Vacant PhD topics at Delft University of Technology as of 2011

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Feb 22, 2014 (3 years and 1 month ago)

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1


Vacant PhD topics at Delft University of Technology
as of 2011


Note that below overview is by no means exhaustive, so in case you wish to
pursue

a PhD on topics
other

than given below, please
contact Mr
Cees Timmers
at
c.timmers@tudelft.nl





Subject

Design of Pd
-
alloys for hydrogen separation membranes

Researcher

To be decided

Contact TU Delft

Assoc. Professor. Dr. A. J. Böttger, Materials Science and
Engineering, Delft University of Technology

Short de
scription

The development of highly selective hydrogen membranes is one
of the main technical challenges associated with the production
of high
-
purity hydrogen in membrane reactors. The membranes
should withstand the demanding industrial conditions of high

temperatures and pressures in multi
-
component corrosive
gaseous environments.
Metal
-
based membranes, in particular,
Pd
-
based membranes are suitable for this purpose. The lifetime
of pure Pd membranes in thermal cycles from operational
conditions to room t
emperature is limited. Failure occurs due to
deformation and fracture caused by the large specific volume
change upon hydride formation. Longer operation lifetime can
be achieved through the addition of specific alloying elements
that prevent hydride forma
tion. The nature of the specific
alloying elements i.e. their concentration and distribution in the
metal lattice influences the hydrogen solubility and the diffusion
through these membranes
.

This implies that knowledge of the
structure and the stability o
f phases formed during hydrogen
absorption/desorption in Pd alloys is crucial for the prediction of
properties such as permeation.


This research project aims at the design of metal alloys (fcc and
bcc) with tailored properties such as a particular critica
l
temperature for hydride formation. The design is based on a
thermodynamic model, developed at the Delft University, that
incorporates the interactions of a binary host metal alloy with
interstitials (hydrogen). This enables to predict order
-
disorder
tran
sitions, phase stabilities and specific volumes. In this project
(i) the model has to be extended to multi
-
component alloys and
(ii) has to be applied to design new multi
-
component alloys.

To be able to develop new alloys with not yet know properties,
i.e
. for systems for which no experimental thermodynamic data
are available, ab
-
initio calculations are required. The
calculations of the ground state energies will be preformed using
VASP. The results of the ab
-
initio calculations serve as an input
to the e
xtended statistical thermodynamic model that will be
used to determine phase boundaries and other properties.




2

Subject

Development of stable Pd
-
membranes for hydrogen
separation from gas mixtures

Researcher

To be decided

Contact TU Delft

Assoc. Profess
or. Dr. A. J. Böttger, Materials Science and
Engineering, Delft University of Technology

Short description

Hydrogen is widely used in petroleum refining, production of
fertilizers, metallurgical processes and as clean fuel. The energy
needed to fulfill th
e current worldwide H
2

production, i.e. 1.7
billion m
3
/day, is huge and amounts 1000 TW per year. Most of
the H
2

is produced from steam reforming of methane that is
obtained from natural gas and coal gasification. The energy
efficiency o
f CH
4

conversion

ca
n be improved considerably by
using membrane reactors. By removing

H
2

from the reacting
gases, during the combined steam reforming and water gas shift
reactions, the CH
4
conversion increases from 40% in
conventional plants to > 90%
in a membrane reactor. B
esides
its energy efficiency, the high purity of the H
2

manufactured and
the lack of green
-
house gas emission by capture of CO
2

are big
advantages with respect to conventional technologies. The use
of membrane reactors is hindered by the limited lifetime o
f the
membrane material, i.e. the mechanical, thermal and chemical
stability under process conditions. Stringent requirement for
membrane performance, high perm
-
selectivity and stability,
restrict the materials choice. Pd
-
based membranes are currently
the
most promising. The lifetime is limited by mechanical failure
due to phase transformation, temperature
-
induced grain growth
and segregation as well as fouling.
Grain growth and segregation
can occur at operation temperatures of a membrane reactor.
The chan
ges in the microstructure and surface characteristics
largely reduce the permeability.
By careful alloying many of
these issues can be solved.


This project aims at the development of thin film membranes
with a stable microstructure. To this end experiment
al
observations will be used to determine the dominating processes
that cause microstructural changes and to describe these
processes on the basis of physical
-

chemical models. The main
experimental tools will be X
-
ray diffraction and mechanical
testing.
The MSE
-
lab is equipped with several diffractometers, an
in
-
situ tensile test set
-
up and an in
-
situ high
-
temperature
chamber are available.



Subject

Shockwave
-
induced spraying of reinforced composite
coatings

Researcher

To be decided

Contact TU Delft

Assoc. Professor Dr. A. J. Böttger, Materials Science and
Engineering, Delft University of Technology

Short description

Shockwave
-
Induced Spraying process (also indicated by pulsed
gas dynamic spraying) is a recently developed solid
-
state
spraying process

for deposition of metals, alloys, cermets on
virtually any type of substrate at low temperatures. The
relatively low temperatures used prevent phase transformations


3

of the feedstock powder. The spraying technique shows higher
deposition efficiencies and d
eposition rates than traditional
thermal spray processes. Shockwave
-
induced spraying can
produce relative thick layers (from 200 micron up to 5 mm).
Contrary to laser cladding or hot spraying, where the powder is
melted, the (pre
-
heated) powder is fused t
o the substrate mainly
by means of the kinetic energy of the powder jet. This has
several potential advantages over laser cladding and
conventional hot spraying: no development of brittle
intermetallics and the residual stresses in the coatings are
negligi
ble. The coatings also have a
significantly improve wear
resistance.


The project aims at exploring new feedstock powders and
applications of the shockwave
-
induced spraying process and
investigating the microstructural changes in the material upon
depositi
on. In relation to properties.


___________________________________________________________________________

Investigation of the unsteady aerodynamics and fluid
-
structure interactions of a
flapping
-
wing MAV






Flapping wing aerodyn
amics: CFD simulation (left) and the Delfly MAV (right)


Flapping
-
wing propulsion is an attractive configuration for small observation MAVs, in view of
the advantages for the flight envelope, permitting both efficient and stable hovering and
forward flight

conditions. The present research aims to support this development by
increasing the understanding of the aerodynamics of flapping wings. More in particular, the
aerodynamic performance of the “Delfly” is investigated, which is a flapping
-
wing MAV
develope
d as an autonomous camera platform for observation (see
www.delfly.nl
). The
higher goal objectives of the research are to exploit this better knowledge of the
aerodynamic behaviour of the Delfly in improving its design and performance, especially in
the ne
xt step of further miniaturization of the design. In this project the Aerodynamics Group
closely cooperates with the development lab of the Delfly.

The interest in the research lies in identifying the relevant phenomena that determine the
Delfly’s flight
performance, where in particular the following aspects are involved: (1) the
highly unsteady and complex vertical flow induced by the flapping wings, especially in the


4

clap
-
and
-
fling phase, and the role of vortex generation on flight performance; (2) the i
mpact
of wing structure and skin foil flexibility in the interaction of the wing with the flow (fluid
-
structure interaction). These topics will be investigated by a combination of experimental and

numerical analysis techniques.


Supervisors:

Dr.ir. B.W. v
an Oudheusden, Prof.dr.drs.ir. H. Bijl (Aerodynamics Group) and Ir.ing B. Remes
(MAV lab)

___________________________________________________________________________


Multi

浯de氠c潵p汩湧 景爠晬u楤

s瑲tc瑵牥 楮te牡c瑩t渠

Nonlinear aeroelastic phenomena occ
ur in aircraft and wind turbine applications. Accurate
prediction of these unwanted fluid

structure interactions requires solution of the coupled
flow and structure equations. Typically these are solved in a partitioned manner, coupling a
separate (Navier

Stokes) flow and structure solver.

In partitioned fluid

structure interaction computations, strongly coupled physical problems
may require a sub

iterating technique, solving the flow and structure equations several times
per time step. These sub

iteration
s are computationally expensive as they require solving
flow and structure multiple times for a single time step. Acceleration of these sub

iterations
can be obtained by using a multi

level approach, resolving a correction term on a coarse
level representa
tion for a defect on the fine level. When the coarse level model consists of a
coarse computational mesh, the method resembles a multigrid

like technique.

In this project the aim is to use a reduced order model as coarse level representation of the
fluid

structure interaction problem. The idea is that the reduced order model can accelerate
the convergence of the high

fidelity model and that the high

fidelity model can be used to
improve (e.g. coefficients of) the reduced order model. The challenge is to de
velop an
algorithm that defines the defect and correction terms and the transfer of data between the
fine and coarse level models. Possible complications are differences in dimensionality,
non

matching computational domains, etc.

__________________________
_________________________________________________


Ground and fuselage engine inlet vortex study for aircraft engine
integration

Under certain, not very well classified/understood conditions, the flow induced around a
stationary or slowly moving (taxiing)

aircraft on the ground will separate from the fuselage,
roll up into an axial vortex and cause significant distortion of the flow in the engine intake
plane. Just like in the case with the wake of the aileron, the distortion of the flow not only
reduces t
he engine efficiency, it also introduces unsteady loads on the engine parts and
thereby reduces the life expectancy of the engine adding to the operational costs. The
passenger discomfort is a secondary disadvantage.

Since the trend in modern aero engines

is to increase the inlet diameter driven by quieter
and more efficient operations, the proximity of the engines to the ground or fuselage is
affected. This may put the engines in a position that may be more susceptible to be in a
condition where inlet vor
tices could occur. Also new configurations like the blended wing
-
body configuration, where up to now no research about this problem has been done, need to
be considered. Other developments in engine technology like the unducted fan, in the near
future a se
rious alternative for the turbofan engine in e.g. fuselage mounted engine
configurations where no information is available on this subject, need to be considered
seriously.



5

The inlet vortex itself is known for more than fifty years and several studies hav
e been
conducted to analyze this phenomenon. From simple observational studies to numerical
simulations performed in recent years. The analysis of the problem in terms of fluid dynamic
characteristics is still rather sparse.

A thorough research project sh
ould consider the low speed phenomenological aspects of the
engine flow. Starting with the concept of a modern high bypass ratio engine (VHBR or
UHBR), several configurations should be studied for their tendency to create an inlet vortex
in various ambient

flow conditions: still air, head wind, tail wind and side wind. This should
be further studied in order to obtain deeper insight into the interaction of the pressure field
with the solid boundary in order to obtain configuration independent criteria for t
he
occurrence of vortices upstream of an engine inlet. Also the severity of the negative effects
on the engine should be taken into account. It should follow logically that this is then
expanded into propellers and unducted fans.

In summary, for the estab
lishment of reliable design rules and design tools a thorough
analysis is required. This analysis can only be successfully performed by combination of a
numerical and an experimental simulation into a single approach. The numerical approach
will need good
experiments to provide validation of turbulence modeling and separation
locations. The experiments validate parameter space and modifications with great efficiency.
They must start with simple preliminary data gathering tests at the TUD and end (with the
s
upport of the EU commission) in a large
-
scale simulation of realistic future configurations in
the LLF of the DNW.

___________________________________________________________________________

Error Estimation and Uncertainty quantification for Coupled Fluid

却牵c瑵re
卩浵污瑩l湳n

The good news is that nowadays we can solve nonlinear fluid

structure interactions,
numerically solving the coupled flow and structure equations. The bad news is that the result
of the simulation often does not coincide with observa
tions. This can be due to numerical
errors or model errors or uncertainties.

In this project an error and uncertainty quantification technique will be further developed
and applied to aeroelastic problems. For the numerical error
a posteriori
error estima
tion has
been demonstrated as a valuable tool in aerodynamic analysis, delivering reliable estimates
of error in integrated quantities that allow an engineer to judge seriously the quality of a
simulation. The coupled fluid

structure case is more difficult but also more critical, as there
are a greater number and variety of sources of numerical error

and the results have more
practical value. Model uncertainties (i.e. in the structural model parameters or the turbulence
mo
del) can be efficiently quantified with uncertainty quantification techniques developed in
Delft. In this project they will be further developed and applied to aeroelastic problems.


_________________________________________________________________________
__

Experimental Data
-
Assimilation in CFD with Least
-
Square Finite Element Methods

Current practice for flow analysis is to either perform a computational simulation or an
experiment. In case both are performed only end results are compared. We believe tha
t
much can be gained by truly combining both approaches in one rigorous methodology. As
the Aero Group in delft both has an experimental as well as a numerical section, there lies an
opportunity.

Integration of modern CFD and experimental capabilities for

aerodynamic analysis has the
potential for enormous synergistic effects. The usefulness of experimental data could be
enhanced greatly by computing values that can not be directly measured (e.g. obtaining
pressure and boundary information from PIV velocit
y data), and the accuracy and reliability


6

of simulation could be improved by incorporating experimental information (particularly with
respect to turbulence modeling). However there is currently no general framework for
performing this assimilation of expe
rimental data. This PhD will concentrate on one possible
approach based on the Least

Squares Finite Element Method (LSFEM). This method allows
the flexible introduction of additional constraints on the numerical discretization in an
appropriate and meaningful way. The over

determined system is then solved in a
least

squares manner. The ac
curacy of the experimental input information can be rigorously
accounted for by weighting. The finite element context makes high

order accuracy,
adaptation and error estimation possible.

After its development, the data assimilation method is applied to an
alyse steady and
unsteady flows around airfoils. Experimental PIV data are available.

___________________________________________________________________________


Active flow separation control using plasma actuators


In the design of future transport airc
raft the need for high fuel efficiency aircraft over the
complete flight envelope is of crucial importance. The cruise condition requires further
improvement in the development of low drag designs. To enable a reduction of the induced
drag generated by the

wings application of light weight structures is inevitable. Hence
smooth wing designs with limited number of moving parts is required. The profile drag of
these designs may be reduced by postponement boundary layer transition through the
applications of s
o called Dielectric
-
Barrier
-
Discharge (DBD) plasma actuators. Currently a
research project on this topic is being performed within the aerodynamics group of the
Faculty of Aerospace Engineering.


However in the low speed, high lift regime, the maximum lif
t that can be attained is the
limiting factor through the occurrence of flow separation on either the main wing of the
extended flap.


To enable a further performance improvement of conventional fowler flap designs as well as
novel flapless future wing de
signs, the application of plasma flow control actuators will
investigated.


The project will be performed both numerically and experimentally and is based on
experience with single DBD actuators that was recently obtained in the aerodynamics labs of
the f
aculty. High Reynolds and Mach number tests are foreseen in larger wind tunnel
facilities of DNW at a later stage.


This project will be performed in close cooperation with:



NLR, the Dutch Aerospace Laboratory



Dassault Aviation / AirBus



NeqLab b.V.

__
_________________________________________________________________________


Reduced
-
Order Models for

Wall
-
Bounded Turbulent Flow Control


(
S. J. Hulshoff
,
Aerodynamics Group, TU Delft
)




7



Wall
-
bounded turbulent flows are widespread in engineering applicati
ons, and have
substantial negative economic impact due to their high rates of energy dissipation.
Consequently, there is considerable motivation to develop microscale sensor and control
systems which canreduce turbulent energy dissipation [2]. However, due

to the limitations
inherent in turbulent flow characterisation using only surface measurements, such systems
require accurate reduced
-
order flow models in order to become fully effective.

The standard approach to reduced
-
order modelling is to determine a
modal expansion of
experimental or computational data, and then to derive a model using Galerkin projection of
the Navier
-
Stokes equations onto a limited number of modes. Modal expansions are normally
found using proper orthogonal decomposition (POD), as P
OD modes are optimal in the sense
that they minimise the average mean
-
square error of the solution obtained from truncated
versions of the expansion [3, 4].

Recently, however, goal
-
oriented procedures have been developed which allow the
determination of no
n
-
POD expansions which are optimised for the prediction of a chosen
output of the reduced
-
order model [1]. These procedures have yet to be applied to turbulent
flows, but have the potential to produce reduced
-
order models which are closely focused on
accur
ate representations of the interactions between the flow and flow
-
control device.

In this research, goal
-
oriented reduced
-
order modelling procedures will be developed
specifically for application to wall
-
bounded turbulent
-
flow control via forced wall motio
n. A
number of candidates for optimal outputs will be investigated, and the robustness of the
associated model
-
construction algorithms assessed. The accuracy and range of the resulting
models will be tested using experimental data and highly
-
resolved large
-
eddy simulations.

If successful, this project would represent a substantial step towards the identification and
control of a ubiquitous energy
-
consuming phenomenon.


[1] T. Bui
-
Thanh, K. Willcox, O. Ghattas, and B. van Bloemen Waanders. Goal
-
oriented,
mod
el
-
constrained optimization for reduction of large
-
scale systems. JCP, 224:880

896,
2007.

[2] M. G. el Hak. Flow control: Passive, Active and Reactive Flow Management.

[3] P. Holmes, J. L. Lumley, and G. Berkooz. Turbulence, Coherent Structures, Dynamical
Systems and Symmetry.

[4] B. Podvin. A proper
-
orthogonal
-
decomposition
-
based model for the wall layer of a
turbulent channel flow. Physics of Fluids, 21:015111, 2009.

___________________________________________________________________________


Investigatio
n of jet aero

ac潵s瑩cs⁢礠 i浥 牥s潬ve搠d潭潧牡灨pc⁐IV


Incompressible and compressible jets are to be investigated experimentally by a novel
three

dimensional technique: Tomographic Particle Image Velocimetry. The main objective
of the work is to identi
fy the most important phenomena governing the generation of
acoustic noise from jets with several configurations. In the last part of the research attempts
will also be made to study possible control techniques aiming at minimizing the jet noise


8

emissions.

Candidates should have a good background in theoretical and experimental aerodynamics.
Some background knowledge in turbulence is also favored.

Hosting section
: Aerodynamics
Supervisor
: Prof. Dr. Fulvio Scarano
Co

s異e牶楳o牳
: Dr.
Peter Moore, D. Violato


References
:

Time

resolved analysis of circular and chevron jets transition by Tomo

PIV, Fulvio Scarano,
Kristof Bryon, Daniele Violato, 15th Int Symp on Applications of Laser Techniques to Fluid
Mechanics, Lisbon, Portugal, 05

08 July, 2010, paper #1835

3
D laser diagnostics of jets by tomographic PIV

Measured instantaneous vortex topology and axial velocity

___________________________________________________________________________

Aero
-
elastic analysis of tethered flexible membrane wings


Flexible membran
e wings are used for a variety of technical applications, such as parachute
systems for payload deployment and landing or tethered kite systems for High Altitude Wind
Power (HAWP) generation. In contrast to rigid wings, the flight dynamics of parachutes or

kites is generally governed by strong fluid
-
structure
-
interaction phenomena, which need to
be taken into account for predictive aero
-
elastic models. The particular challenge is that the
aerodynamic load distribution not only determines the shape of the me
mbrane struc
ture but
is affected substantially by the shape itself. This two
-
way coupling of structural dynamics
and aerodynamics, i.e. the aero
-

elastic characteristics of the wing, influences the
instantaneous lift and drag of the wing and thus its flight dynamic be
havior. For example,
recent research indicates that the twisting shape deformation of a ram
-
air or a Leading Edge
Inflatable (LEI) kites is an essential contribution to the steering mechanism. In addition to
this, the dynamic characteristics of tether and
bridle system need to be taken into account.

The objective of this research project is to develop a modal model of the aero
-
elastic
membrane wing. Starting point will be an existing multibody model of a tethered LEI tube
kite which is based on a discretiza
tion by ~400 connected rigid elements and a parametric
aerodynamic model. This model, the “Kite Simulation Toolbox” built in MSC Adams, will be
used to investigate the deformation of the wing for various nominal flight maneuvers such as
figure
-
eight “cross
-
wind” maneuvers during cable reel
-
out and de
-
powered “flagging” of the
kite during cable reel
-
in. The major deformation modes of the wing (e.g. “jellyfish” or
“twist”) will be identified and quantitatively assessed. Based on this modal description, the
ae
rodynamic model will be revised to include the effect of shape deformations.
Computational Fluid Dynamic analysis such as Vortex Lattice methods (tornado) and/or Finite
Volume methods (Fluent) will be used for this purpose.

References

J. Breukels, W.J. Ock
els: “Simulation of a flexible arc
-
shaped surf kite”. Manuscript,
submitted to AIAA Journal of Aircraft. J. Breukels: “An Engineering Methodology for Kite
Design”, PhD dissertation, Delft University of Technology, 2010.


___________________________________
________________________________________

Flameless Combustion for Aircraft Engines


Flameless Combustion (FC) is a promising combustion regime that forms highly transparent
flames (and hence the name
Flameless Combustion
) with low thermo acoustic oscillati
ons,
distributed combustion and uniform temperature profile within the combustor.
Flameless
Combustion
is also referred to in the literature as FLameless OXidation (FLOX
®
), High
Temperature Air Combustion (HiTAC), Moderate and Intense Low oxygen Dilution
(MILD)
combustion, and heat
-
recirculating combustion. FC can reduce NOx emission by more than
80%.



9


There are several challenges in applying this technology to gas turbine combustors. The
main objective of the research would be to investigate the fundamen
tals of FC numerically
and experimentally and to design a combustion chamber that can generate appropriate
boundary conditions for flameless combustion to sustain under sever operating conditions of
an aero engine.


Prior knowledge of Gas turbines and CF
D would be desirable.

















__________________________________________________________________________


Radiation damage on nuclear graphite


The aim of this PhD project is the investigation of radiation damage in nuclear graphite by
combining

structural information obtained by positron annihilation, neutron and X
-
ray
scattering techniques. Positron annihilation gives unique information on the defects, the
formation of pores and their size. Neutrons have a large penetration power and will be us
ed
to investigate the structure at the atomic level (neutron diffraction). Furthermore small angle
neutron scattering (SANS) will follow the formation of pores at length scales from 1 nm up to
60 nm. Structural information at length scales up to 15
μ
m will be obtained by the high
-

resolution spin echo SANS (SESANS), which has been developed at Delft and is unique in the
world. These results will be complemented by X
-
ray tomography, which will extend the
structural information to the macroscopic lengt
h scales. The combination of these
experimental techniques will provide unique structural information, which will be used to
validate the computer simulations and theories. Nuclear graphite is an important moderation
material in nuclear reactors and the st
ructural changes due to radiation damage affect its
mechanical
-

thermal properties and consequently its lifetime. The results obtained in the
frame of this PhD project will shed a new light on this research field and will be of decisive
importance for the

design of next generation nuclear power plants.









300
600
900
1200
1500
1800
2100
0
3
6
9
12
15
18
21
24
27
30
Lifted flames
Hot Flames
Non Combustible
zone
Ignition Boundary
4
8
2
1
0
Recirculation Ratio
% Dilutants (N
2
+CO
2
+H
2
O)
100
97
95
92
88
85
82
79
76
73
70
%
O
2
in reactants
Temp. of Reactants (K)
Auto Ignition Temp
Normal
Combustion
Flameless
Combustion
16
0.5
Oxy
-
rich Flames
300
600
900
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2100
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2100
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0
3
6
9
12
15
18
21
24
27
30
Lifted flames
Hot Flames
Non Combustible
zone
Ignition Boundary
4
8
2
1
0
Recirculation Ratio
% Dilutants (N
2
+CO
2
+H
2
O)
100
97
95
92
88
85
82
79
76
73
70
%
O
2
in reactants
Temp. of Reactants (K)
Auto Ignition Temp
Normal
Combustion
Flameless
Combustion
16
0.5
Oxy
-
rich Flames
Different combustion regimes