scholarly journals Prediction of Crosswind Separation Velocity for Fan and Nacelle Systems Using Body Force Models: Part 2: Comparison of Crosswind Separation Velocity with and without Detailed Fan Stage Geometry

2019 ◽  
Vol 4 (4) ◽  
pp. 41 ◽  
Author(s):  
Quentin J. Minaker ◽  
Jeffrey J. Defoe
Keyword(s):  
Design Process ◽  
Body Force ◽  
Computational Cost ◽  
External Flow ◽  
Force Model ◽  
Aircraft Engines ◽  
Model Design ◽  
Propulsive Efficiency ◽  
Separation Velocity ◽  
Engine Nacelle

Modern aircraft engines must accommodate inflow distortions entering the engines as a consequence of modifying the size, shape, and placement of the engines and/or nacelle to increase propulsive efficiency and reduce aircraft weight and drag. It is important to be able to predict the interactions between the external flow and the fan early in the design process. This is challenging due to computational cost and limited access to detailed fan/engine geometry. In this, the second part of a two part paper, we apply the fan gas path and body force model design process from Part 1 to the problem of predicting flow separation over an engine nacelle lip caused by crosswind. The inputs to the design process are based on NASA Stage 67. A body force model using the detailed Stage 67 geometry is also used to enable assessment of the accuracy of the design process based approach. In uniform flow, the model produced by the design process recreates the spanwise loading distribution of Rotor 67 with a 7% RMS error. Both models are then employed to predict crosswind separation velocity. The two approaches are found to agree in their prediction of the crosswind separation velocity to within 5%.

scholarly journals Prediction of Crosswind Separation Velocity for Fan and Nacelle Systems Using Body Force Models: Part 1: Fan Body Force Model Generation without Detailed Stage Geometry

2019 ◽  
Vol 4 (4) ◽  
pp. 43 ◽  
Author(s):  
Quentin J. Minaker ◽  
Jeffrey J. Defoe
Keyword(s):  
Design Process ◽  
Body Force ◽  
Pressure Ratio ◽  
Computational Cost ◽  
The Body ◽  
Force Model ◽  
Limited Access ◽  
Turbofan Engines ◽  
Simplifying Assumptions ◽  
Dynamics Simulations

Modern aircraft engines must accommodate inflow distortions entering the engines as a consequence of modifying the size, shape, and placement of the engines and/or nacelle to increase propulsive efficiency and reduce aircraft weight and drag. It is important to be able to predict the interactions between the external flow and the fan early in the design process. This is challenging due to computational cost and limited access to detailed fan/engine geometry. In this, the first part of a two part paper, we present a design process that produces a fan gas path and body force model with performance representative of modern high bypass ratio turbofan engines. The target users are those with limited experience in turbomachinery design or limited access to fan geometry. We employ quasi-1D analysis and a series of simplifying assumptions to produce a gas path and the body force model inputs. Using a body force model of the fan enables steady computational fluid dynamics simulations to capture fan–distortion interaction. The approach is verified for the NASA Stage 67 transonic fan. An example of the design process is also included; the model generated is shown to meet the desired fan stagnation pressure ratio and thrust to within 1%.

The Effect of Blade Count on Body Force Model Performance for Axial Fans

2020 ◽  
Author(s):  
Palak Saini ◽  
Jeff Defoe
Keyword(s):  
Body Force ◽  
Computational Cost ◽  
Model Performance ◽  
Aircraft Engine ◽  
The Body ◽  
Force Model ◽  
Cooling Flows ◽  
Cooling Fans ◽  
Axial Fans ◽  
Spanwise Flow

Abstract Body force models enable inexpensive numerical simulations of turbomachinery. The approach replaces the blades with sources of momentum/energy. Such models capture a “smeared out” version of the blades’ effect on the flow, reducing computational cost. The body force model used in this paper has been widely used in aircraft engine applications. Its implementation for low speed, low solidity (few blades) turbomachines, such as automotive cooling fans, enables predictions of cooling flows and component temperatures without calibrated fan curves. Automotive cooling fans tend to have less than 10 blades, which is approximately 50% of blade counts for modern jet engine fans. The effect this has on the body force model predictions is unknown and the objective of this paper is to quantify how varying blade count affects the accuracy of the predictions for both uniform and non-uniform inflow. The key findings are that reductions in blade metal blockage combined with spanwise flow redistribution drives the body force model to more accurately predict work coefficient as the blade count decreases, and that reducing the number of blades is found to have negligible impacts on upstream influence and distortion transfer in non-uniform inflow until extremely low blade counts (such as 2) are applied.

The Effect of Blade Count on Body Force Model Performance for Axial Fans

2021 ◽  
pp. 1-37
Author(s):  
Palak Saini ◽  
Jeff Defoe
Keyword(s):  
Body Force ◽  
Computational Cost ◽  
Model Performance ◽  
Aircraft Engine ◽  
The Body ◽  
Force Model ◽  
Cooling Flows ◽  
Cooling Fans ◽  
Axial Fans ◽  
Spanwise Flow

Abstract Body force models enable inexpensive numerical simulations of turbomachinery. The approach replaces the blades with sources of momentum/energy. Such models capture a “smeared out” version of the blades' effect on the flow, reducing computational cost. The body force model used in this paper has been widely used in aircraft engine applications. Its implementation for low speed, low solidity (few blades) turbomachines, such as automotive cooling fans, enables predictions of cooling flows and component temperatures without calibrated fan curves. Automotive cooling fans tend to have less than 10 blades, which is approximately 50% of blade counts for modern jet engine fans. The effect this has on the body force model predictions is unknown and the objective of this paper is to quantify how varying blade count affects the accuracy of the predictions for both uniform and non-uniform inflow. The key findings are that reductions in blade metal blockage combined with spanwise flow redistribution drives the body force model to more accurately predict work coefficient as the blade count decreases, and that reducing the number of blades is found to have negligible impacts on upstream influence and distortion transfer in non-uniform inflow until extremely low blade counts (such as 2) are applied.

scholarly journals Streamwise-body-force-model for rapid simulation combining internal and external flow fields

2016 ◽  
Vol 29 (5) ◽  
pp. 1205-1212
Author(s):  
Rong Cui ◽  
Qiushi Li ◽  
Tianyu Pan ◽  
Jian Zhang
Keyword(s):  
Body Force ◽  
Flow Fields ◽  
External Flow ◽  
Force Model

scholarly journals A New Loss Generation Body Force Model for Fan/Compressor Blade Rows: An Artificial-Neural-Network Based Methodology

2021 ◽  
Vol 6 (1) ◽  
pp. 5
Author(s):  
Syamak Pazireh ◽  
Jeffrey J. Defoe
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Body Force ◽  
Computational Cost ◽  
Force Model ◽  
Flow Conditions ◽  
Local Flow ◽  
Blade Section ◽  
Artificial Neural ◽  
Profile Loss

Body force models of fans and compressors are widely employed for predicting performance due to the reduction in computational cost associated with their use, particularly in nonuniform inflows. Such models are generally divided into a portion responsible for flow turning and another for loss generation. Recently, accurate, uncalibrated turning force models have been developed, but accurate loss generation models have typically required calibration against higher fidelity computations (especially when flow separation occurs). In this paper, a blade profile loss model is introduced which requires the trailing edge boundary layer momentum thicknesses. To estimate the momentum thickness for a given blade section, an artificial neural network is trained using over 400,000 combinations of blade section shape and flow conditions. A blade-to-blade flow field solver is used to generate the training data. The model obtained depends only on blade geometry information and the local flow conditions, making its implementation in a typical computational fluid dynamics framework straightforward. We show good agreement in the prediction of profile loss for 2D cascades both on and off design in the defined ranges for the neural network training.

scholarly journals Innovations in Body Force Modeling of Transonic Compressor Blade Rows

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
David J. Hill ◽  
Jeffrey J. Defoe
Keyword(s):  
Total Pressure ◽  
Body Force ◽  
Computational Cost ◽  
Pressure Rise ◽  
The Body ◽  
Force Model ◽  
Axial Fan ◽  
Compressor Blades ◽  
Time Resolved ◽  
Transonic Compressor

Aeroengine fans and compressors increasingly operate subject to inlet distortion in the transonic flow regime. In this paper, innovations to low-order numerical modeling of fans and compressors via volumetric source terms (body forces) are presented. The approach builds upon past work to accommodate any axial fan/compressor geometry and ensures accurate work input and efficiency prediction across a range of flow coefficients. In particular, the efficiency drop-off near choke is captured. The model for a particular blade row is calibrated using data from single-passage bladed computations. Compared to full-wheel unsteady computations which include the fan/compressor blades, the source term model approach can reduce computational cost by at least two orders of magnitude through a combination of reducing grid resolution and, critically, eliminating the need for a time-resolved approach. The approach is applied to NASA stage 67. For uniform flow, at 90% corrected speed and peak-efficiency, the body force model is able to predict the total-to-total pressure rise coefficient of the stage to within 1.43% and the isentropic efficiency to within 0.03%. With a 120∘ sector of reduced inlet total pressure, distortion transfer through the machine is well-captured and the associated efficiency penalty predicted with less than 2.7% error.

scholarly journals A body force model to assess the impact of a swimmer’s arm on propelled swimming resistance

2019 ◽  
pp. 175433711987266 ◽  
Author(s):  
Joseph Banks ◽  
Alexander B Phillips ◽  
Dominic A Hudson ◽  
Stephen R Turnock
Keyword(s):  
Body Force ◽  
Computational Cost ◽  
Navier Stokes ◽  
Resistance Force ◽  
Force Model ◽  
Dynamic Simulations ◽  
Passive Resistance ◽  
Flow Features ◽  
Pressure Resistance ◽  
The Impact

The dynamic forces acting on a swimmer’s body are notoriously difficult to measure experimentally, thus motivating many researchers to use computational fluid dynamics to assess the propulsion and resistance forces. To assess both the thrust generated and the self-propelled resistance, fully dynamic simulations are required, including the large range of body motions involved in swimming. This comes with a heavy computational cost and often limits the ability of the method to resolve detailed flow features associated with resistance force. This article applies a body force approach to propelled swimming simulations by combining an unsteady Reynolds Averaged Navier–Stokes simulation of the passive resistance with momentum source terms which accelerate the fluid in the location of the arm to represent the impact the arm has on the flow. Both passive and active towed swimming experiments were conducted and compared with the simulations. Despite observing a 24% variation in the pressure resistance associated with the arm entry, the arms had no significant effect on the mean propelled resistance of a swimmer. The passive resistance methodology agreed well with experimental data.

scholarly journals Optimization of the Propulsive Efficiency of a Fast Catamaran

2021 ◽  
Vol 9 (5) ◽  
pp. 492
Author(s):  
Yan Xing-Kaeding ◽  
Apostolos Papanikolaou
Keyword(s):  
Body Force ◽  
Parametric Model ◽  
Local Optimization ◽  
Continuous Method ◽  
Numerical Results ◽  
Force Model ◽  
Propulsive Efficiency ◽  
Model Experiments ◽  
Hydrodynamic Calculations

The present study deals with the local optimization of the stern area and of the propulsive efficiency of a battery-driven, fast catamaran vessel. The adopted approach considers a parametric model for the catamaran’s innovative transom stern and a QCM (Quasi-Continuous Method) body-force model for the effect of the fitted propellers. Hydrodynamic calculations were performed by the CFD code FreSCO+, which also enabled a deep analysis of the incurring unique propulsive phenomena. Numerical results of achieved high propulsive efficiency were verified by model experiments at the Hamburgische Schiffbau Versuchsanstalt (HSVA), proving the feasibility of the concept.

scholarly journals Computational Modeling of Vortex Generators for Turbomachinery

2002 ◽  
Author(s):  
R. V. Chima
Keyword(s):  
Computational Models ◽  
Body Force ◽  
Secondary Flows ◽  
The Body ◽  
Vortex Generators ◽  
Force Model ◽  
Suction Surface ◽  
Near Surface ◽  
Compressor Rotor ◽  
Surface Particle

In this work computational models were developed and used to investigate applications of vortex generators (VGs) to turbomachinery. The work was aimed at increasing the efficiency of compressor components designed for the NASA Ultra Efficient Engine Technology (UEET) program. Initial calculations were used to investigate the physical behavior of VGs. A parametric study of the effects of VG height was done using 3-D calculations of isolated VGs. A body force model was developed to simulate the effects of VGs without requiring complicated grids. The model was calibrated using 2-D calculations of the VG vanes and was validated using the 3-D results. Then three applications of VGs to a compressor rotor and stator were investigated: 1. The results of the 3-D calculations were used to simulate the use of small casing VGs used to generate rotor preswirl or counterswirl. Computed performance maps were used to evaluate the effects of VGs. 2. The body force model was used to simulate large partspan splitters on the casing ahead of the stator. Computed loss buckets showed the effects of the VGs. 3. The body force model was also used to investigate the use of tiny VGs on the stator suction surface for controlling secondary flows. Near-surface particle traces and exit loss profiles were used to evaluate the effects of the VGs.

Three body force model for lattice dynamics of copper

1986 ◽  
Vol 57 (8) ◽  
pp. 559-562 ◽  
Author(s):  
H. Nait-Laziz ◽  
K.K. Chopra
Keyword(s):  
Lattice Dynamics ◽  
Body Force ◽  
Force Model ◽  
Three Body
Sign in / Sign up

Export Citation Format

Share Document