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by Nick Lavery
2006, Advances in Engineering Software
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2023, CFD Open Series
A design is a plan or specification for the construction of an object or system or for the implementation of an activity or process, or the result of that plan or specification in the form of a prototype, product or process. The verb to design expresses the process of developing a design. In some cases, the direct construction of an object without an explicit prior plan (such as in craft work, some engineering, coding, and graphic design) may also be considered to be a design activity. The design usually has to satisfy certain goals and constraints, may take into account aesthetic, functional, economic, or socio-political considerations, and is expected to interact with a certain environment
2003
A PrandtlPlane aircraft configuration is based on the concept of “Best Wing System”. Reference is made to a theoretical result published by Prandtl in 1924, showing that the lifting system with the minimum induced drag, under certain conditions, is a wing box in the front view. The properties of the Prandtl’s Best Wing System are independent from the sweep angles of the wings and, then, an aircraft configuration based on these properties is valid also for the transonic range. This configuration, in honour of Prandtl, has been named as "PrandtlPlane". In order to develop a PrandtlPlane configuration, a large amount of aerodynamic analyses is needed. These computations can be carried out by means of Boundary Element method or CFD (Computational Fluid Dynamics) codes. The main problem connected to the application of the aerodynamic codes is the shape generation of the aircraft; even more so, in the case of such a complex configuration. At the University of Pisa, a proper code...
PLOS ONE
2012, Engineering Applications of Artificial Intelligence
2011, Integrative and Comparative Biology
2008
a low-cost alternative to evaluate its performance. This paper presents and discusses a method for the numerical evaluation of a given shape and its possible optimization regarding its aerodynamic performance. The computational domain is obtained by means of a b-spline curve shape parametrization, the control points are described in an input le and 2D geometry is constructed with a 2D mesher. A valid CFD domain is obtained from constructing a 3D geometry from the 2D information, additional parameters and a volumetric mesher. The aerodynamic information is obtained by solving the Navier-Stokes equations using the OpenFOAM (Opensource Field Operation And Manipulation) toolkit. The method is particularly useful to narrow a design search space for an aerodynamic shape, in which case the proof of concept that this paper presents is an airfoil. This model could be used for initial approximations to improve aerodynamic behavior of a given shape. CFD simulation could deliver accurate predic...
2011, Marine Technology Society Journal
The biomimetic approach seeks technological advancement through a transfer of technology from natural technologies to engineered systems. The morphology of the wing-like flipper of the humpback whale has potential for marine applications. As opposed to the straight leading edge of conventional hydrofoils, the humpback whale flipper has a number of sinusoid-like rounded bumps, called tubercles, which are arranged periodically along the leading edge. The presence of the tubercles modifies the water flow over the wing-like surface, creating regions of vortex generation between the tubercles. These vortices interact with the flow over the tubercle and accelerate that flow, helping to maintain a partially attached boundary layer. This hydrodynamic effect can delay stall to higher angles of attack, increases lift, and reduces drag compared to the post-stall condition of conventional wings. As the humpback whale functions in the marine environment in a Reynolds regime similar to some engin...
2012, Volume 8: Turbomachinery, Parts A, B, and C
A composite investigation with panel code and Reynolds-Averaged Navier-Stokes (RANS) meth- ods is conducted on 3D and 2D hydrofoil geometries and NACA sections to quantify the forces and the performance of these structures. This methodology is aimed to prove that it is possible to combine different numerical methods for a time-effective hydrofoil design approach. This combination will use panel method and thinship theory to investigate 3D NACRA F20 C-foil geometries. RANS, with k - ω SST as turbulent model, is used to analyse 2D NACA 0012 sections. The results will be compared between the two methods and with the experimental data available. Results proved to be satisfactory being able to encompass in the study many different performance criteria of hydrofoil design. The data between the codes showed similar trends although some differences were encountered. A design methodology has been presented to show how each code is adapt to study which part of the physics involved with this flow prob- lem. Time proved to be a major restriction but the main objectives of the project have been met. A consideration on future works was proposed based on the outcomes of the research.
2021, PLOS One
Tail flukes as well as the dorsal fin are the apomorphic traits of cetaceans which appeared during the evolutionary process of adaptation to the aquatic life. Both appendages present a winglike shape associated with lift generation and low drag. We hypothesized that the evolution of fins as lifting structures led to a generic wing design, where the dimensionless parameters of the fin cross-sections are invariant with respect to the body length and taxonomy of small cetaceans (Hypothesis I). We also hypothesized that constraints on variability of a generic fin shape are associated with the primary function of the fin as a fixed or flapping hydrofoil (Hypothesis II). To verify these hypotheses, we examined how the variation in the fin's morphological traits is linked to the primary function, species and body length. Hydrodynamic characteristics of the fin crosssections were examined with the CFD software and compared with similar engineered airfoils. Generic wing design of both fins was found in a wing-like planform and a streamlined cross-sectional geometry optimized for lift generation. Divergence in a generic fin shape both on the planform and cross-sectional level was found to be related with the fin specialization in fixed or flapping hydrofoil function. Cross-sections of the dorsal fin were found to be optimized for the narrow range of small angles of attack. Cross-sections of tail flukes were found to be more stable for higher angles of attack and had gradual stall characteristics. The obtained results provide an insight into the divergent evolutionary pathways of a generic wing-like shape of the fins of cetaceans under specific demands of thrust production, swimming stability and turning control.
Proceedings
The surfing performance of two shortboard fin types with surface features were compared to a standard (control) fin with a smooth surface using dynamic computational fluid dynamics (CFD) simulations. The fins with surface features included designs with a partially grooved and serrated surface (CR), and humpback whale-inspired fins with tubercles and other features (RW). Surfboard roll, pitch and yaw during cutback maneuvers were simulated based on field data from surfers of intermediate, expert and professional (WCT) skill level surfing on ocean waves. Sustained resultant forces relative to the rider direction were significantly different between fin types, and lowest for RW at WCT-level rotations. CFD results also revealed RW’s ability to dampen effects of turbulent flow. RW fins were always the last to stall during a turn, and always exhibited the most gradual stall. CR fins had significantly lower pre-turn drag, and the highest mean resultant forces during the turn. Overall, CR f...
1993, ODURF
An algorithm is developed to obtain the grid sensitivity with respect to design parameters for aerodynamic optimization. Two distinct parameterization procedures are developed for investigating the grid sensitivity with respect to design parameters of a wing-section as an example. The first procedure is based on traditional (physical) relations defining NACA four-digit wing-sections. The second is advocating a novel (geometrical) parameterization using spline functions such as NURBS (Non-Uniform Rational B-Splines) for defining the wing-section geometry. An interactive algebraic grid generation technique, known as Two-Boundary Grid Generation (TBGG) is employed to generate C-type grids around wing-sections. The grid sensitivity of the domain with respect to design and grid parameters has been obtained by direct differentiation of the grid equations. A hybrid approach is proposed for more geometrically complex configurations. A comparison of the sensitivity coeffÉcients with those obtained using a finite-difference approach is made to verify the feasibility of the approach. The aerodynamic sensitivity coefficients are obtained using the compressible two-dimensional thin-layer Navier-Stokes equations. An optimization package has been introduced into the algorithm in order to optimize the wing-section surface using both physical and geometric parameterization. Results demonstrate a substantially improved design, particularly in the geometric parameterization case.
Journal of Marine Science and Engineering
Much work has been done over the past years to obtain a better understanding, predict and alleviate the effects of cavitation on the performance of lifting surfaces for hydrokinetic turbines and marine propellers. Lifting-surface sheet cavitation, when addressed as a free-streamline problem, can be predicted up to a desirable degree of accuracy using numerical methods under the assumptions of ideal flow. Typically, a potential solver is used in conjunction with geometric criteria to determine the cavity shape, while an iterative scheme ensures that all boundary conditions are satisfied. In this work, we propose a new prediction model for the case of partially cavitating hydrofoils in a steady flow that treats the free-streamline problem as an inverse problem. The objective function is based on the assumption that on the cavity boundary, the pressure remains constant and is evaluated at each optimization cycle using a source-vorticity BEM solver. The attached cavity is parametrized u...
2019
Article history: Received 10 October 2018 Received in revised form 2 January 2019 Accepted 20 March 2019 Available online 23 March 2019 This research work is about numerical simulation and experimental study of the effect of varying sinusoidal bumps (or tubercles) height at the leading edge of the airfoil on efficiency using NASA LS (1)-0413 cross-section profiles. Spalart Allmaras turbulence model was used for numerical solutions. The parameters investigated include, lift, and drag, the angle of attack and bumps height at very low Reynolds number of 4.9 x 104. The results show that bumps on the blade leading edge have an advantage at post-stall angles of attack on the performance and varies with bumps height.
1993, 31st Aerospace Sciences Meeting
TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES
2018
Renewable energies, such as solar and wind, have been employed in the recent past to power and propel unmanned marine vehicles. In most cases however, the possibility of using wave energy is not considered. Therefore, in this thesis project, the thrust generating capacity of an oscillating hydrofoil in head seas is investigated. A mathematical model is presented that computes the forces on a two-dimensional hydrofoil oscillating in pitch. Existing empirical force coefficients are used to estimate the horizontal and vertical forces generated by the hydrofoil based on the effective angle of attack. A simulation case is then developed in OpenFOAM enabling the effects of wave height, wave frequency, foil pitch amplitude, and forward speed to be studied. To evaluate theoretical and simulation results, a hydrodynamic testing platform is developed using a DC motor to actuate the foil and a four load cell arrangement to measure forces. The experiments are performed in the wave tank of Memor...
2009, Biomimetics and Bioinspiration
2019, VIII International Conference on Computer Methods in Marine Engineering
A hydrodynamic design procedure is presented, combining multi-objective sampling, metamodeling, and optimization. A design study of a flapped surface for a passenger hydrofoil is discussed. Hydrodynamics, stability and control are optimized with focus on maximum lift, minimum drag, and maneuverability/stability performance during takeoff and turning maneuvers. Shape optimization and control design are applied in combination with validated CFD simulations. Specifically, the hydrodynamic design of the foil sections is achieved though optimization , combining automatic shape/grid modification, adaptive sampling and metamodeling, and multi-objective optimization algorithms for maximum lift and minimum drag. A robust control scheme is designed for the optimized shape. Flaps and rudders are commanded to stabilize roll and pitch motions, as well as steering the vessel during the desired maneuvers.
2006, Sports Engineering
York, ISBN 978–0–387–34680–9. in the model, perception, emotion, status symbol and trend-setting, are of interest. Some examples will illustrate the model. This approach can be used to assist the designer of performance oriented sports equipment and thus to support a systematic product design process in sports.
Day 1 Wed, October 21, 2009
The use of computational methods in design engineering is growing rapidly at all stages of the design process, with the final goal of a substantial reduction of the cost and time for the development of a design. Simulations and optimization algorithms can be combined together into what is known as Simulation-Based Design (SBD) techniques. Using these tools the designers may find the minimum of some user defined objective functions with constraints, under the general mathematical framework of a Non-Linear Programming problem. There are problems of course: computational complexity, noise, robustness and accuracy of the numerical simulations, flexibility in the use of these tools; all these issues will have to be solved before the SBD methodology can become more widespread. In the paper, some derivative-based algorithms and methods are initially described, including efficient ways to compute the gradient of the objective function. Derivative-free methods - such as genetic algorithms an...
2014, 52nd Aerospace Sciences Meeting
Energies
Horizontal axis turbines are commonly used for harnessing renewable hydrokinetic energy, contained in marine and river currents. In order to encourage the expansion of electricity generation using micro-hydrokinetic turbines, several design improvements are investigated. Firstly, optimization-based design of rotor blade is used to get as close as possible to the efficiency limit of 59.3% (known as Betz limit), that counts for bare turbine rotors, placed in the free flow. Additional diffuser elements are further added to examine the potential to overcome the theoretical efficiency limit by accelerating water at the axial direction. Various diffuser geometrical configurations are investigated using the computational fluid dynamics (CFD) to obtain insight into hydrodynamics of augmented micro-hydrokinetic turbines. Moreover, the turbines are compared from the energy conversion efficiency point of view. The highest maximum power coefficient increase of 81% is obtained with brimmed (flan...
2014, Energy Conversion and Management
Elevators are flight control surfaces, usually at the rear of an aircraft, which control the aircraft's lateral attitude by changing the pitch balance, and so also the angle of attack and the lift of the wing. The elevators are usually hinged to a fixed or adjustable rear surface, making as a whole a tailplane or horizontal stabilizer. The effect on lift coefficient due to an elevator deflection is going to find by assuming the baseline value, initializing the aircraft at a steady state flight condition and then commanding a step elevator deflection. By monitoring the aircraft’s altitude and other related measurements, you can record the effect of a step elevator deflection at this flight condition. Repetitions of this experiment with various values will demonstrate how variations in this parameter affect the aircraft’s response to elevator deflection. Deflection of the control surface creates an increase or decrease in lift and moment. In this paper we are going to derive the different equations related to the longitudinal stability and control. The design of the horizontal stabilizer and elevator is going to do in CATIA V5 and the analysis is going to perform in ANSYS 12.0 FLUENT.
2013, Physics of Fluids
2012, Computers & Fluids
Mechanical Sciences
2011, Aerospace Science and Technology
Determining the airfoil geometry from a given CpCp-distribution is an inverse problem of paramount importance specially in the context of variable geometry aerodynamic platforms. This work describes the implementation of artificial neural nets for the airfoil geometry determination. Instead of using full coordinates of the airfoil, Bezier–PARSEC 3434 parameters have been used to describe an airfoil. Some of these parameters have been determined using a Genetic Algorithm. In the second stage CpCp-distribution in terms of clcl, cdcd and cmcm for 10 angles of attack has been input into three different neural nets for learning and then estimating the corresponding BP3434 parameters. Feed-forward backpropagation, Generalized regression and Radial basis neural nets have been trained and then compared in terms of performance and regression statistics. The work establishes the superiority of feed-forward backpropagation neural nets. The result is partly due to good function approximation properties of the neural architecture and partly due to the use of Bezier–PARSEC 3434 parameterization scheme.
2007, IEEE Transactions on Robotics
Abstract— In this paper, techniques from geometric mechanics and geometric nonlinear control theory are applied to modeling and construction of trajectory tracking algorithms for a free- swimming,underwater vehicle that locomotes and maneuvers using a two-link actuated “tail” and,independently actuated “pectoral fin” bow planes. Restricting consideration of fluid force s to the simple effects of added mass and quasisteady lift and
2016, Volume 6: Ocean Space Utilization; Ocean Renewable Energy
2018
The depletion of fossil fuel and the increase of fuel consumption globally create an increased demand for the use of renewable energy. Vertical axis tidal turbines are a promising renewable energy device which needs to be improved. One problem appears in its operation is the structural instability and noise coming from the vibration of the long slender vertical axis blades. The vibration is a result of fluid structure interaction between turbine blades and the unsteady tidal current. This interaction of the tides and the blade generates vortical features which can excite the turbine blades to vibrate and causes a tonal noise known as singing. The aim of this work is to predict the blade response and locked-in condition by controlling the vortex shedding. The vortex is controlled by modifying blade’s trailing edge shape. The modifications include truncated, sharp and rounded trailing edge shapes. The response is modeled by vibrations using a spring damper system. A 2D numerical model o...
2020
icas-proceedings.net
The Aerodynamic characteristics of an airfoil play a very important role in terms of design aspects and experimental validation. A distinctive supercritical airfoil is found to give inappropriate results at peak operating conditions. This led to design changes and optimization of the foil with the help of a cusp like structure added to the trailing edge of the foil. The present work emphasizes the computation of a supercritical airfoil with and without wedge profiles at different angles of attack and free stream velocities. The formation of a shock wave is observed when the free stream approaches a transonic mach number. This shock wave is a type of propagating disturbance which greatly effects the aerodynamic performance of the airfoil. The flow properties such as pressure, temperature and density experience a drastic change upstream and downstream of the generated shock. The main goal of the proposed paper is to carryout the simulation and analysis of RAE 2822 supercritical airfoil with and without wedge profiles along with the study of aerodynamic characteristics such as Lift and drag coefficients at different Mach numbers. The objective is to improve the stability of the airfoil when the flow approaches transonic Mach speeds. The design profile chosen is based upon existing literature studies.
2010, Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy