Three-Dimensional Simulation of Turbulent Rectangular and Square Impinging Jet Flows

2004 ◽  
Author(s):  
Qingguang Chen ◽  
Zhong Xu ◽  
Yulin Wu ◽  
Yongjian Zhang
Keyword(s):  
Recirculation Zone ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Adverse Pressure Gradient ◽  
Impinging Jet ◽  
Boundary Layer Separation ◽  
Streamwise Velocity ◽  
Impinging Jets ◽  
Jet Flows ◽  
Dimensional Simulation

Flow characteristics of turbulent impinging jets issuing, respectively, from a rectangular and a square nozzles have been investigated numerically through the solution of three-dimensional Navier-Strokes equations in steady state. Two geometries with two nozzle-to-plate spacings of four and eight times of hydraulic diameters of the jet pipes, and two Reynolds numbers of 20000 and 30000 have been considered with fully developed inlet boundary conditions. An RNG based k–ε turbulence model and a deferred correction QUICK scheme in conjunction with the wall function method have been applied to the prediction of the flow fields within semi-confined spaces. A common feature revealed by the computational results is the presence of a toroidal recirculation zone around the jet. An adverse pressure gradient is found at the impingement surface downstream the stagnation point. Boundary layer separation will occur if the gradient is strong enough, and the separation manifests itself as a secondary recirculation zone at the surface. In addition, three-dimensional simulations reveal the existence of two and four pronounced streamwise velocity off-center peaks at the cross-planes near to the impingement plate, respectively, in the rectangular and square impinging jet flows. These peaks are found forming at the horizontal planes where the wall jets start forming accompanied by two or four pairs of counter-rotating vortex rings. It is believed that the formation of the off-center velocity peaks is due to the vorticity diffusion along the wall jet as the jet impinges on the target plate.

Three-Dimensional Simulation of Laminar Rectangular Impinging Jets, Flow Structure, and Heat Transfer

1999 ◽  
Vol 121 (1) ◽  
pp. 50-56 ◽  
Author(s):  
I. Sezai ◽  
A. A. Mohamad
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Streamwise Velocity ◽  
Impinging Jets ◽  
Navier Stokes ◽  
Aspect Ratios ◽  
Laminar Jets ◽  
Nusselt Number Distribution ◽  
Dimensional Simulation ◽  
Energy Equations

The flow and heat transfer characteristics of impinging laminar jets issuing from rectangular slots of different aspect ratios have been investigated numerically through the solution of three-dimensional Navier-Stokes and energy equations in steady state. The three-dimensional simulation reveals the existence of pronounced streamwise velocity off-center peaks near the impingement plate. Furthermore, the effect of these off-center velocity peaks on the Nusselt number distribution is also investigated. Interesting three-dimensional flow structures are detected which cannot be predicted by two-dimensional simulations.

scholarly journals Interactions between Tandem Cylinders in an Open Channel: Impact on Mean and Turbulent Flow Characteristics

Water ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 1718
Author(s):  
Hasan Zobeyer ◽  
Abul B. M. Baki ◽  
Saika Nowshin Nowrin
Keyword(s):  
Turbulent Flow ◽  
Open Channel ◽  
Recirculation Zone ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Flow Recirculation ◽  
Tandem Cylinders ◽  
Flow Development ◽  
The Mean ◽  
Recirculation Length

The flow hydrodynamics around a single cylinder differ significantly from the flow fields around two cylinders in a tandem or side-by-side arrangement. In this study, the experimental results on the mean and turbulence characteristics of flow generated by a pair of cylinders placed in tandem in an open-channel flume are presented. An acoustic Doppler velocimeter (ADV) was used to measure the instantaneous three-dimensional velocity components. This study investigated the effect of cylinder spacing at 3D, 6D, and 9D (center to center) distances on the mean and turbulent flow profiles and the distribution of near-bed shear stress behind the tandem cylinders in the plane of symmetry, where D is the cylinder diameter. The results revealed that the downstream cylinder influenced the flow development between cylinders (i.e., midstream) with 3D, 6D, and 9D spacing. However, the downstream cylinder controlled the flow recirculation length midstream for the 3D distance and showed zero interruption in the 6D and 9D distances. The peak of the turbulent metrics generally occurred near the end of the recirculation zone in all scenarios.

scholarly journals THREE DIMENSIONAL SIMULATION OF OIL FLOW CHARACTERISTICS IN LUBRICATION SYSTEM OF ROTARY TILLAGE ENGINE

2021 ◽  
pp. 163-172
Author(s):  
Junxiang Gao ◽  
Xiaoliang Gao ◽  
Wei Zou
Keyword(s):  
Pressure Drop ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Lubricating Oil ◽  
Flow Index ◽  
Lubrication System ◽  
Pump Rotor ◽  
Oil Pump ◽  
Oil Flow ◽  
Dimensional Simulation

Taking the lubrication system of rotary tillage engine as the research object, this paper makes a three-dimensional simulation study on the oil flow characteristics in the lubricating oil passage. The oil supply of the oil pump shall be greater than the circulating oil required by the lubrication system to ensure the lubrication of the rotary cultivator. Lubrication system is an important part to ensure the reliability and durability of rotary cultivator. The key component to achieve its performance is the oil pump. The geometric model of lubricating oil flow field in rotary tiller lubrication system is established by using FLUENT software. The results show that the pressure drop in the lubricating oil passage of the main bearing is the largest under the same working conditions. In the oil passage of the cylinder head, the pressure drop of the front main oil passage is the largest and the oil discharge is the largest. Add 1.6mm oil pump rotor on the basis of the thickness of the original oil pump rotor, the oil flow at the connecting rod nozzle reaches the flow index of the original rotary cultivator, and there is no cylinder pulling phenomenon of the rotary cultivator.

Experimental study of physical mechanisms in the control of supersonic impinging jets using microjets

2008 ◽  
Vol 613 ◽  
pp. 55-83 ◽  
Author(s):  
FARRUKH S. ALVI ◽  
HUADONG LOU ◽  
CHIANG SHIH ◽  
RAJAN KUMAR
Keyword(s):  
Shear Layer ◽  
Nozzle Exit ◽  
Feedback Loop ◽  
Large Scale ◽  
Impinging Jet ◽  
Impinging Jets ◽  
Operating Conditions ◽  
Jet Flows ◽  
Streamwise Vorticity ◽  
Control Approach

Supersonic impinging jet(s) inherently produce a highly unsteady flow field. The occurrence of such flows leads to many adverse effects for short take-off and vertical landing (STOVL) aircraft such as: a significant increase in the noise level, very high unsteady loads on nearby structures and an appreciable loss in lift during hover. In prior studies, we have demonstrated that arrays of microjets, appropriately placed near the nozzle exit, effectively disrupt the feedback loop inherent in impinging jet flows. In these studies, the effectiveness of the control was found to be strongly dependent on a number of geometric and flow parameters, such as the impingement plane distance, microjet orientation and jet operating conditions. In this paper, the effects of some of these parameters that appear to determine control efficiency are examined and some of the fundamental mechanisms behind this control approach are explored. Through comprehensive two- and three-component velocity (and vorticity) field measurements it has been clearly demonstrated that the activation of microjets leads to a local thickening of the jet shear layer, near the nozzle exit, making it more stable and less receptive to disturbances. Furthermore, microjets generate strong streamwise vorticity in the form of well-organized, counter-rotating vortex pairs. This increase in streamwise vorticity is concomitant with a reduction in the azimuthal vorticity of the primary jet. Based on these results and a simplified analysis of vorticity transport, it is suggested that the generation of these streamwise vortices is mainly a result of the redirection of the azimuthal vorticity by vorticity tilting and stretching mechanisms. The emergence of these longitudinal structures weakens the large-scale axisymmetric structures in the jet shear layer while introducing substantial three-dimensionality into the flow. Together, these factors lead to the attenuation of the feedback loop and a significant reduction of flow unsteadiness.

Large Eddy Simulation of Round Impinging Jets With Large Stand-Off Distance

2014 ◽  
Author(s):  
Mehrdad Shademan ◽  
Vesselina Roussinova ◽  
Ron Barron ◽  
Ram Balachandar
Keyword(s):  
Large Eddy Simulation ◽  
Flow Characteristics ◽  
Impinging Jet ◽  
Impinging Jets ◽  
Vortical Structures ◽  
Nozzle Height ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Mean ◽  
Good Agreement

Large Eddy Simulation (LES) has been carried out to study the flow of a turbulent impinging jet with large nozzle height-to-diameter ratio. The dynamic Smagorinsky model was used to simulate the subgrid-scale stresses. The jet exit Reynolds number is 28,000. The study presents a detailed evaluation of the flow characteristics of an impinging jet with nozzle height of 20 diameters above the plate. Results of the mean normalized centerline velocity and wall shear stress show good agreement with previous experiments. Analysis of the flow field shows that vortical structures generated due to the Kelvin-Helmholtz instabilities in the shear flow close to the nozzle undergo break down or merging when moving towards the plate. Unlike impinging jets with small stand-off distance where the ring-like vortices keep their interconnected shape upon reaching the plate, no sign of interconnection was observed on the plate for this large stand-off distance. A large deflection of the jet axis was observed for this type of impinging jet when compared to the cases with small nozzle height-to-diameter ratios.

Thermal and Fluid Dynamic Analysis on Impinging Jet for Aircraft Anti-Icing

2010 ◽  
Author(s):  
Assunta Andreozzi ◽  
Fabio Lucibello ◽  
Oronzio Manca ◽  
Sergio Nardini ◽  
Mario Roma
Keyword(s):  
Fluid Dynamic ◽  
Three Dimensional ◽  
Impinging Jet ◽  
Impinging Jets ◽  
Wing Surface ◽  
Temperature Fields ◽  
Ice Formation ◽  
Computational Domain ◽  
System A ◽  
Wing Profile

Ice formation on airplane wing profile is a very dangerous condition because of the change in the profile aerodynamic, so it’s necessary to avoid ice formation on the wings. The hardest condition ice formation are at altitudes between 10.000 and 15.000 ft and at temperature between 0° C and −15° C, because they are particularly suitable for ice formation. In this paper an anti-icing system based on hot air impinging jets on internal wing surface is analyzed in order to check the efficiency of the system. A numerical model is given in order to evaluate the thermal and fluid dynamic behaviors of the impinging jet inside the wing panel. A wing profile with an angle of attack of 4.50° is taken into account with a free stream temperature of 258 K. A piccolo tube with a diameter of 1.00 inch and air temperature of 523 K and at variable distance from the wall of the wing profile, is considered for anti-icing system. A structured mesh is used in the discretization of the computational domain for the two-dimensional and three-dimensional case. A steady state solution with k-ε RNG turbulent model has been found. Numerical simulations of a two and a three dimensional model of an aircraft wing has been carried out taking into account the external convective exchange by means of an average coefficient on the external surface and thermo-fluid dynamic field inside the wing due to the anti-icing system. The analysis is performed by means of the FLUENT code in order to find the optimal geometrical configuration to avoid the ice formation on the external wing surface. Results are presented in terms of temperature fields and wall temperature and air velocity profiles along the wing surfaces.

Unsteady Structure and Development of a Row of Impingement Jets, Including Kelvin–Helmholtz Vortex Development

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Li Yang ◽  
Phillip Ligrani ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Static Pressure ◽  
Structural Characteristics ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Axial Direction ◽  
Impinging Jets ◽  
Navier Stokes ◽  
Vortex Generation ◽  
Local Flow ◽  
Layer Parameter

Considered is a cylinder channel with a single row of ten aligned impinging jets, with exit flow in the axial direction at one end of the channel. For the present predictions, an unsteady Reynolds-Averaged Navier–Stokes (RANS) solver is employed for predictions of flow characteristics within and nearby the ten impingement jets, where the jet Reynolds number is 15,000. Spectrum analysis of different flow quantities is also utilized to provide data on associated frequency content. Visualizations of three-dimensional, unsteady flow structural characteristics are also included, including instantaneous distributions of Y-component vorticity, three-dimensional streamlines, shear layer parameter ψ, and local static pressure. Kelvin–Helmholtz vortex development is then related to local, instantaneous variations of these quantities. Of particular importance are the cumulative influences of cross flows, which result in locally increased shear stress magnitudes, enhanced Kelvin–Helmholtz vortex generation instabilities, and increased magnitudes and frequencies of local flow unsteadiness, as subsequent jets are encountered with streamwise development.

Three-dimensional simulation and experimental investigation of three-dimensional printed guiding devices on lattice-apron compact spinning

2020 ◽  
pp. 004051752098258
Author(s):  
Malik YH Saty ◽  
Nicholus Tayari Akankwasa ◽  
Jun Wang
Keyword(s):  
Experimental Investigation ◽  
Air Flow ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Yarn Properties ◽  
3D Printed ◽  
Dimensional Simulation ◽  
Compact Spinning ◽  
Set Up

The compact spinning system with a lattice apron utilizes air-flow dynamics to condense fibers in a bunch and enhance the yarn properties. One of the main challenges with this method is the lack of a comprehensive understanding of the air-flow field's effect in the condensing zone. This work presents a numerical and experimental investigation of the effects of three-dimensional (3D) printed guiding devices on the air-flow characteristics and yarn properties. Firstly, the 3D numerical model of the compact spinning system was set up based on the compact spinning machine geometrical dimensions. Secondly, different 3D prototypes were developed, simulated, and analyzed using computational fluid dynamics based on ANSYS software. The prototypes (A-type, B-type, and C-type), selected according to the simulation results, were then 3D printed to enable further experimental investigation. Air-flow analysis results in the air-suction flume area exhibiting a very high negative pressure, and the centerline zone was characterized by high velocity. Experimental results revealed that the three yarns spun with guiding devices had better strength, hairiness, and evenness than those spun without a guiding device. The model developed can be further improved and utilized for commercial purposes and is anticipated to improve compact spun yarn properties significantly.

Confinement Effects on Flow Dynamics in Swirling Flames

2005 ◽  
Author(s):  
S. Archer ◽  
A. K. Gupta
Keyword(s):  
Gas Turbine ◽  
Recirculation Zone ◽  
Direct Injection ◽  
Model Development ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Flow Dynamics ◽  
Swirl Number ◽  
Outer Flow ◽  
Lean Direct Injection

Three-dimensional (3-D) flowfield data has been obtained using Particle Image Velocimetry (PIV) for varying swirl distributions in the burner. The 3-D data also allows one determine the local swirl number of the resulting flow. Flow characteristics of the resulting flowfield, both without and with combustion, have been examined for the effect of co- and counter-swirl under lean direct injection conditions using unconfined and confined combustor geometry. Experimental results of the effect of swirl and combustion are presented to simulate the flow dynamics of Lean Direct Injection (LDI) configuration gas turbine combustion. The selected configuration is typical because it does not make use a premixing zone and relies totally on the swirl and the injector to accomplish rapid mixing. Specifically, the effect of radial distribution of combustion air and swirl in a burner are examined under non-burning and burning conditions using propane as the fuel. The present study explores single swirler interaction with the use of an experimental double concentric swirl burner that simulates one swirler of a practical gas turbine combustor. Results showed that both swirl and combustion has significant effect on the characteristics of the internal and external recirculation zones. The calculated local swirl number differs significantly form that estimated using geometrical relationship derived from the vane angle only. The effect of combustion for the confined and unconfined geometries was also been found to be different. In the confined geometry combustion decreases the size of the recirculation zone. This is in contrast to that found for the unconfined conditions. Combustion enhances the recirculation zone in the unconfined geometry. Combustion provides greater velocity magnitudes than their counter non-combustion conditions. The counter-swirl combination resulted in smaller and more well defined internal recirculation regions. The results provide the role of swirl and combustion on the mean and turbulence characteristics of flows over a range of swirl and shear conditions between the inner and outer flow of the burner. This data provides important insights on the flow dynamics in addition to providing data for model validation and model development.

Unsteady Structure and Development of a Row of Impingement Jets, Including Shear Layer and Vortex Development: Part 1 — Turbulent Jets

2015 ◽  
Author(s):  
L. Yang ◽  
P. M. Ligrani ◽  
J. Ren ◽  
H. Jiang
Keyword(s):  
Shear Layer ◽  
Structural Characteristics ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Turbulent Jets ◽  
Axial Direction ◽  
Impinging Jets ◽  
Local Flow ◽  
Layer Parameter ◽  
Unsteady Rans

Considered is a cylinder channel with a single row of 10 aligned impinging jets, with exit flow in the axial direction at one end of the channel. For the present predictions, an unsteady RANS solver is employed for predictions of flow characteristics within and nearby the 10 impingement jets, where the jet Reynolds number is 15,000. Spectrum analysis of different flow quantities is also utilized to provide data on associated frequency content. Visualizations of three-dimensional, unsteady flow structural characteristics are also included, including instantaneous distributions of Y-component of vorticity, three-dimensional streamlines, a shear layer parameter, and local static pressure. Kelvin-Helmholtz vortex development is then related to local, instantaneous variations of these quantities. Of particular importance are the cumulative influences of cross flows, which result in locally increased shear stress magnitudes, enhanced Kelvin-Helmholtz vortex generation instabilities, and increased magnitudes and frequencies of local flow unsteadiness, as subsequent jets are encountered with streamwise development.

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