Some aspects of the flow in S-shaped diffusing ducts

1994 ◽  
Vol 98 (978) ◽  
pp. 305-310 ◽  
Author(s):  
S. C. M. Yu ◽  
E. L. Goldsmith
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Axial Length ◽  
Total Pressure ◽  
Static Pressure ◽  
Flow Distortion ◽  
Cross Sectional ◽  
Group 13 ◽  
Duct Geometry

The circular cross-sectional Royal Aerospace Establishment (RAE) 2129 S-shaped intake diffusing duct series, shown in Fig. 1, which has an offset of the inlet and exit centerline of 0·3 and 0·45 of the axial length of the duct, was designed at the RAE (Bedford) and tested at British Aerospace Filton, at low forward speeds (freestream Mach no. range from 0 – 0·2 but a range of duct inlet Mach numbers up to choking speeds) in the last two decades to fulfil the objectives of collecting systematic experimental data on engine face pressure recovery, total pressure flow distortion and wall static pressures for computational fluid dynamics validation. Some of the measurements have been presented, as for example, by Willmer, Brown & Goldsmith. The measurements from one version of Model 2129 (the 0·3 length offset S-duct geometry) have been used to compare with calculated results from a number of CFD programs, as for example, by Anderson, Horton and by the AGARD Working Group 13. The series of comparison also highlight the need for measurements other than the engine face total pressure and wall static pressure which have already been made.

scholarly journals Modelling of working processes of non-contact oil free vacuum pumps by computational fluid dynamics (CFD) methods

2021 ◽  
Vol 2059 (1) ◽  
pp. 012003
Author(s):  
A Burmistrov ◽  
A Raykov ◽  
S Salikeev ◽  
E Kapustin
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Mathematical Models ◽  
Cfd Models ◽  
Ansys Cfx ◽  
Sst Turbulence Model ◽  
Computational Fluid Dynamics Cfd ◽  
Dynamic Meshing ◽  
Comparison With Experimental Data

Abstract Numerical mathematical models of non-contact oil free scroll, Roots and screw vacuum pumps are developed. Modelling was carried out with the help of software CFD ANSYS-CFX and program TwinMesh for dynamic meshing. Pumping characteristics of non-contact pumps in viscous flow with the help of SST-turbulence model were calculated for varying rotors profiles, clearances, and rotating speeds. Comparison with experimental data verified adequacy of developed CFD models.

Computational Fluid Dynamics Techniques for Flows in Lapple Cyclone Separator

2005 ◽  
Vol 498-499 ◽  
pp. 179-185
Author(s):  
A.F. Lacerda ◽  
Luiz Gustavo Martins Vieira ◽  
A.M. Nascimento ◽  
S.D. Nascimento ◽  
João Jorge Ribeiro Damasceno ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Turbulent Flow ◽  
Reynolds Stress ◽  
Cyclone Separator ◽  
Two Dimensional ◽  
Stress Components ◽  
Computational Fluid Dynamics Cfd

A two-dimensional fluidynamics model for turbulent flow of gas in cyclones is used to evaluate the importance of the anisotropic of the Reynolds stress components. This study presents consisted in to simulate through computational fluid dynamics (CFD) package the operation of the Lapple cyclone. Yields of velocity obtained starting from a model anisotropic of the Reynolds stress are compared with experimental data of the literature, as form of validating the results obtained through the use of the Computational fluid dynamics (Fluent). The experimental data of the axial and swirl velocities validate numeric results obtained by the model.

Computational Fluid Dynamics Modeling of Mixed Convection Flows in Building Enclosures

2013 ◽  
Author(s):  
Alexander Kayne ◽  
Ramesh Agarwal
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Mixed Convection ◽  
Turbulence Model ◽  
Numerical Algorithm ◽  
Navier Stokes ◽  
Cfd Simulations ◽  
Flow And Heat Transfer

In recent years Computational Fluid Dynamics (CFD) simulations are increasingly used to model the air circulation and temperature environment inside the rooms of residential and office buildings to gain insight into the relative energy consumptions of various HVAC systems for cooling/heating for climate control and thermal comfort. This requires accurate simulation of turbulent flow and heat transfer for various types of ventilation systems using the Reynolds-Averaged Navier-Stokes (RANS) equations of fluid dynamics. Large Eddy Simulation (LES) or Direct Numerical Simulation (DNS) of Navier-Stokes equations is computationally intensive and expensive for simulations of this kind. As a result, vast majority of CFD simulations employ RANS equations in conjunction with a turbulence model. In order to assess the modeling requirements (mesh, numerical algorithm, turbulence model etc.) for accurate simulations, it is critical to validate the calculations against the experimental data. For this purpose, we use three well known benchmark validation cases, one for natural convection in 2D closed vertical cavity, second for forced convection in a 2D rectangular cavity and the third for mixed convection in a 2D square cavity. The simulations are performed on a number of meshes of different density using a number of turbulence models. It is found that k-epsilon two-equation turbulence model with a second-order algorithm on a reasonable mesh gives the best results. This information is then used to determine the modeling requirements (mesh, numerical algorithm, turbulence model etc.) for flows in 3D enclosures with different ventilation systems. In particular two cases are considered for which the experimental data is available. These cases are (1) air flow and heat transfer in a naturally ventilated room and (2) airflow and temperature distribution in an atrium. Good agreement with the experimental data and computations of other investigators is obtained.

Detailed Analysis of the Wake Structure of a Straight-Blade H-Darrieus Wind Turbine by Means of Wind Tunnel Experiments and Computational Fluid Dynamics Simulations

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Alessandro Bianchini ◽  
Francesco Balduzzi ◽  
Giovanni Ferrara ◽  
Lorenzo Ferrari ◽  
Giacomo Persico ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Wind Tunnel ◽  
Wind Turbines ◽  
Large Scale ◽  
Vertical Axis ◽  
Performance Estimation ◽  
Small Scale ◽  
Dynamics Simulations

Darrieus vertical axis wind turbines (VAWTs) have been recently identified as the most promising solution for new types of applications, such as small-scale installations in complex terrains or offshore large floating platforms. To improve their efficiencies further and make them competitive with those of conventional horizontal axis wind turbines, a more in depth understanding of the physical phenomena that govern the aerodynamics past a rotating Darrieus turbine is needed. Within this context, computational fluid dynamics (CFD) can play a fundamental role, since it represents the only model able to provide a detailed and comprehensive representation of the flow. Due to the complexity of similar simulations, however, the possibility of having reliable and detailed experimental data to be used as validation test cases is pivotal to tune the numerical tools. In this study, a two-dimensional (2D) unsteady Reynolds-averaged Navier–Stokes (U-RANS) computational model was applied to analyze the wake characteristics on the midplane of a small-size H-shaped Darrieus VAWT. The turbine was tested in a large-scale, open-jet wind tunnel, including both performance and wake measurements. Thanks to the availability of such a unique set of experimental data, systematic comparisons between simulations and experiments were carried out for analyzing the structure of the wake and correlating the main macrostructures of the flow to the local aerodynamic features of the airfoils in cycloidal motion. In general, good agreement on the turbine performance estimation was constantly appreciated.

Three Dimensional Simulation of the Effect of Windcatcher’s Inlet Shape

2019 ◽  
Author(s):  
Peter Abdo ◽  
Rahil Taghipour ◽  
B. P. Huynh
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Indoor Environment ◽  
Natural Ventilation ◽  
Air Flow ◽  
Three Dimensional ◽  
Sectional Area ◽  
Cross Sectional ◽  
Dimensional Simulation ◽  
Convergent Inlet

Abstract Windcatcher has been used over centuries for providing natural ventilation using wind power, it is an effective passive method to provide healthy and comfortable indoor environment. The windcatcher’s function is based on the wind and on the stack effect resulting from temperature differences. Generally, it is difficult for wind to change its direction, and enter a room through usual openings, the windcatcher is designed to overcome such problems since they have vertical columns to help channel wind down to the inside of a building. The efficiency of a windcatcher is maximized by applying special forms of opening and exit. The openings depend on the windcatcher’s location and on its cross sectional area and shape such as square, rectangular, hexagonal or circular. In this study the effect of the inlet design is investigated to achieve better air flow and increase the efficiency of windcatchers. To achieve this, CFD (computational fluid dynamics) tool is used to simulate the air flow in a three dimensional room fitted with a windcatcher based on the different inlet designs. The divergent inlet has captured the highest air flow with a difference of approximately 3% compared to the uniform inlet and 5% difference compared to the bulging-convergent inlet.

Hydrodynamic Analysis of Macroalgae Local Model Using Computational Fluid Dynamics

2020 ◽  
Author(s):  
Ming Chen ◽  
Solomon C. Yim ◽  
Daniel Cox ◽  
Zhaoqing Yang ◽  
Thomas Mumford
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Current Model ◽  
Global Scale ◽  
Local Scale ◽  
Constant Current ◽  
Scale Model ◽  
Effective Diameter ◽  
Hydrodynamic Coefficients

Abstract In this article, a local scale, fully nonlinear coupled fluid-structural interaction (FSI) sugar kelp model has been developed using a computational fluid dynamics (CFD) method. In this model, to be consistent with available experimental data, the sugar kelp is approximated as elongated rectangles with smoothed isosceles triangles at the ends and a single kelp model with one end fixed in a channel with constant current model is developed. Several different current speeds are simulated, and the resulting drag forces and calculated drag coefficients are validated by comparison with experimental data from the literature. In a previous study, a global scale model was developed using a computational structural dynamics (CSD) method to simulate macroalgae farming system and guide the system configuration design. In the global scale model, the hydrodynamic forces are calculated using Morison’s equation and the kinematics and dynamics of the sugar kelp are simplified and the group of kelps attached to the long line is modeled as a slender structure with the same length and an effective diameter such that the volumes are consistent with the real physical system. This simplified model matches the weight and buoyancy but adjusting the hydrodynamic properties when the general hydrodynamic coefficients are employed. Therefore, optimal hydrodynamic coefficients used in global scale model were determined to obtain the hydrodynamic force more accurately. The validated local scale model is then be applied to determine the hydrodynamic coefficients of the simplified sugar kelp model for global dynamic analysis.

scholarly journals Analysis of a Converging, Annular, Isothermal Melt Blowing Jet Using Computational Fluid Dynamics

2005 ◽  
Vol os-14 (3) ◽  
pp. 1558925005os-14
Author(s):  
Eric M. Moore ◽  
Dimitrios V. Papavassiliou ◽  
Robert L. Shambaugh
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Kinetic Energy ◽  
Near Field ◽  
Flow Characteristics ◽  
Sectional Area ◽  
Melt Blowing ◽  
Mean Velocity ◽  
Cross Sectional ◽  
Computational Fluid Dynamics Cfd

An unconventional melt blowing die was analyzed using computational fluid dynamics (CFD). This die has an annular configuration wherein the jet inlet is tapered (the cross-sectional area decreases) as the air approaches the die face. It was found that the flow characteristics of this die are different from conventional slot and annular dies. In particular, for the tapered die the near-field normalized turbulent kinetic energy was found to be lower at shallow die angles. Also, it was found that the peak mean velocity behavior was intermediate between that of conventional annular and slot dies. The centerline turbulence profiles were found to be qualitatively similar to those of annular dies; quantitatively, higher values were present for tapered dies.

scholarly journals Modulating yaw with an unstable rigid body and a course-stabilizing or steering caudal fin in the yellow boxfish ( Ostracion cubicus )

2020 ◽  
Vol 7 (4) ◽  
pp. 200129 ◽  
Author(s):  
Pim G. Boute ◽  
Sam Van Wassenbergh ◽  
Eize J. Stamhuis
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Rigid Body ◽  
Body Shape ◽  
Cross Sectional ◽  
Caudal Fin ◽  
Stabilizing Effect ◽  
Flow Speeds ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations

Despite that boxfishes have a rigid carapace that restricts body undulation, they are highly manoeuvrable and manage to swim with remarkably dynamic stability. Recent research has indicated that the rigid body shape of boxfishes shows an inherently unstable response in its rotations caused by course-disturbing flows. Hence, any net stabilizing effect should come from the fishes' fins. The aim of the current study was to determine the effect of the surface area and orientation of the caudal fin on the yaw torque exerted on the yellow boxfish, Ostracion cubicus , a square cross-sectional shaped species of boxfish. Yaw torques quantified in a flow tank using a physical model with an attachable closed or open caudal fin at different body and tail angles and at different water flow speeds showed that the caudal fin is crucial for controlling yaw. These flow tank results were confirmed by computational fluid dynamics simulations. The caudal fin acts as both a course-stabilizer and rudder for the naturally unstable rigid body with regard to yaw. Boxfishes seem to use the interaction of the unstable body and active changes in the shape and orientation of the caudal fin to modulate manoeuvrability and stability.

Inlet Losses in Counterflow Wet-Cooling Towers

2001 ◽  
Vol 123 (2) ◽  
pp. 460-464 ◽  
Author(s):  
E. de Villiers ◽  
D. G. Kro¨ger
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Numerical Model ◽  
Loss Coefficient ◽  
Cooling Towers ◽  
Empirical Correlations ◽  
Dependent Variables ◽  
Loss Coefficients

The inlet loss coefficients for dry, isotropically packed, circular and rectangular counterflow cooling towers are determined experimentally and empirical correlations are formulated to fit this data. Computational fluid dynamics is used to investigate the dependence of the inlet loss coefficient on the rain zone characteristics. The rain zone generally dampens the inlet loss, but the coupling is indirect and involves a large number of dependent variables. The numerical model is validated by means of experimental data for dry towers and it is found that the degree of accuracy achieved for circular towers exceeds that for rectangular towers. Consequently, the correlation derived to predict this occurrence for circular towers can be applied more confidently than its rectangular counterpart.

Discharge Coefficient for Venturi Flowmeter With Short Laying Length

1982 ◽  
Vol 104 (4) ◽  
pp. 463-467
Author(s):  
Masahiro Inoue
Keyword(s):  
Experimental Data ◽  
Potential Flow ◽  
Total Pressure ◽  
Discharge Coefficient ◽  
Empirical Equation ◽  
Static Pressure ◽  
Computational Technique ◽  
One Dimensional ◽  
Streamline Curvature ◽  
Venturi Flowmeter

This paper presents a method for predicting the discharge coeffcient for a venturi flowmeter with a short laying length where the static pressure is not uniform at the throat due to streamline curvature. The discharge coefficient is determined by combining potential flow calculations and one-dimensional viscous flow considerations. For the potential flow, an accurate computational technique proposed by the author is used to calculate the pressure at the throat tap by assuming that the total pressure is equal to the average one at the throat. The average total pressure is related to the inlet pressure by use of a generalized empirical equation based on one-dimensional considerations. Validity of the method is verified by comparison with published experimental data for short venturi flowmeters.

Sign in / Sign up

Export Citation Format

Share Document