سعید کریمیان علی ابادی

This research evaluates two types of vertical axis turbines from both an aerodynamic and economic perspective. The turbines used in this study have straight (H-shaped) and angled (V-shaped) blades, with equivalent dimensional characteristics that are suitable for the climatic conditions and average wind speed distribution in Zahedan city. The aerodynamic evaluation of the turbines was conducted using the semi-analytical DMST method. The results indicate that the V-shaped turbine generates significantly less power than the H-shaped turbine due to the reduction of the effective area of the turbine and the torque produced by its rotor. However, during startup, the V-shaped turbine exhibits about seven times less negative power than the H-shaped turbine, which improves the overall startup process. Economically, the cost of energy production per kWh for a V-shaped turbine is approximately 20% lower than that of an H-shaped one. This makes the V-shaped turbine a more suitable option for urban and small-scale applications.

This review paper examines the aerodynamic simulation methods of helicopter rotor. First, the classification of the researches carried out in the field of helicopter rotor blade geometry and the field related to each one has been briefly explained. In the following, the material used in helicopter rotor blades is evaluated. Then, considering the emergence of computers and their ability to analyze since the 1970s, the important researches conducted from this date until 2023 have been examined. With the conducted investigations, it can be seen that with the change of materials used in making blades from metal to composite, and as a result of better malleability and more freedom of action in making various shapes, there has been an increasing interest in improving blade geometry among helicopter manufacturing companies and researchers. This confirms the need to improve helicopter rotor simulation methods. At first, these methods were used only for the purpose of analyzing and evaluating the performance of rotors, but with the advancement of computers and commercial software, these simulations were moved towards optimization processes.

Airborne wind energy system (AWES) is a novel approach in wind energy harvesting. It has several advantages against conventional horizontal axis wind turbine (HAWT), like using less material and thus lower manufacturing cost, higher efficiency, stable electricity output and higher capacity for energy harvesting. It is obviously embedding a complex control system which makes the appropriate flight trajectory for the vehicle. These systems need to be carefully designed so using virtual flight simulators in design process is crucial. The main components of a typical AWES are: tether, flyer, and rotors. The flyer is designed to have a tether-constrained flight across the wind in a circular path. Consequently, the mounted rotors on the flyer’s wings will capture energy and this mechanical/electrical energy would be sent back to the ground via the same tether. It is notable that the flight path and the special design of the flyer, would make it capable to have a sustained motion in the circular loop with no energy consumption. A tethered drone equipped with several rotors is an example of such devices, already has been built and tested. In previous literature, the flight simulators usually contain some simple aerodynamic models for predicting the forces and moments generated by the rotors. It is derived by constant aerodynamic coefficients. In the current study, it has been developed a flight simulator for a typical AWES having onboard rotors. To make this flight simulator more accurate and to improve its fidelity in different environmental conditions, proper estimation of the external forces, particularly the aerodynamic forces and moments, seems to be necessary. Therefore, toward developing a high-fidelity simulator, Lagrangian dynamics and a new algorithm for estimation of the rotor aerodynamics, has been utilized. This new method is shown to have more accurate approximations of the system performance and also better description of the vehicle trajectory. By this framework, one could design optimized blades of the rotors and also the rotors arrangement. Implementing the new simulator, a single drone, as the flyer in AWES, having 3m wing span, would experience 40 percent improvement in the average power extracted which is near 2 KW.

The use of renewable energy has recently become very common in most countries of today's society. Among these renewable energies, wind energy is one of the most attractive methods of mechanical energy production, and different methods of flow control, including active, semi-active and passive, have been investigated by various researchers. To control the fluid flow in an active way on the wind turbine blade, the corona discharge actuator based on plasma is considered the most appropriate method to reduce the fluid flow separation on the wind turbine blade. In this paper, we present a numerical simulation to integrate active load control using a corona discharge based on plasma actuators over the roughness blade. Effects of roughness, actuators voltage and frequency on aerodynamics parameters such as separation point, lift and drag coefficients have been showed. Present results showed that, the lift coefficient increase with increase in the voltage and frequency of plasma actuators. Overall, using the roughness for outer surface of blade would decrease the critical pressure coefficient by approximately 50% compared to that for the smooth surface.

Today, many countries are trying to reduce their dependence on fossil fuels and acquire the energy they need through renewable energy such as wind energy. On the other hand, the design and analysis of wind turbines is suitable for more energy one of the challenges of engineers. Therefore, in this study, momentum models, which is one of the basic methods in the aerodynamics modeling of the vertical axis wind turbine, are examined. These methods are based on the theory of the momentum (actuator disc) and are widely used to evaluate the performance of vertical axis wind turbines. Also it has been attempted to collect basic fair models for designing and analyzing the performance of these turbines. The following are the three models of the stream tubes: the SST model, the MST model, and the dual actuator MST or the same DMST. Each of these models has the advantages and disadvantages that are fully discussed in this research.

In the current study, the 3D mesh generation and numerical solution of the flow within an INVELOX system, a modern wind energy harvesting structure, was presented. Based on the numerical results, a semi-analytical BEM framework was developed to model the aerodynamics and to estimate the performance characteristics of the system. It is implemented via an offline coupling mechanism. A particular and optimum blade shape was designed to be installed in the venture section of the INVELOX system. It was performed based on the prescribed sections mentioned in the literature. Considering the Prandtl's tip and hub loss factors as well as the Glauert’s and Berton turbulent wake corrections, the behavior of the power coefficient and force coefficients were depicted. A comprehensive study was organized in terms of the tip speed ratio and the normalized length or dimensionless radius. From validation study, it was concluded that both numerical and analytical approaches were in acceptable agreement with the experimental and prior approved data. Based on these results, one may deduce that wind velocity can be magnified by about 70 percent by the Invelox system in the venture section. It is considerably more than the traditional ducts or shrouds used for wind acceleration. In order to make a comparison among the turbulent wake correction formulas, according to the proposed semi-analytical code results, it was found that the Berton and Glauert models would make a maximum difference of 15 percent when the power estimation was expected. By using this proposed hybrid model and related numerical and analytical frames, it is definitely possible to conduct the optimization study considering all the geometric and environmental parameters.

In this research, the internal flow of open-end pressure-swirl atomizer, which has many applications in gas turbine engines and space propulsion, is investigated numerically. A multi-phase fluid volume model is used to simulate the internal flow of the atomizer. Also, due to the nature of the rotational flow inside the atomizer, the RNG k-ε turbulence model was used. Structured mesh has been used to achieve better results. In this research, spray parameters such as liquid film thickness, spray cone angle, discharge coefficient and velocity and pressure distribution contours have been studied. Simulation of an open-end atomizer with an L⁄D = 5 ratio, as well as the use of a structured mesh and the inclusion of kerosene fuel to create conditions close to the operation of a gas turbine, are among the things that differentiate the present study from other studies. The results also show that at a pressure of 0.5 MPa, the time required to reach the fuel in the atomizer used is less than 1.5 milliseconds and the failure of the to spray cone and turn into larger droplets can be observed. The spray angle and discharge coefficient for the studied atomizer were 74.8 and 0.17, respectively.

In previous studies on the INVELOX system, the effect of turbine blades embedded in the venturi section has not accounted. In addition, the design and modeling of an optimal wind turbine in accordance with the geometry and aerodynamic conditions of the venturi section has not been done. Therefore, in this paper, using the BEM (blade element momentum) theory and considering Prandtl's tip and hub loss factors, and also turbulent wake correction, a semi-analytical code has been developed. First of all, an optimal wind turbine according to geometrical and operational assumed INVELOX system is designed. In the continuation, modeling and performance study of geometric parameters of the designed wind turbine has been done. The validation results show that the developed code agrees accurately with the previous experimental, numerical, and analytical results, and therefore the geometry designed for the blades will be reliable. In addition, the application of Glauert and Burton's corrections has been evaluated in this manuscript. Based on the research findings, it is concluded that under the same conditions, Burton's correction yields more conservative results than Glauert's correction. So that assuming 3 blades and a wind speed of 11 meters per second m/s and taking into account Prandtl's tip and hub loss factor, the maximum power coefficient and blade tip speed corresponding to Burton's correction are 0.335 and 7.178, respectively, and corresponding to Glauert's correction, are 0.385 and 7.825, respectively. The provided substrate can be used to optimize the blade shape and structure of the INVELOX wind turbine system.

In this research the aerodynamic performance of a discrete wing capable of morphing, has been studied based on the numerical techniques. In the proposed wing the chord-wise strips have been implemented to resemble a bird wing’s feathers. The morphing mechanism composed of changing the wrist angle which is equal to the partially sweep angle and the wing planform area. Here it is shown that by utilizing this proposed simple mechanism, the MAV/UAV could enhance its aerodynamic performance and also produce control power in the longitudinal and lateral maneuvers. Firstly, the benchmark geometry and a suitable numerical scheme are introduced. The results are then compared and validated against the reference available data. Consequently, the parametric study is performed by selecting the morphing wing tip sweep angle and the angle of attack as the variables and the force coefficients and efficiency as the performance indices. This kind of morphing could make the efficiency increase, up to 13 percent. Flow simulations around the wing are depicted for various morphing angles and for two angles of attack, both in the steady and unsteady manner. The results are also compared and analyzed. Based on the current research, one may continue to estimate the control forces produced by this simple mechanism to expedite the longitudinal and lateral maneuvers in a specified MAV.

In the present work, the numerical investigation of a wind turbine airfoil with suction flow control is initially performed to find the relative improvement in its erodynamic efficiency. Consequently the study of turbine performance is accomplished using 2D simulation results as extending the flow control to wind turbine blades. The latter is incorporated via definition of new input data file in Q-blade code including complete set of section aerodynamic coefficients for both with and without suction control against variety of angles of attack and velocities. The benchmark turbine in this study is NREL 5 MW. It is shown that using suction in 1/3 of chord length would lead in better enhancement. Simulation of the airflow with and without suction control has been presented in three different locations in the chord-wise direction (26%C, 33.5%C and 50%C) and for several intensities or suction speed ratios (0.022, 0.045, 0.11, and 0.155). The turbulence model is transitional 4-equation SST model. The aerodynamic improvement in section is dominant and this method could tolerate stall behavior. Wind turbine power and thrust coefficients were analyzed via Q-blade versus tip speed ratio and flow control parameter. The range of tip speed ratio studied here is 3.5 to 15. The results depicted that applying suction in certain part of the blades could increase output power at low tip speed ratio. Applying suction at 33.5% of chord length improves the average power coefficient by 4.1%.

In this paper performance of vertical-axial wind turbine has been studied based on 5 different flow control techniques. The active methods selected here are suction and blowing and the passive methods are composed of using riblet, cavity and porous media, which the latter one is a new method. The benchmark turbine selected here is Darrieus type and the performance parameter is considered as power coefficient of the turbine. The geometry, location and depth of the actuators are assumed to be approximately equal in different methods aiming the better comparison. Two-dimensional CFD and flow simulation was carried out in Star-ccm+ software. The governing equations are unsteady Navier-Stokes equations and turbulence model is selected k-u{03b5}. The numerical result of the original wind turbine has been validated against experimental data. Then for each control method, numerical solution has been performed and being evaluated. The results show that the power coefficient or efficiency could be improved as much as the control method would reduce the wake region. The results also show that the blowing and suction control methods with about 6% improvement for TSR 1.7 and 2.64 have the better performance among all other methods. Using porous media as a new control method, improves power by about 1% in TSR 1.7. Considering the advantages in noise reduction, this new technique may be further investigated. In this paper also parametric study of each control methods have been performed. The change in power coefficient depends on both TSR and actuator intensity. Based on the numerical simulations it is recommended that a hybrid layout consisting active and passive flow control method applied over turbine blades.

The aim of this research is to redesign and optimize of a rotor blade in small size wind turbine. The objective of such optimization is both running time and power coefficient. The aerodynamic modeling of rotor has been presented based on blade element momentum theory. The output parameters have been calculated subsequently. For validation the model is being compared with NREL phase VI turbine data. The technique of optimization is NSGA-II which is appropriately cope with multi objective problems. Variable are assumed to be pitch or twist angle and chord length and the cost function or performance index is composed of drive time and power. The max tip speed ratio and the bounds of variables are constraints. Based on the Pareto diagram it can be deduced by increasing the power, time would be influenced and degraded. It is recommended 3 points and all the characteristics are being drawn for each one. By choosing the compromise point, it is achievable to enhance the power coefficient by approximately 9 percent and to reduce the time of reaching nominal speed by approximately 10 percent

In this paper, the effects of a floating platform rotational motion on performance of an offshore wind turbine are investigated. For this sake, the unsteady blade element momentum method is used as the aerodynamic modelling tool. The proposed model has been validated based on data available for the reference turbine in the ground or fixed platform. To estimate the pitch angle as the control parameter in the power adjusting system, the PI controller is being utilized. The rotation of floating platform including three main angular motion as pitch, roll and yaw have been studied which are approximated by a sinusoidal function. Results showed that among rotational motions, the effect of pitch motion is more considerable than roll and yaw motions. In case of pitching motion input, reduction of mean power coefficient for tip speed ratios less that 7 is expected. For high tip speed ratios more than a critical TSR, the trend is reverse with respect to fixed-platform case. Magnitude of change in the power coefficient however depends on several parameters which is explained more in the paper. The same but degraded trend also occurs in the case of roll and yaw disturbances. Moreover, the mean value of blade pitch angle which is an index of control effort is being increased.

In this paper, the Semi-Empirical and numerical methods that can be used to investigate the effects of dynamic stall are compared with each other, and the capabilities of the methods are studied. The experimental measurements have been used in order to compare the methods. The Semi-Empirical Leishman-Beddoes (L-B), Snel and ONERA methods have been used, and the finite volume method was being used for numerical simulations. The lift coefficient was being calculated by all the methods at various conditions, and the drag coefficient had been computed by the numerical and Leishman-Beddoes methods. The parameters that have been used in order to compare the methods, are the maximum lift coefficient value, the angle of attack of the largest lift coefficient, the error at upstroke phase and the error at down stroke phase. The results show among the semi-empirical models; the L-B method has the highest precision to predict the lift coefficient, and although the numerical method can investigate the flow with more details, but the error percentage at the down stroke phase is higher than expectations. The results from the drag coefficient modeling show that the numerical method can predict this coefficient better than the L-B method. The results also can help other researchers to select the best dynamic stall model in order to investigate the wind-turbine aerodynamics.

In this paper, the importance of accurate estimation of the aerodynamic performance of delta wing has been mentioned. Some available and conventional methods of estimating the aerodynamic coefficients composed of CFD methods and industrial and commercial software have been selected and for comparison, a wing similar to delta wing mounted on Pegasus Air-launch-to-orbit missile as a template is being selected. The reason for this selection, mainly is the lack of wind tunnel in design process and flying in a wide range of flow regimes. As many parameters may be utilized in design process such as the aerodynamic force and moment coefficients, stability derivatives, heat transfer coefficient and the structural loading parameters are being required. In this study, the accuracy of the results of different methods in estimating the force and moment coefficients, as the most significant quantities for performance analysis, at any flow regime has been checked and the suitable method has been introduced in terms of the flight condition. With respect to available parallel processing system, different CFD methods are compared together. Then validity of solution of Reynolds-averaged equations (RANS) and Euler method have been evaluated based on the comparison by DES solutions. Therefore, the valid intervals of the subsequent methods have been presented. Results are indicating the advantage of computational methods to industrial and semi-empirical software. Semi-empirical code and industrial software are shown satisfactory for computation in the linear range i.e. the small angle of attacks.

A new complete system model of a flapping wing has been derived which consists of all effective parameters. Flapping mechanism can deliver maneuverability as well as low speed flight capability in MAVs. Here a validated aeroelastic model is being developed based on the wing torsional deformation assumption. Based on the proposed model complete parameter study could be performed and consequently the optimization requirements can be extracted. Experimental results of a static test stand have been used for validation. Performance indices، composed of force generated، power consumption and efficiency are depicted in terms of stiffness and kinematic properties. The average behavior is being referred. It is revealed that by changing frequency and speed، the optimum values for stiffness and amplitude are independent. Therefore using suitable kinematics one can utilize specified constant stiffness to optimize the flapping robot flight.