provide information about mean and wave-induced modifications on the velocity fields. Results show that mean flow velocities in the liquid and gas phases close to the pipe walls adhere well to the single-phase flow log-law profile. In the liquid layer, this agreement was observed up to half of the water depth. Controlled disturbances enabled the estimation of the wave amplitude thresholds for the appearance of relevant nonlinear wave effects on the flow field. Results suggest that such a threshold can be fairly represented by a constant value of the non-dimensional parameter proposed in the work of Kirby (2008). Within the non-linear wave regimes investigated, noticeable changes in the flow field were observed close to the interface. However, near the wall the flow was weakly affected by the presence of waves, suggesting that interfacial wave effects are weakly coupled with near-wall disturbances and might be modelled independently. Moreover, contributions to interfacial shear stress due to the presence of waves were obtained experimentally. The results presented here are useful for validation and improvement of models used to predict flow characteristics in stratified flows. In addition, they contribute to shed further light on the physical mechanisms involved in the phenomenon.

Assessment of aortic and cerebral haemodynamics and vascular brain injury with 3 and 7 T magnetic resonance imaging in patients with aortic coarctation.

Coarctation of the aorta (CoA) is characterized by a central arteriopathy resulting in increased arterial stiffness. The condition is associated with an increased risk of stroke. We aimed to assess the aortic and cerebral haemodynamics and the presence of vascular brain injury in patients with previous surgical CoA repair. Twenty-seven patients with CoA (median age 22 years, range 12-72) and 25 age- and sex-matched controls (median age 24 years, range 12-64) underwent 3 T (heart, aorta, and brain) and 7 T (brain) magnetic resonance imaging scans. Haemodynamic parameters were measured using two-dimensional phase-contrast images of the ascending and descending aorta, internal carotid artery (ICA), basilar artery (BA), middle cerebral artery (MCA), and perforating arteries. Vascular brain injury was assessed by rating white matter hyperintensities, cortical microinfarcts, lacunes, and microbleeds. Pulse wave velocities in the aortic arch and descending aorta were increased and ascending aortic distensibility was decreased in patients with CoA vs. controls. Patients with CoA showed a higher mean flow velocity in the right ICA, left ICA, and BA and a reduced distensibility in the right ICA, BA, and left MCA. Haemodynamic parameters in the perforating arteries, total cerebral blood flow, intracranial volumes, and vascular brain injury were similar between the groups. Patients with CoA show an increased flow velocity and reduced distensibility in the aorta and proximal cerebral arteries, which suggests the presence of a generalized arteriopathy that extends into the cerebral arterial tree. No substantial vascular brain injury was observed in this relatively young CoA population, although the study was inadequately powered regarding this endpoint.

Coregistered positron emission particle tracking (PEPT) and X-ray computed tomography (CT) for engineering flow measurements

Increasingly, fully 3D experimental measurements of flow in complex engineering geometries are required to validate computational fluid dynamics models that support and inform reactor design and licensing. One barrier to such measurements is the complexity of typical reactor components and subsequent lack of optical access in these systems. To overcome this, the deployment of coregistered positron emission particle tracking (PEPT) and X-ray computed tomography (CT) is explored for flow measurement in reactor thermal hydraulic components and model (scaled) systems. Through this methodology, fully 3D flow information (via PEPT) and detailed internal geometry (via CT) are captured in opaque systems such as pipes, rod bundles, packed beds, etc. The reconstructed flow field and geometry can then be overlain to reveal detailed flow features around internal structures within a given test section. This is enabled through the use of a combined preclinical PET/CT scanner with overlapping PET and CT fields of view. Such measurements are useful for characterizing flow inside such intricate nuclear thermal hydraulic components as core geometries and heat exchangers, among others, and providing valuable 3D validation data for CFD models. In this work, basic tests of this 3D flow/geometry mapping are presented, and the implications of such measurements are discussed. Preliminary measurements are made with both point sources and flow in a simple pipe flow geometry to evaluate the capabilities of this technique. PEPT and CT features are coregistered with up to 0.1 mm precision, and pipe flow mean velocity and Reynolds stresses are reconstructed with similar accuracy to previous PEPT demonstrations. The utility of PEPT/CT is shown herein, and suggestions for future measurements are made.

Application value of transcranial contrast-enhanced ultrasonography in evaluating middle cerebral artery stenosis.

To detect the display rate and flow velocity of intracranial circle of Willis (anterior, middle, and posterior cerebral arteries) with transcranial contrast-enhanced transcranial color-coded sonography (CE-TCCS), using digital subtraction angiography (DSA) as the golden diagnostic standard. We collected data from 104 patients with suspected stroke treated in our hospital between December 2019 and October 2021. The detection rate of the intracranial circle of Willis, anterior cerebral artery (ACA), middle cerebral artery (MCA), and posterior cerebral artery (PCA) were analyzed based on routine TCCS and CE-TCCS data. Based on digital subtraction angiography (DSA) data, the degree of MCA stenosis was divided into mild stenosis (<50%), moderate stenosis (50-69%), severe stenosis (70-99%), and bilateral middle cerebral artery CE-TCCS examinations were performed. We evaluated MCA color blood flow on CE-TCCS, and recorded the peak systolic velocity (PSV), end-diastolic velocity (EDV), and mean flow velocity (MFV). The display rates of ACA, MCA, and PCA were significantly improved on the CE-TCCS, and the PSV, EDV and MFV of the MCA stenosis group were higher than those of the normal group. The flow velocity of each stenosis subgroup was increased compared to the normal group. The optimal cutoff values of normal and stenosis under the receiver operating characteristic (ROC) curve were PSV = 168.5 cm/s, EDV = 61.5 cm/s, and MFV = 110.5 cm/s. The optimal cutoff values for mild and moderate stenosis and for moderate and severe stenosis were PSV = 201.5 cm/s and 249.5 m/s, EDV = 95.2 cm/s and 141.5 cm/s, and MFV = 137.6 cm/s and 160.5 cm/s, respectively. PSV and MFV had the most significant sensitivity, specificity, and accuracy. Transcranial contrast-enhanced ultrasonography can improve the display rate of intracranial blood vessels and can accurately diagnose MCA stenosis.

Effect of 23 % low-sodium salt applied to Chinese modified DASH diet on cerebrovascular function in patients with hypertension and type 2 diabetes: a pilot study.

Aim: to investigate the effects of low sodium formula salt combined with the Chinese Modified Dietary Approaches to Stop Hypertension (DASH) diet on cerebrovascular function in patients with hypertension and type 2 diabetes. Methods: an eight-week single-arm trial was conducted in 66 patients with hypertension and type 2 diabetes to investigate effects of low sodium formula salt (potassium chloride 56 %, sodium chloride 23 %, 5 g/day) combined with Chinese Modified DASH diet on cerebrovascular function (measured by transcranial Doppler sonography), indicators of chronic diseases (blood pressure, blood glucose and blood lipids) and urinary excretion. The above indicators were performed before and after intervention. Results: fifty-nine subjects completed the study. Peak systolic velocity, mean flow velocity, end-diastolic velocity, pulsatility index and resistance index of internal cerebral artery and vertebral artery decreased significantly (p < 0.05); pulsatility index and resistance index of anterior cerebral artery and middle cerebral artery decreased significantly (p < 0.05); and end-diastolic velocity and pulsatility index of basilar artery decreased significantly (p < 0.05). Systolic blood pressure, diastolic blood pressure, fasting blood glucose and postprandial blood glucose decreased significantly (p < 0.001; p < 0.001; p < 0.001; p < 0.001). Blood pressure and blood glucose control rates increased significantly (p < 0.001). Conclusions: based on the study, 23 % low-sodium formula combined with CM-DASH diet pattern can improve cerebrovascular function in community patients with hypertension complicated with diabetes and has a good short-term benefit of blood pressure and glucose control.

Monitoring debris flows in the Gadria catchment (eastern Italian Alps): Data and insights acquired from 2018 to 2020

This work analyses seven debris flows recorded between 2018 and 2020 in the Gadria instrumented catchment (South Tirol). We focus on three aspects not previously explored in this catchment: (i) the debris-flow transfer times between the headwaters and the outlet; (ii) the longitudinal variability of debris-flow velocity between the three downstream monitored cross-sections, and (iii) the characteristics of the secondary surges observed in three debris flows. In most cases, the mean velocity of the debris flow estimated from the upper to the lower channel reaches (for travel distance of 2155 m) is rather low, ranging between 1.9 and 3.9 m/s. This result could indicate a progressive slowing down, and possibly even temporary stops of debris flows along the path. Some variability in flow velocity was observed between two channel reaches in the lower part of the catchment (0.7 – 2.3 m/s in the upstream reach, and 1.4 – 4.7 in the downstream one). Regarding the secondary surges, these have been noted to occur superimposed on slow-moving slurry-type phases. The mean velocity of the secondary surges varied between 3.5 and 8.9 m/s, with an average value close to 6 m/s for all three events. Their regular shape, duration, and depth suggest that such surges were generated by flow instabilities, with no external forcing.

Close Correlations Between Carotid Arterial Mean Blood Flow Velocity, Body Mass Index, and Temperature in Normal Individuals

Objective: Assessing carotid and radial pulses is an essential sphygmology method in traditional Chinese medicine (TCM). It is believed in TCM and by doctors that pulse force is markedly linked with the physiological state of a human, including body mass index (BMI) and temperature. However, comprehensive analysis elucidating these potential correlations remains undetermined. Therefore, this investigation aimed to assess the association of pulse strength with human metabolism. Materials and Methods: The mean blood flow velocity (MBFV) of the carotid artery and pulse force of 122 healthy adults included in this investigation were assessed using ultrasound and manual palpation. Their thermal texture map was also acquired. Results: No substantial variation was observed in the carotid arterial MBFV among normal individuals (P &gt; 0.05) regardless of body side and gender. However, young individuals had higher blood velocity than middle-aged individuals (P &lt; 0.05). Furthermore, it was identified that MBFV was negatively associated with BMI and torso temperature; however, it was positively linked with hand temperature. Conclusions: This investigation revealed that carotid arterial MBFV could indicate the physical state of humans, including BMI and temperature, and therefore, is valuable for elucidating the effect of TCM on yin–yang. The data validated some TCM beliefs and supported the implementation of sphygmology in TCM.

МОЗГОВОЙ КРОВОТОК И СОСТОЯНИЕ НЕКОТОРЫХ КОГНИТИВНЫХ ФУНКЦИЙ ПОСЛЕ 520 СУТОЧНОЙ ИЗОЛЯЦИИ У ЗДОРОВЫХ ЛИЦ

Six male volunteers at the age of 27 to 39 years were participants in an investigation of cerebral circulation and cognitive functions in a 520-d isolation study. Transcranial doppler ultrasonography was used for continuous recording the mean linear blood flow velocity in medial cerebral arteries (MCAs) at rest, during voluntary maximal breath-holding (hypercapnia), and cognitive tests. After the long-term isolation, both MCAs retained a statistically significant increase of the standard deviation of blood flow velocity relative to the values at rest. This finding reflects changes in amplitude of blood flow fluctuations in response to physiological and cognitive tests. Cognitive functions and mean blood flow velocity in both MCAs were not affects by long-term isolation.

A numerical study on the relationship between particle dispersion, accumulation, and indoor airflow in different ventilated rooms

AbstractThis study serves as a basic study of the indoor dispersion of pollen particles, simulating the flow field and discussing the behavior of particles of different diameters in different rooms. By comparing the vertical velocity components of particles () and the mean flow velocity of z‐direction component () plus the terminal settling velocity in a gravitational field (), the differences between values and plus values are found to occur mainly at locations close to the opposite wall of the inlet. The location of the differences between values and plus values is important findings of this study, which facilitates the improvement of the simulation method at a later stage and the rational design of indoor ventilation patterns to easily remove particles from the room.

Influence of Limb Position on Venous Blood Flow After Total Knee Arthroplasty: A Prospective Randomized Study.

Previous studies have suggested a clinical advantage when placing the limb in flexion after total knee arthroplasty (TKA). We sought to measure venous flow compared with control values after TKA. Our hypothesis was that the knee flexed positioning would not adversely affect venous flow. Two cohorts were prospectively evaluated. First, volunteers were randomized to positions with the knee flexed to approximately 90° or placed in a fully extended (control) position. Venous flow velocity was measured in the femoral vein every 15 minutes for 2 hours. Subsequently, 32 patients were randomized to 1 of these 2 positions after TKA, and venous flow velocity was measured in both the operative and the contralateral limb. In the healthy volunteer cohort, mean venous flow velocity was significantly higher at all time points in the flexion group compared with the extended control group (P<.05). After TKA, mean flow velocity for an extended knee (control) was 28.5 cm/s. Mean flow velocity for the flexed knee, foot-dependent group was 47.2 cm/s (P=.036) and for the flexed knee, foot-elevated group was 30.4 cm/s (P=.618). Placing the limb in a flexed position after TKA is not detrimental to venous flow velocity and resulted in higher velocities relative to the extended position. Placing the limb at 90° flexion does not cause venous stasis and should not increase the risk of deep venous thrombosis. [Orthopedics. 2023;46(1):8-12.].

Slurry flow characteristics through a horizontal pipeline at different Prandtl number

The settling behavior of solid particles in the slurry pipeline leads to bed formation and sedimentation at the bottom of the pipeline. This in turn causes the blockage of the pipeline resulting in more energy consumption and a pressure drop in the slurry pipeline. The present work investigates the effect of the different Prandtl numbers on the slurry flow characteristics through a horizontal pipe. Since the flow is a liquid-solid mixture, therefore, a steady-state three-dimensional Eulerian two-phase model in combination with the RNG k-ε turbulence model is implemented for the current simulation in the commercial software ANSYS FLUENT. Numerical predictions and procedures for the mixture of solid concentrations are generally in good agreement with the past experimental data available in the literature. Slurry flow features are examined at four different Prandtl numbers i.e., 2.88, 3.42, 4.62 and 5.83 for different-sized glass beads (125, 200, 275, 350 and 440 μm) slurry for the concentration ranging from 40 to 60% (by weight) at a mean flow-velocity of 5 m/s. The findings show that the pressure drop rises with the escalation in particle sizes and Prandtl number for chosen efflux concentration range. Furthermore, low Prandtl fluid demonstrates relatively higher granular pressure, temperature and wall shear stress, which further increases with raise in solid concentration and particle size. In addition, higher Prandtl number fluid demonstrates maximum specific energy consumption (SEC) for every particle and efflux concentration range. • 3D CFD modeling of slurry flow via horizontal straight pipe is investigated. • Effect of different Prandtl number on slurry flow characteristics is studied. • Effect of particle size and concentration on slurry pressure drop is presented. • At lower Prandtl number, maximum granular pressure and temperature is established. • Transportation of slurry with higher Prandtl fluid is more energy efficient.

A comparison of hydrodynamic and thermal properties of artificially generated against realistic rough surfaces

The mathematical roughness generation approaches enjoy outstanding flexibility in delivering desired roughness geometries to perform systematic research. However, whether an mathematically (artificially) generated roughness can be considered an adequate surrogate of a realistic surface in terms of its influence on the flow remains nonetheless an open question. Motivated by this, the present study discusses the possibility of reproducing flow properties over realistic roughness with artificial roughness. To this end, six types of artificial rough surfaces are generated through imitation of the realistic height probability density function (PDF) and the roughness power spectrum (PS) preserving the stochastic nature of the roughness structure. The flow properties of the artificial surfaces are assessed using direct numerical simulations (DNS) in a fully-developed turbulent channel flow at Reτ=500−2000. An excellent match in terms of global flow properties, mean velocity and temperature profiles, Reynolds stresses as well as equivalent sand grain sizes is found compared to their original counterpart with exception of a strongly anisotropic sample (surface anisotropy ratio SAR≈1.7). Additionally, some artificial surfaces are generated by matching only the PS, and it was shown that only at adequately low effective slopes this can lead to similar flow properties. Overall, the results suggest that artificial roughness generated using the employed method by mimicking realistic PDF and PS can be applied as a full-fledged surrogate for realistic roughness under the premise of surface isotropy.

Computational Fluid Dynamics Analysis of Blood Flow Changes during the Growth of Saccular Abdominal Aortic Aneurysm.

Computational fluid dynamics analysis of the growth process of saccular abdominal aortic aneurysm was performed. A 3D model of aortic aneurysm was created based on CT images. Properties in terms of wall shear stress, mean flow velocity, mean pressure, energy loss, and pressure loss coefficient were calculated using thermal fluid analysis software "ANSYS CFX." As the aneurysm expanded, the mean flow velocity decreased and the wall shear stress, mean pressure, energy loss, and pressure loss coefficient increased. Wall shear stress increased when the aneurysm was small, suggesting that is related to the development and growth of the aneurysm. (This is secondary publication from J Jpn Coll Angiol 2021; 61: 3-10.).