scholarly journals A Two-Point Approximation Approach to Determining Aircraft Aerodynamic Force Coefficients for a Maximal-Duration Horizontal Flight

2021 ◽  
Vol 2021 (3) ◽  
pp. 71-80
Author(s):  
Andriy Viktorovich Goncharenko
Keyword(s):  
Aerodynamic Force ◽  
Aviation Fuel ◽  
Fuel Gas ◽  
Approximation Approach ◽  
Force Coefficients ◽  
Numerical Example ◽  
Aircraft Flight ◽  
Point Approximation ◽  
Horizontal Flight ◽  
Optimization Theories

Abstract This paper proposes a two-point approximation approach to determining aircraft aerodynamic force coefficients, and compares it to the traditional methods. A variational concept is used to conduct aircraft flight trials for the maximal duration of quasi-horizontal flights. The advantages of the described optimization theories are demonstrated, in terms of aviation fuel gas savings. The results of a numerical example are presented.

Effects of Ice Thickness on the Aerodynamic Characteristics of Crescent Shape Iced Conductors

2012 ◽  
Vol 166-169 ◽  
pp. 2696-2703 ◽  
Author(s):  
Dong Yan ◽  
Wen Juan Lou ◽  
Ming Feng Huang ◽  
Wei Lin
Keyword(s):  
Lift Force ◽  
Aerodynamic Force ◽  
Wind Tunnel Test ◽  
Aerodynamic Characteristics ◽  
Ice Thickness ◽  
Force Curve ◽  
Force Coefficients ◽  
Variation Patterns ◽  
The Difference ◽  
Force Characteristics

Aerodynamic characteristics of iced conductors were investigated by the wind tunnel test. Under the homogeneous turbulence of 5% intensity, aerodynamic force coefficients of single and bundled conductors were obtained at wind angles of 0°~180°. The variation patterns of aerodynamic forces on the iced conductors with respect to wind angels of attack were systematically studied for the ice thickness of 0.25, 0.5, 0.75 and 1 times of the conductor diameter. The difference of aerodynamic force characteristics for single and bundled conductors were identified and discussed. Based on the Den Hartog and Nigol’s mechanisms of galloping, the wind angle ranges sensitive to galloping were analyzed. The results show that lift and torsion force coefficients reach peak values at wind angles of 15°~20°. For bundled conductors, lift force curve is approximately agreed with the curve of single conductor. Drag force coefficients were smaller than these of single conductor at some wind angles. There are noticeably differences of torsion coefficients existed between bundled conductors and single conductor. According to two classical galloping mechanisms, wind angles of 15°~30°are critical for the galloping of iced conductors with crescent shapes.

scholarly journals Development and Application of Computational Tool Using Local Surface Inclination Methods for Preliminary Analysis of Hypersonic Vehicles

2020 ◽  
Author(s):  
Tiago Cavalcanti Rolim ◽  
Sheila Cristina Cintra ◽  
Marcela Marques da Cruz Pellegrini
Keyword(s):  
Preliminary Analysis ◽  
Aerodynamic Force ◽  
Dynamic Pressure ◽  
Pressure Coefficient ◽  
Angle Of Attack ◽  
Hypersonic Vehicles ◽  
Computational Tool ◽  
Local Surface ◽  
Force Coefficients ◽  
Surface Inclination

This work presents a computational tool for preliminary analysis of hypersonic vehicles, based on local surface inclination methods: the HipeX. This program was developed for reading standard triangulation language (STL) geometry files and calculating pressure coefficient and temperature distributions over vehicle’s surface using the Newtonian, modified Newtonian or tangent-wedge methods. Validations were made with a cylinder and a sphere, where only the Newtonian method was applied, and with experimental data from Apollo capsule at Mach 10, where the Newtonian and the modified Newtonian methods were applied. These validations presented the code capability to read geometries as well as to estimate aerodynamic force coefficients. A preliminary application was to predict the aerodynamic force coefficients of a generic hypersonic vehicle over constant dynamic pressure trajectories of 23,940, 60,000 and 95,760 N/m2 with zero angle of attack. With a fixed dynamic pressure of 60,000 N/m2, this vehicle was tested over several Mach numbers and with angle of attack variation from -10 to 10 deg. Zero angle of attack investigation showed minor changes on the force coefficients with altitude, while the variation of angle of attack produced more pronounced variations on these parameters. Maximum flow temperatures over vehicle’s surface were estimated ranging from 850 to 5,315 K.

scholarly journals Experimental Investigation on Glaze Ice Accretion and Its Influence on Aerodynamic Characteristics of Pipeline Suspension Bridges

2020 ◽  
Vol 10 (20) ◽  
pp. 7167 ◽  
Author(s):  
Haiyan Yu ◽  
Fuyou Xu ◽  
Mingjie Zhang ◽  
Aoqiu Zhou
Keyword(s):  
Inclination Angle ◽  
Aerodynamic Force ◽  
Aerodynamic Characteristics ◽  
Climatic Conditions ◽  
Suspension Bridges ◽  
Ice Accretion ◽  
Atmospheric Conditions ◽  
Force Coefficients ◽  
Size And Shape ◽  
Ice Accretions

Pipeline suspension bridges may experience ice accretion under special atmospheric conditions, and the aerodynamic characteristics of the bridges may be modified by the ice accretion. Under some specific climatic conditions of freezing rain, the dependencies of the ice size and shape on the icing duration and some structural properties (including pipeline diameter, inclination angle of wind hanger, inclination angle and size of section steel, and girder geometry) were experimentally investigated in a refrigerated precipitation icing laboratory. Typical ice accretions on pipelines, wind hangers, section steels, and girders of pipeline suspension bridges are summarized. Then the effects of some selected ice accretions on aerodynamic force coefficients of a bridge girder were further investigated through wind tunnel tests. The ice size and shape on the pipeline were closely related to the pipeline diameter and icing duration. The engineering geometric models of ice accretion on pipelines were extracted. The ice shape and size on wind hangers and section steels changed with their inclination angles. The aerodynamic force coefficients of a girder with ice accretion were much higher than those of an ice-free one. The results can provide references for simulating the ice accretion and further evaluating the effect of ice accretion on the aerodynamics of pipeline suspension bridges.

Deep Learning Techniques for Effective Prediction of Aerodynamic Properties of Elliptical Bluff Bodies

2021 ◽  
Author(s):  
W. M. U. Weerasekara ◽  
H. M. C. D. B. Gunarathna ◽  
W. A. K. P. Wanigasooriya ◽  
T. P. Miyanawala
Keyword(s):  
Neural Network ◽  
Reynolds Number ◽  
Deep Learning ◽  
Aerodynamic Force ◽  
Flow Behavior ◽  
Reynolds Numbers ◽  
Bluff Bodies ◽  
Flow Conditions ◽  
Force Coefficients ◽  
Drag And Lift

Abstract Predicting aerodynamic forces on bluff bodies remains to be a challenging task due to the unpredictable flow behavior, specifically at higher Reynolds numbers. Experimental approaches to determine aerodynamic coefficients could be costly and time consuming. In the meantime, use of numerical techniques could also require a considerable computational cost and time depending on complexity of the flow behavior. The research focusses on developing an effective deep learning technique to predict aerodynamic force coefficients acting on elliptical bluff bodies for a given aspect ratio and given flow condition. Collecting data for drag and lift coefficients of several aspect ratios for flow conditions starting from onset of vortex shredding to verge of subcritical region is conducted by an accurate full order model. The specified region will provide a transient flow behavior and thus lift coefficient will be represented in terms of root mean square value and drag coefficient in terms of a mean value. With variations in flow behavior and vortex shredding frequencies, it requires to select an appropriate turbulence model, optimum discretization of fluid domain and time step to obtain an accurate result. Flow simulations are conducted primarily using Unsteady Reynolds Averaged Navier-Stokes Equations (URANS) model and Detached Eddy Simulations (DES) model. Effectiveness in using different turbulence models for specified flow regimes are also explored in comparison to available experimental results. At lower Reynolds numbers, aerodynamic force coefficients for a specified body will only depend on Reynolds number. But after a certain specific Reynolds number, aerodynamic forces are dependent on the Mach number in addition to Reynolds number. Therefore, for higher Reynolds numbers, aerodynamic force coefficients are recorded for multiple Mach numbers with same Reynolds number and will be fed to the neural network. With the development of the machine learning and neural network modelling, many of the fields have nourished and created effective and efficient technologies to ease complex functions and activities. Our goal is to ease the complexity in the computational fluid dynamic field with a deep neural network tool created to predict drag and lift coefficient of elliptical bluff bodies for a given aspect ratio with an acceptable accuracy level. Researchers have developed deep neural network tools to predict various flow conditions and have succeeded with sufficient accuracy and a satisfying reduction of computational cost. In our proposed deep learning neural network, we have chosen to model the network with inputs as the geometry setup and the flow conditions with validated drag and lift coefficients. The model will extract the necessary flow features into filters with the convolution operation performed on the inputs. Our main directive is to create a deep learned neural network tool to predict the target values within an acceptable range of accuracy while minimizing the computation cost.

Sign in / Sign up

Export Citation Format

Share Document