scholarly journals Numerical Study of Turbulent Air and Water Flows in a Nozzle Based on the Coanda Effect

2019 ◽  
Vol 7 (2) ◽  
pp. 21
Author(s):  
Youssef El Halal ◽  
Crístofer Marques ◽  
Luiz Rocha ◽  
Liércio Isoldi ◽  
Rafael Lemos ◽  
...  
Keyword(s):  
Mass Flow ◽  
High Speed ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Working Fluid ◽  
Coanda Effect ◽  
Water Flows ◽  
Operational Principle ◽  
Coandǎ Effect ◽  
Marine Applications

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.

scholarly journals Experimental and Numerical Study of the Coanda Effect Used to Reduce Self-Sustained Tones

2002 ◽  
Author(s):  
C. Allery ◽  
S. Gue´rin ◽  
A. Hamdouni ◽  
A. Sakout
Keyword(s):  
Horizontal Plane ◽  
Numerical Study ◽  
Coanda Effect ◽  
Inclined Plane ◽  
Flow Configuration ◽  
Large Hysteresis ◽  
Dimensional Dynamical System ◽  
Coandǎ Effect ◽  
Low Dimensional ◽  
Proper Orthogonal

We present in this paper an experimental and numerical study about the Coanda effect which causes the sudden reattachment of a jet to an inclined plane. This phenomenon induces a large hysteresis loop, which can be used to reduce the noise produced by an airflow crossing two diaphragms in tandem inside a duct. The angle of the inclined wall with horizontal plane and the flow velocity are the two main parameters studied here. With the aim of doing optimal control, we propose to construct for this flow configuration a low-dimensional dynamical system with a basis issued from a Proper Orthogonal Decomposition.

Three-Dimensional CFD Analysis of Meshing Losses in a Spur Gear Pair

2018 ◽  
Author(s):  
T. Fondelli ◽  
D. Massini ◽  
A. Andreini ◽  
B. Facchini ◽  
F. Leonardi
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Spur Gear ◽  
Computational Domain ◽  
Gear Pair ◽  
Transient Pressure ◽  
Numerical Effort ◽  
Free Environment

The reduction of fluid-dynamic losses in high speed gearing systems is nowadays increasing importance in the design of innovative aircraft propulsion systems, which are particularly focused on improving the propulsive efficiency. Main sources of fluid-dynamic losses in high speed gearing systems are windage losses, inertial losses resulting by impinging oil jets used for jet lubrication and the losses related to the compression and the subsequent expansion of the fluid trapped between gears teeth. The numerical study of the latter is particularly challenging since it faces high speed multiphase flows interacting with moving surfaces, but it paramount for improving knowledge of the fluid behavior in such regions. The current work aims to analyze trapping losses in a gear pair by means of three-dimensional CFD simulations. In order to reduce the numerical effort, an approach for restricting computational domain was defined, thus only a portion of the gear pair geometry was discretized. Transient calculations of a gear pair rotating in an oil-free environment were performed, in the context of conventional eddy viscosity models. Results were compared with experimental data from the open literature in terms of transient pressure within a tooth space, achieving a good agreement. Finally, a strategy for meshing losses calculation was developed and results as a function of rotational speed were discussed.

A New Concept in Design of Rheolytic Thrombectomy Devices: The Coanda Effect

2009 ◽  
Author(s):  
Cheng-Shiu Chung ◽  
Sergio L. Cornejo ◽  
Ming Huo ◽  
Ender A. Finol
Keyword(s):  
Pressure Distribution ◽  
High Speed ◽  
Experimental Studies ◽  
Pressure Sensors ◽  
Surface Velocity ◽  
Coanda Effect ◽  
Ambient Fluid ◽  
Mixing Rate ◽  
Coandǎ Effect ◽  
Coanda Flow

The Coanda effect, which was first named by Henri Coanda in 1910, is the phenomenon when a fluid, gas or liquid, attaches to a solid surface, called the Coanda surface. The direction of this adhered flow changes along with the surface because of the Van der Walls forces or surface tension. Therefore, the pressure distribution of the ambient fluid is also altered due to the bent attached Coanda flow. The fluid material properties, Coanda flow velocity, curvature of the Coanda surface, velocity of the ambient fluid flow, and distance to the wall above the Coanda flow are the primary factors affecting this pressure distribution. In experimental studies, Panitz and Wasan [1] evaluated the pressure distribution of the Coanda effect by using pressure sensors on the Coanda surface and a colored dye solution in the flow. By means of photographs and experimental data, they describe the influence of different heights of the shroud (a sheath plate above the Coanda surface) and the secondary flow entrainment (flow of ambient fluid) on the pressure profiles. Vortices occur beneath the Coanda flow when the height of the shroud is lower than a specified reference. Cutbill et al. [2] developed a high speed Coanda flow k-ε turbulence model in the application of PHOENICS to improve the prediction of the mixing rate, shock wave structure and flow separation. The pressure drop occurs near the Coanda surface in both experimental and computational prediction results.

Numerical study of the dimensionless characteristics and modeling experiment of a molten salt pump that transports viscous fluids

2017 ◽  
Vol 27 (9) ◽  
pp. 2131-2153 ◽  
Author(s):  
Chunlei Shao ◽  
Yang Zhao
Keyword(s):  
Reynolds Number ◽  
Molten Salt ◽  
High Speed ◽  
Critical Reynolds Number ◽  
Numerical Study ◽  
Working Fluid ◽  
High Speed Photography ◽  
Content Type ◽  
Modeling Experiment ◽  
External Characteristics

Purpose The purpose of this paper is to study the dimensionless characteristics of a molten salt pump and propose an approach to carry out the modeling experiment by using water instead of molten salts. Design/methodology/approach External characteristics of the pump were estimated by using the steady flow model and compared with the experimental results. By taking water as the working fluid, the pathlines in the volute of the model pump were validated by the results obtained of high-speed photography. According to the derived dimensionless characteristics of the molten salt pump, the modeling experimental schemes were proposed. Adopting the validated numerical simulation model, the performance of the molten salt pump was studied in detail. Findings The modeling experimental schemes designed according to the dimensionless characteristics are theoretically feasible. However, to carry out the experiment successfully, factors such as rotational speed, geometric size, flow rate and head should be taken into account. The flow in the pumps is similar under the similar operating condition and the external characteristics of the similar pump can be converted to each other. Compared with transporting water, the decline of the head and efficiency is within 5 per cent when the viscosity is lower than 0.01453 Pa · s. The pump is not suitable for running under the critical Reynolds number of 1.0 × 107. Originality/value The current work revealed the relationships among the dimensionless performances of a molten salt pump and proposed a critical Reynolds number ReQcr for the pump running.

scholarly journals 1315 Numerical Study on Coanda Effect of Synthetic Jet

2009 ◽  
Vol 2009.46 (0) ◽  
pp. 525-526
Author(s):  
Koichi NISHIBE ◽  
Chikashi NAKAGAWA ◽  
Shimpei OKAYASU ◽  
Kotaro SATO ◽  
Kazuhiko YOKOTA
Keyword(s):  
Numerical Study ◽  
Synthetic Jet ◽  
Coanda Effect ◽  
Coandǎ Effect

Coanda Effect on the Impact of Distribution Characteristics of Oil-Air Annular Flow

2014 ◽  
Vol 620 ◽  
pp. 166-170
Author(s):  
Qi Guo Sun ◽  
Dong Xu Chen ◽  
Xiong Shi Wang ◽  
Zheng Hui Zhou
Keyword(s):  
Pressure Gradient ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Annular Flow ◽  
Branch Pipe ◽  
Coanda Effect ◽  
Distribution Characteristics ◽  
Coandǎ Effect ◽  
The Impact

The T-junction model is simulated in Fluent by changing the curvature of branch pipe, and then the distribution characteristics of the annular flow was studied in T-junction distributor. The mass flow and pressure of the annular flow in this T-junction are studied, and the impact of Coanda Effect on the annular flow distribution characteristic is analyzed in oil-air two phases flow. The results show that, Coanda Effect affects the distribution of oil-air annular flow unevenly. The mass flow rate of air phase and the air velocity of outlet increase with decreasing the curvature, while the mass flow rate of liquid decrease with decreasing the curvature of the branch pipe connection; T-shaped junction inlet pressure is high, but the pressure gradient is small, the pressure gradient in the small curvature manifold is larger than that in the large curvature manifold.

An Experimental and Computational Fluid Dynamic Study of Axis-Symmetric Coanda Configuration for VTOL MAV Applications

2014 ◽  
Vol 629 ◽  
pp. 42-47 ◽  
Author(s):  
Baramee Wessapakdee ◽  
Pranchalee Makarasut ◽  
Chinnapat Thipyopas
Keyword(s):  
Fluid Dynamic ◽  
Surface Shape ◽  
Coanda Effect ◽  
Ansys Fluent ◽  
The Third ◽  
Actuator Disk ◽  
Parabolic Shape ◽  
Coandǎ Effect ◽  
Set Up ◽  
Vertical Takeoff

This project is designed to find out a proper shape for the Coanda effect and use them for helping a vertical takeoff vehicle to create additional lift. Experiment and numerical calculations were conducted. The model was set up by placing a propeller at 10 cm above the surface. Shape, height and model with a hold at the center were investigated by ANSYS Fluent. Propeller was simulated by applying actuator disk. First shape is a semi sphere with 50 cm diameter. Second, surface in invert parabolic shape with 50 cm diameter with varying height 15, 25 and 35 cm are considered. The last shape is similar to the second case with 15 and 35 cm height, but it is made hollow by varying the hold's diameter as 7, 11 and 15 cm. The total number of the entire cases is 10. The result shows that the best shape for the Coanda effect is a semi sphere shape but total lift of all models without a hole in the middle, in the first and the second cases, are negative and tend to decline when the height of the shape increases. For the third case, the shape with a height of 35 cm and 15 cm hold diameter has the least negative lift.

Computational Fluid Dynamics of a Radial Compressor Operating With Supercritical CO2

2012 ◽  
Author(s):  
Rene Pecnik ◽  
Enrico Rinaldi ◽  
Piero Colonna
Keyword(s):  
Critical Point ◽  
Gas Turbine ◽  
Supercritical Co2 ◽  
High Speed ◽  
Power Plants ◽  
Compressible Flows ◽  
High Efficiency ◽  
Fluid Dynamic ◽  
Working Fluid ◽  
Maximum Pressure

The merit of using supercritical CO2 (scCO2) as the working fluid of a closed Brayton cycle gas turbine is now widely recognized, and the development of this technology is now actively pursued. scCO2 gas turbine power plants are an attractive option for solar, geothermal and nuclear energy conversion. Among the challenges which must be overcome in order to successfully bring the technology to the market, the efficiency of the compressor and turbine operating with the supercritical fluid should be increased as much as possible. High efficiency can be reached by means of sophisticated aerodynamic design, which, compared to other overall efficiency improvements, like cycle maximum pressure and temperature increase, or increase of recuperator effectiveness, does not require an increase in equipment cost, but only an additional effort in research and development. This paper reports a three-dimensional CFD study of a high-speed centrifugal compressor operating with CO2 in the thermodynamic region slightly above the vapor-liquid critical point. The investigated geometry is the compressor impeller tested in the Sandia scCO2 compression loop facility [1]. The fluid dynamic simulations are performed with a fully implicit parallel Reynolds-averaged Navier-Stokes code based on a finite volume formulation on arbitrary polyhedral mesh elements. The CFD code has been validated on test cases which are relevant for this study, see Ref. [2,3]. In order to account for the strongly nonlinear variation of the thermophysical properties of supercritical CO2, the CFD code is coupled with an extensive library for the computation of properties of fluids and mixtures [4]. Among the available models, the one based on reference equations of state for CO2 [5,6] has been selected, as implemented in one of the sub-libraries [7]. A specialized look-up table approach and a meshing technique suited for turbomachinery geometries are also among the novelties introduced in the developed methodology. A detailed evaluation of the CFD results highlights the challenges of numerical studies aimed at the simulation of technically relevant compressible flows occurring close to the liquid-vapor critical point. The data of the obtained flow field are used for a comparison with experiments performed at the Sandia scCO2 compression-loop facility.

scholarly journals Experimental and Numerical Study on the Performance Change of a Simple Propeller Shape Using the Coanda Effect

2021 ◽  
Vol 11 (9) ◽  
pp. 4112
Author(s):  
Ju-Han Lee ◽  
Kwang-Jun Paik ◽  
Soon-Hyun Lee ◽  
Gu-Hyeon Kim ◽  
Jun-Hui Cho
Keyword(s):  
Numerical Study ◽  
Open Water ◽  
Coanda Effect ◽  
Blade Surface ◽  
Jet Injection ◽  
Numerical Computations ◽  
Injection Volume ◽  
Performance Change ◽  
Coandǎ Effect

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.

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