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 Aerodynamic assessment of axisymmetric launchers in the context of multidisciplinary optimisation

2020 ◽  
Vol 12 (1) ◽  
pp. 135-144 ◽  
Author(s):  
Alexandru-Iulian ONEL ◽  
Teodor-Viorel CHELARU
Keyword(s):  
Mathematical Model ◽  
Mach Number ◽  
Aerodynamic Force ◽  
Angle Of Attack ◽  
Force Coefficients ◽  
Optimisation Algorithm

The paper presents a fast mathematical model that can be used to quickly assess the aerodynamic force coefficients of axisymmetric launchers as functions of Mach number and angle of attack. The tool developed based on the proposed mathematical model can be used separately or it can be integrated in a multidisciplinary optimisation algorithm for a preliminary small launcher design.

scholarly journals Analisis Airfoil Double-Slot Flap LS(01)-0417 MOD Dengan Airfoil Tanpa Flap Nasa SC(2) 0610

2018 ◽  
Vol 11 (2) ◽  
pp. 49
Author(s):  
Gaguk Jatisukamto ◽  
Mirna Sari
Keyword(s):  
Computational Fluid Dynamic ◽  
Static Pressure ◽  
Fluid Dynamic ◽  
Dynamic Pressure ◽  
Lift Coefficient ◽  
Pressure Coefficient ◽  
Angle Of Attack ◽  
Airflow Velocity ◽  
The Difference ◽  
The Stability

Kestabilan pesawat terbang ditentukan oleh desain airfoil sayap dan ekor. Perbedaan kecepatan aliran udara antara permukaan atas dan bawah airfoil menghasilkan perbedaan tekanan sehingga akan memberikan gaya angkat (lift) pada sayap. Perbedaan tekanan udara pada permukaan sayap dinyatakan dengan pressure coefficient (Cp), yaitu perbedaan tekanan statik lokal dengan tekanan statik aliran bebas. Koefisien lift (Cl) adalah rasio antara gaya angkat (lift) dengan tekanan dinamis. Peningkatan angka CL sebesar 20,4% pada riset sebelumnya diperoleh berdasarkan simulasi penambahan flap. Tujuan penelitian ini adalah membandingkan hasil simulasi airfoil double slot flap LS(01)-0417 MOD  dengan airfoil NASA SC(2) 0610 yang tanpa flap dan mencari korelasi antara sudut serang (?) dengan koefisien lift (Cl ).Metodologi penelitian dilakukan dengan simulasi Computational Fluid Dynamic (CFD). Hasil penelitian dapat disimpulkan bahwa koefisien lift CL untuk airfoil double slot flap LS(01)-0417 MOD menghasilkan CL = 1,498 sedangkan dengan sudut serang ? = 16o sedangkan airfoil NASA SC(2) 0610 tanpa flap memiliki nilai CL = 1,095 dengan sudut serang 13o. The stability of the aircraft is ordered by the airfoil design of the wings and the tail. The difference in flow velocity between the surface and the bottom of the airfoil will produce styles that will present lift  on the wings. The difference in airflow velocity between the top and bottom surfaces of the airfoil produces a pressure difference so it will provide lift (lift) on the wing. The lift coefficient (CL) is the ratio between lift with dynamic pressure. The difference of air pressure on the wing surface is expressed by pressure coefficient (Cp), the difference of local static pressure with free flow static pressure. The lift coefficient (Cl) is the ratio of lift to dynamic pressure. An increase in CL value of 20.4% in previous research was obtained based on the simulation of flap addition. The purpose of this research is comparison between airfoil double slot flap LS (01)-0417 MOD with airfoil NASA SC (2) 0610 without flap and search between angle of attack (?) with coefficient of lift (Cl). Method research is done by Computational Fluid Dynamic (CFD). The result of this research can be concluded that lift coefficient CL for double slot airfoil flap LS (01)-0417 MOD yield CL = 1,498 while with angle of attack ? = 16o while airfoil NASA SC (2) 0610 without flap have value CL = 1,095 with angle of attack 13o

scholarly journals Disturbed transatmospheric motion of the first stage of an aerospace system

2020 ◽  
Vol 19 (3) ◽  
pp. 18-30
Author(s):  
M. M. Krikunov
Keyword(s):  
Optimal Control ◽  
Comparative Analysis ◽  
Reference Values ◽  
Aerodynamic Force ◽  
Angle Of Attack ◽  
Atmospheric Density ◽  
Optimal Angle ◽  
Force Coefficients ◽  
Control Programs

The paper deals with disturbed transatmospheric motion of the first stage of an aerospace system. Deviations of atmospheric density and deviations of aerodynamic force coefficients from reference values are taken as disturbances. Optimal angle-of-attack schedules for the first stage are specified. Comparative analysis of optimal control programs for disturbed and undisturbed motion is carried out.

Thermal and structural response of aerospike mounted on blunt-nose body

2020 ◽  
pp. 095441002097648
Author(s):  
Zhang ZhunHyok ◽  
Won CholJin ◽  
Ri CholUk ◽  
Kim CholJin ◽  
Kim RyongSop
Keyword(s):  
Aerodynamic Force ◽  
Coupling Effect ◽  
Angle Of Attack ◽  
Structural Response ◽  
Response Characteristic ◽  
Wave Drag ◽  
Hypersonic Vehicle ◽  
Loosely Coupled ◽  
Calculation Results ◽  
Blunt Nose

The inclusion of aerospike on blunt nose body of hypersonic vehicle has been considered to be the simplest and most efficient technique for a concurrent reduction of both aeroheating and wave drag due to hypersonic speed. However, the thermal and mechanical behavior of aerospike structure under the coupling effect of aerodynamic force and aeroheating remains unclear. In this study, the thermal and structural response of aerospike mounted on the blunt nose body of hypersonic vehicle was numerically simulated by applying 3 D fluid-thermal-structural coupling method based on loosely-coupled strategy. In the simulation, the angle-of-attack and the spike’s length and diameter are differently set as α = 0°–10°, L/D = 1–2 and d/D = 0.05–0.15, respectively. Through the parametric study, the following results were obtained. Firstly, the increase of vehicle’s angle-of-attack and spike’s length unfavorably affect the thermal and structural response of aerospike. Secondly, the increase of spike’s diameter can improve its structural response characteristic. Finally, the aerospike with the angle-of-attack of 0° and the length and diameter of L/D = 1 and d/D = 0.15, respectively, is preferred in consideration of the effect of flight angle-of-attack and spike’s geometrical structure on the thermal and structural response of spike and the drag reduction of vehicle. The numerical calculation results provide a technical support for the safe design of aerospike.

scholarly journals Numerical simulation of flapping airfoil with alula

2020 ◽  
Vol 12 ◽  
pp. 175682932097798
Author(s):  
Han Bao ◽  
Wenqing Yang ◽  
Dongfu Ma ◽  
Wenping Song ◽  
Bifeng Song
Keyword(s):  
Aerodynamic Force ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Aerodynamic Performance ◽  
Geometric Parameters ◽  
Flight Performance ◽  
Relative Angle ◽  
Vertical Distance ◽  
Unsteady Effect ◽  
Flapping Airfoil

Bionic micro aerial vehicles have become popular because of their high thrust efficiency and deceptive appearances. Leading edge or trailing edge devices (such as slots or flaps) are often used to improve the flight performance. Birds in nature also have leading-edge devices, known as the alula that can improve their flight performance at large angles of attack. In the present study, the aerodynamic performance of a flapping airfoil with alula is numerically simulated to illustrate the effects of different alula geometric parameters. Different alula relative angles of attack β (the angle between the chord line of the alula and that of the main airfoil) and vertical distances h between the alula and the main airfoil are simulated at pre-stall and post-stall conditions. Results show that at pre-stall condition, the lift increases with the relative angle of attack and the vertical distance, but the aerodynamic performance is degraded in the presence of alula compared with no alula, whereas at post-stall condition, the alula greatly enhances the lift. However, there seems to be an optimal relative angle of attack for the maximum lift enhancement at a fixed vertical distance considering the unsteady effect, which may indicate birds can adjust the alula twisting at different spanwise positions to achieve the best flight performance. Different alula geometric parameters may affect the aerodynamic force by modifying the pressure distribution along the airfoil. The results are instructive for design of flapping-wing bionic unmanned air vehicles.

The Effects of Upstream Flexible Barrier on the Debris Flow Entrainment and Impact Dynamics on a Terminal Barrier

2021 ◽  
Author(s):  
Hervé Vicari ◽  
C.W.W. Ng ◽  
Steinar Nordal ◽  
Vikas Thakur ◽  
W.A. Roanga K. De Silva ◽  
...  
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Impact Force ◽  
Dynamic Pressure ◽  
Pressure Coefficient ◽  
Flexible Barrier ◽  
Impact Forces ◽  
Flexible Barriers ◽  
The Impact ◽  
Bed Entrainment

The destructive nature of debris flows is mainly caused by flow bulking from entrainment of an erodible channel bed. To arrest these flows, multiple flexible barriers are commonly installed along the predicted flow path. Despite the importance of an erodible bed, its effects are generally ignored when designing barriers. In this study, three unique experiments were carried out in a 28 m-long flume to investigate the impact of a debris flow on both single and dual flexible barriers installed in a channel with a 6 m-long erodible soil bed. Initial debris volumes of 2.5 m<sup>3</sup> and 6 m<sup>3</sup> were modelled. For the test setting adopted, a small upstream flexible barrier before the erodible bed separates the flow into several surges via overflow. The smaller surges reduce bed entrainment by 70% and impact force on the terminal barrier by 94% compared to the case without an upstream flexible barrier. However, debris overflowing the deformed flexible upstream barrier induces a centrifugal force that results in a dynamic pressure coefficient that is up to 2.2 times higher than those recommended in guidelines. This suggests that although compact upstream flexible barriers can be effective for controlling bed entrainment, they should be carefully designed to withstand higher impact forces.

scholarly journals 2D Numerical Simulation Study of Airfoil Performance

2021 ◽  
Author(s):  
Nasser Shelil
Keyword(s):  
Experimental Data ◽  
Wind Tunnel ◽  
Air Temperature ◽  
Wind Turbines ◽  
Aerodynamic Force ◽  
Angle Of Attack ◽  
Turbulence Models ◽  
Aerodynamic Characteristics ◽  
Operating Conditions ◽  
Ansys Fluent

Abstract. The aerodynamic characteristics of DTU-LN221 airfoil is studied. ANSYS Fluent is used to simulate the airfoil performance with seven different turbulence models. The simulation results for the airfoil with different turbulence models are compared with the wind tunnel experimental data performed under the same operating conditions. It is found that there is a good agreement between the computational fluid dynamics (CFD) predicted aerodynamic force coefficients with wind tunnel experimental data especially with angle of attack between −5° to 10°. RSM is chosen to investigate the flow field structure and the surface pressure coefficients under different angle of attack between −5° to 10°. Also the effect of changing air temperature, velocity and turbulence intensity on lift and drag coefficients/forces are examined. The results show that it is recommended to operate the wind turbines airfoil at low air temperature and high velocity to enhance the performance of the wind turbines.

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