Decrease In Flow Velocity Research Articles

Аэродинамические характеристики перфорированных органов управления летательных аппаратов при дозвуковых скоростях обтекания

The vortex separation from the aircraft control surfaces often leads to undesirable shaking and pitch of the structure. One way to eliminate this effect is to perforate surfaces. The paper considers the aerodynamic characteristics of the aircraft flight control element in the form of a single elongation perforated flat plate. Experimental studies were carried out in a subsonic wind tunnel of Bauman Moscow State Technical University. The aerodynamic coefficients of plates with different degrees of perforation 0...28.3% were obtained at free stream velocities of 15.. 35 m/s in a wide range of angles of attack from 0 to 90 degrees. The graphs of the aerodynamic coefficients of the plates versus the angle of attack were analyzed. Findings of the research show that the aerodynamic characteristics of perforated plates differ from the corresponding characteristics of solid plates, an increase in the degree of perforation leads to a decrease in the values of aerodynamic coefficients, while a decrease in the free flow velocity causes their increase.

Origin and Forming of Hacham Island in Khor Al-Zubair Channel, Southern Iraq

The marine geophysical survey was conducted using Sub Bottom Profiler and Side Scan Sonar techniques, integrated by petrographic analyses including grain size distribution, mineralogical and fauna analyses of the Hacham island and surrounding area. The island is located in the south part of the Khor Al Zubair channel southwest of the Basrah, Southern Iraq. The study aims to determine the origin and stages of the island formation. This study concluded that there is more than one factor that contributes forming this island represented by tectonic, morphological and sedimentological factors. The results of marine geophysical surveys revealed that the island and its surroundings were affected by the neotectonic activity that exposed the lower part of the Mesopotamian Basin, which in turn caused the lower part of the Khor Al-Zubair channel to meander eastward because of its impact by the fault that separated Warbah island from the Iraqi coast, forming Khor Shaitanah. The meandering of the Khor Al-Zubair course was accompanied by a decrease in flow velocity and thus a decrease in the channel’s ability to carry more sediments, therefore the Khor has to take another course, this waterway separated the island from the main east Iraqi coast. The results of the grain size distribution, mineral identification and fauna analyses indicated a variety of sediment supplying sources of the island, represented by the floods deposits of rivers and side drifts of the surrounding area, in addition to the aeolian deposits transported from the west and northwest Dibdibba Formation. The present study also concluded that the central East shore part of the island is exposed to erosion as a result of a submerged wreck in the waterway that separates the island from the coast.

Using Landscape analysis techniques to prevent silt accumulation in the reservoir of the Dwerige weir project and developing River basin, Missan, South Eastern IRAQ

Water harvesting techniques developed globally during the last decades with highly increasing water crisis and climate changes. The Yeoman keyline method was spread widely with increased use for sustainable permaculture development. The main aim of the current study is to analyze and solve the siltation problem in Dwerige weir and to develop water resources in the basin area. The remote sensing data, field surveying, and hydrology are used together to build a new geotechnical approach. The results show that a huge siltation quantity was not considered in the weir design studies, which were represented by sand sheet materials and eroded soils washed by flooding and entering the weir reservoir through four main channels. The topography and hydrology of the study area are analysed, and the key points- keylines principle used by selecting the suitable contour lines to dig trenches along them to control soil erosion by decreasing flow velocity and holding part of floodwater to increase soil water content and recharge groundwater. The floodwater quantities are estimated in normal and storm cases, finally, the extra drain water is evaluated.

Experimental Investigation of the Steady-State Flow Field with Particle Image Velocimetry on a Nozzle Check Valve and Its Dynamic Behaviour on the Pipeline System

In the present work, to investigate the hydraulic losses and safe operation of nozzle check valves in industrial piping systems, the static characteristics of the valve and its dynamic behavior in the pipeline system were studied using an experimental bench with a visual DN300 nozzle check valve. Besides, basing on the PIV (Particle Image Velocimetry) technique measures the valve steady-state flow field under the different flow rates. The study has shown that as the flow rate rises, the valve disc displacement slowly increases to 44 mm, then rapidly increases to a maximum displacement of 72 mm. When the Reynolds number exceeds 5 × 105, the relationship between pressure drop and flow obeys a quadratic function. The local vortex area formed by the flow passage near the downstream deflector expands with the flow improvement. As the increase of flowrate, at low flow operating conditions, the downstream flow velocity in the local high-speed area near the valve body increases; at medium operating conditions, the area’s flow velocity decreases; at high flow work, this local high-speed area disappears. When the fluid deceleration is lower than 4 m/s2, the dynamic behavior satisfies the quadratic curve when the maximum slope is only 0.354, which shows that this nozzle check valve has a favorable response to the system.

A numerical simulation of tube geometry effect on the performance of regenerators in Organic Rankine Cycle systems using the Volume of Fluid method

In this work, the tube geometry effect on the performance of regenerators in ORC systems is numerically studied using the Volume of Fluid (VOF) method. Three tube geometries are investigated: normal, divergent, and convergent tubes. The divergent tube offers increasing space, which is beneficial to bubble growth and delay the tube clogging induced by the increasing bubble size. The delay of tube clogging in the divergent tube can benefit the boiling heat transfer performance. The decreasing flow velocity due to the increasing space can also reduce the friction pressure drop. As a result, the divergent tube induces smaller total pressure drop as well as less pressure fluctuation, which are good for pump efficiency. It is found that the pressure drop can be up to 34.5% lower in divergent tube while the averaged wall heat flux is 2.94% higher comparing with the normal one. The features of enhancing heat transfer performance and reducing total pressure drop with less pressure fluctuation of the divergent tube can be used as a novel design for the liquid side of regenerators. The convergent tube will induce higher pressure drop with higher heat flux before the tube is clogged by the bubbles. However, the heat flux decreases as the tube clogging occurs. Due to the higher pressure drop induced, the convergent tube might not be suitable for the design of the liquid side of regenerators. It is the first time to study the heat transfer problem with a single vapor bubble considering the geometric effect, and this work provides physical insights on heat transfer performance and pressure drop for a two-phase boiling flow. The optimized geometry can increase the energy efficiency, whch could profoundly impact many industrial applications.

Powers’ anomaly: clinic, diagnosis and surgical treatment results

Aim. To present the results of the complex clinical-instrumental diagnostics and surgical treatment of patients with Powers’ anomaly. Material and methods. The results of complex diagnostics, surgical treatment and medical examination of 6 patients (4 females and 2 males) with Powers’ anomaly at the age from 17 till 36 years old were analyzed. In all cases, the Powers anomaly was unilateral - in 4 cases, the right side and in 2 cases, the left side. According to the classification of A. V. Pokrovsky (1978), only one patient was asymptomatic and the rest had grade II or III chronic cerebrovascular insufficiency. Results and discussion. Except for one case, all the remaining patients had the main triad of VBI symptoms - dizziness, gait disturbance, and visual disturbances, which were indicative of severe brainstem and cerebellar ischemia. The diameter of the Powers anomaly in the first segment was 2.9 ± 0.81 mm and in the second segment was 3.6 ± 0.55 mm. There was also a decrease in the linear velocity of blood flow, and 2 patients had hypoplasia of the opposite vertebral artery. The average inflection angle of Powers’ anomaly in the near-osteal segment was 87.5 ± 10.5о. Conclusion. The nonspecific nature and similarity of clinical manifestations of Powers anomaly are the main causes of their late diagnosis and development of marked hemodynamic disturbances of the cerebral vertebrobasilar basin. Duplex scanning and contrast studies play a significant role in the diagnosis of hemodynamic abnormalities of the vertebrobasilar basin in Powers anomaly. The efficacy of reconstructive surgery for Powers’ anomaly in the long-term postoperative period is registered in all cases.

Potential Contribution of Hypertension to Evolution of Chronic Migraine and Related Mechanisms.

To investigate the potential contributions of diastolic and systolic blood pressure (BP) and the circadian rhythm of BP to chronic migraine evolution. This cross-sectional study included four groups of patients selected based on migraine frequency (high frequency ≥ 10 days per month and low frequency < 10) and on the presence of hypertension. Among-group and pairwise comparisons were carried out to investigate potential neurophysiologic differences in the cerebral vessel reactivity to a nitroglycerin test, in autonomic balance (tilting test), and BP circadian rhythm. A more marked decrease in cerebral blood flow velocity was observed in hypertensive high-frequency migraineurs compared to all other groups (P = .037). Moreover, a smaller decrease in vagal tone was recorded in the orthostatic position in hypertensive subjects, whether they were high- (P = .032) or low-frequency migraineurs (P = .014), with a consistently higher vagal to sympathetic tone ratio (P = .033). Finally, in nonhypertensive subjects, a higher but not significant prevalence of systolic nondippers was detected in high-frequency migraineurs (67%) compared to low-frequency subjects (25%; P = .099). These findings suggest that hypertension may contribute to the chronic evolution of headache with mechanisms shared with migraine; ie, vascular tone alteration and autonomic dysregulation.

Evaluation of extracranial carotid flow velocities in patients presenting with acute ischemic stroke: A clinical study conducted in Turkey

Objective. The mechanism underlying the relationship between carotid flow velocities and stroke events remains unclear. This study aimed to reveal the relationship of flow velocity measurements with risk factors in patients with acute ischemic stroke. Material and methods. A group of patients between the ages of 41-90 who applied to Mengücek Training and Research Hospital in the Eastern Anatolia Region of Turkey between 2014-2015 due to acute ischemic stroke were included. Groups with large artery atherosclerosis and small-vessel occlusion according to the Toast classification were included in the study. Brain tomography and magnetic resonance imaging, echocardiography, high-resolution color Doppler Ultrasonography examinations were performed. Internal carotid artery peak-systolic and end-diastolic flow velocity, common carotid artery peak-systolic and end-diastolic flow velocity, internal carotid artery peak systolic-common carotid artery peak-systolic velocity ratio and common carotid artery intima-media thickness were measured with Doppler Ultrasonography. The relationship between carotid flow velocities and brain infarction volume, comorbid factors, biochemical variables, left ventricular systolic-diastolic dysfunction was defined by using Statistical Package for Social Sciences version 21.0. Outcomes. In acute ischemic stroke groups, a significant negative correlation between common carotid artery end-diastolic flow velocity and brain infarction volume, a significant positive relationship between common carotid artery peak-systolic velocity and smoking, a significant positive correlation between common carotid artery intima-media thickness and blood glucose and hba1c, a significant negative correlation between common carotid artery end-diastolic flow velocity and hypertension, a significant relationship between common carotid artery end-diastolic flow velocity and ischemic heart disease, an increase in cerebral infarction in patients with left ventricular systolic dysfunction and a decrease in Internal carotid artery peak-systolic flow velocity in patients with left ventricular diastolic dysfunction were detected. Conclusions. In clinical practice, Doppler ultrasound is currently the main diagnostic tool for evaluating the diagnosis of carotid stenosis. In stenosis in the carotid artery system, it should be known as a basic rule that the flow velocity in the stenosis area increases, except for in severe stenosis and four basic measurements should be made to determine the degree of stenosis clearly. These measurements are peak systolic flow velocity (PSV), end-diastolic flow velocity (EDV), peak-systolic flow velocity ratio (ICA/CCA PSV). The purpose of sonographic evaluation of the extracranial cerebral arteries is to prevent bad sequelae and permanent deficits together with cerebral infarction.

QS16. The Effects of Variations in the Skin Surface Temperature on Capillary Blood Flow Using Video-capillaroscopy

Purpose: Video-capillaroscopy (VC) can be used to evaluate real-time flow of red blood cells in capillaries at a depth of 1-mm from the skin surface. Therefore, this device could be used in microsurgery to assess the perfusion of flaps, replanted fingers, skin grafts, and keloids. The details of capillary changes during skin cooling under VC observations are not known. By investigating the adaptations of capillaries after cooling using VC, we determined the effects of temperature on skin capillaries with those at room temperature, establishing temperature criteria for future VC applications. Therefore, we observed and compared VC findings on skin areas often used for flap harvest at a normal and lower body temperature. Methods: Twenty healthy Japanese adults were included. Skin capillaries were observed at the lateral thigh, forearm, mid-axillary line, abdomen, and fingertip using VC (GOKO Bscan-Z). Ice packs were used to lower the skin temperature to less than 35°C. The VC findings were recorded for three minutes before and after cooling. By means of the ImageJ software, we measured the total blood vessel area (pixels) as a percentage of the total area of the visual field (pixels). Also, we measured the blood flow velocity (μm/s) using GOKO-VIP software and the results for both temperatures (normal and after cooling) were then compared. Results: The average age and BMI were 37.5±9.72 years and 22.4±2.45 kg/m2 respectively. The mean arterial pressure was 89.4±3.1 mmHg. In accordance with the Fitzpatrick phenotype, eleven patients were type II, five were type III, and four were type IV. The average skin temperature before and after cooling were 36.4±0.2°C and 34.7±0.8°, respectively. The blood vessel areas were significantly different before and after cooling in all anatomical areas (p <.001). The average reduction rate of the vessel area after cooling was 63% for the thigh, 30% for the forearm, 43.3% for the mid-axillary line, 35% for the abdomen, and 65% for fingertips. The mean reduction rate of the vessel area was significantly different among anatomic regions (p <.001). The average blood flow velocities were significantly different before and after cooling in all anatomical areas (p <.001). The average blood flow velocity reduction rate after cooling was 75.7% for the thigh, 55.3% for the forearm, 68.9% for the mid-axillary line, 61.6% for the abdomen, and 79.2% for fingertips. The average blood flow velocity reduction rate after cooling was significantly different among anatomic regions (p <.001). Conclusion: Decrease in skin surface temperature resulted in capillary vasoconstriction and a decrease of capillary blood flow velocity in all areas. When VC is used for flap monitoring, it is important to keep the observation area warm since decreasing the temperature in the monitored area might result in the false diagnosis of arterial occlusion.

Transport of Microplastics in Shore Substrates over Tidal Cycles: Roles of Polymer Characteristics and Environmental Factors.

Tidal zones providing habitats are particularly vulnerable to microplastic (MP) pollution. In this study, the effects of tidal cycles on the transport of MPs (4-6 μm polyethylene, PE1; 125 μm polyethylene, PE2; and 5-6 μm polytetrafluoroethylene, PFTE) in porous media combined with various environmental and MPs properties were systemically investigated. The results indicated that smaller substrate sizes exhibited higher retention percentages compared to those of larger substrate sizes under different tidal cycles. In terms of the size of MPs, a larger size (same density) was found to result in enhanced retention of MPs in the column. As the number of tidal cycles increased, although the transport of MPs from the substrate to the water phase was enhanced, PE1 was washed out more with the change in water level, compared to PTFE. Additionally, more MPs were retained in the column with the increase of salinity and the decrease of flow velocity under the same tidal cycles. Ultraviolet and seawater aged PE1 showed enhanced transport, while aged PTFE showed enhanced retention under the same tidal cycles. These results can help understand the MP behaviors in the shoreline environment and provide support for future cleanup and sampling in tidal zones.

An Experimental Model of Unconfined Bubbly Lava Flows: Importance of Localized Bubble Distribution

AbstractMost lava flows carry bubbles and crystals in suspension. From earlier works, it is known that spherical bubbles increase the effective viscosity while bubbles deformed by rapid flow decrease it. Changes in the spatial distribution of bubbles can lead to variable rheology and flow localization and thus modify the resulting lava flow structure and morphology. To understand the roles of bubble and solid phase crystal distributions, we conducted a series of analog experiments of high bubble fraction suspensions. We poured the analog lava on an inclined slope, observed its shape, calculated the velocity field, and monitored its local thickness. A region of localized rapid flow and low vesicularity, whose thickness is thinner than the surrounding area, develops at the center of the bubbly flows. These features suggest that the locally higher liquid fraction decreases the effective viscosity, increases the fluid density, and accelerates the flow. We also found that a halted particle‐bearing bubbly flow can resume flowing. We interpret this to result from the upward vertical separation of bubbles, which generates a liquid‐rich layer at the bottom of the flow. In our experiment, bubbles are basically spherical and decrease the flow velocity, while our estimate suggests that bubbles in natural lava flows could increase or decrease flow velocity. Downstream decreases in flow velocity stops the bubble deformation and can cause a sudden increase of effective viscosity. The vertical segregation of the liquid phase at the slowed flow front may be a way to generate a cavernous shelly paho’eho’e.

Dam-induced flow velocity decrease leads to the transition from heterotrophic to autotrophic system through modifying microbial food web dynamics

The impoundment of reservoirs changes the river from a riverine heterotrophic system to a lacustrine autotrophic system, which could be attributed to the shift of pelagic microbial food webs in response to the dam-induced disturbances. However, little is known about what is the key factor controlling this variation and how different underlying interactions affect the food web dynamics. This study investigated the effects of flow velocity and nutrient supply on microbial plankton using a microcosm experiment. The results showed that flow velocity decrease was the main factor inducing the detritus-based food web transformed to the autotroph-based food web, with heterotrophic bacteria and protozoan dominated at high velocity, whereas phytoplankton and metazoan were prevalent in the lentic environment. The lentic-acclimated genera, such as Chlorella sp., Mallomonas sp. and Microcystis sp., showed hysteresis after the velocity recovery, suggesting the potential of algae bloom in reservoirs and even downstream of dams. We further conducted a flow-velocity manipulating experiment and constructed a multi-trophic nitrogen cycling model to provide a mechanistic explanation for the microbial food web dynamics and the nitrogen transformation performances. As indicated in model prediction and sensitivity analysis, the abiotic and biotic variations were directly or indirectly controlled by nutrient utilization and predator-prey interactions. Quantification of these bottom-up and top-down forces revealed the buffer role of predators in mitigating the positive effects of nutrient availability on autotrophs at low velocity and on heterotrophs at high velocity, respectively. This study highlights the importance of mastering the whole information of different trophic levels, in order to better capture the complex microbial food web interactions and the consequent biogeochemical processes in river-reservoir systems.

Inner and outer flow of an adhering droplet in shear flow

Adhering droplets in shear flow start to move downstream when a critical velocity ucrit is reached, i.e. the adhesion force is overcome by aerodynamic force. It is still not clear, whether drag-coefficient-estimation based on an approximation of the droplet as a rigid spherical cap is a valid approach. In contrast to rigid hemispheres there is a gas-liquid-interface, i.e. the velocity of the interface is not zero by all means. Therefore, there is a fluid transport inside the drop that depends on the outer flow structure. We report on a combined numerical and experimental investigation to find out the characteristic inner and outer flow structure of an adhering droplet in shear flow in order to evaluate the rigid-hemisphere-approach.The inner flow structure of the droplet is measured by particle-image velocimetry (PIV) while the wake flow of the droplet in the gas-phase is measured by a modified laser-doppler-velocimeter (laser-doppler profile sensor). Numerical simulations of a droplet have been carried out using a modified volume of fluid (VOF) model taking into account contact angle hysteresis effects in OpenFOAM®. The complete two-phase fluid motion of the liquid droplet and surrounding gas phase is simulated, i.e. the inner and outer flow of the droplet are captured with a three-dimensional simulation model.Experimental and numerical results agree very well concerning flow pattern inside and outside the droplet. There is a strong connection between the inner and outer flow of the droplet. For lower Reynolds numbers based on droplet diameter (Red < 800) the flow inside the droplet rotates in direction of the channel flow. On the leeward side of the droplet there is a small wake flow with slightly decreased flow velocity. At higher Reynolds numbers (Red ≥ 800) the flow pattern inside the droplet changes completely: A strong reverse flow close to the droplet surface appears. Concurrently a strong recirculation zone emerges in the wake of the droplet. This is due to the roll-up process of a separated shear layer originating from the droplet. Due to the coupling of the inner flow with the outer flow via the gas-liquid-interface our data show that at higher Reynolds numbers flow separation takes place on the windward half of the droplet. This is in contrast to the case of a rigid hemisphere, where the separation is located at approximately 90°, i.e. the top of the droplet, and does not move upstream with increasing Reynolds number. The height of the separation zone increases up to 1.29 times the droplet height, which is not observed for rigid hemispheres. Since the pressure field around an obstacle is governed by the flow separation location and the corresponding size of the recirculation zone, the coupling of the inner and outer flow changes the pressure distribution around the droplet with respect to a similar rigid structure. This will affect the aerodynamic forces acting on the droplet, which is why the approximation by a rigid spherical cap does not seem to be a suitable approach. Nevertheless, additional experimental and numerical efforts need to be done to assess the flow structures, pressure distributions and forces acting on the droplet in a suitable precision also considering possible aero-elastic effects.

Granular Flow–Obstacle Interaction and Granular Dam Break Using the S-H Model with the TVD-MacCormack Scheme

An accurate second-order spatial and temporal finite-difference scheme is applied to solve the dynamics model of a depth-averaged avalanche. Within the framework of the MacCormack scheme, a total variation diminishing term supplements the corrector step to suppress large oscillations in domains with steep gradients. The greatest strength of the scheme lies in its high computational efficiency while maintaining satisfactory accuracy. The performance of the scheme is tested on a granular flume flow–obstacle interaction scenario and a granular dam breaking scenario. In the former, the flume flow splits into two granular streams when an obstacle is encountered. The opening between the two granular streams widens when the side length of the obstacle increases. In the simulation, shock waves with a fan-shaped configuration are captured, and successive waves in the tail of the avalanche between the two streams are observed. In the latter scenario, the average values and the fluctuations in the flow rate and velocity (at relatively steady state) decrease with the width of the breach. The capture of complex and typical granular-flow phenomena indicates the applicability and effectiveness of combining the TVD-MacCormack Scheme and S-H model to simulate dam breaking and inclined flow–obstacle interaction cases. In this study, the dense granular flow strikes on a rigid obstacle that is described by a wall boundary, rather than a topographic feature with a finite slope. This shows that the TVD-MacCormack scheme has a shock-capturing ability. The results of granular dam break simulations also revealed that the boundary conditions (open or closed) affect the collapse of the granular pile, i.e., the grains evenly breached out under closed boundary conditions, whereas the granules breaching out of the opening were mostly grains adjacent to the boundaries under open boundary conditions.

Aspect ratio-dependent hysteresis response of a heavy inverted flag

The bistable fluttering response of heavy inverted flags with different aspect ratios ( $AR$ ) is investigated to determine how the vortical structures affect the intermittent vibration response of the flag. A heavy inverted flag in a uniform flow may exhibit several response modes; amongst them are three major modes that occur over an extended velocity range: stationary, large-scale periodic oscillation and one-sided deflected modes. Significant hysteretic bistability is observed at the transition between these modes for all $AR$ , which is notably different from the conventional flag vibration with a fixed leading edge and free trailing edge where no hysteresis is observed at the lower $AR$ limit ( $AR&lt;1$ ). The difference is associated with the distinct roles of vortices around the flag. Experiments with flags made of spring steel are conducted in a wind tunnel, where the flow speed is steadily increased and later decreased to obtain different oscillatory modes of the heavy inverted flags. The experimental results are used to validate the numerical model of the same problem. It is found that different critical velocities exist for increasing and decreasing flow velocities, and there is a sustained hysteresis for all $AR$ controlled by the initiation threshold and growth of the leading-edge and side-edge vortices. The effect of the vortices in the bistable oscillation regime is quantified by formulating a modal force partitioning approach. It is shown that $AR$ can significantly alter the static and dynamic vortex interaction with the flexible plate, thereby changing the flag's hysteresis behaviour and bistable response.

Assessment of blood flow in the prostate before and after transuretral enucleation of benign hyperplasia prostate

BACKGROUND: Transrectal Doppler ultrasound is the leading method for studying blood flow in the prostate. Despite a significant number of studies on the use of ultrasound of the prostate in patients with BPH, many aspects of its clinical use remain unclear. One of these issues is the features of changes in blood flow in the prostate after transurethral surgical interventions.&#x0D; AIM: to assess the state of blood flow in the prostate gland in patients with BPH before and after transurethral enucleation by laser and bipolar methods.&#x0D; MATERIALS AND METHODS: The study included 88 patients with BPH aged 50 to 79 years who complained of urinary disorders. All patients underwent transurethral enucleation of BPH: 41 patients with the laser method (HoLEP) (1st group) and 47 patients with the bipolar method (TUEB) (2nd group). Before surgical treatment, 4, 12 and 24 weeks after surgery, patients underwent transrectal Doppler ultrasound of the prostate.&#x0D; RESULTS: The results of the study indicate a significant impact of surgery on the state of blood flow in the prostate gland. Examination 12 weeks after the operation showed a significant decrease in the peak blood flow velocity and values of the resistance index in patients of the 1st and 2nd groups compared with the corresponding values before the surgery and 4 weeks after the surgery. By 24 weeks after surgery, all patients showed normalization of blood flow parameters, while in patients of the 1st group (HoLEP) this process occurred faster than in patients of the 2nd group (TUEB).&#x0D; CONCLUSIONS: The high diagnostic efficiency and informativeness of transrectal Doppler ultrasound in the assessment of blood circulation in the prostate in patients with BPH has been confirmed. The blood flow velocity in the subcapsular and especially paraurethral arteries, as well as the values of the resistance index, were higher in patients with large prostates, which must be taken into account when planning surgical interventions.

Extraction of moringa essential oil (Moringa Oleifera) with conventional solvents and supercritical fluid / Extração do óleo essencial de moringa (Moringa Oleifera) usando solventes convencionais e fluído supercrítico

Essential oils (EO) are substances extracted from different parts of plants and have specific characteristics that guarantee their application in different processes. EO extraction processes involve different methods. Among the methods mentioned in the literature, those related to the minimization of effluent production rates are commonly used. In this context, studies were conducted on the extraction of essential oil from the seed of Moringa Oleífera, using a mixture of carbon dioxide (supercritical fluid) and ethanol or acetone (conventional fluids) as a solvent, to evaluate the influence of the flow rates of fluid mixture flow. Several experiments have demonstrated that the process performance is strongly dependent on the flow velocity of the fluid mixture and the type of co-solvent used. In this case, the decrease in CO2 flow velocity increases the residence and contact time between the fluid and solid particles. The ethanol is more effective than acetone, mainly due to its intrinsic physical properties. The relationship described above results in the highest diffusion rate of the solute contained in the solid pores to the fluid mixture. The results obtained from these studies are similar to those in the literature and can support scale-up models of the process that aim to enhance the development and proposition of essential oils to meet the country's needs, supported by the use of biomass produced in Angola.

Numerical simulation of a viscoelastic pipeline vibration under pulsating fluid flow

PurposeThe purpose of this study is to create a mathematical model, a numerical algorithm and a computer program for studying the vibration of composite pipelines based on the theory of beams used in the oil and gas industry, agriculture and water management, housing and communal services and other areas.Design/methodology/approachA mathematical model of vibration of a viscoelastic pipeline based on the theory of beams with a pulsating fluid flowing through it was developed. Using the Bubnov-Galerkin method, based on the polynomial approximation of deflections, the problem is reduced to the study of systems of ordinary integro-differential equations, the solution of which is found by a numerical method. A computational algorithm was developed for solving problems of vibrations of composite pipelines conveying pulsating liquid.FindingsThe stability and amplitude-time characteristics of vibration of composite pipelines with a pulsating fluid flowing in it are studied for wide range of changes in the parameters of deformable systems and fluid flow. The critical velocities of fluid flow at which the viscoelastic pipe loses its rectilinear equilibrium shape are found. The effect of singularity in the kernels of heredity on the vibrations of structures with viscoelastic properties was numerically studied. It is shown that with an increase in the viscosity parameter of the pipeline material, the critical flow velocity decreases. It was determined that an increase in the value of the fluid pulsation frequency and the excitation coefficient leads to a decrease in the critical velocity of the fluid flow. It was established that an increase in the parameters of the Winkler foundation and the rigidity parameter of the continuous layer leads to an increase in the critical flow velocity.Originality/valueThe study of the vibration of pipelines made of composite materials is of great theoretical and applied interest. The solution to this problem is an effective application of the theory of viscoelasticity to real processes. Therefore, the methods and problems of pipeline vibrations attract much attention from researchers. This study is devoted to solving the above problems and therefore its subject is relevant. The paper considers the results of numerical simulation of the processes of vibration of a composite pipeline based on the theory of shells during the flow of a pulsating liquid through it. A mathematical model of vibration of a composite pipeline was developed. A computational algorithm was developed for solving problems of vibrations of composite pipelines conveying pulsating liquid.

Cerebrovascular changes in neuro-Behcet's disease and neuropsychiatric lupus by transcranial Doppler ultrasonography and magnetic resonance imaging

IntroductionTranscranial Doppler ultrasonography (TCD) is a technique that allows measurement of blood flow from the basal intracerebral vessels. It is relatively inexpensive, non-invasive, can be performed at the bedside, and allows monitoring in acute emergency settings and for prolonged periods with a high temporal resolution, making it ideal for studying the haemodynamics within the intracranial arteries in neuro-Behcet's disease (NBD) and neuro-psychiatric lupus (NPSLE). Our aim was to assess the cerebral haemodynamic patterns in patients with NBD and NPSLE using TCD, while brain lesions were examined using magnetic resonance imaging (MRI). Material and methodsCase–control prospective study of 30 neuro-Behcet's disease patients, 25 neuro-psychiatric lupus patients and 26 healthy age-matched volunteers. All patients and healthy controls were examined by TCD. Only the groups of patients underwent cranial magnetic resonance imaging (MRI). ResultsTranscranial Doppler (TCD) values for middle cerebral artery (MCA), anterior cerebral artery (ACA), posterior cerebral artery (PCA), vertebral artery (VA) and basilar artery (BA) in NBD, NPSLE and control groups were measured. The results showed that there was a significant decrease in mean blood flow velocities in all the arteries examined in NBD and NPSLE patients. There was also a significant increase in the pulsatile index of PCA, VA and BA between NBD and NPSLE patients. The same results were obtained when comparing NBD versus controls. However, there was no significant difference between the NPSLE patients and the control group. The MRI lesions described were parenchymal lesions in 14 patients (46.7%), and vascular lesions in 4 patients (13.3%). Vascular lesions co-existed with parenchymal lesions (mixed lesion). Parenchymal lesions were in white matter (40%), thalamus (26.7%), brain stem (26.7%) and cerebellum (20%). While, in NPSLE, 23 patients were normal (92%) and only two patients had a vascular lesion (8%). ConclusionThere was a significant decrease in mean blood flow and a significant increase in the pulsatile index among both NBD and NPSLE patients, according to the TCD values.

The left atrial appendage thrombosis of in patients with persistent atrial fibrillation after the novel coronavirus infection

Aim To evaluate the incidence and features of left atrial appendage (LAA) thrombosis in patients with persistent atrial fibrillation (AF) after novel coronavirus infection (COVID-19).Material and methods Percutaneous echocardiography (pcEchoCG) was performed for 128 patients with persistent AF prepared for cardioversion, 36 (28.1 %) of whom had had COVID-19. In 3 (8.3 %) patients, the lung lesion area was 50-75 %; in 31 (86.1 %) patients, 25-50 %; in 1 (2.8 %) patient, less than 25 %. One patient had no lung lesion. Median time from the onset of COVID-19 to the patient enrollment in the study was 76.5 days. At the time of enrollment, the polymerase chain reaction test for SARS-CoV-2 was negative in all patients.Results Patients after COVID-19 and those who had not had COVID-19 were comparable by age (62.5±9.2 and 62.4±9.1 years, respectively; р=0.956), gender (men 52.8 and 59.8 %, respectively; р=0.471), and risk of stroke (score 2.19±1.28 and score 1.95±1.35, respectively; р=0.350). Duration of the last arrhythmia episode was longer for patients after COVID-19 than for the comparison group (76.5 and 45.0 days, respectively; р=0.011). All patients received oral anticoagulants. 55.6 % of COVID-19 patients received rivaroxaban, whereas 62.0% of patients who had not had COVID-19 were treated with apixaban. Median duration of the anticoagulant treatment was longer for COVID-19 patients than for the comparison group (61.5 and 32.0 days; р=0.051). LAA thrombus was detected in 7 (19.4 %) patients after COVID-19 and in 6 (6.5 %) patients of the comparison group (р=0.030). In COVID-19 patients, the thrombus adhered to LAA wall over the entire thrombus length whereas in patients who had not have COVID-19, the thrombus had a free part that formed a sharp angle with LAA walls. In the presence of LAA thrombus, the LAA blood flow velocity was considerably higher for COVID-19 patients than for the comparison group (31.0±8.9 and 18.8±4.9 cm/sec, respectively; p=0.010). At the follow-up examination performed at 24.0 days on the average, the thrombus was found to be dissolved in 80 and 50% of patients after and without COVID-19, respectively (р=0.343).Conclusion In patients with persistent AF after the novel coronavirus infection, LAA thrombosis was detected more frequently than in patients who had never had COVID-19; it was characterized by mural localization and was not associated with a decrease in LAA blood flow velocity.