Small-Scale Rotor Design Variables and Their Effects on Aerodynamic and Aeroacoustic Performance of a Hovering Rotor

2020 ◽  
Vol 142 (8) ◽  
Author(s):  
Quinten Henricks ◽  
Zhenyu Wang ◽  
Mei Zhuang
Keyword(s):  
Figure Of Merit ◽  
Sound Pressure ◽  
Performance Metrics ◽  
Small Scale ◽  
Acoustic Performance ◽  
Rotor Design ◽  
Design Variables ◽  
Lower Reynolds Number ◽  
Hover Performance ◽  
Power Loading

Abstract With the increased prominence of multicopter micro-aerial vehicles, more importance has been placed on the aerodynamic and acoustic performance of these systems, as their small-scale and lower Reynolds number regime provide results that are different from full-scale rotors. A computational methodology was employed in order to study the aerodynamic and aeroacoustic performance from different small-scale rotors used in a multicopter configuration. Three rotor design variables (twist, taper, and pitch) were investigated in order to understand their influence on aerodynamic and acoustic performance of a hovering rotor. Variables such as rotor rotation rate and rotor radius were kept constant. Common aerodynamic performance metrics such as the ratio of coefficient of thrust to coefficient of power and figure of merit (FM) were used to assess aerodynamic hover performance of the designed rotors. Acoustic performance was assessed by recording acoustic pressure in the far-field at two separate receivers. Acoustic results are presented in the frequency domain as one-third octave band data and as overall sound pressure level (SPL). Flow fields and pressure contours were calculated and displayed in order to help explain aerodynamic and acoustic results. From the results, insights are provided for rotor designs that are more aerodynamically and acoustically efficient in hover. Specifically, rotors that provided lower values of disk loading and higher values of power loading were typically more acoustically efficient. Using greater rotor twist and taper increased both aerodynamic and acoustic performance.

Numerical investigation of aerodynamic and acoustic characteristics of bionic airfoils inspired by bird wing

2018 ◽  
Vol 233 (11) ◽  
pp. 4004-4016 ◽  
Author(s):  
Menghao Wang ◽  
Xiaomin Liu
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Leading Edge ◽  
Pressure Level ◽  
Aerodynamic Noise ◽  
Small Scale ◽  
Airfoil Surface ◽  
Acoustic Characteristics ◽  
Bionic Coupling ◽  
Bionic Airfoil

Airfoil is the basic element of fluid machinery and aircraft, and the noise generated from that is an important research aspect. Aiming to reduce the aerodynamic noise around the airfoil, this study proposes an airfoil inspired by the long-eared owl wing and another airfoil coupled with the bionic airfoil profile, leading edge waves, and trailing edge serrations. Numerical simulations dependent on the large eddy simulation method coupled with the wall-adapting local eddy-viscosity model and the Ffowcs Williams and Hawkings equation are conducted to compare the aerodynamic and acoustic characteristics of two types of bionic airfoils at low Reynolds number condition. The simulations reveal the dipole characteristic of acoustic source and sound pressure level distribution at various frequencies. Two types of bionic airfoils show lower noise compared with the conventional NACA 0012 airfoil with a similar relative thickness of 12%. Compared with the bionic airfoil, the average value of sound pressure level at the monitoring points around the bionic coupling airfoil is decreased by 9.94 dB, meanwhile the lift-to-drag ratio also keep higher. The bionic coupling airfoil exerts a suppression of sound pressure fluctuation on the airfoil surfaces, which result from that the range and size of separation vortices are reduced and the distance between vortices and airfoil surface are increased. The tube-shaped vortices in the wake of airfoil are effectively restrained and split into small scale vortices, which are important to cause less aerodynamic noise around the bionic coupling airfoil. Consequently, a novel bionic coupling airfoil is developed with the excellent aerodynamic and acoustic performance.

scholarly journals A Numerical Approach for Sound Quality of Vehicle Doors

2020 ◽  
Vol 25 (1) ◽  
pp. 9-16
Author(s):  
Erkut Yalçın ◽  
Halil Bilal ◽  
Ayhan Yağcı ◽  
Haluk Erol
Keyword(s):  
Sound Pressure ◽  
Sound Quality ◽  
Numerical Approach ◽  
Design Sensitivity ◽  
Point Of View ◽  
Vehicle Body ◽  
Fem Model ◽  
Body Development ◽  
Design Variables

A Vibro-Acoustic Finite Element Method (FEM) model capable of calculating the transient sound pressure generated by the door slam of a vehicle was developed in this study. A design sensitivity analysis (DSA) was performed for investigating the effects of major design variables on the related sound quality metrics. The methodology was developed using a sedan-car and its FEM model. This paper shows that a Computer Aided Engineering (CAE) model can be used as a rather powerful tool for giving design change decisions for the door components from sound quality point of view during vehicle body development according to psychoacoustic parameters.

An enhanced performance of a horizontal diamagnetic levitation mechanism–based vibration energy harvester for low frequency applications

2016 ◽  
Vol 28 (5) ◽  
pp. 578-594 ◽  
Author(s):  
Sri Vikram Palagummi ◽  
Fuh-Gwo Yuan
Keyword(s):  
Figure Of Merit ◽  
Permanent Magnets ◽  
Energy Harvester ◽  
Performance Metrics ◽  
Low Frequency ◽  
Experimental System ◽  
Vibration Energy ◽  
Vibration Energy Harvesting ◽  
Vibration Energy Harvester ◽  
Diamagnetic Levitation

This article identifies and studies key parameters that characterize a horizontal diamagnetic levitation mechanism–based low frequency vibration energy harvester with the aim of enhancing performance metrics such as efficiency and volume figure of merit. The horizontal diamagnetic levitation mechanism comprises three permanent magnets and two diamagnetic plates. Two of the magnets, lifting magnets, are placed co-axially at a distance such that each attracts a centrally located magnet, floating magnet, to balance its weight. This floating magnet is flanked closely by two diamagnetic plates which stabilize the levitation in the axial direction. The influence of the geometry of the floating magnet, the lifting magnet, and the diamagnetic plate is parametrically studied to quantify their effects on the size, stability of the levitation mechanism, and the resonant frequency of the floating magnet. For vibration energy harvesting using the horizontal diamagnetic levitation mechanism, a coil geometry and eddy current damping are critically discussed. Based on the analysis, an efficient experimental system is setup which showed a softening frequency response with an average system efficiency of 25.8% and a volume figure of merit of 0.23% when excited at a root mean square acceleration of 0.0546 m/s2 and at a frequency of 1.9 Hz.

scholarly journals Optimisation of confinement in a fusion reactor using a nonlinear turbulence model

2018 ◽  
Vol 84 (2) ◽  
Author(s):  
E. G. Highcock ◽  
N. R. Mandell ◽  
M. Barnes ◽  
W. Dorland
Keyword(s):  
First Principles ◽  
Figure Of Merit ◽  
Large Scale ◽  
Unit Volume ◽  
Fusion Reactor ◽  
Small Scale ◽  
Zonal Flows ◽  
Novel Approach ◽  
First Time ◽  
Turbulent Cascade

The confinement of heat in the core of a magnetic fusion reactor is optimised using a multidimensional optimisation algorithm. For the first time in such a study, the loss of heat due to turbulence is modelled at every stage using first-principles nonlinear simulations which accurately capture the turbulent cascade and large-scale zonal flows. The simulations utilise a novel approach, with gyrofluid treatment of the small-scale drift waves and gyrokinetic treatment of the large-scale zonal flows. A simple near-circular equilibrium with standard parameters is chosen as the initial condition. The figure of merit, fusion power per unit volume, is calculated, and then two control parameters, the elongation and triangularity of the outer flux surface, are varied, with the algorithm seeking to optimise the chosen figure of merit. A twofold increase in the plasma power per unit volume is achieved by moving to higher elongation and strongly negative triangularity.

scholarly journals Proposal of an Assessment Method of the Impact Sound Insulation of Lightweight Floors

Buildings ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 13
Author(s):  
Łukasz Nowotny ◽  
Jacek Nurzyński
Keyword(s):  
Sound Pressure ◽  
Residential Buildings ◽  
Assessment Method ◽  
Sustainable Construction ◽  
Sound Insulation ◽  
Indicator Values ◽  
Floor Covering ◽  
Acoustic Performance ◽  
Quality Rating ◽  
The Impact

Lightweight floors are in line with a sustainable construction concept and have become increasingly popular in residential buildings. The acoustic performance of such floors plays a pivotal role in the overall building quality rating. There is, however, no clear and complete method to predict their impact sound insulation. A new approximation method and new acoustic indicators—equivalent weighted normalized impact sound pressure levels for lightweight floors—are proposed and outlined in this article. The prediction procedure and indicator values were initially validated on the basis of laboratory measurements taken for different lightweight floors with the same well-defined floor covering. These preliminary analyses and comparisons show that the proposed method is promising and should be fully developed on the basis of further research.

scholarly journals Assessment of current rotor design comparison practices based on high-fidelity CFD methods

2020 ◽  
Vol 124 (1275) ◽  
pp. 731-766
Author(s):  
T. Fitzgibbon ◽  
M. Woodgate ◽  
G. Barakos
Keyword(s):  
High Speed ◽  
Performance Metrics ◽  
Rotor Blades ◽  
High Fidelity ◽  
Rotor Design ◽  
Performance Predictions ◽  
Accurate Performance ◽  
Cfd Method ◽  
Drag Ratio ◽  
Design Comparison

ABSTRACTThis paper provides an assessment of current rotor design comparison practices. First, the employed CFD method is validated for a number of rotor designs and is shown to achieve accurate performance predictions in hover and high-speed forward flight. Based on CFD results, a detailed investigation is performed in terms of comparing different rotor designs. The CFD analysis highlighted the need of high fidelity methods due to the subtle aerodynamics involved in advanced planforms. Nevertheless, the paper suggests that the correct basis for comparison in terms of performance metrics must be used to inform decisions about the suitability of the rotor blades designs for specific applications. In particular, when comparing blades of advanced planforms, direct torque and thrust comparisons are better than the commonly used lift to drag ratio and figure of merit.

scholarly journals Discovering implicit constraints in design

2011 ◽  
Vol 25 (1) ◽  
pp. 57-75 ◽  
Author(s):  
Madan Mohan Dabbeeru ◽  
Amitabha Mukerjee
Keyword(s):  
Design Space ◽  
Performance Metrics ◽  
General Purpose ◽  
Error Rates ◽  
Design Variables ◽  
Functional Aspects ◽  
Machine Learning Approach ◽  
Design Function ◽  
Function Approximator

AbstractDesigners who are experts in a given design domain are well known to be able to Immediately focus on “good designs,” suggesting that they may have learned additional constraints while exploring the design space based on some functional aspects. These constraints, which are often implicit, result in a redefinition of the design space, and may be crucial for discovering chunks or interrelations among the design variables. Here we propose a machine-learning approach for discovering such constraints in supervised design tasks. We develop models for specifying design function in situations where the design has a given structure or embodiment, in terms of a set of performance metrics that evaluate a given design. The functionally feasible regions, which are those parts of the design space that demonstrate high levels of performance, can now be learned using any general purpose function approximator. We demonstrate this process using examples from the design of simple locking mechanisms, and as in human experience, we show that the quality of the constraints learned improves with greater exposure in the design space. Next, we consider changing the embodiment and suggest that similar embodiments may have similar abstractions. To explore convergence, we also investigate the variability in time and error rates where the experiential patterns are significantly different. In the process, we also consider the situation where certain functionally feasible regions may encode lower dimensional manifolds and how this may relate to cognitive chunking.

Robust Optimization of Cylindrical Gear Tooth Surface Modifications Within Ranges of Torque and Misalignments

2013 ◽  
Author(s):  
Alessio Artoni ◽  
Massimo Guiggiani ◽  
Ahmet Kahraman ◽  
Jonny Harianto
Keyword(s):  
Performance Metrics ◽  
Gear Tooth ◽  
Surface Modifications ◽  
Transmission Error ◽  
Robust Design Optimization ◽  
Tooth Surface ◽  
Global Optimality ◽  
Cylindrical Gear ◽  
Geometry Design ◽  
Design Variables

Tooth surface modifications are small, micron-level intentional deviations from perfect involute geometries of spur and helical gears. Such modifications are aimed at improving contact pressure distribution, while minimizing the motion transmission error to reduce noise excitations. In actual practice, optimal modification requirements vary with the operating torque level, misalignments, and manufacturing variance. However, most gear literature has been concerned with determining optimal flank form modifications at a single design point, represented by fixed, single load and misalignment values. A new approach to the design of tooth surface modifications is proposed to handle such conditions. The problem is formulated as a robust design optimization problem, and it is solved, in conjunction with an efficient gear contact solver (LDP), by a direct search, global optimization algorithm aimed at guaranteeing global optimality of the obtained micro-geometry solutions. Several tooth surface modifications can be used as micro-geometry design variables, including profile, lead, and bias modifications. Depending on the contact solver capabilities, multiple performance metrics can be considered. The proposed method includes the capability of simultaneously and robustly handling several conflicting design objectives. In the present paper, peak contact stress and loaded transmission error amplitude are used as objective functions (to be minimized). At the end, two example optimizations are presented to demonstrate the effectiveness of the proposed method.

Optimal Vibration Reduction of Flexible Rotor Systems by the Virtual Bearing Method

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Shibing Liu ◽  
Bingen Yang
Keyword(s):  
Optimization Problem ◽  
Rotor System ◽  
Flexible Rotor ◽  
Rotor Systems ◽  
Rotor Design ◽  
Design Variables ◽  
Real Coded Genetic Algorithm ◽  
Minimum Number ◽  
Unique Method ◽  
Distributed Transfer Function

This paper presents a new approach to optimal bearing placement that minimizes the vibration amplitude of a flexible rotor system with a minimum number of bearings. The thrust of the effort is the introduction of a virtual bearing method (VBM), by which a minimum number of bearings can be automatically determined in a rotor design without trial and error. This unique method is useful in dealing with the issue of undetermined number of bearings. In the development, the VBM and a distributed transfer function method (DTFM) for closed-form analytical solutions are integrated to formulate an optimization problem of mixed continuous-and-integer type, in which bearing locations and bearing index numbers (BINs) (specially defined integer variables representing the sizes and properties of all available bearings) are selected as design variables. Solution of the optimization problem by a real-coded genetic algorithm yields an optimal design that satisfies all the rotor design requirements with a minimum number of bearings. Filling a technical gap in the literature, the proposed optimal bearing placement approach is applicable to either redesign of an existing rotor system for improvement of system performance or preliminary design of a new rotor system with the number of bearings to be installed being unforeknown.

Twin-rotor hover performance examination using overlap tests

2017 ◽  
Vol 89 (1) ◽  
pp. 155-163
Author(s):  
Farid Shahmiri
Keyword(s):  
Mathematical Models ◽  
Cross Sections ◽  
Test Model ◽  
Test Plan ◽  
Optimal Test ◽  
Content Type ◽  
Hover Performance ◽  
Power Loading ◽  
Overlap Ratio ◽  
Twin Rotor

Purpose The aim of this paper was to experimentally examine twin-rotor hover performance for different rotor overlap ratios at practical rotor loading. Design/methodology/approach The methodology was formed based on data measurements for a designed twin-rotor test model and development of hover performance mathematical models. Thus, measurements were made using a central composite test plan, and then mathematical models for thrust power required power loading (PL) and figure of merit (FM) as functions of collective pitch tip speed; rotor overlap ratio was obtained. In the present paper, the test model consisted of two three-bladed rotors with a diameter of 220 mm and a blade aspect ratio of 16.05. The blades were of a rectangular planform with NACA 0012 cross sections and had no twist or taper. The model was built such that the rear rotor was fixed on the fuselage, and the front rotor could move longitudinally for tests up to about 40 per cent overlap ratio in hover. Findings The best hover aerodynamic efficiency (maximum PL of 14.6 kg/kW) was achieved for non-overlapped rotors at a low value of disc loading (DL) and also at FM of 0.6 at that DL. This result was in agreement with blade element momentum theory predictions. Practical implications Results for the twin-rotor test model can be generalized for actual tandem helicopters through the Reynolds number transformation technique and also some modifications. Originality/value Design and construction of the twin-rotor test model and experimental measurements of hover performance based on an optimal test plan were performed for the first time.

Sign in / Sign up

Export Citation Format

Share Document