Suction Flow Research Articles

Neural Network-based Estimation of Microbubbles Generated in Cardiopulmonary Bypass Circuit: A Clinical Application Study.

The cardiopulmonary bypass system used in cardiac surgery can generate microbubbles (MBs) that may cause complications, such as neurocognitive dysfunction, when delivered into the blood vessel. Estimating the number of MBs generated, thus, is necessary to enable the surgeons to deal with it. To this end, we previously proposed a neural network-based model for estimating the number of MBs from four factors measurable from the cardiopulmonary bypass system: suction flow rate, venous reservoir level, blood viscosity, and perfusion flow rate. However, the model has not been adapted to the data collected from actual surgery cases. In this study, the accuracy of MBs estimated by the proposed model was examined in four clinical cases. The results showed that the coefficient of determination between estimated MBs and the measured MBs throughout the surgeries was R2=0.558 (p<0.001). We found that the surgical treatments, such as administration of drugs, fluids and blood transfusions, increased the number of measured MBs. The coefficient of determination increased to R2= 0.8762 (p<0.001) by excluding the duration of these treatments. This result indicates that the model can estimate the number of MBs with high accuracy under the clinical environment.

CARD19: In vitro and In vivo Testing of the Pulsatile CorWave Membrane LVAD

Background: Lack of physiologic pulsatility with the use of continuous flow (CF) LVADs has been associated with serious adverse events including stroke, bleeding, and aortic insufficiency. CorWave is developing a unique LVAD employing an undulating membrane to generate a physiologic pulse while improving hemocompatibility. The present studies focused on in vitro and in vivo testing of the pump control algorithms for hemodynamic performance and hemocompatibility. Methods: The pump actuator, membrane, and blood flow path were designed using respectively electromagnetic simulations (MAGNET), Fluid-Structure Interaction (COMSOL), and Computational Fluid Dynamics. Algorithms were developed for actuator control, synchronization with the native left ventricle (LV), suction detection, and adaptive physiologic control. They were tested in a mock circulation loop (MCL) with INTERMACS 1-2, 3-4, and 5-6 heart failure (HF) profiles using LV pressure-volume loops to examine performance. The algorithms were then tested in chronic implants in healthy sheep for up to 3 months, and in acute implants in sheep with induced HF (ejection fraction < 40%). Results: During MCL tests, in synchronous pulsation (SynchPuls) mode, the membrane pump generated a more physiologic PV loop, with lower mean left atrial pressures (LAP), increased native LV stroke volume, and 1:1 opening of the aortic valve. CF pumps generated a characteristic, non-physiologic narrow PV loop with elevated mean LAP and aortic valve opening once per 3-5 beats. These results demonstrated the SynchPuls algorithm could respond to changes in pre-load to better unload the LV, restore more physiologic hemodynamics, and ensure aortic valve opening, so we proceeded to animal trials, which present more dynamic and challenging conditions. During acute implants in sheep with HF, using SynchPuls, the membrane pump increased cardiac output from ~2 to ~4 LPM. The physiologic control algorithm adjusted pump output to prevent LV suction and retrograde flow during hemodynamic manipulations, including epinephrine administration, and head up or down tilt. The algorithms switched to continuous mode, as intended, when arrhythmias or tachycardia were detected. In chronic implants, the SynchPuls algorithm successfully synchronized with the LV for > 97% of heartbeats and adapted to circadian cycles. Biomarkers of end-organ function returned to baseline within 2 weeks of implant, hemolysis was < 20 mg/dL, and VWF activity was preserved during the chronic implants. Conclusion: These studies showed that the membrane pump can provide physiologic pulsatility and restore cardiac output in HF models. The algorithms’ robustness was confirmed in chronic implants. Overall, these successful tests demonstrated that the CorWave membrane pump can deliver the hemocompatibility, pulsatility, and adaptability required to advance the LVAD field.

Advanced exergy analysis of a CO2 two-phase ejector

Ejector is meaningful and valuable to improve the transcritical CO2 refrigeration system. To study in-depth on the exergy destruction is significant for the performance enhancement of CO2 ejector. This paper presents a comprehensive investigation on the exergetic performance of CO2 two-phase ejector using conventional and advanced exergy analysis method to explore the interactions among ejector components and their improvement potential. The effects of primary flow pressure, suction flow temperature and area ratio (motive nozzle throat area to mixing chamber area) on the ejector exergy destruction are discussed. The results indicate the largest exergy destruction in the ejector is caused by the mixing chamber, followed by the motive nozzle, diffuser and suction chamber. Based on the avoidable exergy destruction rate and exergy destruction proportion, the order of optimization potential for ejector components is motive nozzle, diffuser, mixing chamber and suction chamber. However, the sum of avoidable exergy destruction of mixing chamber is the largest, which has the highest priority for improvement of overall ejector performance. The exogenous exergy destructions of the mixing chamber and diffuser are largely caused by the motive nozzle, and the exergy destructions would be increased with the improvement of motive nozzle performance. There exists an optimal primary flow pressure 9.5 MPa to minimize the exergy destruction of the each component of the ejector. To reduce the suction flow temperature and the ejector area ratio can decrease the avoidable exergy destruction of the components. Moreover, the variation of operating parameter has no effect on the optimization sequence of the overall ejector and its components. This work would provide a helpful way to guide the optimization on the ejector efficiency.

Combined application of passive and active boundary layer aspiration in a transonic compressor rotor for shock wave/boundary layer interaction control

Shock wave/boundary layer interaction (SWBLI) is one of the key factors that limits the improvement of aerodynamic performance and stability for supersonic/transonic compressors. In this research, a combined flow control device (CFCD) was designed for controlling SWBLI in the NASA transonic compressor Rotor 35. The original flow fields for Rotor 35 were numerically analyzed first. The results show that the SWBLI is severe, resulting in much flow loss and partly leading to the compressor instability. Based on this phenomenon, the CFCD was designed with a novel three-dimensional passive self-recirculation flow channel and an active suction slot. The flow channel is mounted on the rotor blade suction surface to connect the low- and high-pressure regions ahead of and behind the shock, respectively. The effect of the CFCD on the rotor performance and corresponding working mechanism are then researched as well. With the help of CFCD, the rotor-achieved total pressure ratio (TPR) is maximally increased by 3.0%, and the stall margin (SM) is improved by 4.1% as well. But the rotor isentropic efficiency (IE) considering additional energy expenditure caused by active suction flow has the maximum increment at choke point of 0.27% and highest reduction at near-stall point of 0.54%. The working mechanisms of CFCD include two aspects: one is forming a stable and low-entropy generated lambda shock wave and the other one is reducing the magnitude of flow separation. The dominant mechanism varies with the rotor working condition and depends on whether the leading-edge shock moves upstream of the passive bleed slot.

Enhanced X-ray Emissions Arising from High Pulse Repetition Frequency Ultrashort Pulse Laser Materials Processing.

The ongoing trend in the development of powerful ultrashort pulse lasers has attracted increasing attention for this technology to be applied in large-scale surface engineering and modern microfabrication. However, the emission of undesired X-ray photon radiation was recently reported even for industrially relevant laser irradiation regimes, causing serious health risks for laser operators. In the meantime, more than twenty influencing factors have been identified with substantial effects on X-ray photon emission released by ultrashort pulse laser processes. The presented study on enhanced X-ray emission arising from high pulse repetition frequency ultrashort pulse laser processing provides new insights into the interrelation of the highest-contributing parameters. It is verified by the example of AISI 304 substrates that X-ray photon emission can considerably exceed the legal dose rate limit when ultrashort laser pulses with peak intensities below 1 × 1013 W/cm² irradiate at a 0.5 MHz pulse repetition frequency. The peak intensity threshold value for X-ray emissions decreases with larger laser spot sizes and longer pulse durations. Another key finding of this study is that the suction flow conditions in the laser processing area can affect the released X-ray emission dose rate. The presented results support the development of effective X-ray protection strategies for safe and risk-free ultrashort pulse laser operation in industrial and academic research applications.

Influence of secondary flow with a Coanda surface on the direction of jets

Abstract We propose a method for fluidic thrust vectoring by studying the effect of excited secondary Coanda flow on the direction of jets. The primary flow is the steady continuous jet, while the the secondary flow is synthetic jet or continuous flow. In this experiment, speaker is used to adjusted the frequency and velocity amplitude of synthetic jets, while a blower is used to adjust the continuous jet and suction flow.We visualize and compare the primary flow under the influence of various secondary flows. Additionally, computational fluid dynamics is used to investigate the flow characteristics, including the deflection angle. The main results of this study is that both synthetic jets and continuous suction flow are capable of deflection.

Towards Designing an Innovative Industrial Fan: Developing Regression and Neural Models Based on Remote Mass Measurements

This article presents the process of the construction and testing a remote, fully autonomous system for measuring the operational parameters of fans. The measurement results obtained made it possible to create and verify mathematical models using linear regression and neural networks. The process was implemented as part of the first stage of an innovative project. The article presents detailed steps of constructing a system to collect and process measurement data from fans installed in actual operating conditions and the results of analysis of this data. In particular, a measurement infrastructure was developed, defined, and implemented. Measuring equipment was mounted on selected ventilation systems with relevant fans. Systems were implemented that allowed continuous measurement of ventilation system parameters and remote transmission of data to a server where it was regularly analysed and selected for use in the process of modelling and diagnostics. Pearson’s correlation analysis for p &lt; 0.05 indicated that all seven parameters (suction temperature, discharge temperature, suction pressure, current consumption, rotational speed, humidity, and flow) were significantly correlated with efficiency (p &lt; 0.001). A satisfactory level of correlation between the selected parameters measured in actual conditions and the characteristics of the fan and the ventilation system was experimentally verified. This was determined by finding 4 statistically significant parameters at a confidence level of 95%. This allowed the creation of two mathematical models of the fan system and the ventilation system using linear regression and neural networks. The linear regression model showed that the suction temperature, discharge temperature, and air humidity did not affect the fan efficiency (they are statistically insignificant, p &gt; 0.05). The neural model, which considered all measured parameters, achieved the same accuracy as the model based on four significant parameters: suction pressure, current consumption, rotational speed, and flow.

Performance of an oxygen-consuming inerting system for an aircraft fuel tank with RP-3 aviation fuel in flight

Aircraft fuel tank inerting system is an important guarantee for flight safety. A novel oxygen-consuming inerting system-3CIS (low-temperature controllable oxygen-consuming catalytic inerting system) was proposed and studied with RP-3 aviation fuel. Based on the designed inerting system, the mathematical model of the system in flight was established based on the conservation law of mass and energy. The system performance under different flight conditions was firstly analyzed, and the effects of the initial fuel loading, fan flow rate and preheating temperature on the system performance were studied. Meanwhile, a test bench was built to verify the correctness of the established model. The following conclusions can be drawn from the results: The 3CIS can reduce the oxygen concentration in the fuel tank quickly to prevent fires and suppress explosions. What's more, the inerting time is the longest when the fuel tank is initially empty if all other system conditions are the same. Therefore, it is suggested the no-load state should be used for the system parameters design for the purpose of maximum safety. As for the influence of key parameters on system performance, the inerting rate increases with the increase of fan suction flow and preheating temperature, and low fan flow rate during the climb and cruise stages and high fan flow rate during descent are suggested for the control system designing. Finally, a regenerator is recommended when designing the system since it can effectively reduce the preheating power and cooling power of the system.

Characteristic investigation of a flow-dependent inertia hydraulic converter driven by an equivalent fast switching valve

To acquire a linear load pressure with the potential of energy-saving compared with conventional throttling hydraulic systems, a switched hydraulic circuit (referred to as a flow-dependent inertia hydraulic converter) featuring a flow-dependent inertial effect was proposed. In this device, the flowing fluid modulated by an equivalent fast switching valve allows the fluid inertance at the connection pipe and rotation inertia incorporated in the flywheel to be combined. The theoretical and simulation models of the flow-dependent inertia hydraulic converter were established, and then the flow-dependent inertia was discussed and quantified. The predictions of the load pressure, flywheel speed and system efficiency were confirmed by experimental measurements. Results indicated that the theoretical and simulation predictions match well with the experiments for this configuration. The pressure wave propagation effect within the connection pipe is responsible for the variation in the transient load pressure and flywheel speed that is initially modulated by the rotation inertia theoretically, which seriously questions the predecessor's hypothesis of using a compressible volume to model the upstream connection pipe. The parabolic mean suction flow induced by the flow-dependent inertia draw our attention to the available supply flowrate and duty cycle. Finally, the throttling loss and system efficiency that varies with the desired characteristics is superior to that of conventional throttling hydraulic systems theoretically, and an acceptable system efficiency was obtained under the premise of ignoring friction experimentally.

Generalized differential quadrature analysis of MHD mixed convective motion of Casson fluids past an isothermal irregular slender geometry via Cattaneo–Christov's approach

AbstractClassical Fourier's theory is well‐known in continuum physics and thermal sciences. However, the primary drawback of this law is that it contradicts the principle of causality. To explore the thermal relaxation time characteristic, Cattaneo–Christov's theory is adopted thermally. In this regard, the features of magnetohydrodynamic (MHD) mixed convective flows of Casson fluids over an impermeable irregular sheet are revealed numerically. In addition, the resulting system of partial differential equations is altered via practical transformations into nonlinear ordinary differential equations. An advanced numerical algorithm is developed in this respect to get higher approximations for temperature and velocity fields, as well as their corresponding wall gradients. For validating our numerical code, the current outcomes are compared with the available literature results. Moreover, it is revealed that the velocity field is more prominent in the suction flow situation as compared with the injection flow case. It is also found that the Casson fluid is hastened in the case of lower yield stress. Larger values of thermal relaxation parameters create a lessening trend in the temperature distribution and its related boundary layer breadth.

Greedy Non-Intrusive Reduced-Order Model’s application in dynamic blowing and suction flow control to suppress the flow separation

The Greedy Non-Intrusive Reduced-Order Model (GNIROM) is applied in dynamic blowing and suction’s flow control to suppress the GAW1 airfoil’s flow separation. The effects of the uniform blowing and uniform suction on the flow fields and aerodynamic coefficients have been studied firstly. By comparing a uniform suction control with a dynamic blowing and suction control, it has been found that the dynamic blowing and suction can provide a higher lift coefficient and a lower energy loss. Finally, for the sake of achieving an optimal dynamic blowing and suction control, an optimization of the dynamic blowing and suction’s parameters is taken based on the GNIROM, consisting of a Non-Intrusive ROM (NIROM) built by the two-level POD and Radial Basis Function (RBF), and the relative greedy method. A cost function has been proposed by considering suppressing the flow separation, improving the lift-drag characteristics and reducing the energy loss together. The GNIROM has been built for unsteady vorticity fields with the parameters of the dynamic blowing and suction varying. Based on the GNIROM’s approximation, the optimal control parameters’ values have been determined quickly. Compared to the initial dynamic blowing and suction control, the optimal one has reduced the drag coefficient by 43.4 percents and the energy loss by 42 percents.

Analysis of pulsed suction flow control behavior based on a nonlinear reduced-order model

The use of pulsed suction is an effective unsteady flow control method. However, compared with steady suction, which simply eliminates low-energy boundary layer, pulsed suction flow control presents unique phenomena and complex control mechanisms that are not explained fully. Thus, in this paper, pulsed suction flow control in a compressor cascade is investigated by numerical simulation. Numerical results show that the control performance depends on the suction frequency, momentum, and location, as any unsteady active flow control method. To further reveal the mechanism and explain the phenomena of pulsed suction, a nonlinear reduced-order model for pulsed suction flow control is established on the basis of the Navier–Stokes equation, Stuart vortex row model, Oseen vortex model, and Stuart–Landau equation. The entrainment degree and maximal Lyapunov exponent are used as indices to evaluate the flow losses and control performance in this model. By solving the equations of this model under different parameters, the model presents similar phenomena as found in the numerical simulations with various suction frequencies, momentum, and locations. Thus, it is innovative that the model with calibrated parameters has the ability to roughly predict control performance of unsteady pulsed suction in an efficient way. Also, based on this reduced-order model, one can explain that, unlike steady suction, chaos control, momentum transfer and lock-in mechanisms are especially relevant with the control physics of pulsed suction.

Rancang Bangun Smoke Generator pada Kecepatan Angin Rendah dengan Wind Tunnel Rangkaian Terbuka

Flow Visualization is the process of making the physical flow of a fluid visible. The air fluid used is transparent, so the flow pattern must be shown by several special methods. There are three methods for visualizing flow: surface flow visualization, particle tracking method, and optical method. Turbulence is one of the most important subjects related to testing the test section in a wind tunnel, at different wind speeds turbulence levels and other flow quality parameters must be kept as close as possible to free flow conditions. The flow visualization test is carried out using a slow motion camera at speeds of 1 m/s, 2 m/s, 3 m/s, 4 m/s and 5m/s which will form a fluid flow in the form of lines of smoke coming out of the nozzle holes inside. Test section. From the research results, the authors can conclude that the flow obtained forms a laminar flow and good suction power from various wind speed variables.&#x0D;

Turbulent Flow in Forced Convection Heat Transfer - Numerical Validation

Forced convective heat transfer of airflow through circular pipe with constant heat input and different free stream velocities is numerically validated. The significance of the present work is that the suction flow has been employed in the forced convection set up domain kept in the wind tunnel. From first law of thermodynamics and applying the energy balance equation, experimental heat transfer coefficient is determined. Further correlations are used to validate the experimental results. Although correlations provide reasonable estimates from the point of feasibility and accuracy, computational methods are used to estimate the convective heat transfer coefficient. Hence in this paper experimental, theoretical and computational analysis is carried out. The results reveal that the numerical validation is an effective tool from the point of feasibility and accuracy to determine the convective heat transfer coefficient.

FSI simulation of the suction valve on the piston for reciprocating compressors

The suction valve is an essential one-way valve inside the reciprocating compressor controlling the suction gas flow. It is usually installed on the cylinder head of the compressor. However, the suction valve in oil-free mini compressors was preferred to be installed on the piston to cool down the bearing inside the piston by the suction flow. In this case, the motion of the piston will act varying accelerated speed on the valve plate. During its opening process, the valve plate would be pushed by resultant force of the inertia force generated by the accelerated speed and the flow thrust together. It would result in too high valve lift and deformation, and decrease the reliability of the valve plate extremely. For this reason, the stiffness of the valve on the piston should be greater than that on the cylinder head. However, stiffness strengthened valve plate moving with the piston would behaves oscillation motion during its opening and closing process. In this paper, a three-dimensional fluid-structure interaction (FSI) model validated by experiments was established using ADINA to study the oscillation motion of the valve installed on the piston. Obtained results showed that the lift integral of the valve on the piston was 4.5% less than that of the valve on the cylinder head, and the impact speed on the valve seat of the valve on the piston was smaller than that of the valve on the cylinder head, which indicated that the suction valve installed on the piston had higher reliability.

Investigation of Suction Flow Control on Centrifugal Compressor with Vaned Diffuser

In this study, the effect of suction flow control on a centrifugal compressor at operation and stall flow rates was investigated using computational fluid dynamics (CFD). The compressor geometry was reconstructed from available open source profile data and the CFD analyses have been performed on this geometry using the appropriate mesh. To validate the CFD results, the compressor performance line was acquired and compared with the experimental results obtained at the design rotational speed. Then, suction flow control was employed at various suction slot positions with different suction flow rates to improve the performance of the compressor at operation and stall flow rates. As a result of the suction flow control trials, 0.85% increase in pressure ratio and 0.8% increase in adiabatic efficiency were achieved while the compressor was running at operation flow rate. The performance improvements corresponding to the stall flow rate of the compressor were 2.5% increase in pressure ratio and 2% increase in adiabatic efficiency.

Trophic guilds of suction-feeding fishes are distinguished by their characteristic hydrodynamics of swimming and feeding.

Suction-feeding in fishes is a ubiquitous form of prey capture whose outcome depends both on the movements of the predator and the prey, and on the dynamics of the surrounding fluid, which exerts forces on the two organisms. The inherent complexity of suction-feeding has challenged previous efforts to understand how the feeding strikes are modified when species evolve to feed on different prey types. Here, we use the concept of dynamic similarity, commonly applied to understanding the mechanisms of swimming, flying, walking and aquatic feeding. We characterize the hydrodynamic regimes pertaining to (i) the forward movement of the fish (ram), and (ii) the suction flows for feeding strikes of 71 species of acanthomorph fishes. A discriminant function analysis revealed that feeding strikes of zooplanktivores, generalists and piscivores could be distinguished based on their hydrodynamic regimes. Furthermore, a phylogenetic comparative analysis revealed that there are distinctive hydrodynamic adaptive peaks associated with zooplanktivores, generalists and piscivores. The scaling of dynamic similarity across species, body sizes and feeding guilds in fishes indicates that elementary hydrodynamic principles govern the trophic evolution of suction-feeding in fishes.

Low-frequency shock train oscillation control in a constant area duct

The self-excited shock train oscillation control using partial removal of boundary layer flow in a constant area duct is studied numerically using unsteady Reynolds Averaged Navier–Stokes simulation. The effect of varying the suction flow ratio on the shock train oscillatory characteristics is analyzed using steady and unsteady statistics, space–time contour, power spectra, and cross correlation analysis. For the present study, a constant area duct of height 0.032 mm, and the aspect ratio of 25, at freestream Mach number of 2.0 and back pressure ratio of 0.52 is considered. The removal of the boundary layer through an angled suction slot with three different suction flow ratios is performed. Numerical results indicate that the removal boundary layer restricts the bifurcation process of the shock train and appears to be a single curved normal shock at a higher suction flow ratio. Also, the transition of regular reflection to the Mach reflection type is noted. The suction flow from the top and bottom slot tends to initiate a lateral oscillation that forms a wavy mixing flow region. The power spectral density contour suggests that the increase in suction flow ratio will tend to increase the dominant frequency ranges from (0.034 to 0.094). The cross correlation indicates the presence of downstream pressure disturbance that moves toward the upstream direction. With suction flow, a disturbance that emerges from the suction slot moves in the opposite direction and dominates at a lower suction flow ratio and these disturbances disappear at a large suction flow ratio.

Sediment Removal from Deep Reservoir Dams by Suction and Jet Flow

One method of sediment removal from dam reservoirs is the use of submerged pumps and suction mixes of sediment and water. This method is usually considered for shallow rivers but we want to adopt this method for large dams. In this research, a system based on suction with a submerged pump structure is designed to collect fine sediments close to body of the dam from a large depth and to be transmitted by floating pipes to the margin of lake. And also, by pumping of jet fresh water flow and creating turbulence by the jet on sedimentary bed is simultaneously used to increase harvesting efficiency. The usage of simple equipment for removing fine grains near the dam body without the need for discharging of water resources is one of the essential features of this method which is suitable for arid and dry areas such as Iran. By using turbulent flow of water jet and simultaneous suction with a submerged pump, a vortices stretch is produced to suction the sediment mixture. Overall, the discharged sediment separates from water on the margin of lake to restores water to the reservoir.

Application of Optical Measurement for Skin Friction Field around Tires of a Simplified Vehicle Model

The objective of this study is to apply the Global Luminescent Oil-Film Skin-Friction (GLOF) meter, which optically observes the skin friction vectors on the object surface, to reveal the fluid structure around the wheelhouse. The image analysis results show characteristic longitudinal vortices on the side surface of the front wheel and the wheelhouse. In contrast, the separation line at the rear end of the side near the rear wheelhouse is curved significantly upstream, and the separation area expands in the lower half of the rear end, probably due to the suction flow generated between the wheel and the wheelhouse.