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Ore collection devices are important for the collection of deep-sea polymetallic nodules. Based on the CFD-DEM solid–liquid two-phase flow coupling calculation method, this paper simulated the rise and transport phases of polymetallic nodules using the Coanda effect ore collection device. The validity of the numerical simulation method was confirmed through experimental testing. On this basis, the effects of different working and structural parameters on the collection rate were studied. The results indicate that the flow rate of the collection jet and the bottom clearance were the primary factors affecting the collection rate of the polymetallic nodules. An increase in the collection jet flow rate leads to a substantial rise in the collection rate of polymetallic nodules. Conversely, an increase in bottom clearance results in a decrease in the collection rate. A collection rate exceeding 90% can be achieved in both scenarios: a 10 mm bottom clearance with an 8 m/s collection jet flow rate, and a 30 mm bottom clearance with a 10 m/s collection jet flow rate. The collection nozzle slant angle has no substantial impact on the collection rate, and the recommended collection nozzle slant angle is 35° to reduce energy loss. [ABSTRACT FROM AUTHOR]

The Coanda effect is a fluid dynamics phenomenon in which a fluid jet adheres to a convex or flat surface. This effect occurs when a liquid or gas jet emerging from an orifice clings to an adjacent surface and entrains the surrounding fluid, creating a lower-pressure region along its path that maintains its attachment to the surface. The Coanda effect accounts for the behavior of blood flow in the fetal right atrium and the dispersion of eccentric mitral regurgitation jets along atrial walls. This series of interesting images depicting a large 4 × 3.75 cm saccular intracranial aneurysm suggests that the Coanda effect may play a role in the pathophysiology of intracranial aneurysms and could be an underlying factor in their formation, progression, or rupture. [ABSTRACT FROM AUTHOR]

Fluidic thrust vectoring (FTV) control is a cutting-edge method used to manipulate the motion of an unmanned air vehicle when traditional control surfaces like elevators are not available. The primary purpose of employing FTV is to make the aircraft less detectable. This research centers around the exploration of the co-flow variation of the FTV concept. In this approach, a secondary jet with a significant velocity is injected into the boundary layer of the primary jet. As a consequence, the primary jet is diverted, leading to the formation of a pitch moment. Numerical simulations were conducted to analyze different ratios of secondary and primary jet velocities, providing valuable insights into the effectiveness of the proposed technique. The test rig, designed with a pitch-constraint dynamic setup, utilized electric ducted fans to generate primary and secondary flows. At 19 m/s primary velocity, the experimental testing shows a maximum vertical force of 0.4 N, producing a deflection of 25°, which is deemed adequate for thrust vectoring. This research builds upon the authors' previous work on characterizing a static co-flow FTV rig. The comparison between the computational fluid dynamics analyses and the experimental results demonstrates agreement in the behavior of the vectored jet. This validation further strengthens the findings presented in this paper. [ABSTRACT FROM AUTHOR]

It is yet unknown how the formation of an aneurysm inside the human body occurs. Thus, understanding and analyzing the Coanda effect will result in a better overview of the overall fluid mechanics that develop inside such a structure, leading not only to better treatment plans, but also to diminished postoperative risks. This paper presents how the fluid behaves in this situation, and takes into consideration how this physical phenomenon influences the hemodynamics inside numerous anatomical regions, located in the central nervous system, where aneurysms usually develop. Analyzing the three main areas in which cerebral aneurysms form, the Coanda effect can potentially lead to the rupture of the aneurysm by changing the blood flow trajectory; this should be taken into consideration when choosing a treatment plan, especially in postoperative care. In addition, there are other factors that can influence the evolution of an aneurysm, such as its shape, size, localization and the patient's health condition. Understanding and analyzing the Coanda effect will result in a better overview of the overall fluid mechanics that develop inside such a structure, leading not only to better treatment plans, but also to diminished postoperative risks. [ABSTRACT FROM AUTHOR]

Pitch control of an unmanned aerial vehicle (UAV) using fluidic thrust vectoring (FTV) is a relatively novel technique requiring no moving control surfaces, such as elevators. In this paper, the authors' previous work on the characterization of a static co-flow FTV rig is further validated using the free to pitch dynamic test bench. The deflection of a primary jet after injection of a high-velocity secondary jet was captured using the tuft flow visualization technique, along with the experimental recording of subsequent normal force impinged on the Coanda surface resulting in the pitching moment. The effect of primary and secondary flow velocities on exhaust jet deflection, as well as on the pitch angle of the aircraft, is examined. Aerodynamic gain as well as the inertia of a delta wing UAV test bench are computed through experiments and fed into the equation of motion (e.o.m). The e.o.m developed aided in the design of a model-based PID controller for pitch motion control using the multi-parameter root locus technique. The root locus tuned controller serves as a benchmark controller for performance evaluation of the genetic algorithm (GA) and particle swarm optimization (PSO) tuned controllers. Furthermore, the frequency domain metric of gain and phase margins were also employed to reach a robust control design. Experiments conducted in a simulation environment reveal that PSO-PID results in a better response of the UAV in comparison to the baseline pitch controller. [ABSTRACT FROM AUTHOR]

Bladeless fans are more energy efficient, safer due to the hidden blades, easier to clean, and more adjustable than conventional fans. This paper investigates the influence of the airfoil's outlet slit thickness on the discharge ratio by varying the outlet slit thickness of an Eppler 473 airfoil from 1.2 mm to 2 mm in intervals of 0.2 mm by using a k-omega SST turbulence model with an all y + wall treatment used to numerically simulate in CFD. The computational results indicated that smaller slits showed higher discharge ratios. The airfoil with a 1.2 mm slit thickness showed a discharge ratio of 18.78, a 24% increase from the discharge ratio of the 2 mm slit. The effect of outlet angle on the pressure drop across the airfoil was also studied. Outlet angles were varied from 16 ° to 26 ° by an interval of 2 ° . The airfoil profile with a 24 ° outlet angle showed a maximum pressure difference of 965 Pa between the slit and leading edge. In contrast, the 16 ° outlet angle showed the least pressure difference of 355 Pa. Parameters such as average velocity (U), turbulent kinetic energy, the standard deviation of velocity, and outlet velocity magnitude are used to assess the performance of airfoil profiles used in bladeless fan. [ABSTRACT FROM AUTHOR]

This study carried out a simplified baffle filter shape study on the over the range (OTR) filter used in a general kitchen. In order to improve the filter's efficiency, the simulation was performed using ANSYS FLUENT and COMSOL Multiphysics, and a wind tunnel test apparatus was manufactured to minimize the error rate of dust collection efficiency in the experiment. In the case of a physical filter, it was confirmed through a theoretical review that dust is collected in the filter by the inertial collision method, and the flow velocity must be increased to increase the dust collection efficiency. To increase the flow velocity and increase the filter contact area, the use of sub-filters and the Coanda effect was proposed and simulated. When only the Coanda effect was applied, the collection efficiency increased by about 7–15% compared to the original filter, and when the three types of sub-filters were proposed, and among them, a circular sub-filter was applied, it increased by 25%. When applying the sub-filter and the Coanda effect at the same time, it was confirmed that the sub-filter was more efficient than the Coanda effect. However, in the case of a physical filter, since it cannot collect particles less than PM2.5, the electric dust collection method was proposed and a simulation was conducted. The possibility of removing ultrafine dust below PM2.5 was secured by using an electric dust-collection filter simulation, and it is expected that the reliability will be secured by using experimental devices and products in the future. [ABSTRACT FROM AUTHOR]

The deep-sea mining vehicle is the main component of the undersea exploitation system, which gathers polymetallic nodules with its professionally designed seabed collector. The Coandă effect-based collecting method is an improved hydraulic method that forms an adverse pressure gradient over the nodules by performing wall jet flow over a rounded convex surface. In comparison to the circular cylinder surface, the effect of wall jet over the logarithmic spiral surface has a self-preserving nature, which can be advantageous to the nodule collecting. However, this effect on lift capability has seldom been studied before. In the present investigation, a reduced form modelling jet flows over logarithmic spiral surfaces was performed to study the flow characteristics and lift ability of the newly designed Coandă effect-based collector. The jet-half width has been optimized to study the influence of wall curvature on the growth rate. The lift ability was found to be stronger with larger jet exit velocity, local curvature, or non-dimensional jet slot height. The growth rate, which represents the width of the main jet flow, went up in proportion to the downstream distance. The lift capability of jet flow in logarithmical spiral of x/R = 1 is significantly better than that of x/R = 2/3. [ABSTRACT FROM AUTHOR]

Precise prediction of ventilation flow is essential to create a comfortable, economical, and healthy indoor environment. In the past three decades, the computational fluid dynamics (CFD) method has been used more often, and it is now one of the primary methods for studying building ventilation. The most common CFD method is RANS simulation because of the low cost of computational resources and good accuracy. This paper presents a numerical investigation of a transitional ventilation flow with the Coanda effect, which makes the initial free jet transform into a wall jet. Six low-Reynolds number k-ε models proposed by Abid (AB), Lam and Bremhorst (LB), Launder and Sharma (LS), Yang and Shih (YS), Abe Kondoh and Nagano (AKN), and Chang, Hsieh and Chen (CHC) are applied. The performance of the six models is evaluated by comparing the computational results with the PIV measurements of Van Hooff et al. The predictions revealed that the LS model has a good approximation of velocity profiles because of its two extra terms in k and ε equations, and the AB model is in good agreement with experimental results for predicting the Coanda effect. The LB model provides the worst agreement with experimental data on account of the wrong prediction of turbulent kinetic energy and dissipation rate. [ABSTRACT FROM AUTHOR]

To date, hydraulic collection is the most widely considered technology in polymetallic-nodule mining, since there is no direct contact between hydraulic collectors and ocean floor. To construct a hydraulic collector that results in the least sediment disturbance, it is critical to develop an insightful understanding of the interaction between the collector and sediment bed. To this end, we conducted a set of small-scale experiments in which several operational conditions were tested, delivering the first quantitative data for sediment erosion resulting from a hydraulic collector driving over a sand bed. This paper presents and discusses the experimental results and observations. It is found that the collector's forward velocity is inversely proportional to the bed-sediment erosion depth, since the bed is exposed to the flow for a longer time when the collector drives slower and vice versa. In contrast, an increased jet velocity leads to a larger erosion depth. Furthermore, when the collector underside is nearer to the sediment bed, a larger sediment layer is exposed to the water flow, resulting in a larger erosion depth. Finally, the experimental results show that collector water jets strike the sediment bed under an inclined angle, destabilizing the upper sediment layer and consequently dragging sediment particles along toward the collection duct and behind the collector head. This study improves the predictability of sediment erosion created by Coandă-effect-based collectors, which is a crucial asset to optimize the collector design and decrease the extent of the associated sediment plumes. [ABSTRACT FROM AUTHOR]

Aiming at the problem where the current engineering wake model does not describe the wind speed distribution of the wake in the complex terrain wind farm completely, based on the three-dimensional full wake model (3DJGF wake model), this paper proposed a wake model that can predict the three-dimensional wind speed distribution of the entire wake region in the complex wind farm, taking into account the Coanda effect, wind shear effect, and wake subsidence under the Gaussian terrain. Two types of Doppler lidar were used to conduct wind field experiments, and the inflow wind profile and three-dimensional expansion of the wake downstream of the wind turbine on the Gaussian terrain were measured. The experimental results showed that the wake centerline and terrain curve showed similar variation characteristics, and the near wake profile was similar to a super-Gaussian shape (asymmetric super-Gaussian shape) under low-wind-speed conditions, while the near wake profile presented a bimodal shape (asymmetric bimodal shape) under high-wind-speed conditions. The predicted profiles of the Gaussian terrain wake model were compared with the experimental data and the three typical wake models. The comparison results showed that the newly proposed Gaussian terrain wake model fit well with the experimental data in both near wake and far wake regions, and it had better performance in predicting the wake speed of the Gaussian terrain wind farm than the other three wake models. It can effectively predict the three-dimensional velocity distribution in the whole wake region of complex terrain. [ABSTRACT FROM AUTHOR]

Thrust, propulsion, vector control of supersonic jets has been applied to jet and rocket engines, ejectors, and other many devices. In general, there are two approaches to this type of control, namely mechanical moving systems and fluidic thrust vector control systems without moving parts, with mechanical moving systems being the most common. However, generally speaking, these systems are very complicated, and more simple methods and devices are desired. In this study, an extremely simple method for the thrust vector control of a supersonic jet by a fluidic Coanda nozzle (FC-nozzle) using the entrainment of the surrounding fluid and Coanda effect is newly proposed. The FC-nozzle consists of a pipe nozzle (Pi-nozzle), spacer, and linearly expanded Coanda nozzle (Co-nozzle) with eight suction pipes (Su-pipes) installed to surround the jet from the Pi-nozzle. The jet from the Pi-nozzle flows straight with the entrainment flow of the surrounding fluid. When some Su-pipes are closed, the pressure between the jet and Co-nozzle wall decreases, and subsequently, the jet deflects to the closed side of the Su-pipe and reattaches to the wall by the Coanda effect. The flow characteristics and deflection characteristics of the supersonic jet from the FC-nozzle are examined by the visualized flow pattern using the Schlieren method and measurements of the velocity distribution. As a result, it is shown that by changing the number of Su-pipes and the locations at which they are closed, the deflection angle and circumferential position of the jet from the Pi-nozzle can be easily controlled. [ABSTRACT FROM AUTHOR]

The undersea collecting vehicle is one of the three main parts in the deep-sea exploitation system. The Coandă effect-based collector picks up manganese nodules by providing an adverse pressure difference over the nodule, through the jet flowing around a curved wall. In order to overcome the drawbacks of repeated prototyping and experimenting in the traditional design procedure of the Coandă effect-based collector, the theoretical guide should be well placed to ensure correct design of the strongly related parameters of the collector. In this paper, a simplified model of curved wall jets was developed and the solution of approximate closed form was obtained to predict the lift force of the nodules. The variational tendencies of velocity, pressure and single-particle lift index perpendicular to the curved wall were investigated and the Coandă effects were found to be stronger with higher initial velocity, higher non-dimensional jet slot height and lower non-dimensional wall height. A CFD-DEM simulation of a number of particles was additionally performed to give more insight into the predictive accuracy of the simplified theory. Target lift force was found to be related to high efficiency in collection of particles, resulting in certain predictability of the theoretical model to the nodule lifting in a pre-prototype hydraulic device based on the Coandă effect. [ABSTRACT FROM AUTHOR]

The Coanda effect nozzle is a fluid thrust vectoring technology that uses the Coanda effect to control jet vector deflection. The jumping phenomenon often occurs in the process of controlling jet vector deflection. This phenomenon leads to the nonlinearity of thrust vector control. It destroys the control performance of the aircraft and brings potential dangers to the safety of the aircraft. The jumping phenomenon occurs in an unsteady flow field different from the traditional flow phenomenon. The flow structure in an unsteady flow field changes with time, so it is not easy to control by the traditional active flow control method. This paper explains the reasons for the jumping phenomenon from two aspects: flow field stability and flow structure. Secondly, the unsteady flow field with the jumping phenomenon is studied and analyzed by a flow visualization experiment and dynamic force measurement. Furthermore, the dynamic modal decomposition (DMD) method is used to extract the characteristic frequencies of the critical vortices causing jets to jump in unsteady flow fields. Finally, a pulsed jet with the same characteristic frequency is used to control the varying vortices in the unsteady flow field. The experimental results show that the active flow control method, which extracts the characteristic frequency of the critical flow field structure by DMD, effectively suppresses the jumping phenomenon in the unsteady flow field. It also linearizes the process of jet nonlinear vector deflection. [ABSTRACT FROM AUTHOR]

Water purification by non-equilibrium atmospheric pressure plasma has attracted much attention and is expected to be a next-generation method. However, general approaches to improve the energy efficiency of the water purification have not been revealed. Therefore, to investigate important factors for increasing its energy efficiency, we developed coaxial cylindrical plasma reactors where pulsed streamers were generated between a high-voltage electrode and running water film. To evaluate the performance of the plasma reactors, we measured hydroxyl (OH) radicals in solution based on a chemical probe method using disodium terephthalic acid (NaTA) and decolorized indigo carmine solution. Our experimental results showed that the production rate of the OH radicals was approximately 20 nmol/s and that the energy efficiency of the decolorization was on the order of 10 g/kWh. In addition, we found that controlling liquid flow based on the Coandă effect and introducing the intermittent operation of the streamer discharges to use post-discharge reactions increased the energy efficiency by a factor of approximately 3.5, which indicated that these approaches are effective to improve the performance of the water purification by plasma. [ABSTRACT FROM AUTHOR]

In this study, a jet injection propeller was designed to increase its efficiency, and the results were compared by open water tests and numerical computations. Also, the change in shape of the slit and injection volume conditions, which are difficult to perform experiments with, were analyzed through computations. The jet injected from the blade surface generates additional thrust due to the Coanda effect, and the jet injection generates a moment in the direction of propeller rotation, resulting in a decrease in the total torque. Computations were performed for three slit heights. When the height of the slit is high, the efficiency of the propeller increases, even if the power of the pump required for jet injection is considered. The result was found to increase the efficiency by about 8.7%, even when the efficiency was compared under the condition of generating the same thrust by controlling the injection volume of the jet by designing a normal propeller that does not inject a jet. [ABSTRACT FROM AUTHOR]

There is an increasing need to screen water in surface water collection systems to remove floating debris and small aquatic organisms to protect receiving water bodies. Recently, the Albuquerque Metropolitan Arroyo Flood Control Authority (AMAFCA, New Mexico, USA) has actively introduced structural debris removal from storm-water facilities as a best management practice. In the South Diversion Channel Project, AMAFCA's objective is to divert the flow at the upstream end of the existing concrete structure and remove debris from this flow using Coanda-effect screens before allowing it to re-enter the channel. Design limitations, such as access to the debris removal site, existing components of the concrete structure, topography of the site, and need for flow-regulating structures complicate the design. This paper shows how numerical modeling tools (Delft3D-FLOW model) and physical modeling can be used in conjunction to observe flow patterns in a diversion structure and around Coanda-effect screens, estimate design parameters and thereby provide design recommendations. [ABSTRACT FROM AUTHOR]

Energy-saving ventilation systems are designed to improve the energy efficiency of buildings. Low energy efficiency in buildings poses a considerable problem that needs to be addressed. Mechanical ventilation with heat recovery has gained increased popularity in recent years. Mechanical ventilation has numerous advantages, including easy adjustment and control, high indoor air quality and elimination of indoor pollutants. Mixing ventilation is the most popular type of mechanical ventilation, in particular in residential buildings. Unsteady ventilation is a type of mixing ventilation that involves stronger mixing effects and smaller vertical temperature gradients to improve indoor air quality (IAQ) and minimize energy consumption. This study examines the possibility of controlling and modifying Coanda effect hysteresis (CEH) to generate unsteady flow and simulate the conditions of unsteady mixing ventilation. The experiment was performed on a self-designed test bench at the University of Warmia and Mazury in Olsztyn. It demonstrated that an auxiliary nozzle can be applied at the diffuser outlet to control CEH and the angles at which the air jet becomes attached to and separated from the flat plate positioned directly behind the nozzle. The study proposes an innovative mixing ventilation system that relies on CEH. The potential of the discussed concept has not been recognized or deployed in practice to date. This is the first study to confirm that an auxiliary nozzle by the diffuser outlet can be operated in both injection and suction mode to control CEH. In the future, the results can be used to design a new type of nozzles for unsteady ventilation systems that are based on CEH control. [ABSTRACT FROM AUTHOR]

The reason for the asymmetry phenomenon of Shock/Boundary Layer Interactions (SBLI) in a completely symmetric duct with symmetric flow conditions is still an open question. A theoretical model for the asymmetry of shock train in supersonic flows is proposed based on the properties of fluid entrainment in the mixing layer and momentum conservation. Flow deflection angles downstream from different SBLI regions were deduced from this model. Steady numerical simulations were conducted to model the asymmetry of the SBLI in an isolator tested by Carroll. The obtained deflection angles using the theoretical model with the aerodynamic parameters from the numerical results of forced symmetric isolator flow give a larger range estimation and a close average value compared with the asymmetric full duct flow. This showed that the entrainment of shear layer on the separation induced by SBLI plays a dominant role in the asymmetry of the confined SBLI. [ABSTRACT FROM AUTHOR]

In the present work it is performed a numerical study for simulation of turbulent air and water flows in a nozzle based on the Coanda effect named H.O.M.E.R. (High-Speed Orienting Momentum with Enhanced Reversibility). The main purposes of this work are the development of a numerical model for simulation of the main operational principle of the H.O.M.E.R. nozzle, verify the occurrence of the physical principle in a device using water as working fluid and generate theoretical recommendations about the influence of the difference of mass flow rate in two inlets and length of septum over the fluid dynamic behavior of water flow. The time-averaged conservation equations of mass and momentum are solved with the Finite Volume Method (FVM) and turbulence closure is tackled with the k-ε model. Results for air flow show a good agreement with previous predictions in the literature. Moreover, it is also noticed that this main operational principle is promising for future applications in maneuverability and propulsion systems in marine applications. Results obtained here also show that water jets present higher deflection angles when compared with air jets, enhancing the capability of impose forces to achieve better maneuverability. Moreover, results indicated that the imposition of different mass flow rates in both inlets of the device, as well as central septum insertion have a strong influence over deflection angle of turbulent jet flow and velocity fields, indicating that these parameters can be important for maneuverability in marine applications. [ABSTRACT FROM AUTHOR]