scholarly journals Vortex Dynamics Study of the Canard Deflection Angles’ Influence on the Sukhoi Su-30-Like Model to Improve Stall Delays at High AoA

Aerospace ◽  
2019 ◽  
Vol 6 (2) ◽  
pp. 12
Author(s):  
Sutrisno ◽  
Tri Agung Rohmat ◽  
Setyawan Bekti Wibowo ◽  
Sigit Iswahyudi
Keyword(s):  
Vortex Dynamics ◽  
Deflection Angle ◽  
Aircraft Wing ◽  
Vortex Merging ◽  
Computational Fluid Dynamics Cfd ◽  
Essential Function ◽  
Delay Phenomenon ◽  
Strong Vortex ◽  
Very High ◽  
High Angles Of Attack

The maneuverability of the Sukhoi Su-30 at very high angles of attack (AoA) was remarkably appealing. Canard angle, in cooperation with aircraft wing, created a flow pattern whereby, in that position, the fighter still had as much lifting force as possible in order not to stall. The behavior of changing canard angle configuration played an essential role in creating the strong vortex core so that it could delay the stall. The study of vortex dynamics at canard deflection angle gave an essential function in revealing the stall delay phenomenon. In this study, one could analyze the flow patterns and vortex dynamics ability of the Sukhoi Su-30-like model to delay stall due to the influence of canard deflection. The used of water tunnel facilities and computational fluid dynamics (CFD) based on Q-criterion has obtained clear and detailed visualization and aerodynamics data in revealing the phenomenon of vortex dynamics. It was found that between 30° and 40° canard deflection configurations, Sukhoi Su-30-like was able to produce the most robust flow interaction from the canard to the main wing. It was clearly seen that the vortex merging formation above the fighter heads was clearly visible capable of delaying stall until AoA 80°.

Vortex-Induced Vibration and Frequency Lock-In of an Airfoil at High Angles of Attack

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Fanny M. Besem ◽  
Joshua D. Kamrass ◽  
Jeffrey P. Thomas ◽  
Deman Tang ◽  
Robert E. Kielb
Keyword(s):  
Secondary Flows ◽  
Common Source ◽  
Structural Failure ◽  
Vortex Induced Vibration ◽  
Fluid Instability ◽  
Unsteady Force ◽  
Computational Fluid Dynamics Cfd ◽  
Shedding Frequency ◽  
Lock In ◽  
High Angles Of Attack

Vortex-induced vibration is a fluid instability where vortices due to secondary flows exert a periodic unsteady force on the elastic structure. Under certain circumstances, the shedding frequency can lock into the structure natural frequency and lead to limit cycle oscillations. These vibrations may cause material fatigue and are a common source of structural failure. This work uses a frequency domain, harmonic balance (HB) computational fluid dynamics (CFD) code to predict the natural shedding frequency and lock-in region of an airfoil at very high angles of attack. The numerical results are then successfully compared to experimental data from wind tunnel testings.

scholarly journals Analysis of Cyclist’s Drag on the Aero Position Using Numerical Simulations and Analytical Procedures: A Case Study

2020 ◽  
Vol 17 (10) ◽  
pp. 3430 ◽  
Author(s):  
Pedro Forte ◽  
Daniel A. Marinho ◽  
Pantelis T. Nikolaidis ◽  
Beat Knechtle ◽  
Tiago M. Barbosa ◽  
...  
Keyword(s):  
Linear Regression ◽  
Numerical Simulations ◽  
Three Dimensional ◽  
Three Dimensional Model ◽  
Paired Samples ◽  
Computational Fluid Dynamics Cfd ◽  
Analytical Procedures ◽  
Previous Training ◽  
Very High

Background: Resistance acting on a cyclist is a major concern among the cycling fraternity. Most of the testing methods require previous training or expensive equipment and time-consuming set-ups. By contrast, analytical procedures are more affordable and numerical simulations are perfect for manipulating and controlling inputs. The aim of this case study was to compare the drag of a cyclist in the aero position as measured using numerical simulation and analytical procedures. Methods: An elite male cyclist (65 kg in mass and 1.72 m in height) volunteered to take part in this research. The cyclist was wearing his competition gear, helmet and bicycle. A three-dimensional model of the bicycle and cyclist in the aero position was obtained to run the numerical simulations. Computational fluid dynamics (CFD) and a set of analytical procedures were carried out to assess drag, frontal area and drag coefficient, between 1 m/s and 22 m/s, with increments of 1 m/s. The t-test paired samples and linear regression were selected to compare, correlate and assess the methods agreement. Results: No significant differences (t = 2.826; p = 0.275) between CFD and analytical procedures were found. The linear regression showed a very high adjustment for drag (R2 = 0.995; p < 0.001). However, the drag values obtained by the analytical procedures seemed to be overestimated, even though without effect (d = 0.11). Conclusions: These findings suggest that drag might be assessed using both a set of analytical procedures and CFD.

Gas Liquid Vane Separators in High Pressure Applications

2010 ◽  
Author(s):  
Dani Fadda ◽  
David Barker
Keyword(s):  
Separation Efficiency ◽  
Pressure Vessels ◽  
Cfd Modeling ◽  
Test Results ◽  
Capacity Curves ◽  
Liquid Handling ◽  
Wide Range ◽  
Computational Fluid Dynamics Cfd ◽  
Very High ◽  
High Separation

Vane separators are inertial devices used to remove entrained liquids from gas. They are utilized in pressure vessels operating at a wide range of temperatures and pressures. Computational Fluid Dynamics (CFD) modeling and sizing calculations are used to evaluate the loading to a vane separator and determine the maximum overall gas and liquid handling capacity of the pressure vessel. Test results, performed at operating pressures up to 133 bar (1931 psia) using live natural gas illustrate that, when sized correctly based on the vane’s capacity curves and CFD modeling, vane separators continue to have high separation efficiency at very high operating pressures.

CFD Analysis Comparing Steady Flow and Pulsatile Flow Through the Aorta and its Main Branches

2016 ◽  
Author(s):  
John D. Martin
Keyword(s):  
Blood Flow ◽  
Steady Flow ◽  
Pulsatile Flow ◽  
Close Association ◽  
Beating Heart ◽  
Pressure Data ◽  
Heart Model ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Through ◽  
Very High

A computational fluid dynamics (CFD) study has been done comparing pulsatile and non-pulsatile blood flow through the aortic arch and its main branches. The pulsatile flow was to mimic the blood flow due to a beating heart and the non-pulsatile or steady flow was to mimic cardiopulmonary bypass (CPB). The purpose of the study was too narrow in on possible reasons CPB may contribute to the development of atherosclerosis. The main focus of the study was to look at the wall shear stress (WSS) values due to their close association with the development of atherosclerosis. In addition velocity and pressure data were also analyzed. The results of this study showed a stark contrast between the WSS values between the CPB model and the beating heart model. The CPB model did not have any points of oscillating WSS combined with the fact that there were regions of very high and very low constant WSS values in comparison with the beating heart analysis suggests that there may be potential for atherosclerotic development or plaque buildup within the artery. The beating heart model showed a range of WSS values within the aorta that were much lower overall compared with the CPB model.

Analysis of the Thermal-Hydraulic and Mechanical Performance of Intermediate Heat Exchangers Used in Systems With Very High Temperature Nuclear Reactors

2018 ◽  
Author(s):  
Raciel de la Torre Valdés ◽  
Juan Luis Francois Lacouture
Keyword(s):  
High Temperature ◽  
Heat Exchangers ◽  
Mechanical Performance ◽  
Nuclear Reactors ◽  
Optimized Design ◽  
Solid Region ◽  
Computational Fluid Dynamics Cfd ◽  
The One ◽  
Time Of Operation ◽  
Very High

Intermediate heat exchangers are one of the most critical devices in the safety of facilities with very high temperature nuclear reactors. In this application, the printed circuit heat exchanger (PCHE) design has been the one that has shown the greatest advantages in terms of heat transfer, compaction and structural strength. In this work, a thermal-hydraulic and mechanical model of the PCHE was developed using computational fluid dynamics (CFD) techniques and finite element methods, respectively. The CFD model was validated by comparison with experimental data and empirical correlations of Nusselt number and friction factor published by other authors. A methodology was proposed to evaluate the operation of the exchanger based on the analysis of capital and operating costs. As a relevant aspect of this methodology, the relationship between the maximum Von Misses stress in the structure and the time of operation was considered. In the structural calculations it was observed that increasing the temperature gradient between the channels caused by the increase of the mass flows of gases, causes the displacement of the solid region and the maximum stress increase. The Taguchi method was applied to identify the dimensions that have the greatest influence on the operation of the PCHE and to obtain an optimized design of the device.

Vortex Shedding and Frequency Lock in on Stand Still Wind Turbines: A Baseline Experiment

2017 ◽  
Author(s):  
Matthew Lennie ◽  
Alireza Selahi-Moghaddam ◽  
David Holst ◽  
Georgios Pechlivanoglou ◽  
Christian Navid Nayeri ◽  
...  
Keyword(s):  
Strouhal Number ◽  
Wind Turbines ◽  
Rotor Blades ◽  
Power Spectral ◽  
Vortex Induced Vibrations ◽  
Power Spectral Densities ◽  
Shedding Frequency ◽  
Lock In ◽  
Very High ◽  
High Angles Of Attack

During the commissioning and stand-still cycles of wind turbines, the rotor is often stopped or even locked leaving the rotor blades at a standstill. When the blades are at a stand still, angles of attack on the blades can be very high and it is therefore possible that they experience vortex induced vibrations. This experiment and analysis helps to explain the different regimes of flow at very high angles of attack, particularly on moderately twisted and tapered blades. A single blade was tested at two different flow velocities at a range of angles of attack with flow tuft visualisation and hotwire measurements of the wake. Hotwire wake measurements were able to show the gradual inception and ending of certain flow regimes. The power spectral densities of these measurements were normalized in terms of Strouhal number based on the projected chord to show that certain wake features have a relatively constant Strouhal number. The shedding frequency appears then to be relatively independent of chord taper and twist. Vortex generators were tested but were found to have little influence in this case. Gurney flaps were found to modify the wake geometry, stall onset angles and in some cases the shedding frequency.

NASA space transportation architecture study at very high angles of attack

2001 ◽  
Author(s):  
Osama Kandil ◽  
Zhi Yang ◽  
Juan Pelaez ◽  
Dimitri Mavriplis
Keyword(s):  
Very High ◽  
High Angles Of Attack ◽  
Space Transportation

Simulation of Airflow in the Engine Compartment of a Light Aircraft

2013 ◽  
Vol 284-287 ◽  
pp. 930-936
Author(s):  
Hsu Jeng Liu ◽  
Chih Chun Su ◽  
Sheng Liang Huang
Keyword(s):  
Guide Vane ◽  
Prototype Model ◽  
Engine Compartment ◽  
Air Inlet ◽  
Engine Cylinder ◽  
Improvement Method ◽  
Computational Fluid Dynamics Cfd ◽  
Simulation Results ◽  
Very High ◽  
Economic Improvement

This paper applies the software of Computational Fluid Dynamics (CFD)-FLUENT to analyze the flow field in the engine compartment of a light aircraft. The simulation results of the prototype model indicates that the airflow rapidly flows to the back of the engine compartment along the inside cowling after entering the engine compartment, rather than to the engine cylinder which will result in a very high cylinder temperature. Hence, this paper designs the air inlet, air duct, guide vane, and air outlet to improve the airflow in the engine compartment according to the drawbacks of the prototype model. The results show that the air duct and the guide vane help lead the airflow to the cylinder, and the air outlet effectively reduces the pressure in the engine compartment so that the airflow accelerates through the engine compartment, which is considered a feasible and economic improvement method in terms of the production cost.

Design of an Aggressive Flow-Controlled Turbine Duct

2008 ◽  
Author(s):  
Fredrik Wallin ◽  
Lars-Erik Eriksson
Keyword(s):  
Fluid Dynamics ◽  
Boundary Layer ◽  
High Pressure ◽  
Response Surface Methodology ◽  
Design Space ◽  
Vortex Generator ◽  
Vortex Generators ◽  
Computational Fluid Dynamics Cfd ◽  
Very High ◽  
Optimum Flow

Demands on improved efficiency, reduced emissions and noise restrictions result in the need for very high by-pass ratio turbo-fan engines. Large fans and small high-pressure cores require aggressive intermediate transition ducts connecting the low-pressure and high-pressure systems. In the present work the design of an aggressive flow-controlled turbine duct is presented. A number of vortex generators are installed in a turbine duct to control the boundary layer. The objective is to suppress the existing separation and thus minimize overall duct loss. In doing so the turbine duct design space will be extended toward more aggressive configurations. By using response surface methodology, together with design of experiments based on computational fluid dynamics (CFD), an optimum flow control arrangement is determined. A vortex generator model was adopted in order to be able to investigate a large number of different configurations. The vortex generator installation is optimized with respect to vortex generator position, height, length and angle of attack.

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