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Investigation of effects of sand particles on aerodynamic performance of NACA 0012 airfoilNACA 0012 kanat profilinin aerodinamik performansı üzerinde toz partiküllerinin etkilerinin incelenmesi
Abstract
The purpose of this paper is to study the effects of turbulence kinetic energy structures formed during flow and particles of different diameters and different flow velocities in the air in different regional areas on aerodynamic performance characteristics in NACA 0012. Single and two phase fluid flows were worked out by using Ansys Fluent Computational Fluid Dynamics (CFD) code. Computational results obtained from Ansys Fluent CFD code for pure air and the air containing sand particles were compared with numerical values gained in the literature for validation. Results obtained from the numerical tests demonstrate good agreement with the value in the literature. These results indicate the turbulence kinetic energy value occurred in the tail region of the airfoil increases with the increase in the angle of attack and shifts towards the upper region of the airfoil at high attack angle. Moreover, the upper region of the airfoil at high attack angle becomes larger at low Reynolds numbers due to viscous effects. The drag and lift coefficients obtained in the numerical tests of the airfoils and in the experimental tests in the wind tunnel will differ from the values in the application area. Because, in the operation of airfoils in different regional environments, there are always particles of various concentrations and diameters in the air. In this case, the drag coefficient increases and the lift coefficient decreases.
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Need of micro aerial vehicles and Unmanned Air Vehicles is increasing due to military, defense and civilian requirements. These vehicles fly at very small Reynolds numbers and have to move in confined spaces with a bare minimum speed, to achieve high lift coefficient is the main concern. The main focus of this research paper is to carry out the computational analysis and study the unsteady flow over NACA0012 airfoil with right angle triangular protrusion at the Reynolds number 105. The location of the protrusion is 0.05c, with three different heights of protrusion 0.005c, 0.01c, and 0.02c, normal to the surface of the airfoil. Geometric modeling and grid generation are created using the ICEM CFD software and numerical analysis carried out using CFD Software at various angle of attacks ranging from 00 to 160 with 20 intervals. Numerical validation has done and compared. The results obtained from the research work is recommend that for smaller protrusions the lift and drag coefficients are unaffected in the low angle of attacks while the lift characteristic is significantly improved at the higher angle of attacks.
A symmetrical NACA 0018 airfoil is often used in such applications as small-to-medium scale vertical-axis wind turbines and aerial vehicles. A review of the literature indicates a large gap in experimental studies of this airfoil at low and moderate Reynolds numbers in the previous century. This gap has limited the potential development of classical turbulence models, which in this range of Reynolds numbers predict the lift coefficients with insufficiently accurate results in comparison to contemporary experimental studies. Therefore, this paper validates the aerodynamic performance of the NACA 0018 airfoil and the characteristics of the laminar separation bubble formed on its suction side using the standard uncalibrated four-equation Transition SST turbulence model and the unsteady Reynolds-averaged Navier-Stokes (URANS) equations. A numerical study was conducted for the chord Reynolds number of 160,000, angles of attack between 0 and 11 degrees, as well as for the free-stream turbulence intensity of 0.05%. The calculated lift and drag coefficients, aerodynamic derivatives, as well as the location and length of the laminar bubble quite well agree with the results of experimental measurements taken from the literature for validation. A sensitivity study of the numerical model was performed in this paper to examine the effects of the time-step size, geometrical parameters and mesh distribution around the airfoil on the simulation results. The airfoil data sets obtained in this work using the Transition SST and the k-ω SST turbulence models were used in the improved double multiple streamtube (IDMS) to calculate aerodynamic blade loads of a vertical-axis wind turbine. The characteristics of the normal component of the aerodynamic blade load obtained by the Transition SST approach are much better suited to the experimental data compared to the k-ω SST turbulence model.
The aim of the work is to investigate the aerodynamic characteristics such as lift coefficient, drag coefficient, pressure distribution over a surface of an airfoil of NACA-4312. A commercial software ANSYS Fluent was used for these numerical simulations to calculate the aerodynamic characteristics of 2-D NACA-4312 airfoil at different angles of attack (α) at fixed Reynolds number (Re), equal to 5 × 10 5. These simulations were solved using two different turbulence models, one was the Standard − model with enhanced wall treatment and other was the SST − model. Numerical results demonstrate that both models can produce similar results with little deviations. It was observed that both lift and drag coefficient increase at higher angles of attack, however lift coefficient starts to reduce at α =13° which is known as stalling condition. Numerical results also show that flow separations start at rare edge when the angle of attack is higher than 13° due to the reduction of lift coefficient.
In the present study, two complex physical phenomena have been completely simulated and discussed in detail to predict the aerodynamic degradation and aeroacoustic mechanism of a NACA 0012 airfoil in both dry and heavy rain conditions. For this purpose, a CFD-based multiphase model was adopted to numerically investigate the process of formation of the water film layer on the airfoil surface by coupling the Lagrangian Discrete Phase Model (DPM) and the Eulerian Volume of Fluid (VOF) models. The Ffowcs Williams–Hawkings (FW–H) method was used to predict the aerodynamic noise of the airfoil in a heavy rain condition. The results showed that there were significant degradations of the airfoil aerodynamic performance because of water film formation especially at lower angles of attack. The maximum value of lift-to-drag ratio degradation was 56% at the angle of attack of 2°. Also, the Sound Pressure Level (SPL) increased due to the rain condition. The SPL was sensitive to the raindrop impact on airfoil surface and caused to increase SPL especially in the frequency region less than 2000 Hz. By increasing the angle of attack, the SPL increased especially in the high-frequency region higher than 2500 Hz in rain condition.
This paper presents an analysis of a Total Energy Control System (TECS) introduced by Lambregts to control unmanned aerial vehicle (UAV) velocity and altitude by using the total energy distribution. Furthermore, an extended Kalman filter (EKF) approach was used to predict aircraft response in terms of angular rates and linear acceleration during a test flight campaign. From both approaches, state equations were obtained to model the aircraft using Matlab-Simulink. From an aerodynamic study, airplane characteristics were obtained in terms of non-dimensional derivatives and compared to those obtained from the experimental methods. It was determined that TECS approach was very accurate; however, disturbance errors could be decreased by adjusting some model parameters. On the other hand, it was difficult to obtain a real estimation from the EKF method due to the presence of turbulence during flight and the relatively low inertia of the scale model. Dynamic characteristics were validated using a low-cost inertial sensor that cab be easily integrated in UAV platforms. The gathered data can be used to predict model characteristics by integrating the information into flight simulators for future design development.
Rainfall has been considered as an important meteorological factor to threat aircraft flight safety. Adverse effects of rainfall on aircraft aerodynamics have been a constantly hot subject in meteorological aviation community for decades. This paper presents a systematic and comprehensive overview of the effects of rainfall on aircraft aerodynamics. The overview includes an introduction of rain-induced aviation accidents, a list of the hazards of rainfall to aircraft, the natural characteristics of rain, the existing rain research techniques, some aerodynamic considerations for rainfall simulation and the current state-of-the-art research achievements in the field of effects of rainfall on aircraft aerodynamics. Raindrop impingement, splashback and flow of the formed water film upon lifting surfaces effectively degrade aircraft aerodynamic performance, leading to severe aviation accidents. The previous lessons learned should be disseminated and accepted by later generations to avoid aviation accidents due to flight in heavy rain.
Airfoil performance degradation in heavy rain has attracted many aeronautical researchers’ eyes. In this work, a two-way momentum coupled Eulerian-Lagrangian approach is developed to study the aerodynamic performance of a NACA 0012 airfoil in heavy rain environment. Scaling laws are implemented for raindrop particles. A random walk dispersion approach is adopted to simulate raindrop dispersion due to turbulence in the airflow. Raindrop impacts, splashback and formed water film are modeled with the use of a thin liquid film model. The steady-state incompressible air flow field and the raindrop trajectory are calculated alternately through a curvilinear body-fitted grid surrounding the airfoil by incorporating an interphase momentum coupling term. Our simulation results of aerodynamic force coefficients agree well with the experimental results and show significant aerodynamic penalties at low angles of attack for the airfoil in heavy rain. An about 3ｏ rain-induced increase in stall angle of attack is predicted. The loss of boundary momentum by raindrop splashback and the effective roughening of the airfoil surface due to an uneven water film are testified to account for the degradation of airfoil aerodynamic efficiency in heavy rain environment.
Unsteady boundary-layer separation from an Eppler 387 airfoil at low Reynolds number is studied numerically. Through a series of computations, the effects of Reynolds number and angle of attack are investigated. For all cases, vortex shedding is observed from the separated shear layer. From linear stability analysis, a Kelvin-Helmholtz instability is identified as causing shear layer unsteadiness. The low-turbulence wind-tunnel tests of the Eppler 387 airfoil are used to compare with the time-averaged results of the present unsteady computations. The favorable comparison between computational and experimental results strongly suggests that the unsteady large-scale structure controls the low-Reynolds-number separation bubble reattachment with small-scale turbulence playing a secondary role.
Significant momentum loss was found to occur at moderate and higher torrential rainfall rates. The weight of a water film on transport category aircraft was found to be only a small fraction of landing weight. Roughness of an airfoil in rain is caused by drop cratering and waviness to a thin film on the airfoil and fuselage. Both sources of roughness were found to separately produce drag increases of from 5 to 10% for a 100-mm/h rain increasing to 15 to 25% for a 2000-mm/h rain. In addition, lift decreases of 10% for a 100-mm/h rain to more than 30% for a 2000-mm/h rain were estimated.
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