Ad-Hoc Boundary Conditions for CFD Analyses of Turbomachinery Problems With Strong Flow Gradients at Farfield Boundaries

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
M. Sergio Campobasso ◽  
Mohammad H. Baba-Ahmadi
Keyword(s):  
Flow Field ◽  
Boundary Conditions ◽  
Ad Hoc ◽  
Navier Stokes ◽  
Cfd Analysis ◽  
Computational Fluid Dynamics Cfd ◽  
Space Discretization ◽  
Flow Gradients ◽  
Cfd Analyses ◽  
Better Than

This paper reports on the improvements of flux enforcement and auxiliary state farfield boundary conditions for Euler and Navier–Stokes computational fluid dynamics (CFD) codes. The new conditions are based on 1D characteristic data and also on the introduction in the boundary conditions of certain numerical features of the numerical scheme used for the interior of the domain. In the presence of strong streamwise gradients of the flow field at the farfield boundaries, the new conditions perform significantly better than their conventional counterparts in that they (a) preserve the order of the space-discretization and (b) greatly reduce the error in estimating integral output. A coarse-grid CFD analysis of the compressible flow field in an annular duct for which an analytical solution is available yields a mass flow error of 62% or 2%, depending on whether the best or the worst farfield boundary condition (BC) implementation is used. The presented BC enhancements can be applied to structured, unstructured, cell-centered, and cell-vertex solvers.

Ad-Hoc Boundary Conditions for CFD Analyses of Turbomachinery Problems With Strong Radial Flow Gradients at Farfield Boundaries

2010 ◽  
Author(s):  
M. Sergio Campobasso ◽  
Mohammad H. Baba-Ahmadi ◽  
Grant McLelland
Keyword(s):  
Flow Field ◽  
Boundary Conditions ◽  
Ad Hoc ◽  
Radial Flow ◽  
Navier Stokes ◽  
Cfd Analysis ◽  
Space Discretization ◽  
Flow Gradients ◽  
Cfd Analyses ◽  
Better Than

This paper reports on the improvements of flux enforcement and auxiliary state farfield boundary conditions for Euler and Navier-Stokes Computational Fluid Dynamics codes. The new conditions are based on 1D characteristic data and also on the introduction in the boundary conditions of certain numerical features of the numerical scheme used for the interior of the domain. In the presence of strong radial gradients of the flow field at the farfield boundaries, the new conditions perform significantly better than their conventional counterparts, in that they a) preserve the order of the space-discretization, and b) greatly reduce the error in estimating integral output. A coarse-grid CFD analysis of the compressible flow field in an annular duct for which an analytical solution is available yields a mass flow error of 62% or 2%, depending on whether the best or the worst farfield BC implementation is used. The presented BC enhancements can be applied to structured, unstructured, cell-centered and cell-vertex solvers.

CFD Simulation of Propeller and Tunnel Thruster Performance

2014 ◽  
Author(s):  
Ping Lu ◽  
Sue Wang
Keyword(s):  
Flow Field ◽  
Cfd Simulation ◽  
Open Water ◽  
Ship Hull ◽  
Hydrodynamic Performance ◽  
Navier Stokes ◽  
Computational Domain ◽  
Flow Features ◽  
Computational Fluid Dynamics Cfd ◽  
Drag And Lift

In the present study, the hydrodynamic performance of a typical North Sea dynamic positioning (DP) shuttle tanker consisting of two main propellers, two rudders, and two bow tunnel thrusters is investigated by solving Reynolds-averaged Navier-Stokes (RANS) equations for a viscous flow. The focus of the numerical simulation is on the performance of propellers/rudders and bow tunnel thrusters considering the hydrodynamic interactions between propellers/thrusters, hull and current. The numerical model includes hull, propeller, rudder, bow tunnel thruster and flow field. First, an analysis of a propeller performance in open water is carried out by calculating the coefficient of thrust, torque, and propeller efficiency. Then, rudders are included in the analysis for the assessment of propeller/rudder performance. The pressure distribution on rudders, rudder’s drag and lift coefficients for different angles of attack, and flow field around the rudder are obtained. The interaction effects between propeller, rudder, ship hull, as well as bow tunnel thruster and ship hull are analyzed by adding detailed ship hull geometry in the computational domain. The tunnel thruster efficiency reduction due to current and ventilation is also analyzed. The presence of current leads to significant changes in the flow velocity and distribution of pressure in the tunnel outflow area as well as significant deflection of the propeller jet emitting from the tunnel. A comparison between Computational Fluid Dynamics (CFD) and model test results of flow features near the tunnel area with various current speeds is presented.

scholarly journals Computational Analysis of High Lift Generating Airfoils for Diffuser Augmented Wind Turbines

2019 ◽  
Author(s):  
Anhad Singh Bajaj ◽  
Jayakrishnan Radhakrishnan ◽  
Raahil Nayak
Keyword(s):  
Fluid Dynamics ◽  
Computational Analysis ◽  
Aerodynamic Performance ◽  
Rotor Blades ◽  
Navier Stokes ◽  
Cfd Analysis ◽  
High Lift ◽  
Actuator Disk ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Through

The present study aims to asses the aerodynamic performance of Diffuser Augmented Wind Turbine (DAWT) using high lift generating airfoils in the construction of the shroud/diffuser. The study is a Computational Fluid Dynamics (CFD) analysis which is carried out using Reynolds Averaged Navier-Stokes (RANS) simulations. The flow across the duct and rotor blades, which are modeled as an actuator disk (AD), is analyzed. Various High-Lift generating airfoils and their geometries were taken into consideration and analyzed with additional geometric modifications, such as a flange, to improve flow through the AD and increase the augmentation factor

Influence of Turbulence Modelling on Predicting the Round Jet Flow Field: Technical Note

2019 ◽  
Vol 11 (5) ◽  
Author(s):  
D. Hasen ◽  
S. Elangovan ◽  
M. Sundararaj ◽  
K.M. Parammasivam
Keyword(s):  
Flow Field ◽  
Boundary Conditions ◽  
Flow Regime ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Technical Note ◽  
The Other ◽  
Round Jets ◽  
Mesh Density ◽  
Better Than

In this study, the effects of different turbulence models on the decay characteristics of round jets were studied. The turbulence models considered for the current study is SST, k-ε, k-ω, RNG kε. For the entire turbulence model mesh density and boundary conditions were mentioned same. By comparing the simulated results with the experiments interesting results were obtained. SST predicts the flow better than the other models in this flow regime.

RANS Analyses of Turbofan Nozzles With Internal Wedge Deflectors for Noise Reduction

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
James R. DeBonis
Keyword(s):  
Kinetic Energy ◽  
Flow Field ◽  
Noise Reduction ◽  
Turbulent Kinetic Energy ◽  
Large Scale ◽  
Navier Stokes ◽  
Core Flow ◽  
The Core ◽  
Computational Fluid Dynamics Cfd ◽  
Performance Results

Computational fluid dynamics (CFD) was used to evaluate the flow field and thrust performance of a promising concept for reducing the noise at take-off of dual-stream turbofan nozzles. The concept, offset stream technology, reduces the jet noise observed on the ground by diverting (offsetting) a portion of the fan flow below the core flow, thickening and lengthening this layer between the high-velocity core flow and the ground observers. In this study a wedge placed in the internal fan stream is used as the diverter. Wind, a Reynolds averaged Navier–Stokes (RANS) code, was used to analyze the flow field of the exhaust plume and to calculate nozzle performance. Results showed that the wedge diverts all of the fan flow to the lower side of the nozzle, and the turbulent kinetic energy on the observer side of the nozzle is reduced. This reduction in turbulent kinetic energy should correspond to a reduction in noise. However, because all of the fan flow is diverted, the upper portion of the core flow is exposed to the freestream, and the turbulent kinetic energy on the upper side of the nozzle is increased, creating an unintended noise source. The blockage due to the wedge reduces the fan mass flow proportional to its blockage, and the overall thrust is consequently reduced. The CFD predictions are in very good agreement with experimental flow field data, demonstrating that RANS CFD can accurately predict the velocity and turbulent kinetic energy fields. While this initial design of a large scale wedge nozzle did not meet noise reduction or thrust goals, this study identified areas for improvement and demonstrated that RANS CFD can be used to improve the concept.

CFD Analysis of Gear Windage Losses: Validation and Parametric Aerodynamic Studies

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Matthew J. Hill ◽  
Robert F. Kunz ◽  
Richard B. Medvitz ◽  
Robert F. Handschuh ◽  
Lyle N. Long ◽  
...  
Keyword(s):  
Experimental Data ◽  
Spur Gear ◽  
Mitigation Strategies ◽  
Test Facility ◽  
Cfd Analysis ◽  
Physical Mechanisms ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Method ◽  
Cfd Analyses ◽  
Good Agreement

A computational fluid dynamics (CFD) method has been applied to gear configurations with and without shrouding. The goals of this work have been to validate the numerical and modeling approaches used for these applications and to develop physical understanding of the aerodynamics of gear windage loss. Several spur gear geometries are considered, for which experimental data are available. Various canonical shrouding configurations and free spinning (no shroud) cases are studied. Comparisons are made with experimental data from open literature, and data recently obtained in the NASA Glenn Research Center Gear Windage Test Facility, Cleveland, OH. The results show good agreement with the experiment. The parametric shroud configuration studies carried out in the Glenn experiments and the CFD analyses elucidate the physical mechanisms of windage losses as well as mitigation strategies due to shrouding and newly proposed tooth contour modifications.

CFD Analysis of a 15 Stage Axial Compressor: Part II — Results

2005 ◽  
Author(s):  
T. Belamri ◽  
P. Galpin ◽  
A. Braune ◽  
C. Cornelius
Keyword(s):  
Steady State ◽  
Flow Field ◽  
Transient Flow ◽  
Axial Compressor ◽  
Navier Stokes ◽  
Cfd Analysis ◽  
Pitch Change ◽  
Leakage Flows ◽  
Transient Models ◽  
Good Agreement

The flow field of a 15 stage axial compressor is analyzed using a 3-D Navier-Stokes CFD tool. The compressor under investigation is a prototype engine, first compressor version before optimization of the Siemens V84.3A family. The paper describes steady state and transient flow simulations of the entire 15 stages compressor in one computation (not piece by piece). The simulation includes tip gaps, mass bleeds, hub leakage flows, and ranges from single passage to full 360 degrees analysis. The work is divided into two companion papers. The second paper, “CFD Analysis of a 15 Stage Axial Compressor Part II: Results” describes the application of the methods in Part I to the entire 15 stage compressor (Belamri et al, 2005). The flow in the compressor is modeled first with one blade passage per component (periodicity assumed, an interface pitch change model employed). Steady state and transient models are compared. In a second series of computations, all blade passages in 360 degrees are modeled, (no periodicity or pitch change assumptions required), for portions of the compressor. The various simulation approaches are compared to each other, and to experimental data. Good agreement between predictions and experimental results, both in the details of the flow field and the integral prediction of operating range of the compressor, were found.

scholarly journals Validation and Verification of CFD Prediction of Fluid Flow of a Submerged Vertical Round Jet

2018 ◽  
Vol 3 (2) ◽  
pp. 113-121
Author(s):  
Nurul Hasan ◽  
Ahmed Oliur Rahman ◽  
Md. Shah Alam
Keyword(s):  
Symmetric Domain ◽  
Navier Stokes ◽  
Computational Error ◽  
Navier Stokes Equation ◽  
Validation And Verification ◽  
Fluent Software ◽  
Computational Fluid Dynamics Cfd ◽  
Volume Method ◽  
Grid Independence ◽  
Better Than

This paper presents a step by step verification and validation process of a vertical round submerged jet into a cylindrical bath. Taking advantage of the axi-symmetric domain, Navier-Stokes equation of primary is solved by finite volume method (FVM) using commercial computational fluid dynamics, CFD (Fluent) software. For verification and to minimise the computational error, step by step grid independence tests were performed. For validation, experimental data was produced using laser Doppler velocimetry (LDV). Among the turbulence model,  SST was found to predict the flow behaviour better than k-e-  realization or RSM models. 

scholarly journals Computational Analysis of High Lift Generating Airfoils for Diffuser Augmented Wind Turbines

2020 ◽  
Author(s):  
Aniruddha Deepak Paranjape ◽  
Anhad Singh Bajaj ◽  
Shaheen Thimmaiah Palanganda ◽  
Radha Parikh ◽  
Raahil Nayak ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Cross Section ◽  
Computational Analysis ◽  
Aerodynamic Performance ◽  
Rotor Blades ◽  
Navier Stokes ◽  
Cfd Analysis ◽  
High Lift ◽  
Actuator Disk ◽  
Computational Fluid Dynamics Cfd

Abstract. The present study aims to analyze the basic aerodynamic performance of a Diffuser Augmented Wind Turbine (DAWT) using high lift generating airfoils in the diffuser cross-section that encloses the turbine. The study is a Computational Fluid Dynamics (CFD) analysis of the flow across the rotor blades and through the diffuser, which is carried out using Reynolds Averaged Navier-Stokes (RANS) simulations. The rotor blades are modeled as a porous Actuator Disk (AD). Various high-lift generating airfoils are used in the diffuser geometries with additional geometric modifications, such as a flange, are taken into consideration and analyzed for the velocity of the flow at the actuator disk to determine the overall aerodynamic performance of the diffuser shape.

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