Numerical Studies on the Effect of Design Trim on Aerodynamic Performance of a Micro Propeller for MAV Application

2013 ◽  
Author(s):  
Sagar Ranjanagi ◽  
Quamber H. Nagpurwala ◽  
S. Subbaramu
Keyword(s):  
Micro Air Vehicles ◽  
Geometrical Model ◽  
Diameter Ratio ◽  
Chord Length ◽  
Base Line ◽  
Ansys Fluent ◽  
Thrust Coefficient ◽  
Propulsive Efficiency ◽  
Advance Ratio ◽  
Line Design

Of late, the aerospace industry has taken increasing interest in Micro Air Vehicles (MAV) powered by electric motor driven micro propellers. The endurance of the MAV largely depends upon the propulsive efficiency of its propeller. This has created a need for improved design of propellers through an in-depth understanding of the relevant aerodynamics. Design of micro propellers operating at low Reynolds numbers with sufficiently high propulsive efficiency is a challenging task. This paper deals with the parametric studies on a micro propeller for MAV application through numerical simulations. A propeller of known geometry was selected from the published literature. Geometrical model of the baseline propeller was prepared using CATIA V5 software and CFD analysis was carried out using ANSYS FLUENT 12.0 software. The baseline geometry of the micro propeller was modified by varying the spanwise position of maximum blade chord, maximum chord length, and pitch to diameter ratio to generate new design variants. The performances of these design variants were analysed through CFD simulations and compared in terms of variation of efficiency, torque coefficient and thrust coefficient against advance ratio. No significant change was observed in performance by changing the location of maximum blade chord. However, the required thrust of 1 N was achieved by increasing the chord length by 1.2 times the base line design at an efficiency of 64.2%. The propeller efficiency was further increased to 70.8% at an increased pitch to diameter ratio of 1.2 and at an advance ratio of 1.033.

scholarly journals Aerodynamic Performance Characterization and Structural Analysis of Slotted Propeller: Part A Effect of Position

2020 ◽  
Vol 12 (2) ◽  
pp. 183-198
Author(s):  
Aravind SEENI
Keyword(s):  
Pressure Distribution ◽  
Structural Integrity ◽  
Power Coefficient ◽  
Propeller Blade ◽  
Ansys Fluent ◽  
Thrust Coefficient ◽  
Baseline Design ◽  
Propeller Design ◽  
Advance Ratio ◽  
C 50

Novel slotted propeller design performance is presented in terms of thrust coefficient, power coefficient and efficiency by utilizing ANSYS Fluent. The effects of slotted positions were discussed with respect to baseline APC Slow Flyer 10’ x 7’ configurations. Seven slot locations with respect to chord length(c) namely 12.5%c, 25%c, 37.5%c, 50%c, 62.5%c, 75%c and 87.5%c were tested. The result shows that introduction of slot along the propeller blade increases the thrust coefficient, in the range of 0.1% to 4.74% for low advance ratios. However, increase in thrust coefficient also increases power coefficient compared to baseline design, hence reducing propeller efficiency. In addition, structural integrity of the blade was tested. The pressure distribution of the propeller blade demonstrated higher pressure on the back section, and lower pressure at the front section which results in thrust. In addition, the result shows that the pressure distribution is highly influenced by changes in advance ratio. The analysis shows that the novel propeller design managed to withstand stress and strain breaking point when operated at high advance ratio.

Performance Modeling of Ducted Vertical Axis Turbine Using Computational Fluid Dynamics

2013 ◽  
Vol 47 (4) ◽  
pp. 36-44 ◽  
Author(s):  
Prasun Chatterjee ◽  
Raymond N. Laoulache
Keyword(s):  
Performance Modeling ◽  
Flow Direction ◽  
Computational Cost ◽  
Vertical Axis ◽  
Area Ratio ◽  
Diameter Ratio ◽  
Turbulent Model ◽  
Ansys Fluent ◽  
Second Order In Time ◽  
Vertical Axis Turbine

AbstractVertical axis turbines (VATs) excel over horizontal axis turbines in their independent flow direction. VATs that operate in an enclosure, e.g., a diffuser shroud, are reported to generate more power than unducted VATs. A diffuser-shrouded, high solidity of 36.67%, three-blade VAT with NACA 633-018 airfoil section is modeled in 2-D using the commercial software ANSYS-FLUENT®. Incompressible, unsteady, segregated, implicit, and second order in time and space solver is implemented in association with the Spalart-Allmaras turbulent model with a reasonable computational cost. The computational results are assessed against experimental data for unducted VAT at low tip speed ratios between 1 and 2 for further numerical analysis on diffuser models. Different diffuser designs are investigated using suitable nozzle size, area ratio, length-to-diameter ratio and angles between the diffuser inner surfaces. The numerical model shows that, for a specific diffuser design, the ducted VAT performance coefficient can be augmented by almost 90% over its unducted counterpart.

Existence of a sharp transition in the peak propulsive efficiency of a low- pitching foil

2016 ◽  
Vol 800 ◽  
pp. 307-326 ◽  
Author(s):  
Anil Das ◽  
Ratnesh K. Shukla ◽  
Raghuraman N. Govardhan
Keyword(s):  
Power Coefficient ◽  
Energetic Cost ◽  
Mean Power ◽  
Thrust Coefficient ◽  
Propulsive Efficiency ◽  
Von Karman ◽  
Wide Range ◽  
The Mean ◽  
The One ◽  
Von Kármán

We perform a comprehensive characterization of the propulsive performance of a thrust generating pitching foil over a wide range of Reynolds ($10\leqslant Re\leqslant 2000$) and Strouhal ($St$) numbers using a high-resolution viscous vortex particle method. For a given $Re$, we show that the mean thrust coefficient $\overline{C_{T}}$ increases monotonically with $St$, exhibiting a sharp rise as the location of the inception of the wake asymmetry shifts towards the trailing edge. As a result, the propulsive efficiency too rises steeply before attaining a maximum and eventually declining at an asymptotic rate that is consistent with the inertial scalings of $St^{2}$ for $\overline{C_{T}}$ and $St^{3}$ for the mean power coefficient, with the latter scaling holding, quite remarkably, over the entire range of $Re$. We find the existence of a sharp increase in the peak propulsive efficiency ${\it\eta}_{max}$ (at a given $Re$) in the $Re$ range of 50 to approximately 1000, with ${\it\eta}_{max}$ increasing rapidly from about 1.7 % to the saturated asymptotic value of approximately $16\,\%$. The $St$ at which ${\it\eta}_{max}$ is attained decreases progressively with $Re$ towards an asymptotic limit of $0.45$ and always exceeds the one for transition from a reverse von Kármán to a deflected wake. Moreover, the drag-to-thrust transition occurs at a Strouhal number $St_{tr}$ that exceeds the one for von Kármán to reverse von Kármán transition. The $St_{tr}$ and the corresponding power coefficient $\overline{C_{p,}}_{tr}$ are found to be remarkably consistent with the simple scaling relationships $St_{tr}\sim Re^{-0.37}$ and $\overline{C_{p,}}_{tr}\sim Re^{-1.12}$ that are derived from a balance of the thrust generated from the pitching motion and the drag force arising out of viscous resistance to the foil motion. The fact that the peak propulsive efficiency degrades appreciably only below $Re\approx 10^{3}$ establishes a sharp lower threshold for energetically efficient thrust generation from a pitching foil. Our findings should be generalizable to other thrust-producing flapping foil configurations and should aid in establishing the link between wake patterns and energetic cost of thrust production in similar systems.

Numerical Study on Thrust Generation Performance of Plunging Airfoils

2013 ◽  
Vol 312 ◽  
pp. 235-238
Author(s):  
Ji Gao ◽  
Rui Shan Yuan ◽  
Ming Hui Zhang ◽  
Yong Hui Xie
Keyword(s):  
Viscous Flow ◽  
Numerical Study ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Thrust Coefficient ◽  
Propulsive Efficiency ◽  
Propulsion Performance ◽  
Incompressible Viscous Flow ◽  
Thrust Generation ◽  
The Difference

In this paper, the effects of angle of attack, camber and camber location on propulsion performance of flapping airfoils undergoing plunging motion were numerically studied at Re=20000 and h=0.175. The unsteady incompressible viscous flow around four different airfoil sections was simulated applying the dynamic mesh. The results show that the time averaged thrust coefficient CTmean and propulsive efficiency η of the symmetric airfoil decrease with the increasing angle of attack, and the variation of CTmean is more obvious than that of CPmean. Both CTmean and η for NACA airfoils studied in this paper decrease with the increasing camber and the difference between the propulsion performances of different airfoils is not obvious, and the thrust generation and power of various NACA airfoils gradually increase during the downstroke and decrease during the upstroke. Under the same conditions, the airfoil with a further distance between the maximum camber location and the chord of the leading edge leads to higher propulsive efficiency.

scholarly journals Influence of Thickness Variation on the Flapping Performance of Symmetric NACA Airfoils in Plunging Motion

2010 ◽  
Vol 2010 ◽  
pp. 1-19 ◽  
Author(s):  
Liangyu Zhao ◽  
Shuxing Yang
Keyword(s):  
Lift Coefficient ◽  
Parametric Method ◽  
Leading Edge ◽  
Thickness Variation ◽  
Thrust Coefficient ◽  
Propulsive Efficiency ◽  
Maximum Thickness ◽  
Class Function ◽  
Edge Vortex ◽  
The Impact

In order to investigate the impact of airfoil thickness on flapping performance, the unsteady flow fields of a family of airfoils from an NACA0002 airfoil to an NACA0020 airfoil in a pure plunging motion and a series of altered NACA0012 airfoils in a pure plunging motion were simulated using computational fluid dynamics techniques. The “class function/shape function transformation“ parametric method was employed to decide the coordinates of these altered NACA0012 airfoils. Under specified plunging kinematics, it is observed that the increase of an airfoil thickness can reduce the leading edge vortex (LEV) in strength and delay the LEV shedding. The increase of the maximum thickness can enhance the time-averaged thrust coefficient and the propulsive efficiency without lift reduction. As the maximum thickness location moves towards the leading edge, the airfoil obtains a larger time-averaged thrust coefficient and a higher propulsive efficiency without changing the lift coefficient.

scholarly journals Study of a New Type of Flettner Rotor in Merchant Ships

2021 ◽  
Vol 28 (1) ◽  
pp. 28-41
Author(s):  
Boyang Li ◽  
Rui Zhang ◽  
Yajing Li ◽  
Baoshou Zhang ◽  
Chao Guo
Keyword(s):  
Wind Speed ◽  
Inflection Point ◽  
Lift Coefficient ◽  
Rotating Cylinder ◽  
Ansys Fluent ◽  
Thrust Coefficient ◽  
New Type ◽  
Lift And Drag ◽  
Lift And Drag Coefficient ◽  
Maximum Thrust

Abstract Wind energy is a clean and renewable source of energy. This study seeks to explore the potential for utilising wind power for merchant ships. A new type of Flettner rotor (rotating cylinder) mounted on the superstructure of a ship is proposed and numerically simulated. The construction and installation of the rotating cylinder is designed and a numerical simulation of the ship-mounted cylinder is carried out, using the commercially available CFD code Ansys Fluent to obtain parameters such as lift and drag coefficient of the cylinder in different conditions. Specifically, it is found that the cylinder type superstructure can play a certain role in reducing the effect of friction by comparing traditional and cylindrical superstructures; the rotating cylinder can generate auxiliary thrust for the ship. After analysis, the wind speed around the cylinder and spin ratio will have a direct influence on its thrust effect; there is an inflection point in the lift coefficient with the increase of α; the thrust coefficient (8.63) reaches the maximum environmental wind speed at 10 m/s and spin ratio is 2.5. For the rotating cylinder, the greater the environmental wind, the greater the thrust contribution generated under the same spin ratio conditions. The maximum thrust can reach 750,000 N; the cylinder’s auxiliary propulsion contribution shows a better advantage in α = 2.0. The effective power generated by the cylinder reaches a maximum of 2,240 kW for environmental wind speed = 20 m/s and α = 1.0.

Aerodynamic Characterization of a High Speed Propeller

2014 ◽  
Author(s):  
Adel Ghenaiet ◽  
Akila Halimi
Keyword(s):  
Mach Number ◽  
Boundary Conditions ◽  
High Speed ◽  
Numerical Study ◽  
Twist Angle ◽  
Computational Domain ◽  
Propulsive Efficiency ◽  
High Rotational Speed ◽  
Open Rotor ◽  
Advance Ratio

This paper presents a numerical study aimed at characterizing the aerodynamics of an advanced propeller distinguished by its high rotational speed, blade sweep and airfoil sections. Many of the difficulties encountered when applying CFD to an open rotor (a propeller) arise due to removal of the casing existing in a conventional aero-engine turbomachinery. For this purpose the propeller computational domain needed to be well parameterized to keep sufficient outer domains distances where the appropriate boundary conditions are imposed. The mesh of a certain resolution was extended radially, five times the tip radii, to fully capture the stream-tube and minimize the effect of free-stream boundary conditions. Comparisons of obtained flow field results with some available experimental data shows in general similar quantitative results and trends. The estimated propulsive efficiency is shown to be strongly dependent upon the cruise flight Mach number, advance ratio and pitch angle. The maximum propulsive efficiency reached a value of 76.2 % around flight Mach number of 0.8, twist angle of 66 deg and advance ratio of 4.1. The effect of blades number has revealed a higher propulsive efficiency for the six and eight-bladed propellers but at the expense of lower power and thrust coefficients.

Wake Structures and Effect of Hydrofoil Shapes in Efficient Flapping Propulsion

2021 ◽  
Author(s):  
John Kelly ◽  
Pan Han ◽  
Haibo Dong ◽  
Tyler Van Buren
Keyword(s):  
Shape Change ◽  
Leading Edge ◽  
Chord Length ◽  
Immersed Boundary ◽  
Shape Transformation ◽  
Propulsive Efficiency ◽  
Favorable Pressure Gradient ◽  
Edge Vortex ◽  
And Performance ◽  
Numerical Solver

Abstract In this work, direct numerical simulation (DNS) is used to investigate how airfoil shape affects wake structure and performance during a pitching-heaving motion. First, a class-shape transformation (CST) method is used to generate airfoil shapes. CST coefficients are then varied in a parametric study to create geometries that are simulated in a pitching and heaving motion via an immersed boundary method-based numerical solver. The results show that most coefficients have little effect on the propulsive efficiency, but the second coefficient does have a very large effect. Looking at the CST basis functions shows that the effect of this coefficient is concentrated near the 25% mark of the foils chord length. By observing the thrust force and hydrodynamic power through a period of motion it is shown that the effect of the foil shape change is realized near the middle of each flapping motion. Through further inspection of the wake structures, we conclude that this is due to the leading-edge vortex attaching better to the foil shapes with a larger thickness around 25% of the chord length. This is verified by the pressure contours, which show a lower pressure along the leading edge of the better performing foils. The more favorable pressure gradient generated allows for higher efficiency motion.

Note on optimum propulsion of heaving and pitching airfoils from linear potential theory

2017 ◽  
Vol 826 ◽  
pp. 781-796 ◽  
Author(s):  
R. Fernandez-Feria
Keyword(s):  
Phase Shift ◽  
Potential Theory ◽  
Linear Theory ◽  
Leading Edge ◽  
Linear Potential ◽  
Thrust Coefficient ◽  
Propulsive Efficiency ◽  
Pitching Motion ◽  
Reduced Frequency ◽  
Linear Potential Theory

The conditions that maximize the propulsive efficiency of a heaving and pitching airfoil are analysed using a novel formulation for the thrust force within the linear potential theory. Stemming from the vortical impulse theory, which correctly predicts the decay of the thrust efficiency as the inverse of reduced frequency$k$for large$k$(Fernandez-Feria,Phys. Rev. Fluids, vol. 1, 2016, 084502), the formulation is corrected here at low frequencies by adding a constant representing the viscous drag. It is shown first that the thrust coefficient and propulsive efficiency thus computed agree quite well with several sets of available experimental data, even for not so small flapping amplitudes. For a pure pitching motion, it is found that the maximum propulsion efficiency is reached for the airfoil pitching close to the three-quarter chord point from the leading edge with a relatively large reduced frequency, corresponding to a relatively low thrust coefficient. According to the theory, this efficiency peak may approach unity. For smaller$k$, other less pronounced local maxima of the propulsive efficiency are attained for pitching points ahead of the leading edge, with larger thrust coefficients. The linear theory also predicts that no thrust is generated at all for a pitching axis located between the three-quarter chord point and the trailing edge. These findings contrast with the results obtained from the classical linear thrust by Garrick, with the addition of the same quasi-static thrust, which are also computed in the paper. For a combined heaving and pitching motion, the behaviour of the propulsive efficiency in relation to the pitching axis is qualitatively similar to that found for a pure pitching motion, for given fixed values of the feathering parameter (ratio between pitching and heaving amplitudes) and of the phase shift between the pitching and heaving motions. The peak propulsive efficiency predicted by the linear theory is for an airfoil with a pitching axis close to, but ahead of, the three-quarter chord point, with a relatively large reduced frequency, a feathering parameter of approximately$0.9$and a phase shift slightly smaller than $90^{\circ }$.

Hydromechanics of lunate-tail swimming propulsion

1974 ◽  
Vol 64 (2) ◽  
pp. 375-392 ◽  
Author(s):  
M. G. Chopra
Keyword(s):  
Aspect Ratio ◽  
Leading Edge ◽  
Vortex Sheet ◽  
The Body ◽  
Uniform Motion ◽  
Physical Parameters ◽  
Thrust Coefficient ◽  
Propulsive Efficiency ◽  
Reduced Frequency ◽  
General Motion

This paper investigates the non-uniform motion of a thin plate of finite aspect ratio, with a rounded leading edge and sharp trailing edge, executing heaving and pitching oscillations at zero mean lift. Such vertical motions characterize the horizontal lunate tails with which cetacean mammals propel themselves, and the same motions, turned through 90° to become horizontal motions of sideslip and yaw, characterize the vertical lunate tails of certain fast-swimming fishes. An oscillating vortex sheet consisting of streamwise and spanwise components is shed to trail behind the body and it is this additional feature of the streamwise component resulting from the finiteness of the plate that makes this study a generalization of the two-dimensional treatment of lunate-tail propulsion by Lighthill (1970). The forward thrust, the power required, the energy imparted to the wake and the hydromechanical propulsive efficiency are determined for this general motion as functions of the physical parameters defining the problem: namely the aspect ratio, the reduced frequency, the feathering parameter and the position of the pitching axis. The dependence of the thrust coefficient and propulsive efficiency on these physical parameters, for the complete range of variation consistent with the assumptions of the problem, has been depicted graphically.

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