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Passing manoeuvres and crosswind can have significant effects on the stability and fuel consumption of road vehicles. When two vehicles overtake or cross, they mutually influence the flow field around each other, and under certain conditions, can generate sever gust loads that acts as an additional forces on both vehicles. The forces acting on them are a function of the longitudinal and transverse spacings and of the relative velocity between the tow vehicles. In this paper, the models were designed to study the effects of various parameters such as the longitudinal and transverse spacing, the relative velocity and the crosswind on the aerodynamic forces and moments generated on the overtaken and overtaking vehicles using Ansys CFX. The aerodynamic forces have been predicted by a SST model solution of the Navier-Stokes equations for turbulent flow. The numerical predictions for the evaluation of aerodynamic coefficients agree well with the scaled-down air tunnel experimental work.

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In this paper a continuous-time state-space aerodynamic model has been developed based on the boundary element method. First, boundary integral equations for unsteady potential subsonic flow around lifting bodies are presented with emphasis on a modified formulation for thin wings. Next, the BEM discretized problem of unsteady flow around an arbitrary wing is recast in the form of a state-space model using some auxiliary assumptions. To validate the proposed model, its predictions for unsteady aerodynamic coefficients due to various unsteady flows about different wing geometries were compared to the verified results of the direct boundary element solution and good agreement was observed. Because of the resulting aerodynamic model has been constructed in the continuous-time domain, it is particularly useful for optimization and nonlinear analysis purposes. Moreover, its state-space representation is the appropriate form for an aerodynamic model in control applications.

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For mechanized harvesting of crops, sufficient information from the physical, mechanical and aerodynamic properties is required. The aim of this research study is determine some physical, mechanical and aerodynamic properties of the four varieties of olive in Iran named Oily, Yellow, Shenge and Mary. The measured physical properties including dimensions, weight, volume, mean diameters, sphericity factor, porosity and surface area. To determine the mechanical properties of olives, materials testing machine was utilized. The upload speed at pressure test was 8 mm/min. Failures force and energy variables, stresses and toughness variables were obtained from this test. Average failure force in four varieties of olives (Oily, Yellow, Shengeh and Mary) was calculated, 108.01, 121.53, 123.1 and 90.08 N respectively. Average fracture energy at varieties was calculated 0.246, 0.256, 0.304 and 0.204 J respectively. Average stresses and toughness variables were obtained 0.151, 1.578, 1.012, 0.862 MPa and 0.81, 0.072, 0.099, 0.049 MJ/m³ respectively for Oily, Yellow, Shengeh and Mary varieties. The results of mechanical properties showed that the variety of olive has significant effect (level was 0.1) over fracture energy, force and it has not effect on stress. Olive aerodynamic properties were measured using wind tunnels, including the speed and the drag coefficient. The speed limit in four varieties of olives was 22.34, 25.07, 24.03 and 25.6 m/sec respectively. Drag coefficient in the four varieties were calculated 0.61, 0.84, 0.65 and 0.7 respectively. The information obtained from this study was used to design and fabricate of olive harvesting machine.  

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This paper has been presented a new method for optimum design of multi-stage axial flow compressor blades considering overall performance and stage matching. This tool is made up of an optimization algorithm, a flow solver and a parametric geometry generation system. A two-dimensional streamline curvature code has been improved to evalute the compressor performance parameters and flow field. Design parameters consist of geometrical parameters and aerodynamic performance parameters include the minimum loss of blade and allowable range of incidence. The efficiency increment of a 10-stage compressor has been investigated to evaluate the proposed method. The geometry of three front stages of compressor is fixed, the geometry of three middle stages is optimized and four rear stages have been re-staggered. At the first, compressor is optimized by re-designing middle stages and second, it is optimized by re-designing middle stages and re-staggering rear stages. In best case, compressor efficiency has been improved by 1.18 in nominal speed and 1.83 percent in 95% of nominal speed.

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In this research, the aerodynamic design of a radial inflow turbine impeller is carried out using a direct design Method.This new method consists of 2 steps; one dimensional design and three dimensional design. In this design, the blade 3D geometry is obtained with new method. Moreover flow properties in various blade points can be investigated. The advantages this method in comparison with previous other method is less time & cost consuming and more accuracy. At the first step of the aerodynamic design, 1D design is done. This program’s inputs consists of; stagnation temperature, stagnation pressure, mass flow rate and pressure ratio. The goal of 1-d design is to obtain according to optimum experimental data. This procedure based on impeller efficiency convergence. At the second part of this research, by developing a novel design method, the 3D profiles of blade and impellers will be obtained. To validate of one dimensional design results, experimental results and for three dimensional designs, Computational fluid dynamic (CFD) analysis is used. In all this steps, good agreement is observed.

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This work is the result of a research on the lifting forces during upward bird flight via modeling and manufacturing dynamical structures resembling bird wings of sizes between half to about 2 meters. The variables in this work included the wings sizes and their oscillation frequencies. In our formulations the lifting force and the consumed power at the beginning of a bird flight in a fixed frequency is proportional to the fourth and fifth power of the wings sizes, and for fixes sizes is proportional to the second and third power of the frequency, respectively. The lift force here is taken to be of two forms. The first is the very form relevant to the manufactured and used wing systems in the present work. In the second form the wings are assumed to stay horizontal during their vertical periodic motion. The extent of validity of these formulations when practicing for our manufactured wings, and for the real functioning of bird wings as well, has been the most important question in the present research. As far as the lifting force is concerned, the extrapolation of final results seems to be in consistence with the sizes relevant to human “bird-like” flight. However, provision of the needed power necessitates requirements to be thought of deliberately for restoring the energy in an effective way.

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A homogenous 2D plate with simply support boundary conditions is assumed. The effect of plate curvature and nonlinear deformation effects with cylindrical shell model and von Karman’s relation, has been introduced. Linear and Non-linear Frequency analysis with the effect of curvature and in-plane load has been investigated for the first time. Curved plate panel flutter, with the effect of supersonic aerodynamic and in-plane load has been studied for the first time. First and third order piston theory aerodynamic (PTA) is employed to model supersonic aerodynamic loading. Equations of motion have been derived by the use of Hamilton’s principle and resultant nonlinear PDEs have been transformed into nonlinear ODEs via Galerkin’s method. Forth and fifth order rang-kutta numerical method has been used to solve ODEs and define panel behavior. Results show that, structural linear frequencies increase with panel curvature, while, it is more complicated for non-linear frequencies due to the effects of in-plane loads. Fuethermore, 3rd order PTA theory has more critical effect on the instability boundary in comparison with 1st order PTA. The effect of in-plane load in aeroelastic phenomena make limite cycle osilation to chaotic motion for curve plates.

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A homogenous 2D plate with simply support boundary conditions and local imperfection is assumed. The effect of nonlinear deformation with Reddy and marguerre plate model has been introduced. The effect of local imperfection in non-Linear vibration analysis with the effect of thermal and in-plane load has been investigated for the first time. The plate softening and hardening type with the effect of imperfection size is investigated. Flutter boundary of local imperfect plate with the effect of supersonic aerodynamic, thermal and mechanical load has been studied for the first time. First and third order piston theory aerodynamic (PTA) is employed to model supersonic aerodynamic loading. Equations of motion have been derived by the use of Hamilton’s principle and resultant nonlinear PDEs have been transformed into nonlinear ODEs via Galerkin’s method. Forth and fifth order rang-kutta numerical method has been used to solve ODEs and define panel behavior. Results show that, imperfection amplitude increase structural non-linear frequencie, and change plate softening type to hardening. Also, amplitude of plate vibration increase and flutter speed decrease continuously. Plate amplitude oscillation increase for small imperfection and decrease for larger imperfection versus flow speed.

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The scope of the current investigation incorporates the entire process involved in design and development of a Shape Memory Alloy (SMA) actuated wing intended to fulfill morphing missions. At the design step, a two Degree-of-Freedom (DOF) mechanism is designed that is appropriate for morphing wing applications. The mechanism is developed in such a way that it can undergo different two DOF, i.e. gull and sweep, so that the wing can have maneuvers that are more efficient. Smart materials commonly are selected as the actuators due to their suitable thermo-mechanical characteristics. Shape Memory Alloy (SMA) actuators are capable of providing more efficient mechanisms in comparison to the conventional actuators due to their large force/stroke generation, smaller size with high capabilities in limited spaces, and lower weight. As SMA wires have nonlinear hysteresis behavior, their modeling should be implemented in a meticulous way. In this work, after proposing a two DOF morphing wing, an aerodynamic analysis of the whole wing for unmorphed and morphed wings is presented. The results show that the performance of the morphed wing in special flight regimes is improved.

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In the recent years, wind energy had a faster growth compared with the other renewable energies. The interaction between fluid and structure becomes more important as the wind turbine size and its power production capacity increases. In the present research, the effect of wind speed and blade materials on static deformation of a small size horizontal axis wind turbine blade has investigated. The shaft torque and root flap bending moment values obtained from simulation are in a good agreement with experimental data. Results demonstrated that the deformation of the blade increases as the wind speed grows although the increase rate has declined in the mean wind speed range because of the occurrence of separation phenomenon on the blade surface. The effect of blade components materials on blade deformation was investigated and the least deformed configurations were introduced. The thickness of the designated blade components has been investigated by means of the maximum strain theory. The final thickness of the skin, spur and root was estimated by 2.1 mm, 2.8 mm and 10 mm respectively which are 30% less than the primary one.

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A theoretical nonlinear droplet deformation model with an accurate estimation of aerodynamic force, which is appropriate for Lagrangian droplet tracking schemes, is presented and validated. The modeling is based on keeping track only of the fundamental oscillation mode. This conventional approach has been used in many deformation-based breakup models including Taylor Analogy Breakup, Droplet Deformation and Breakup, and Nonlinear Taylor Analogy Breakup. However, these models have some shortcomings such as the use of several calibration coefficient, two-dimensional analysis, and rough approximation of aerodynamic forces in large deformations. This paper is intended to amend these defects. The formulation is based on mechanical energy equation. The pressure distribution profile around the deformed droplet is approximated using a piecewise sinusoidal function which depends on Reynolds number and droplet deformation. The final kinetic equation is numerically solved using a fourth-order Runge-Kutta method and the results are compared with those of other models, experiments, and a Volume of Fluid simulation. Numerical results show that the present model predicts slightly greater deformations in comparison with other models for the unsteady case, which is more consistent with the experimental data. Considering the steady case, the results of present model stand between that of Taylor Analogy Breakup and Nonlinear Taylor Analogy Breakup model, and provide satisfactory predictions. The stream lines obtained from simulation match those of calculated analytically suggesting the appropriateness of the assumptions used in the modeling. Overall, the present model is found to be appropriate for the estimation of droplet deformation.

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The aerodynamic characteristics of nine configurations of supersonic continuous deflectable nose guided missiles have been investigated. Then the optimized geometry is achieved based on the maneuverability from aerodynamic and flight dynamic point of view. The studied configurations consists of a spherical nose tip, a tangent ogive, one set of stabilizing tail fins and a cylindrical body that its mid-section is flexible to form an arc of a circle. So the cylindrical body consists of a fix part in vicinity of nose, middle flexible part and main body with stabilizers. The effects of fix length and flexible length parameters on the aerodynamic and flight dynamics of guided missile have been studied. A code has been developed to solve full Navier-Stokes equations using finite volume and modified Baldwin-Lomax turbulence model. Multi-block technique is also used to solve main body and fin parts flow field. Further, a 3 degree of freedom code has been developed to compare planar flight dynamic of missiles. It is found that missiles with bigger lengths for fix and flexible parts show more aerodynamic maneuverability, but drag force grows concurrently. Flight dynamic analysis shows that drag effect is negligible and aerodynamic maneuverability analysis is compatible with flight maneuverability.

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In this paper, a useful method proposed for aerodynamic design of Megawatt wind turbine's blade based on Blade Element Momentum (BEM) theory‌. In this method first a preliminary design is done based on the ideal BEM and then a method have been offered for geometric modifications to approximate the geometry of the blade to a real and functionally one. The advantage of this method is that needed few design parameters that simplify the design procedure, however its results are in good agreement with 5MW NREL reference wind turbine assumed as validation case and show that with use of this method can achieve a good aerodynamic design. then the twist angle has been optimized using Genetic algorithm and Bezier curve with annual energy production (AEP) as the goal function. At the end, a 2.5 MW wind turbine has been design based on this method with considering the Lootak site specifications in province of Sistan and Baloochestan. Then 3D model of the blade has been made and CFD simulation applied on that for showing the designed turbine operation in real conditions and comparison with BEM method and there is acceptable compatibility between two analytical methods.

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The flight dynamics of nine configurations of supersonic continuous deflectable nose guided missiles have been investigated. The studied configurations consist of a spherical nose tip, a tangent ogive, a set of stabilizing tail fins and a cylindrical body that its mid-section is flexible to form an arc of a circle. So the cylindrical body consists of a fix part in vicinity of nose, middle flexible part and main body with stabilizers. The effects of fix length and flexible length parameters on the flight dynamics of surface to surface, antiaircraft and antimissile missiles have been studied. A code has been developed to solve full Navier-Stokes equations using finite volume and modified Baldwin-Lomax turbulence model. Further, a 3 degree of freedom code has been developed to compare planar flight dynamics of missiles. This code consists of a guidance subroutine based on pure persuit law. The results show that even increase of fixed and flexible lengths enhance the maneuverability of the missile, but in some scenarios this can lead to increased flight time and more errors in the target engagement. Deflected nose relocates mass center away from the axis and a thrust vector torque is created. Study of surface to surface scenario shows that this torque improves accuracy of targeting and the ability of target dislocation. In air defense missiles, increase of Fix and Flex variables, will extend the limits of allowable firing angle. However, a heavy nose increases the role of thrust torque and subsequently decreases the role of nose geometry.

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In this research, a new numerical approach which is capable of modifying the shape of three dimensional massive bodies like tall buildings respect to aerodynamic loads is presented; therefore, the aerodynamic forces are improved; consequently, the comfortability of the buildings is increased. This method is drawn into 2 parts; a numerical simulation of fluid flow and Adjoint method. As a result of it, some modifications are performed in the different parts of the building. In the primarily step, the building shape and its setting position are investigated in different flow conditions as effective parameters on the aerodynamic of buildings. Subsequently, the sensitivity level of each variable is studied on aerodynamic loads. The results illustrate that the building pattern has the highest impressments (76%) on the excited forces. In the next step, the amount of sensitivity of the fluid flow on the various areas of the tower is assessed by solving Adjoint equation in the whole fluid domain. As a result of that, some aerodynamic modifications are performed and it has been proved that the imposed loads on the tower have been declined around 31% whereas this amount of improvement is interested for designing of tall buildings.

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The aerodynamic coefficients characteristics over a lambda-shaped flying wing aircraft with 55°-30° leading edge sweep angles have been investigated in a closed circuit low speed wind tunnel. The experiments were conducted at tunnel velocity of 90 m/s, the angles of attack of -6 to 17 and the side-slip angles of -8 to 8 degrees. All forces and moments were measured using an external six-component force balance located below the wind tunnel. The wall corrections were also performed for all test conditions. To improve the aircraft longitudinal stability characteristics, a new model with an increased leading edge sweep angle of 2 degrees were also tested and compared with the original model. A “pitch-up” phenomenon identified to occur at a rather low angle of attack of α=7.7 degrees, although it occurred at the higher angle of attack of α=8.7 degrees for the increased swept angle model which means an increase in useable lift of the aircraft. Moreover, off-surface pressure measurement over the wing surface was conducted to examine the onset and development of the flow separation over the wing surface. The results showed that the flow separation started at the trailing edge crank location and extended to the other parts of the wing, especially the outer wing.

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One of the mainchallenges existing in the field of missile aerodynamics is how to reduce the aerodynamic drag of aerospace vehicles through different mechanisms. Thus far, many investigations have been performed to determine the performance and influence of various parameters on the effectiveness of these mechanisms. The challenge particularly is more pronounced in missiles with a blunt nose. The aim of this study is to reduce the aerodynamic drag of such missiles using hybrid employment of mounted spike at the stagnation point of the nose in addition to jet injection at different positions on the spike. To this aim, spike and jet injection configurations are extracted from the literature. Jet injection is considered in the sonic regime and perpendicular to the surface of spike. All analyses are performed using Fluent software along with Navier-Stokes equations for compressible and three-dimensional flow in both steady and unsteady states considering free stream at a Mach number of 1.89 and different angles of attach. Since the numerical simulation of these models requires high processing speed and memory, parallel processing system is employed. Additionally, structure grid and κ-ω -SST turbulence models are utilized. Results indicated that a significant drop in the drag is achieved using the hybrid utilization of jet injection and spike.

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Wind turbines are subject to various unsteady aerodynamic effects. This includes the wind gust and the change of wind direction. In this work, the aeroelastic behavior of a reference horizontal axis wind turbine has been investigated under different wind gusts and yaw conditions. Unsteady blade element momentum (UBEM) theory and Euler-Bernoulli beam assumption were used to rotor power estimations. To take into account the time delay in aerodynamic loads due to a sudden change in inflow conditions, a dynamic wake model was implemented. The ONERA dynamic stall model was coupled into the BEM theory to improve the aerodynamic loads prediction in the unsteady inflow and yaw conditions. To verify this method, the results in the case of steady-state are compared with the NREL 5 MW wind turbine and in the unsteady case are compared with the Tjaereborg test turbine. The results indicate that sudden change in wind speed causes sharp fluctuations in terms of elastic torsion of the blade and other parameters such as rotor power. Increasing in wind gradient can leads to increasing time delay to a new equilibrium. The increase in yaw angle can be contributed to the rotor power and the periodic loads reduction. The method presented here may facilitate improvements in the controller design for wind turbines.

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This paper presents a fast and efficient aerodynamic optimization method for megawatt class wind turbines. For this purpose WP_Baseline 1.5 MW wind turbine is used as a test case. Modified particle swarm optimization (PSO) algorithm is used in this study. PSO parameteric studies are conducted, to increase both efficiency and speed of optimization cycle. Since in aerodynamic optimization, it is very desirable to limit the number of the variables, in this study geometric 'class function/shape function' transformation technique (CST) is used for blade geometry parameterization and the appropriate order of shape function polynomial is proposed for S818, S825 and S826 airfoils. Improved Blade Element Momentum (IBEM) theory is implemented for wind turbine power output estimation, validated with experimental and Computational Fluid Dynamic (CFD) data of AOC wind turbine. The aerodynamic data needed for IBEM is provided by XFoil software. XFoil output data for pressure coefficient and wall shear stress which are validated against experimental and CFD data, are applied as the aerodynamic input data for IBEM method.
The twist, the chord and 3 types of airfoil for all sections of the turbine blade are optimized using IBEM method. Optimization is performed with realistic constraints to produce feasible geometry. The performance of the final optimized geometry is simulated via 3D steady incompressible Navier–Stokes equations coupled with Transition SST Model CFD simulation to predict the performance improvement. The results show about 4 percent power enhancement for WP_Baseline wind turbine.

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In this paper, by defining a new paradigm for nonlinear aerodynamic equations of flow separation and static stall, a new form of nonlinear aeroelastic equations for two degrees of freedom airfoils (torsional and bending) are presented. Structural equations are based on the nonlinear mass-spring model; include the nonlinear quadratic and cubic terms. Aerodynamic equations are obtained by combining the unsteady Wagner model and the nonlinear lift coefficient-angle of attack for simulating stall using a cubic approximation. Hamilton’s principle and Lagrange equations were used to derive the aeroelastic equations. The obtained integro-differential nonlinear aeroelastic equations are solved using a new time-history integration method. The aeroelastic behavior of the airfoil is compared in both unsteady and quasi-steady flow. Using the time-history method compared to the phase space method leads to fewer equations. The results show that the aeroelastic behavior of airfoil with a linear structure, using a nonlinear aerodynamic theory for the stall, causes oscillations with a limit cycle in unsteady and quasi-steady flow compared to other linear aerodynamic theories. Also, the use of the cubic curve instead of the piecewise linear curves which is commonly used in other references, although, causes an apparent complication of the equations, reduces the computational time due to faster convergence in solution and makes the reduction in errors. The results show that the use of nonlinear aerodynamic static stall not only reduces the instability velocity, but also reduces the amplitude of limit cycle oscillations in both unsteady and quasi-steady regimes.