Ieuan Owen - Academia.edu (original) (raw)

Papers by Ieuan Owen

Virtual engineering at the ship-helicopter dynamic interface

Using Flight Simulation to Improve Ship Designs for Helicopter Operations

ICCAS 2011: International Conference on Computer Applications in Shipbuilding

The Effect of Ship Size on the Flying Qualities of Maritime Helicopters

This paper describes the use of Computational Fluid Dynamics (CFD) to produce unsteady ship airwa... more This paper describes the use of Computational Fluid Dynamics (CFD) to produce unsteady ship airwakes to investigate the effect of ship size on the pilot workload at the helicopter-ship dynamic interface. A ship model was created to represent modern naval vessels and geometrically scaled to represent smaller and larger scale ships that currently operate maritime helicopters. An unsteady airwake for each ship was computed at 40 knots for both the Headwind and Green 45° Wind Over Deck (WOD) conditions, while the mid-scale ship was also computed at 30 knots. Using Strouhal scaling, the mid-scale ship airwake was scaled both in terms of velocity and ship size. Comparisons of the resulting small and large scaled data were made with the computed CFD data and the use of Strouhal scaling was found to a feasible method for the modification of airwake data. An offline analysis using a SH60B Seahawk-like helicopter was used to determine the impact of the ship size on the pilot workload. As the ...

The application of shape memory alloy as longitudinal vortex generators for enhanced convective heat transfer

ABSTRACT This paper is concerned with the convective heat transfer enhancement of heated surfaces... more ABSTRACT This paper is concerned with the convective heat transfer enhancement of heated surfaces through the use of delta wing and wavy channels as longitudinal vortex generators. A preliminary proof-of-concept investigation has been carried out into the use of active vortex generators manufactured from Shape Memory Alloys (SMAs) which are activated at specified temperatures. The delta wing vortex generators change their shape to intrude further into the flow at high temperatures to enhance heat transfer, while maintaining a low profile at low temperatures to minimise flow pressure losses. Similarly, the wavy channels enhance heat transfer by forming a close to sinusoidal wavy shape when activated at high temperatures and turn into straight channel passages when it is deactivated at lower temperatures. As with the delta wings, a lower flow pressure loss is achieved when the channels are deactivated. One set of vortex generators was made from pre-alloyed powders of SMA material in a rapid prototyping process known as Selective Laser Melting (SLM). Another set of devices were made from commercially available flat annealed thin SMA sheets for comparison. Promising results were obtained for both the vortex generator designs when their temperatures were varied from 20 o to 85 o C. The delta wing vortex generator responded by increasing its angle of attack from 20 o to 35 o while the wavy channel elements acquired a waviness aspect ratio of 0.2. As the designs were two-way trained, they regain their initial position and shape at a lower temperature. The surface temperature of the heated plate on which the active devices were positioned were seen to reduce locally from 120 o C to 40 o C, indicating heat transfer enhancement due to the generated longitudinal vortices.

The NATO generic destroyer – a shared geometry for collaborative research into modelling and simulation of shipboard helicopter launch and recovery

Ocean Engineering, 2021

Abstract The helicopter-ship dynamic interface is the environment above the landing deck of a shi... more Abstract The helicopter-ship dynamic interface is the environment above the landing deck of a ship where a helicopter pilot has to control the aircraft while contending with a moving deck and an unsteady airflow known as the ship airwake. Research into understanding this environment has included modelling the airwake using wind tunnel studies and Computational Fluid Dynamics, and has often used the Simple Frigate Shape (SFS), a generic ship geometry representative of a naval frigate. This paper reviews the contribution that the SFS has made to research into the helicopter-ship dynamic interface, and introduces a new ship geometry for future research. The new ship, developed within a NATO Research Task Group, is the NATO Generic Destroyer (NATO-GD), a concept ship with a simplified geometry that is more representative of a modern helicopter-enabled combat ship with a stealthy superstructure. As well as introducing the NATO-GD as a common platform for research, the paper also introduces a number of ship motion profiles to encourage new research that will include the effect of ship motion on the airwake. It is anticipated that future research on a common ship, with prescribed motion and adopting a common helicopter will lead to improved or new modelling methodologies.

Transient Heat Transfer in a Liquid Sphere

Flight simulation is being used to inform the First of Class Flight Trials for the UK’s new Queen... more Flight simulation is being used to inform the First of Class Flight Trials for the UK’s new Queen Elizabeth Class (QEC) aircraft carriers. The carriers will operate with the Lockheed Martin F-35B Lightning II fighter aircraft, i.e. the Advanced Short Take-Off and Vertical Landing variant of the F-35. The rotary wing assets that are expected to operate with QEC include Merlin, Wildcat, Chinook and Apache helicopters. An F-35B flight simulator has been developed and is operated by BAE Systems at Warton Aerodrome. The University of Liverpool is supporting this project by using Computational Fluid Dynamics (CFD) to provide the unsteady air flow field that is required in a realistic flight simulation environment. This paper is concerned with a research project that is being conducted using the University’s research simulator, HELIFLIGHT-R, to create a simulation environment for helicopter operations to the QEC. The paper briefly describes how CFD has been used to model the unsteady airfl...

CFD investigation of the helicopter-ship dynamic interface

This study has been concerned with numerical predictions of the airwakes resulting from two simpl... more This study has been concerned with numerical predictions of the airwakes resulting from two simplified ship geometries: the internationally agreed Simple Frigate Shape (SFS1) and its successor (SFS2). Extensive steadystate simulations have been carried out for a wide range of wind conditions using Fluent, a commercially available computational fluid dynamics (CFD) code. Preliminary unsteady calculations have also been done. CFD predictions have been validated against wind tunnel data produced by the National Research Council of Canada (NRC) and have shown satisfactory or good agreement. The resulting airwake velocity components have been exported from Fluent, interpolated onto suitable grids and attached to the FLIGHTLAB flight-simulation environment. Using lookup tables, piloted flight trials have been carried out in the Liverpool full-motion simulator. The pilot workload and helicopter control limits resulting from a range of wind-over-deck (WOD) conditions have been used to plot ...

Simulating the Environment at the Aircraft-Ship Dynamic Interface: Development & Application

Copyright © 2019 by the Vertical Flight Society. All rights reserved. This paper describes an inv... more Copyright © 2019 by the Vertical Flight Society. All rights reserved. This paper describes an investigation into the air flow over the flight deck of HMS Queen Elizabeth, the UK’s new aircraft carrier, and how it could affect helicopter recovery. The twin islands on the starboard side of the ship mean that there will be turbulent air flow over the flight deck for starboard winds. The unsteady air flow over the ship was created using time-accurate Computational Fluid Dynamics for a 25kts wind coming from 25° off the starboard, i.e. a Green 25 wind over deck. As well as using the CFD results to show the expected mean velocity field and turbulence intensity over the flight deck, the time-varying velocity components have also been used to assess how the unsteady air flow will affect a helicopter by integrating the velocity components of the ship’s airwake with a flight dynamics model of a helicopter configured to represent a SH-60B Seahawk. The application of the helicopter flight dynam...

The aerodynamics of a bulky mast

Many modern warships have enclosed main masts that are bulky and very different to the lattice or... more Many modern warships have enclosed main masts that are bulky and very different to the lattice or pole masts of earlier ships. While the newer masts are carefully designed to reduce radar cross section, and provide a weather tight enclosure for sensors and systems, they also significantly affect the air flow over the ship. This paper reports some results from a CFD study of the air flow over a generic ship representative of a modern frigate with an enclosed mast. Specific attention has been paid to the unsteady velocities at locations around the mast where a ship’s anemometer might typically be placed. The flow is seen to be highly disturbed and both the wind strength and angle are significantly different to those of the free stream, hence making a true wind over deck measurement difficult. In the context of helicopter launch and recovery this makes it difficult to specify the helicopter’s operational limits which can restrict operational capability. The study has also quantified th...

Assessing the suitability of ship designs for helicopter operations using piloted flight simulation

Ship airwakes have a significant effect on the operation of ship-borne helicopters. This paper de... more Ship airwakes have a significant effect on the operation of ship-borne helicopters. This paper describes a piloted flight simulation study into the effect of three different aerodynamic modifications to a generic ship geometry on pilot workload. Unsteady CFD airwakes have been computed using Detached-Eddy Simulation and integrated into the FlightLab simulation environment with a simulated rotorcraft model, configured to be representative of an SH-60B helicopter. A series of ship-deck landing and hover manoeuvres have been conducted using the University of Liverpool’s HELIFLIGHT-R motion-base flight simulator for the different ship geometries and the pilot workload was assessed using the Bedford Rating Scale. Analysis of the computed CFD airwake data has shown that the ship modifications have created reductions in turbulence intensity levels in the airflow through the flight path. Significant reductions in pilot workload ratings from flight tests indicate improved workload characteri...

Launch and recovery operations of helicopters to and from ships are often carried out in challeng... more Launch and recovery operations of helicopters to and from ships are often carried out in challenging at-sea conditions, such as a confined landing deck, irregular ship motion, sea spray and unsteady airflows over and around the ship’s superstructure. Together, these elements form the Helicopter Ship Dynamic Interface (HSDI) environment, posing a high risk to the helicopter, ship and crew [1]. To determine the safe operability of helicopter to ships, a safety envelope known as Ship Helicopter Operating Limit (SHOL) is constructed, normally through First of Class Flight Trials (FOCFTs). This process can be time-consuming and expensive and new approaches to determine SHOLS are being developed.

Proceedings of the International Naval Engineering Conference and Exhibition (INEC), 2018

The Type 26 City class Global Combat Ship is the latest design of UK frigate. Construction of the... more The Type 26 City class Global Combat Ship is the latest design of UK frigate. Construction of the first ship, HMS Glasgow, began in July 2017 and the expectation is that it will enter service in the mid-2020s as a replacement for the Royal Navy’s Type 23 Duke class frigates. The main contractor for the design and construction of the ship is BAE Systems Maritime – Naval Ships. The Type 26 superstructure is characterised by its smooth sloping surfaces that are continuous along the ship from the fore deck to the flight deck. The tumblehome design reduces the ship’s radar cross-section, as does the minimisation of curved surfaces and internal corners. The Type 26 also has a bulky mast, also with flat sloping sides, while the funnel casing around the gas turbine exhaust uptake is located aft of the main mast and relatively low on the superstructure. In comparison, the earlier Type 23 has a much more fragmented superstructure with few geometric features for reduced radar reflection; it al...

PIV Measurements in Large-scale Cardiovascular Models – The Importance of Dynamic Scaling

Optical and Laser Diagnostics, 2003

Particle Imaging Velocimetry and Laser Doppler Anemometry are often used in research into blood f... more Particle Imaging Velocimetry and Laser Doppler Anemometry are often used in research into blood flow (haemodynamics). This paper shows how a largescale model of an arterial junction (a distal anastomosis, or bypass graft) can be used to represent the in vivo blood flow provided the correct scaling procedures are applied. Blood is a non-Newtonian liquid whose viscosity can be represented by a power law. Dimensional analysis shows that a pulsatile flow of a power-law fluid can be characterised by a generalised Reynolds number, the Strouhal number, the Pulsatility Index, and by the power-law exponent n. It is clearly demonstrated in this paper that a non-Newtonian liquid cannot be properly represented by a Newtonian liquid, but it can be very well represented by a non-Newtonian liquid that has the same power-law exponent. If, however, the common practice of using a Newtonian liquid is adopted, the wall shear stress along the bed of the anastomosis will be seriously over-predicted by as much as 100-200. Â© 2003 IOP Publishing Ltd.

A note comparing the rates of deposition of submicron particles with the rates of heat transfer for ribbed surfaces exposed to turbulent gas streams

Journal of Aerosol Science, 1986

ABSTRACT

Flow Measurement and Instrumentation, 1991

The vapour mass fraction (dryness fraction) of wet-steam flows such as those encountered in the s... more The vapour mass fraction (dryness fraction) of wet-steam flows such as those encountered in the steam main of a power or process plant will rarely be less than 90%. In flowmetering of high-quality saturated steam, the moisture content in the steam is allowed for by correcting the mass flow indicated by the steam flowmeter. Although there are a number of different ways of correcting the mass flow for water content, there is still doubt as to the methods used. In the work reported in this paper, three types of flowmeter were calibrated: first in superheated steam and then in an equilibrium wet-steam mixture to determine their wet-steam correction factors. The correction factors were found to be dependent on the types of flowmeter. For consistency with recommended practice, the method recommended by the "Shell Flowmetering Engineering Handbook" (Ed. G. W. A. Danen, McGraw-Hill, 1985) can be used universally with reasonable accuracy provided a high-efficiency separator is placed upstream of the steam meter to increase the dryness fraction to above 95%.

Experiments in Fluids, 2007

Dimensional analysis has been applied to an unsteady pulsatile flow of a shear-thinning power-law... more Dimensional analysis has been applied to an unsteady pulsatile flow of a shear-thinning power-law non-Newtonian liquid. An experiment was then designed in which both Newtonian and non-Newtonian liquids were used to model blood flow through a large-scale (38.5 mm dia.), simplified, rigid arterial junction (a distal anastomosis of a femorodistal bypass). The flow field within the junction was obtained by Particle Imaging Velocimetry and near-wall velocities were used to calculate the wall shear stresses. Dimensionless wall shear stresses were obtained at different points in the cardiac cycle for two different but dynamically similar non-Newtonian fluids; the good agreement between the measured dimensionless wall shear stresses confirm the validity of the dimensional analysis. However, blood exhibits a constant viscosity at high-shear rates and to obtain complete dynamic similarity between large-scale experiments and life-scale flows, the high-shear viscosity also needs to be included in the analysis. How this might be done is discussed in the paper.