Turbulent Flow Pattern Research Articles

Turbulent thermal characteristics and air flow patterns in a naturally ventilated tunnel with roof openings

Air flow is a major characteristic in the tunnel ventilation design, to avoid severe disasters like smoke suffocation problems in tunnel and fire accidents. Tunnels are best ways to reduce distance between two adjacent places. It may be underground or above ground, depending upon the usage of it. There are different types of tunnel ventilation, e.g. roof vents, side vents, mechanical ventilation, naturally ventilated etc. This paper majorly focuses on roof vents mass extraction with different sizes of the heat sources and it also records the horizontal and normal velocity for different sizes of heat sources. The Reynolds Number is low but still turbulence occurs when we deal with buoyant smoke keeping density as incompressible ideal gas. Ratio of height by width is taken into account and the transient air flow is simulated for 10 seconds, and mass flow is recorded at each time step of 0.1 seconds using Large Eddy turbulence Model to capture the flow physics. It is observed that with changing the heat source size, mass flow rate from each vent changes significantly and it drastically affects the air flow patterns and heat transfer characteristics inside the tunnel.

Transition to turbulence as a result of chaotic distortion of vortex shedding

Abstract The equations of multimoment hydrodynamics supplemented with stochastic terms are used for numerical simulation of chaotic distortion of regular regimes in the problem on flow around a solid sphere. The influence of disordered perturbations arising in the medium due to external influences is investigated. The loss of stability is accompanied by a qualitative change in the behavior of flow. Each perturbation forces the unstable flow to behave purely individually. The possibility of interpreting each of the unstable flows in terms of some average hydrodynamic values passes away. This behavior is called the butterfly effect. Independence in the behavior of disordered perturbations disappears. Conservation laws force disordered perturbations to adapt their behavior in time and space to the behavior of hydrodynamic values. A change in the behavior of disordered perturbations leads to chaotic distortion of both the regular flow in the recirculating zone and the regular regime of vortex shedding. Distortion of regular regimes creates a turbulent flow pattern in the wake behind the sphere. Vortex shedding is called the regular component of turbulence. Disordered perturbations are called the chaotic component of turbulence. The loss of stability is responsible for the growth and accumulation of disordered perturbations in the wake behind the sphere.

KAJI KARAKTERISTIK PERPINDAHAN PANAS PENGARUH BELOKAN TAJAM PADA PENUKAR KALOR TIPE TUBE

Using the thermal machines in the production process or overdone heat power operation require unit of Heat Exchanger (HE) having high level heat transfer coefficient (hc) for transferring to the thermal reservoir. Experimental studies have been done for heat transfer characteristics of forced convection on the round duct with method use that compare three of heat exchanger with a variety of pipe bends and a long pass after a turn that is different. HE pipes have length of tube 500 mm with a 12 bends, HE pipes length of tube 250 mm with 24 bends and HE pipes length of tube 125 mm with 48 bends. The heat fluid flowed into the tube, and the tube is immersed in the cold water tank. For each of test equipments can be done three times experiment with different variations in inlet temperature that is at 600C, 700C and 800C, with a duration of 5 minute intervals for 50 minutes. Many pipe bends and short passes after a HE will increase turbulence flow pattern. The high of turbulence will increase the value of heat transfer coefficient, but it can hold on fluid flow rate. Keywords : heat transfer characteristics, round duct, sharp bends, long pass

Physiologic blood flow is turbulent

Contemporary paradigm of peripheral and intracranial vascular hemodynamics considers physiologic blood flow to be laminar. Transition to turbulence is considered as a driving factor for numerous diseases such as atherosclerosis, stenosis and aneurysm. Recently, turbulent flow patterns were detected in intracranial aneurysm at Reynolds number below 400 both in vitro and in silico. Blood flow is multiharmonic with considerable frequency spectra and its transition to turbulence cannot be characterized by the current transition theory of monoharmonic pulsatile flow. Thus, we decided to explore the origins of such long-standing assumption of physiologic blood flow laminarity. Here, we hypothesize that the inherited dynamics of blood flow in main arteries dictate the existence of turbulence in physiologic conditions. To illustrate our hypothesis, we have used methods and tools from chaos theory, hydrodynamic stability theory and fluid dynamics to explore the existence of turbulence in physiologic blood flow. Our investigation shows that blood flow, both as described by the Navier–Stokes equation and in vivo, exhibits three major characteristics of turbulence. Womersley’s exact solution of the Navier–Stokes equation has been used with the flow waveforms from HaeMod database, to offer reproducible evidence for our findings, as well as evidence from Doppler ultrasound measurements from healthy volunteers who are some of the authors. We evidently show that physiologic blood flow is: (1) sensitive to initial conditions, (2) in global hydrodynamic instability and (3) undergoes kinetic energy cascade of non-Kolmogorov type. We propose a novel modification of the theory of vascular hemodynamics that calls for rethinking the hemodynamic–biologic links that govern physiologic and pathologic processes.

Effect of hybrid nanofluids on thermal and hydraulic characteristics of hexagon tube

The commonly determinations of present study are evaluation numerically the thermal transfer and hydraulic distribution inside the turbulent flow pattern for Al2O3-water nanofluids and hybrids fluid of (Al2O3 and CuO) dispersed in pure water concluded a straight hexagon pipe with constant thermal heat flux thermal conditions. 20 nm average diameters of nano particles and 0.1% volume fraction is employed. The numerical analysis includes the numerical simulation of straight tube model by a package ANSYS FLUENT 18 for constant heat flux value of 1 × 104 W/m2 and the Reynolds number had a range of 6 × 103 to 4 × 104. The consequences displayed that heat transfer coefficient of hybrid fluid was better than that of Al2O3-water and pure water by 12% and 23.4% respectively at all Reynolds numbers. The friction factor of hybrid fluid is superior to that of nanofluid and pure water by 4.6% and 11.7% respectively. It found improvement in thermal performance of hybrid fluid compared to that of nanofluids and the pure water. The numerical consequences of Nusselt number values and friction factor magnitudes are validated with the literature consequences obtained and display significant agreement, with a deviation of 7.8 % and 6.4% respectively.

Modelling study of flue gas flow pattern with pressure, amount and shape variation catalytic converter

Purpose: The purpose of this study is to analyse the modelling of exhaust gas flow patterns with variations in pressure, number, and shape of filters on the catalytic converter. Design/methodology/approach: The research method used is a simulation using ANSYS, which starts by creating a converter catalytic model with pressure variations: (0.5-1.5 atm), number of filters: (2-5), and the form of filter-cut/filter-not-cut. Findings: The decrease in velocity is caused by non-uniform velocity in the exhaust gas flow that occurs when passing through a bend in the filter-cut that serves as a directional flow to create turbulence. Filter-cut type tends to have fluctuating pressure, turbulence flow pattern shape so that contact between filter and exhaust gas is more effective. Based on the analysis of flow patterns, the speed and pressure of the 5 filter-not-cut design at a pressure of 0.5 are the best, while at pressure (1-1.5 atm) the type 5 filter-cut is the best. Research limitations/implications: This study is limited to filter-not-cut and filter-cut types with variations in the number of filters: 2, 3, 4, and 5, and the inlet pressure between 0.5-1 atm. Practical implications: The practical implications of this study are to find a catalytic converter design that has advantages in the effectiveness of exhaust gas absorption. Originality/value: The results show that the filter-not-cut and filter-cut types have the best effectiveness in the number of 5 filters. Filter-not-cut at the pressure of 0.5 atm and filter-cut at pressure (1-1.5 atm).

Genesis of Antibiotic Resistance (AR) LX: Sepsis: Mechanism(s) of differential activation of Extracellular Nucleotide Metabolizing Protein Complex (Ecpx) Augment Cellular Aggregates tethering consequently “Inviscid Instability” for laminar to turbulent transition

The timing, dosage, volume of fluid, antibiotic therapy of the fluid resuscitation strategy for treating sepsis cohort is considered as a pivotal for determining the mortality rate of treating sepsis cohort. NCT01663701 SSSP‐2 noted that the median volume of iv fluid administered between presentation at ER and 6 hours in the sepsis cohort was 3.5 L. The mean volume administered during a similar time interval in prior sepsis resuscitation trials were 5.0 L (N Engl J Med. 2001; 345(19):1368); 5.1 L; and 4.5 L. Given the significance of such as the suggested vs administered median volume of fluid administered during the initial phase of resuscitation, 3.5L may have been higher than the 30 mL/kg recommended by the Surviving Sepsis Campaign guidelines. As presented, the median volume of intravenous fluid administered between presentation in ER and 6 hours for BMI 18.5 kg/m2 ~ 70 mL/kg (NCT01663701). Based on the aforesaid clinical estimates, here we present a plausible physiological the sequel as a contributing contraption for increased mortality rate not withstanding another unknown clinical variable (s) in EGDT. The 6 hrs period between the time of presentation to ER and iv fluid resuscitation is considered physiologically pivotal for the hemodynamic aberration for the transition of laminar to turbulent blood flow pattern in the capillary bed of microcirculation. The plausible role of EC 3.6.1.15–CD36 ∞ Myoglein complex and EC 3.6.1.5 (Thr Hae. 1999;82(5):1538) induced leucocyte tethering causing the formation of eddies with an eventful of “DIC” amalgamated to “CCP” remains to be elucidated. Metabolic studies of CD39/CD73 function in intact intestinal epithelia revealed that hypoxia enhances CD39/CD73 function as much as 6 +/− 0.5‐fold over normoxia (Modified in part & verbatim J Clin Invest. 2002; 110(7):993). “Linear hydrodynamic stability theory” attribute the sheared flow as a fundamental cause for amplification of disturbances and predicted values of the Reynolds numbers (Re) Rex,crit (= Uxcrit/V) amplification and Rex,tr (= Uxtr/V) for fully turbulent flow to occur. Flows with a velocity distortion due to unpredictable size of cellular aggregates represents the point of inflexion (Ref. Compare Figure 3.4 a & b: An Intro to CFD, p 45: ISBN 978‐8131720486) and infinitesimal disturbances in part because of high Re in turn, referred as “inviscid instability”. Such fluctuating velocity profiles are known to form “Jet Flow”, mixing of aggregates inclusive of boundary layer separation, and wakes. Blood flow in sepsis cohort where the cellular aggregates flowing with laminar velocity distributions prior to the fluid resuscitation without a point of inflexion Ref Fig: 3.4b are subjected to viscous instability within the 6hrs period. It is our hypothesis that such flow pattern at high Re likely to cause turbulence in venous end of the capillary bed. Such anomaly would likely to be the contributing factor for higher mortality rate in NCT01663701 sepsis cohort.Support or Funding InformationSupported by professional development funds and in part CME activities of Subburaj Kannan MD PhD for www.aaets.org

Genesis of Antibiotic Resistance LIII: “Virchow’s Triad” of Capillary (Vascular) Leak Syndrome (CLS) tethered Adverse Pressure Gradient exacerbated mortality rate in NCT01663701: A critical appraisal

Based on adverse effects of biosimilar(s), for oncological treatment modalities (radiation/chemotherapy), posted in FAERS and VigiBase, an effort has been made to derive a temporal correlation between CLS and hemodynamic (Fluid dynamic/mechanics properties) dysregulation lead exacerbated mortality rate in NCT01663701. Idiopathic (unknown etiology) systemic capillary leak syndrome (SCLS) or Capillary leak syndrome (CLS), also known as vascular leak syndrome (VLS), with clinical features such as leakage of the plasma (reversible plasma extravasation with fluid resuscitation), vascular collapse accompanied by a classic triad of hypoalbuminemia, hemoconcentration, and hypotension in the absence of secondary causes of shock with edema. Fluid management is an effective clinical management strategy for an improved prognosis (verbatim in part and modified from J Clin Med. 2018; seven (11); J Clin Med. 2019; 8(2)). The clinical presentation of CLS with a corollary of Virchow’s triad ( https://www.ncbi.nlm.nih.gov/books/NBK539697/) and the critical events for a laminar to turbulence transition ( ELTT) is systematically correlated. Virchow’s triad I ‐ Endothelial damage:ELTT 1. Region of instability of small wavy disturbances called Tollmien‐Schlichting wave ELTT 2. Periodicity accompanied by the appearance of vortices ELTT 3. Peak‐Valley development in vortices, ELTT 4. Vorticity concentration and shear layer development with inflectional profile appearance and disappearance in Tollmien‐Schlichting wave pattern, Virchow’s triad II ‐ Venous stasis: ELTT 5. Breakdown: evolution of a staggered vortex pattern twice the wavelength of Tollmien‐Schlichting waves ( a high frequency fluctuations of hairpin eddies ‐ eddy currents, disrupts the laminar flow of blood, bringing platelets in close contact with the vascular wallVirchow’s triad III ‐ Hypercoagulability: ELTT 6. Cascading of vortices and turbulent‐spot development, (spots of thrombus lead to increased turbulence thus reduction in blood flow. Infarction and ischemia Thrombi often result in reduced blood flow to tissue (ischemia) or complete obstruction (absolute irreversible stasis NFP=0 mmHG, ?) of blood flow leading to cell death(infarction) with concurrent impairment of global net filtration pressure (NFP) in mark transition of laminar to turbulent flow pattern. Taken together, herewith it is suggested that a better understanding of the components of multifactorial mode of turbulence modelling in particular on time scale, blood viscosity, velocity profile, NFP gradient, and structural integrity of blood vessels (endothelial damage) of the capillary bed in the context of thromboembolic events [DDx: ischemic stroke(CVA), disseminated intravascular coagulation (DIC), deep vein thrombosis (DVT), pulmonary embolism and CLS], would enable better stratification of clinical risk factors, precision in clinical decision making amalgamating differential diagnosis for an accurate prognosis in early resuscitation protocol on sepsis such as NCT01663701.Support or Funding InformationSupported by professional development funds by SWTJC to Subburaj Kannan

The contribution of wall shear stress insult to the growth of small unruptured cerebral aneurysms in longitudinal 3D-TOF-MRA

ObjectiveAneurysm growth is a risk factor for rupture, however the detailed mechanism remains unclear. The present study was performed to identify whether hemodynamic insult could prompt small unruptured aneurysms to grow. MethodsSix pairs of unruptured small (<5 mm) cerebral aneurysms from patients followed with longitudinally three-dimensional MR imaging were selected and divided into an angiographic confirmed enlarged group (with >50% volume increase; n = 6) and an angiographic stable group (with ±10% volume changes; n = 6). Patient-specific computational fluid dynamic models were created and run under pulsatile flow conditions. Reverse reconstruction technique was used to simulate the status of before aneurysm generation. Relevant hemodynamic variables were calculated and compared between the two groups. ResultsIn the enlarged group, wall shear stress (WSS) decreased from aneurysm neck to dome, whereas WSS at the aneurysm neck (58.68 ± 34.45 Pa) and body (52.68 ± 46.37 Pa) was significantly higher than the stable group (neck: 36.83 ± 18.20 Pa and body: 30.77 ± 18.85 Pa) (P < .05). WSS decreased at the neck, body, and dome and flow patent became stable after aneurysm growth (P < .05). Reverse reconstruction revealed an elevated WSS at the site of aneurysm formation compared with other sites in the parent artery, and WSS at the formation site significantly decreased after aneurysm growth and further enlargement (P < .05). ConclusionLocal elevated WSS to the arterial wall contributed to cerebral aneurysm generation, whereas turbulent flow patterns and elevated WSS at the aneurysm neck and body worked together to result in further growth of small aneurysms.

Effect of the turbulent flow pattern on the interaction between dodecylamine and quartz

In this work, the effect of the turbulent flow pattern on the interaction between dodecylamine and quartz was studied using a stirred tank. The analysis of the adsorption amount and zeta potential shows that the axial flow field leads to a larger enhancement of the dodecylamine adsorption onto the quartz particles than the radial flow, and the microflotation tests verify that the fully developed turbulent flow improves the recovery rate of quartz particles during froth flotation. The results of the numerical simulation imply that the main interact between the quartz surface and the radial turbulent flow is strike and skim over quartz surface, while it is the skim over for the axial turbulent flow. The atomic force microscopy images show that the adsorption morphology of DDA on the surface of quartz chip is closely related to the turbulent flow pattern, and the interaction forces measurement results show that the minimum adhesion force of −70.97 nN is achieved in the quartz chip under the fully developed turbulent flow driven by the combination impeller. The aims of this paper were to elucidate the response mechanism of the turbulent flow field to the interaction between reagent and mineral in the conditioning process.

Blood Flow Pattern Analysis for Carotid Plaque Evaluation

Background and PurposePrevious studies suggested that turbulent flow is closely related to plaque vulnerability. Two-dimensional (2D) flow analysis is a novel modality that enables real-time blood flow analysis by picturing particle movement in the contrast medium. We evaluated flow patterns in the carotid plaque to investigate the correlation between blood flow and plaque vulnerability. Material and MethodsA total of 36 consecutive patients with cervical carotid artery stenosis were evaluated. The flow pattern of carotid artery stenosis was evaluated using 2D real-time flow analysis in the digital subtraction angiography (DSA). The flow pattern was classified into either turbulent or laminar flow as vectors. Plaque vulnerability was evaluated on MR plaque imaging. Univariate analysis was performed to assess the correlation between the flow pattern and plaque features. ResultsThe turbulent pattern was identified in 28 of 36 plaques (77.8%). Turbulence around plaques was significantly associated with Gadolinium enhancement (P = .0004). The maximum degree of stenosis (P = .0005) and concomitant ulceration (P = .02) were significantly associated with the turbulent pattern. There was no relationship between the turbulent pattern and clinical neurological symptoms. ConclusionsIn the present study, the majority of carotid plaques exhibited a turbulent flow pattern, which was significantly associated with Gadolinium enhancement on MR plaque imaging and morphologic factors. Thus, real-time flow analysis may clarify the pathophysiology of plaque instability and the formation of ulceration.

Detailed experimental and numerical characterization of turbulent flow in components of a water treatment plant.

This paper presents a detailed characterization of turbulence in the incoming flow to the clarification component of a water treatment plant, 'Los Molinos' (Córdoba, Argentina). The main problems were related to the presence of turbulent flow patterns throughout the treatment, affecting the proper development of the physical processes required for water clarification. Namely: (a) a poor hydraulic design that could produce a non-homogeneous spatial distribution of the flow, recirculation zones and flow stagnation, and a non-uniform discharge distribution among the sedimentation units as a result of different cross-sectional dimensions of the transverse-channel, and (b) high turbulence intensity that affect the flocs' size as well as the efficiency of the settling tanks and filters. Firstly, a detailed in-situ experimental characterization of the turbulent flow was undertaken. An acoustic Doppler velocimeter (ADV) was used to characterize the flow turbulence, whereas for discharge measurements and mean flow velocity field an acoustic Doppler current profiler (ADCP) was employed. Secondly, a numerical model, based on the Reynolds-averaged Navier-Stokes (RANS) equations and the k-ε turbulence closure model, was validated with the experimental data. Finally, based on the results, a diagnosis and recommendations were made for the optimization of the hydraulic design of the water treatment plant.

First-in-human Study of Biotube Vascular Grafts: A 2 Year Follow-up in A Bypass Model of Stenosed AV Shunt

Introduction - An arteriovenous (AV) fistula is the current gold standard for chronic hemodialysis access. However, a substantial number of shunt will fail because of stenosis or obstruction at anastomotic site or venous outflow. Tissue-engineered blood vessels have been proposed for dialysis access as an alternative to prosthetic grafts. We developed autologous collagenous tubular tissues Biotubes based on in-body tissue architecture (iBTA), which is a novel regenerative medicine technology by using a patient's body as a bioreactor. This report presents the results in the first-in-human study up to 2 year follow-up in the first two patients bypassed with an autologous Biotube. Methods - Two female patients had end-stage renal disease and had been receiving heamodialysis with a high probability of failure, because of repeatable stenosis about every 2 or 3 months at venous outflow regions over 1 year. Biotube with 5 or 6 mm in diameter and 7 cm in length (2 in photos) was prepared as autologous collagenous tubular tissues with wall thickness of ca. 1 mm by subcutaneous embedding of the molds (1 in photos), assembled with a silicone center rod and a stainless steel pipe, into patients abdominal pouches for 2 months. Results -The Biotubes after stored for 1 day in a 70% alcohol solution and washing with a saline solution before surgery were bypassed by end-to-side anastomoses over venous stenosis region of an AV shunt (3 in photos). Palpable thrill and typical turbulent flow pattern by pulsed-wave Doppler were observed. Monthly angiography showed little change in the implanted grafts with no signs of dilation or stenosis with time points up to 3 months (4 in photos). Although shortening of the Biotubes occurred, dialysis was possible without requiring balloon expansion for 2 years. Conclusion - This long-term follow up study successfully supported the concept of creating dialysis access by Biotube grown in patient’s subcutaneous pouches.

PROCESSES OF FORMATION AND DISTRIBUTION OF PETROLEUM HYDROCARBONS TECHNOGENIC FLOWS IN NATURAL ENVIRONMENT

Background The article is devoted to the urgent problem of natural environments state monitoring in territories affected by the oil industry. Aims and Objectives The study of the distribution processes in the underground horizons of secondary technogenic flows of oil hydrocarbons in territories affected by petrochemical enterprises. As an object for research, we chose the left bank of the Belaya River in the region of the industrial hub of Ufa (Republic of Bashkortostan), where as a result of prolonged technogenic impact on the soil cover, surface and groundwater, significant environmental damage was caused. Methods A layered study of the soil profile on the left bank of the river was carried out by laying three sections to the depth of groundwater at different distances from the pollution source, in the center of the study area. Results Studies have shown a significant distribution in the underground horizons of secondary technogenic flows of petroleum hydrocarbons. The resulting clusters are oil product lenses, as well as a film on the surface of groundwater. It has been established that in the process of intra-soil migration of anthropogenic oil flow to the river, the relative content of lighter components decreases. The greatest loss of light petroleum hydrocarbons is observed during the transition of anthropogenic flow from an aqueous medium with laminar conditions (underground flow) into a river with a turbulent flow pattern. It is also safe to assume that one of the important and significant factors in the formation of objects of accumulated environmental damage will be the low rate of self-cleaning of the depositing components of the natural environment. Thus, taking into consideration the scale of oil accumulations on the left bank of the Belaya River, it is quite appropriate to develop a technology for the extraction of petroleum hydrocarbons with their subsequent processing into a marketable product.

Unusual case of combined aortic root replacement and repair of hypertrophic obstructive cardiomyopathy

Hypertrophic obstructive cardiomyopathy (HOCM) in association with aortic disease is uncommon. However, left ventricular outflow tract obstruction (LVOTO) generates turbulent flow patterns that could augment the aneurysmal change in the aortic root in cases of connective tissue disorder.1 Phenotypic heterogeneity in HOCM cases requires a tailored approach to correct all factors contributing to the dynamic LVOTO including the mitral valve and its subvalvular apparatus.2

Three-Dimensional Numerical Simulation of Dam Discharge and Flood Routing in Wudu Reservoir

The main objectives of the present work are to investigate the hydraulic characteristics of the dam discharge flow and its impact downstream. Building information modeling technology is adopted to generate the terrain entity and hydraulic structures. The calculation of the dam discharge and flood routing simulation is achieved by employing Reynolds-Averaged Navier-Stokes equations with the RNG k-ε eddy viscosity model for its turbulence closure, as well as the Volume of Fluid method. An urban flood experiment and the field measurement records are utilized and validated the model accuracy. The flow field is obtained to assess the dam working conditions under different water levels. The results show that the maximum downstream flow depth, the maximum discharge capacity and the hydraulic jump length under normal water level is 18.6 m, 13,800 m3/s, and 108 m, respectively. The dam satisfies the safety demand under different water levels but close attention should be paid to the dam foundation, especially around the incident points of the discharge flow. Complex turbulent flow patterns, including collision, reflection, and vortices, are captured by three-dimensional simulation. The numerical simulation can assist the reservoir management vividly, so as to guarantee the stability of the dam operation.

Application of artificial neural networks to predict flow velocity in a 180° sharp bend with and without a spur dike

This work has compared the performance of three well-known artificial neural network (ANN) approaches in turbulent flow pattern modeling based on geometric characteristics of the channel (angle of horizon, distance from outer bank of the bend, and distance from the bed) in a 180° sharp bend with and without a T-shaped spur dike. ANN methods discussed in this work are feed-forward neural network, cascade feed-forward neural network, and extreme learning machines. Acoustic Doppler velocimetry is used to measure the velocity components in x, y, and z directions. Conducting this research is innovative and significant from three aspects: First, the data of the flow pattern around T-shaped spur dikes in a 180° bend, given its high importance in rivers in nature, are very rarely available; second, application of neural network models for understanding the flow nature is highly efficient at other bend points where no experimental or field measurements have been conducted; and third, with these models, the cost and time required for conducting numerical and experimental modeling for prediction of the flow velocity significantly decrease. Outliers (abnormalities or anomalies) may be generated by various factors in the measured velocities. Before modeling by ANNs, the self-organizing map clustering method is used to detect outliers to obtain more accurate models. Performance of ANN models is evaluated using correlation coefficient (R) and root mean squared error criteria. In order to compare the performance of ANNs in flow velocity modeling at different locations of the bend, seven different data groups are considered using different combinations of samples by random sampling. Results of comparison of ANN models with experimental data indicate that ANNs provide reasonable results in most cases and may be employed successfully in estimating the velocity in sharp bends with and without the presence of a spur dike. Moreover, it may be concluded that ANN models without spur dikes are more accurate than those with spur dikes due to creating less turbulence flow.

Covalently functionalized pentaethylene glycol-thermally treated graphene towards enhanced thermophysical and heat transfer characteristics

The current study outlined the use of synthesized, covalently functionalized pentaethylene glycol-thermally treated graphene (PEG-TGr). Miscible PEG was decorated in order to achieve a long-stable aqueous colloidal dispersion. The experimentations were performed using the Reynolds number range of 6401–11,907, constant wall heat flux of 11,205 W/m2, and mass fraction of 0.025, 0.05, 0.075, and 0.1%. The effective thermophysical characteristics, heat and momentum transfer for fully developed turbulent flow patterns of PEG-TGr nanofluids over a square heated pipe were examined. Performance index, performance evaluation criterion, and pumping power were assessed to evaluate the performance of nanofluids. An augmentation in thermal conductivity of PEG-TGr was observed in 29.74% in comparison with the base fluid. The heat transfer coefficient enhancement of PEG-TGr was about 41.18% with respect to distilled water data. Nonlinear regression correlations were experimentally developed to calculate the thermal conductivity, dynamic viscosity, Nusselt number, and friction number. It seems that PEG-TGr nanofluids perform as working fluids for heat transfer purposes and offer great alternative options to standard operating fluids inside the thermal fluid devices.

An in Vitro Flow Model for Cardiovascular Inflammation.

Cardiovascular disease is modern-day plague with a vast number of lives claimed, and an enormous socio-economic cost incurred. Hemodynamics of the cardiovascular system play an important mechanistic role in disease development. For instance, atherosclerotic plaque depositions are often correlated with regions of turbulent flow patterns and disturbed hemodynamic shear stress. A simplified, rigid, in vitro, flow model of a real-size aortic arch is described. The flow in the arched vessel is attached and healthy at the outer curvature, while it is separated and disturbed at the inner curvature wall, which is an ideal setting to study cardiovascular disease. Endothelial cells can be cultured on the lumen of the aortic arch model under controlled flow conditions and extracted from the inner and outer curvature walls for biochemical signaling studies. The flow velocity field in the model is characterized using particle image velocimetry PIV which allows for the estimation of the wall shear stress. This helps in correlating the underlying hemodynamics to the biomechanical response of the endothelium.

Large eddy simulation of turbulent flow and heat transfer in outward transverse and helically corrugated tubes

Turbulent flow and heat transfer in outward transverse and helically corrugated tubes are performed with large eddy simulation by the ANSYS Fluent software. The prediction accuracy is validated by comparison with experimental data and empirical correlations for a wavy surface wall and smooth tube, respectively. The turbulent flow patterns, local heat transfer, and friction factor are discussed. The results show that the secondary and turbulent eddies are inhibited by the spiral flow. Otherwise, the flow impact of the wall is the key factor for heat transfer enhancement, and the spiral flow has of small effect on heat transfer performance, however it can decrease the flow resistance significantly. The overall heat transfer performance for the helical corrugated tube is 1.23, which is superior to the value of 1.18 for the transverse corrugated tube.