William James Crowther

• PhD, CEng
• Group Leader at The University of Manchester

Attitude control of tailless aircraft is typically achieved through a system of trailing-edge flaps that produce coupled control effects in pitch, roll and yaw due to changes in lift and drag distributions. This paper presents a novel control allocation method which allows conformal trailing-edge controls to generate yawing moments with no coupling...

This paper provides a systematic and critical review of dynamic experimental rigs used for insect wing aerodynamics research. The goal is to facilitate meaningful comparison of data from existing rigs and provide insights for designers of new rigs. The scope extends from simple one degree of freedom rotary rigs to multi degrees of freedom rigs allo...

View Video Presentation: https://doi.org/10.2514/6.2021-2530.vid This paper presents an assessment of the opportunity for full three-axis control of the MAGMA aircraft with the fins removed using a combination of Fluidic Thrust Vectoring, Circulation Control and Wingtip Reaction Jets. Effectiveness of the fluidic actuators is defined by values deri...

This paper proposes a novel method to achieve three-axis control of a tailless aircraft using conventional trailing edge controls only during a rolling maneuver. The method is based on the synthesis of control allocation modes which produce laterally asymmetric drag at constant lift, pitching moment and rolling moment. Required control moments thro...

Tailless aircraft without vertical stabilisers typically use drag effectors in the form of spoilers or split flaps to generate control moments in yaw. This paper introduces a novel control allocation method by which full three-axis control authority can be achieved by the use of conventional lift effectors only, which reduces system complexity and...

Jumping take-off in birds is an explosive behaviour with the goal of providing a rapid transition from ground to airborne locomotion. An effective jump is predicated on the need to maintain dynamic stability through the acceleration phase. The present study concerns understanding how birds retain control of body attitude and trajectory during take-...

Video of a simulated jumping take-off of a Guinea fowl using experimental leg kinematics and a hard ground model; video playback speed is 1/25 (4%) real time

Video of an inclined acceleration angle of 45° with nose-up angular acceleration, and toe-tipping

Video of a simulated perch jumping take-off of a Diamond dove using experimental leg kinematics; video playback speed is 1/25 (4%) real time

Document detailing a simplified 1D mass-spring model of take-off, derivation of centre of pressure location, model sensitivity analysis, and modulation of toe-off and tipping

Maplesim multibody model of a dynamic jumping system driven by input leg joint kinematics

Video of a simulated jumping take-off of a Guinea fowl using experimental leg kinematics and a firm ground model; video playback speed is 1/25 (4%) real time

Jumping take-off in birds is an explosive behaviour with the goal of providing a rapid transition from ground to airborne locomotion. An effective jump is predicated on the need to maintain dynamic stability through the acceleration phase. The present study concerns understanding how birds retain control of body attitude and trajectory during take-...

Scale-resolving turbulent flow simulation for urban environments is computationally expensive and not widely used in industrial practice, despite inherent complexities from geometry and high Reynolds number effects. One way to reduce the computational demand of the simulation is to focus a turbulence-resolving solver on the region of interest, and...

An extension to the source doublet panel method was implemented in order to model the aerodynamic performance of delta wing planforms and their derivatives, in this case specifically moderately swept lambda wings, where the flow is influenced by a leading edge vortex system. The method introduces a doublet sheet representing a free shear layer shed...

Purpose The purpose of this paper is to examine geometrical design influence of various types of flying discs on their flight performance from the aerodynamics perspective. Design/methodology/approach The lift, drag and moment coefficients of the discs were measured experimentally using a wind tunnel. Three types of golf discs and four sets of s...

This presentation describes the characteristics of different CFD models used in video games and in engineering applications. It also states which general techniques used in video games and animation models could be applied to engineering.

The presence of a stable leading edge vortex (LEV) on steadily revolving wings increases the maximum lift coefficient that can be generated from the wing and its role is important to understanding natural flyers and flapping wing vehicles. In this paper, the role of LEV in lift augmentation is discussed under two hypotheses referred to as 'addition...

Theoretical analysis is used to identify the optimum wing planform of a flapping/revolving wing in hover. This solution is of interest as a benchmark to which hovering wing geometries driven by broader multidisciplinary evolutionary or engineering constraints can be compared. Furthermore, useful insights into the aerodynamic performance of untwiste...

Electromechanical coupling defines the ratio of electrical and mechanical energy exchanged during a flexure cycle of a piezoelectric actuator. This paper presents an analysis of the dynamic electromechanical coupling factor (dynamic EMCF) for cantilever based piezoelectric actuators and provides for the first time explicit expressions for calculati...

A novel lifting line formulation is presented for the quasi-steady aerodynamic evaluation of insect-like wings in hovering flight. The approach allows accurate estimation of aerodynamic forces from geometry and kinematic information alone and provides for the first time quantitative information on the relative contribution of induced and profile dr...

Hovering flight for flapping wing vehicles requires rapid and relatively complex reciprocating movement of a wing relative to a stationary surrounding fluid. This note develops a compact analytical aero-kinematic model that can be used for optimization of flapping wing kinematics against aerodynamic criteria of effectiveness (maximum lift) and effi...

Flapping flight is much less efficient for some insects than previously thought. The induced power factor for flapping wings is discussed in terms of a number of non-ideal effects for hovering and for forward flight. These effects include losses due to non-uniform downwash, wake periodicity and effective disk area. For some insects, the induced pow...

This paper introduces a generic, transparent and compact model for the evaluation of the aerodynamic performance of insect-like flapping wings in hovering flight. The model is generic in that it can be applied to wings of arbitrary morphology and kinematics without the use of experimental data, is transparent in that the aerodynamic components of t...

An analytical treatment to quantify the losses captured in the induced power factor, k, is provided for flapping wings in normal hover, including the effects of non-uniform downwash, tip losses and finite flapping amplitude. The method is based on a novel combination of actuator disc and lifting line blade theories that also takes into account the...

A new locomotion method for unmanned (autonomous) ground vehicles (UGV) is proposed based around six independently driven wheels mounted on three separate modules. Each module is attached to the overall robot via a pivot point and capable of independently controlling its orientation and velocity. This configuration allows the UGV to perform maneuve...

Piezoelectric bending actuators utilise the inverse piezoelectric effect to convert input electric energy to useful mechanical work. A comprehensive analytical model of the dynamic electromechanical behaviour of a unimorph piezoelectric actuator has been developed and successfully validated against experimental data. The model provides a mapping be...

A free-wake method is used to simulate the wake from retractable, jointed wings. The method serves to complement existing experimental studies that visualise flying animal wakes. Simulated wakes are shown to be numerically convergent for a case study of the Rock Pigeon in minimum power cruising flight. The free-wake model is robust in simulating wa...

Table showing values of normalised marker position, pnorm nt = number of timesteps per cycle nf = number of filaments per wing nm = number of markers per cycle.

Coordinates of quadrilateral patches Rows 1:4 = patch 1, rows 5:8 = patch 2 etc.

This article documents the development of synthetic jet actuator array hardware to augment high-lift system effectiveness in a wind tunnel model. The study involved the design, manufacture and bench test of a synthetic jet actuator array based on an inclined actuator configuration to reduce volume installation requirements without a loss in jet vel...

The ability of UAVs to perform a “perch and stare” manoeuvre could significantly enhance their effectiveness during surveillance and reconnaissance missions. Herein, the concept of a biologically inspired leg-based landing system has been presented. The controllers have been tested in simulation and designed to minimize the forces experienced by UA...

A new stiffness control method is proposed for robotic systems to capture free-moving objects with minimum jerk. A bell-shaped stiffness curve is shown to minimize the jerk that occurs during capture tasks. The results verify that the method can be used to successfully decelerate objects over a predefined distance, while keeping the jerk experience...

This paper is about the development of a novel type of non coplanar hex rotor with the ability to decouple translational and attitude dynamics. The proposed design features six variable pitch rotors arranged in three different rotor planes in order to point the thrust and torque vectors independently of body attitude. It is envisaged that this desi...

The practice of flow control is seen as offering hope in reviving the importance of aerodynamics in aerospace engineering. However, as yet, this promising area of technology has arguably had little success in delivering science into practice. This article attempts to understand something of the nature of research in flow control and whether there i...

Inverse dynamics methods are used to simulate avian wingbeats in varying flight conditions. A geometrically scalable multi-segment bird model is constructed, and optimisation techniques are employed to determine segment motions that generate desired aerodynamic force coefficients with minimal mechanical power output. The results show that wingbeat...

This paper considers the effect of choice of actuator technology and associated power systems architecture on the mass cost and power consumption of implementing active flow control systems on civil transport aircraft. The research method is based on the use of a mass model that includes a mass due to systems hardware and a mass due to the system e...

The application of circulation control (CC) manoeuvre effectors to a tailless flight vehicle enables the possibility of providing control moments about three axes without the use of conventional control surfaces. Strong similarities exist between the use of split flap elevons and CC units used as trailing edge devices for the provision of three-axi...

The use of flow control (FC) technology on civil transport aircraft is seen as a potential means of providing a step change in aerodynamic performance in the 2020 time frame. There has been extensive research into the flow physics associated with FC. This paper focuses on developing an understanding of the costs and design drivers associated with t...

In this paper we propose a framework that will recognise objects from a moving platform using scale invariant features, high dynamic range (HDR) video and stereoscopic depth information. The paper focuses on initial work involving feature extraction from HDR images using SIFT. Initial results show an increase in the number of features extracted fro...

This paper aims to develop understanding of the systems costs associated with the application of flow control systems to civil transport aircraft based on the use of electrically powered synthetic jet actuators (SJAs). The study is based on the development of a low-order mass model using estimated power specific masses of generation, management, di...

Fluidic flight controls enable forces and moments for flight vehicle trim and manoeuvre to be produced without use of conventional moving surface controls. This paper introduces a methodology for the design of Circulation Control (CC) and Fluidic Thrust Vectoring (FTV) as fluidic controls for roll and pitch. Work was undertaken as part of the multi...

Active Flow Control (AFC) systems for separation control have been proposed for use in future civil transport aircraft. Before this can occur, it is necessary to consider the impact of such systems on the design and process of certification. This paper aims to improve the level of understanding of these processes by discussing the technology and th...

The global evolution of the aerospace market is driving flow control research towards full industrial scale applications. In this approach, technologies need to demonstrate effectiveness, as well as compliance with the aircraft performance constraints. The design of a synthetic-jet-based system for a civil transport aircraft would provide an early...

Understanding of the design trades associated with the use of fluidic aircraft controls is developed through the design of a model scale gas turbine powered flapless flight control demonstrator aircraft. Theory relevant to the design of an integrated propulsion, pneumatic power supply and fluidic flight control system are reviewed, focusing on the...

A guide has been reported for future leading-edge flow control activities conducted in wind tunnels operating at low to medium Reynolds numbers and is specifically applied to civil transport aircraft. The objective of this guide is to provide a review of relevant literature, identify airfoil geometric parameters relevant to designing leading-edge f...

This paper outlines a method of developing a quaternion attitude guidance and con-trol system for a rigid body suborbital spacecraft using cold gas thrusters over a short-duration mission. It has been specifically developed for integration aboard the Thunderstar spacecraft of Starchaser Industries, a three-man capsule designed for space tourism. Th...

The spin-stabilised sports disc, more commonly known as the Frisbee, is used for a variety of recreation and sporting activities. Frisbees have unique flying characteristics compared to other sports projectiles because they depend on spin for stability during flight and, at typical launch speeds, aerodynamic lift is greater than or equal to the wei...

Catching requires the ability to predict the position and intercept a moving object at relatively high speeds. Because catching is a contact task, it requires an understanding of the interaction between the forces applied and position of the object being captured. The application of force to a mass results in a change in acceleration. The rate of c...

A primary design driver for current generation civil high lift systems is the retention of existing performance at lower overall cost. This paper considers the use of flow control to enable relaxation of flap geometric location constraints and hence increase value by reducing overall structural weight. The flow control model adopted is that of enha...

Flow control maneuver effectors offer the potential for flight vehicle control with out the use of conventional hinged control surfaces. This paper describes the design, development and test of a dynamic wind tunnel model to demonstrate two specific flow control technologies for vehicle control, namely Fluidic Thrust Vectoring (FTV) for pitch contr...

A method for predicting flow separation is needed for the industrial application of some types of flow control. This should be on-board the aircraft and must be robust in order to achieve certification. Conventional non-intrusive sensors are unable to measure turbulent boundary layer(TBL) parameters that would be useful for the prediction of separa...

An investigation on the effect of geometry and actuation variables on peak jet velocity of a piezoelectric diaphragm synthetic jet actuator was conducted using hotwire anemometry. Two distinct experiments were conducted; the first at constant excitation amplitude with the aim of identifying the SJA geometry that provides the highest jet velocity. T...

Experiments have been undertaken with two small-scale Synthetic Jet Actuators in a zero-pressure gradient boundary-layer, in order to investigate the effect of relative input signal phase. CTA anemometry techniques were used, demonstrating that changes in the downstream flow structure could be observed. Time-averaged streamwise velocity profiles de...

The ability for geographically separated designers, experimentalists and CFD practitioners to work collaboratively in real time on engineering products has the potential to increase productivity and allow mistakes to be corrected earlier in the design cycle. The GEWiTTS project is concerned with the development of a GRID-enabled set of communicatio...

The control of turbofan intake duct flow separation and the subsequent control of compressor face distortion have the potential to achieve a relaxation of the maximum crosswind constraint at take off. Wind tunnel tests have been conducted using a 10% axis-symmetric scale model. Air jets, simulating micro-electrical mechanical actuators, have been i...

An experimental investigation into fluidic thrust vectoring technology has been conducted at the Goldstein Research Laboratory, University of Manchester, UK. Pitch only thrust vectoring of the primary exhaust jet was achieved by using tangential injection of a secondary control jet - the coflow technique. The work aims to highlight practical engine...

Within nature, mobile organisms often exhibit a form of emergent behaviour known as flocking. Flocking is adaptive because, for a given population density, the information processing required for collision avoidance is minimized. Within human activities, the problem of increasing civil air traffic is leading to consideration of decentralized traffi...

Flocking style behavior is commonplace in nature. It provides a number of benefits for groups of creatures on the move at little cost. Unmanned air vehicles are becoming increasingly popular for a variety of applications and are often used in groups. Manually controlling many UAVs at high densities can be difficult. The simple, efficient and safe n...

The flying sports disc is a spin-stabilised axi-symmetric wing of quite remarkable design. A typical disc has an approximate elliptical cross-section and hollowed out under-side cavity, such as the Frisbee(TM) disc. An experimental study of flying disc aerodynamics, including both spinning and non-spinning tests, has been carried out in the wind tu...

A flush air data system uses surface pressure measurements to obtain speed and aerodynamic orientation of a flight vehicle. This paper investigates the use of a neural network to calibrate the air data system on a low-observable aircraft forebody with 22 pressure tappings. Wind tunnel data were obtained for between 0 and 25 o angle of attack, 0 to...

A review of air-vehicles with circular planform ie discwings includes examples of mid-20 th century innovation and recent developments in UAV (unnamed air vehicle) technology. A spin stabilised axi-symmetric disc-wing has potential application as a highly manoeuvrable, unpowered unmanned air vehicle or guided projectile. This paper considers the me...

Flight flutter testing is a crucial part in the certification of a prototype aircraft. To aid the clearance process, a number of different methods have been proposed to determine the speed at which flutter occurs on the basis of data obtained during the flight envelope expansion. However, the most commonly used approach is simply to extrapolate the...

The perched landing manoeuver enables a conventional fixed wing flight vehicle to be delivered to a point space with nominal zero vertical and horizontal velocity. This provides a novel means of retrieving UAVs in environments where obstructions or adverse terrain preclude the use of a conventional landing approach. The use of an elevated landing s...

This paper presents a neural network approach to fault diagnosis of dynamic engineering systems based on the classification of surfaces in system output vector space. A simple second-order system is used to illustrate graphically the nature of the diagnosis problem and to develop theory. The approach is then applied to the diagnosis of a laboratory...

The work reported in this paper is motivated by the need to define guidelines for building neural network-based diagnostic architectures for engineering systems in the fluid power domain. These systems are necessarily quite complex and whilst some progress has been made it has been difficult establishing the fundamental principles needed to reliabl...

Aircraft yaw control at high angles of attack by tangential forebody blowing has been investigated experimentally. Tests were performed in the University of Bath 21 m x 1.5 m low speed wind tunnel using a 6% scale generic combat aircraft model fitted with blowing slots in the nose cone. Six component strain gauge balance force and moment data were...

This paper describes the application of flow control to a civil turbofan intake for the purpose of relaxing the compressor face distortion due to crosswind constraint at take-off. Wind tunnel experiments were conducted on a 7% scale intake model capable of simulating conditions representative of high thrust at low forward speed and high sideslip an...

Fluidic flight controls enable forces and moments for flight vehicle trim and manoeuvre to be produced without use of conventional moving surface controls. This paper introduces a methodology for the design of Circulation Control (CC) and Fluidic Thrust Vectoring (FTV) as fluidic controls for roll and pitch. Work was undertaken as part of the multi...

A spin stabilised axi-symmetric disc-wing has potential application as a highly manoeuvrable, unpowered unmanned air vehicle or guided projectile. This paper considers the means by which aerodynamic control moments can be generated on such a disc-wing. The present experimental investigation outlines the aerodynamics of a non-spinning axi-symmetric...

Preliminary research using synthetic jets to control the separation line of a turbulent boundary layer on a circular cylinder, has revealed that periodic ejection and suction through an orifice leads to a time averaged jet structure, and a time averaged delay of the separation line. To answer the question of how a periodic ejection and suction can...