design. Propulsion system elements efficiency increase...

MAAT Multibody Advanced Airship for Transport Project ID 285602 / FP7-AAT-2011-RTD-1

Galina Ilieva Jos Pscoa Miguel Silvestre

26.05.2014

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Universidade da Beira Interior, Departamento de Engenharia

Electromecnica,

R. Marqus D'vila e Bolama

Covilh, Portugal

WP3, WP4 JBLADE code innovative software - HAP

design. Propulsion system elements efficiency increase.

Transition modeling new turbulence model

WP4, WP5 Aerodynamics, forces and effects affecting

the propulsive system performance

WP4 Propulsive systems for cruiser and feeder design

UBI

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MAAT Multibody Advanced Airship for Transport Project ID 285602 / FP7-AAT-2011-RTD-1 26.05.2014

6000

7000

8000

9000

10000

11000

12000

0 1 2 3 4 5 6 7 8 9 10

Dra

g [N

]

0

0,2

0,4

0,6

0,8

1

1,2

1,4

1,6

1,8

2

0 1 2 3 4 5 6 7 8 9 10

Use

ful L

oad

[N

]

x10^5

l/d

Dyneema

PET(mylar)

Vectran

Tedlar PV2001

AluminiumAlloy 2024-

T351

Stainless Steel316Ti

PARAMETRIC STUDY OF HIGH ALTITUDE AIRSHIP

Ph.D. Student Joao Morgado

h=0 m

Ve = 20 000 m3

Ve2/3= 736.81 m2

v = 25 m/s

h=0 m

Ve = 20 000 m3

Ve2/3= 736.81 m2

v = 25 m/s

Fig. 1 The influence of fineness ratio on airships drag. Fig. 2 The influence of fineness ratio on useful load.

A methodology to carry out parametric studies for conceptual design evolution of a high altitude airship was

implemented. This methodology is quite useful to identify key parameters and especially to study the what-if

scenarios.

The implementation of methodology is open ended, so it can be continuously updated with new models found in

literature to provide more accurate results.

This methodology can be adopted to Multidisciplinary Design Optimization of an airship system as a way to

determine the optimum combination of design parameters and options that correspond to highest payload

available.

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360 Polar Object

-Lift and drag coefficients;

-Reynolds number;

-Full angle of attack range.

Extrapolated Data

Blade Object

-Geometric parameters;

-Number of stations;

-Number of blades;

360 Polar Objects

Propeller Object

-Propeller Parameters;

Blade Object

Propeller Simulation Object

-Simulation Parameters.

Propeller Object

Blade Data Object

Blade Data Object

-Simulation Results Data along

the blade.

-Induction Factors;

-Inflow Angles;

-Circulation;

-Advance Ratio;

-Speed. BEM Simulation

-Advance Ratio;

-Speed Range.

360 Polar

Extrapolation

Airfoil Object

-Airfoil

Coordinates;

-Airfoi l Camber;

-Airfoil Thickness;

Polar Object

-Lift and drag

coefficients;

-Reynolds number;

-Angle of attack range.

Airfoil Object

Simulation Results

Panel

Simulation

- Angle of attack

Range

XFOIL

BEM CODE

JBLADE SOFTWARE - user-friendly, accurate, validated OS code, that can be used to design and optimize a variety of propellers


Fig. 3 Interaction among different sub-modules of the programm elaborated in UBI

The post stall model plays a

significant role in the low

advance ratio region and may

well be the main source of the

remaining differences relative

to the actual propeller

performance.

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The long term goal of the JBLADE development is to provide a user-friendly, accurate, and

validated open-source code that can be used to design and optimize a variety of propellers. The code

allows the introduction of the blade geometry as an arbitrary number of sections, characterized by

their radial position, chord, twist, length, airfoil and associated complete angle of attack range

airfoil polar.

JBLADE SOFTWARE


An airship propeller must be very efficient in thrust/power ratio during hovering conditions as

well as it should maintain the high propulsive efficiency during cruise flight. Knowing that the

MAAT project will operate an airship under stratospheric conditions, it is crucial for us to have a

numerical tool suitable for the optimization needs of airships propellers.

Optimizing the propeller shape and performance is required in order to maximize effectiveness

over the flight envelope. The optimization process is based in the analysis of numerous designs as to

compare their relative merits.

3D Equilibrium shows better results than the classical BEM formulation but could be improved further for

actual axial velocity (the induced one) distribution.

JBLADE seems superior to other available open source codes.

The post stall model plays a significant role in the low advance ratio region and may well be the main

source of the remaining differences relative to the actual propeller performance.

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The Blade sub-module, contains a 3D tool which allows the user to visualize the blade final shape. In addition it was

also implemented and inverse design methodology for calculation of the blade geometry for only one given

operating point.

The Multi-Parameter Simulation sub-module allows the simulation of the propeller varying the air speed, the

propeller rotational speed and the propeller pitch angle, providing a easy way to evaluate the propeller performance

for further improvements towards optimization.

Fig.5 Simulation environment -Sub-module. Fig.4 Blade Definition process and Inverse Design Sub-

module.

JBLADE SOFTWARE I


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4

5

at 0

.75R

30

at 0

.75R

JBLADE SOFTWARE I


Fig. 6 Validation of

JBLADE code against

NACA TR 594

Propeller C, Martin

Hepperle Code

JAVAPROP and Mark

Drelas code QPROP

The new JBLADE code to propeller design is successfully implemented and its

validation shows promising results. The improvements in the method to extrapolate

the drag coefficient polar besides reducing the errors, introduced by the user, leads

to an improvement in the prediction of all propeller performance coefficients as well

as in its propulsive efficiency prediction.

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Incorporating : blade structure module; electrical motor module in the code such that the thrust per unit

weight for constant power of the complete propulsion set can be optimized as a whole.

JBLADE SOFTWARE I


FUTURE WORK and list of publications

Refereed Conference Papers Morgado, Joo, Miguel ngelo Rodrigues Silvestre, and Jos Carlos Pscoa. 2012. Parametric Study of a High Altitude Airship

According to the Multi-Body Concept for Advanced Airship Transport - MAAT. Proc. of IV Conferncia Nacional Em Mecnica Dos

Fluidos, Termodinmica e Energia. LNEC, Lisbon - Portugal; 28-29 May 2012.

Morgado, J., Silvestre, M. A. R. and Pascoa, J. C.. 2013. Full Range Airfoil Polars for Propeller Blade Element Momentum Analysis.

Proc. of 2013 International Powered Lift Conference. Los Angeles, California: American Institute of Aeronautics and Astronautics.

DOI:10.2514/6.2013-4379.

Silvestre, M. A. R., Morgado, J. and Pascoa, J. C. 2013. JBLADE: a Propeller Design and Analysis Code. Proc. of 2013 International

Powered Lift Conference. Los Angeles, California; American Institute of Aeronautics and Astronautics. DOI:10.2514/6.2013-4220.

Morgado, J., Silvestre, M. A. R. and Pascoa, J. C.. 2013. Low Reynolds Propeller Design and Analysis with JBLADE Accepted for

Presentation at AVIATION 2014.

Journal Submissions

Morgado, J., Silvestre, M. A. R. and Pascoa, J. C.. 2013. Validation of New Formulations for Propeller Analysis Submitted to

Journal of Propulsion and Power AIAA 1st Revision Completed.

Morgado, J., Silvestre, M. A. R. and Pascoa, J. C.. 2013. A software tool for propeller inverse design and aerodynamic performance

prediction Submitted to Aerospace Science and Technology Elsevier

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Ph.D. Student Rui Oliveira

At high altitude the air flow presents low turbulence intensity. This leads to a late transition to turbulence of the laminar

boundary layers. This fact is very important for all the components of a propulsion system. The correct flow state calculation,

turbulent or laminar, is of extremely important. Failure to provide an accurate determination of the flow state will over -or under -

estimate power requirements. Incorrect determination of flow separation will deliver an incorrect operational envelope of the

propulsion system.

That is why we need of correct determination of the transition region . Nowadays turbulence models lack of specific and

correct term for transition determination. Main goal during the MAAT project research activities was to elaborate turbulence model

for correct and exact prediction of the transition regions over streamed bodies, especially in case of high altitudes.

In our team Rui Oliveira is currently working on the elaboration and implementation of a new turbulence code.

Objectives

Implementation of recently developed transition models in OpenFOAM.

Evaluation of transitional model codes performance.

Accuracy refinement of selected transition model.

Validation of implemented turbulence transition models.

Application of selected transition code to geometries with interest to propulsion.

Development of a new transition model.

Validation of the new transition model over a wide range of turbulence flow

conditions.

Application of transition models over 2D and 3D geometries relevant to MAAT

project.

Research and effects of transition flows in high altitude propulsion

system components

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The majority of the performed research up to now was done in order to find the correct model description of each of its terms. Through the available literature and knowledge of the transition mechanism simulated by the model, reasonable changes were applied to

the model. After some trial and error, the final version of the corrected model was achieved.


system components


Fig.7. Skin friction

coefficient

distribution -flat-

plate multiple

boundary

conditions study

prove that the

model behaves

similar to the

commercial one;

(TI, Ekin dis ) .

The model is

validated for classic

geometries against

experiments

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Research and effects of transition flows in high altitude

propulsion system components

Fig. 7a. VALIDATION - Flat-plate ERCOFTAC T3A skin friction coefficient distribution

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Our corrected transition model was tested over 3D geometries, the Onera-M6 wing Fig.8 and a Nacelle,

Fig.9. For the wing geometry, the transition model was compared with the Spalart-Allmaras model, Fig. 8. This was

performed through a direct comparison of skin-friction coefficient contour map over the wing for the two models.

Fig.8. Onera-M6 wing -skin friction

coefficient distribution.

Fig. 9. Nacelle B.C.1 and B.C.2 skin

friction coefficient distribution.

Research and effects of transition flows in high altitude propulsion system components


12


Re=6.5x10^6

U=45 m/s

Tu=0.1%

AoA=15

Fig. 11. Prolate Spheroid 6:1 low turbulence intensity case

skin friction coefficient distribution- obtained from the mid

section-plane normal to the spheroid minor axis.

.

Fig. 10. Prolate Spheroid 6:1 model validation against

other specific turbulence models for transition modeling

Transition pattern similar to the experimental data.

The used geometry has the same length size of 2.4 meters

13



system components


Conclusions

The proposed objectives have been accomplished.

The selected transitional model is able to compute transition over a diverse set of

flow geometries and boundary conditions.

The turbulence transition model was successfully corrected, behaving very similarly

to the commercial version of it.

The corrected model is able to predict transition over a diverse range of geometries.

The newly developed model is able to predict transition over a flat-plate with varying

turbulence intensity.

The new transition model is able to predict transition onset under several pressure

gradient and turbulence conditions.

Future planning

The new transition model will be tested in curved geometries, both bi-dimensional

and three-dimensional. Also the model will require supersonic and transonic

validation in order to assure that it behaves accordingly under the influence of

pressure shock waves interacting with the boundary layer. Considerations regarding

the coupling of the transition model to an already known turbulence model or the

addition of a transport equation for specific turbulence dissipation rate or turbulence

dissipation in order to enable the model to calculate turbulent state will be considered.

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Publications:

R. Vizinho, J. Pascoa, and M. Silvestre. High altitude transitional flow computation for a

propulsion system nacelle of maat airship. SAE International Journal of Aerospace, 6(2):7,

2013.

Conferences:

R. Vizinho, J. Pascoa, and M. Silvestre. By-pass transition effects in propulsion components

of high-altitude airships. 5th European Conference for Aeronautics and Space Sciences

(EUCASS), Munich, Germany, 2013.

R. Vizinho, J. Pascoa, and M. Silvestre. Preliminary assessment of transitional flow

modeling using low-re turbulence closures. IV Conferncia Nacional em Mecnica dos

Fludos, Termodinmica e Energia (MEFTE), Lisboa, Portugal, 2012.

Submissions:

R. Vizinho, J. Pascoa, and M. Silvestre. Development and validation of a transition model

based on a mechanical approximation. Flow Turbulence and Combustion, (Pre-Print), 2014.

R. Vizinho, J. Pascoa, and M. Silvestre. A refurbishing of the k-kl-omega laminar kinetic

energy transition model for improved accuracy. Engineering Applications of Computational

Fluid Mechanics, (Pre-Print), 2014.


system components


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Efficiency increase in high altitude propulsion systems

using plasma actuators

Task - to apply the concept of Plasma Actuators to

improve the efficiency of the PS for air-vehicles. The specific

plasma actuator which is considered for this study is the single-

dielectric barrier-discharge (SDBD).

Airflow control by DBD actuators is based on the

generation of the ionic wind at the wall which adds momentum

to the boundary layer. At low flow velocities, those actuators

have proven to be effective for a wide range of applications.

Exposed Electrode

Encapsulated Electrode

Dielectric Layerplasma

Ionic Wind

Objectives:

Development and improvement of a model for simulation the detail of the plasma discharge.

Development of phenomenological model for modeling the macroscopic effect of plasma actuators.

Implementation of the plasma actuators with sinosoidal and nano-second voltage shape for controlling the flow

(Stall over airfoil) in steady and unsteady mode.

Implementation of the plasma actuators with nano-second pulsed voltage for modification of the shock wave

structure.

The plasma actuators are formed by a pair of electrodes

separated by a dielectric material(Fig 12).. The ionized air in

the presence of the electric field gradient, produced by the

electrodes, results in a body force vector on the external flow

shift for the separation point.

Ph. D. Student M.Abdoullahzadeh

Fig. 12.

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26.05.2014 26.05.2014

Single Dielectric Barrier Discharge (SDBD) actuator (plasma actuators)

Present study Suzan et. al

[10]

Bouchmal

[17]

Maximum velocity 1.054 0.934

Maximum Body force 1315 1250 1440

100100

200

300

400

500

X

Y

-0.002 -0.001 0 0.001 0.002 0.003-0.001

0

0.001

0.002

0.003100 200 300 400 500 600 700 800 900 1000 1100 1200

X

Y

-0.002 -0.001 0 0.001 0.002 0.003-0.001

0

0.001

0.002

0.003

velocity vectors body force

magnitude vector plot of

body force

X

Y

-0.002 -0.001 0 0.001 0.002 0.003-0.001

0

0.001

0.002

0.003


Fig. 13(a,b,c).

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X( m)

Y(m

)

0.005 0.01 0.015

-0.002

0

0.002

0.004

0.006

0.008

0.01

0.012

0.014

0.2 0.6 1 1.4 1.8 2.2 2.6 3 3.4 3.8 4.2 4.6

X(m)0 0.005 0.01 0.015

Ux( m/s)y

(mm

)0 1 2 3 4 5

0

1

2

3

4

5

Present Study

Experimntal results [36]

U/Umax

Y(m

m)

0 0.2 0.4 0.6 0.8 1

0.5

1

1.5

2

2.5

3

A

B

C

D

Fig.15 and Fig. 16 - The comparison of the present

modeling approach with exist model is shown. The

results of present modeling (dashed line) are the

closest to the experimental result.

Ionic wind

formation due to

the effect of

plasma actuator.

The developed

model captures

with acceptable

accuracy the

experimental

results

Results New

phenomenological model


Fig. 14.

Fig. 15.

Fig. 16.

18


P(atm)

Nor

mal

ized

Th

rust

Nor

mal

ized

Bod

yF

orce

0 0.2 0.4 0.6 0.8 10.7

0.75

0.8

0.85

0.9

0.95

1

1.05

0.7

0.75

0.8

0.85

0.9

0.95

1

1.05

p=0.6 atm

p=0.710526 atm

p=0.592105 atm

Ux (m/s)

Y(m

m)

0 0.5 1 1.5 2 2.5 3 3.5

0.5

1

1.5

2

2.5

3

3.5

4

4.5

Expermental results [42], x=5 mm

Expermental results [42], x=10mm

Expermental results [42] x=20 mm

Present study,x=5mm

Present study,x=10mm

Present study,x=20mm

Effect of operating pressure (altitude) was

included in the model. The results show that

the model can provide good results for both

above/below atmospheric pressure level

p( kPa)

T(m

N/m

)

50 100 150 200 250 300 350 400 450-5

0

5

10

15

20

25

30

35

40

45

Experimental results [46]

Present study,

Present study,

Fig. 17.

Fig. 18.

Fig. 19.

19


Successfully validated!!!

NS DBD was used for controling a transonic flow over a profile NACA0012. The induced micro show wave

was shown by isolines of density gradiant and in accordane with experintsal results

X(m)

Y(m

)

0 0.02 0.04 0.06 0.08

0

0.01

0.02

Current Study

contour lines

Peschke et al. [26]



Ph. D. student M.Abdoullahzadeh

Fig. 20 (a, b).

20





M. Abdollahzadeh, J.C. Pscoa, P.J. Oliveira, Two-dimensional numerical modeling of interaction of

micro-shock wave generated by nanosecond plasma actuators and transonic flow, Journal of

Computational and Applied Mathematics, 2014, (Accepted article in press)

M. Abdollahzadeh, J.C. Pscoa, P.J. Oliveira ,Modified Split-Potential Model for Modeling the Effect of

DBD Plasma Actuators in High Altitude Flow Control , 2014, Current Applied Physics ( Submitted).

Abdollahzadeh M., Pscoa J.C., Oliveira P.J. (2013), "Two dimensional numerical Modeling of

nanosecond plasma Actuators, a preliminary study of application in propulsion systems", in Proc.

EUCASS 2013 5th European Conference for Aeronautics and Space Sciences Munich, Germany, 1-5

July 2013.

Abdollahzadeh M., Pscoa J. C. , Oliveira P.J. (2012), "Numerical investigation on efficiency increase in

high altitude propulsion systems using plasma actuators", in Proc. European Congress on

Computational Methods in Applied Sciences and Engineering, ECCOMAS 2012.

M. Abdollahzadeh, J.C. Pscoa, P.J. Oliveira, Numerical Modeling of Boundary Layer Control Using

Dielectric Barrier Discharge, in: Conferncia Nac. Em Mecnica Dos Fluidos, Termodinmica e Energ.

MEFTE, 2012: p. Paper No 61, pp. 110.

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*Objectives:

To obtain CG positioning and changes in velocity, due to the acting

aerodynamic forces and pressure distribution around the airships body.

IMPORTANCE - determine propulsion requirements strong winds and

instabilities; power budget for the docking/undocking procedures; restoring

moment; power needed to maintain the position Identify problems related to

the propulsion system behavior and to assess the stability and control during

this flight phases

CG MOTION AND VELOCITY CHANGES DUE TO FORCES

ACTING ON THE AIRSHIP. EFFECTS ON THE PROPULSION

POWER AND VEHICLES STABILITY

In our case having the final shape need to perform a research on CG,

Munk moment, separation moment, other forces and moments causing

disturbing movements, exerting the propulsion system and leading to

stability problems.

This will help to achieve better propulsion system performance, control

on the airship and see where is the best position for stabilizers. Also, what

should be their profile, dimensions, design

IMPORTANT

!!!

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22

GEOMETRY AND NUMERICAL MODLEING

26.05.2014

Geometry modeling GAMBIT, final concept for feeder - UNIMORE

Domain discretization Hexahedral mesh 2 482 167 grid elements

BOUNDARY ZONES far-field, walls, fluid

BOUNDARY LAYER-first row elements h=0.01 m




Fig. 21.

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*Approach to access the main task:

Dynamic mesh, code with activated 6 DOF, function - forces and moments acting on the airships

hull

Spring-based smoothing, connectivity remains unchanged; local re-mesh, performed every time step .

. .

*UDF Macro to Govern the Dynamic Mesh:

Coupled Mesh Motion via the 6 DOF UDF DEFINE_SDOF_PROPERTIES !!! (ch)

Controlling Rigid Body Motion using DEFINE_CG_MOTION !!!

CG MOTION AND VELOCITY CHANGES DUE TO FORCES ACTING ON THE

AIRSHIP. EFFECTS ON THE PROPULSION POWER AND VEHICLES

STABILITY

26.05.2014

GEOMETRY AND NUMERICAL MODLEING

Very important function for reading obtained results over the feeders walls,

extract results, insert in a file and then integrate for CG motion is:

*Compute_Forces_And_Moments (domain, tf1, x_cg, f_glob, m_glob, TRUE).

HOW THESE CHANGES IN CG, position EXERT PROP.SYSTEM???

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CG MOTION AND VELOCITY CHANGES DUE TO FORCES ACTING ON

THE AIRSHIP. EFFECTS ON THE PROPULSION POWER AND VEHICLES

STABILITY

FLOWCHART -HOW WORKS THE CODE - CFD ANALYSIS AND RIGID BODY

MOTION

1. STEADY SOLUTION 2. UNSTEADY WITH ACTIVATED UDF MACRO

Fig. 22.

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CG MOTION AND VELOCITY CHANGES DUE TO FORCES ACTING ON

THE AIRSHIP. EFFECTS ON THE PROPULSION POWER AND VEHICLES

STABILITY

The motion of airship can be splitted into two motions, the desired motion which are the values on the equilibrium, and the disturbing

motion which are the values away from the equilibrium.

+Propulsion vector with prop. forces and moments!!!

+Gravity and buoyancy effects !!!

-mass matrix

-aerodynamic vector with total aerodynamic forces and moments

-dynamic terms associated with inertial linear and angular velocities

6-DOF non-linear mathematical model of the airship flight for computer simulation

Math model in FLUENT (shown below) must be updated in order to follow the model already presented!!!

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Altitude/

imposed

paramete

rs/conditi

ons

Density

[kg/m3]

Viscosity

[kg/m.s]

Static

pressure

Pst [Pa]

Static

temperatur

e

Tst [K]

Mach

number

M [-]

Turb.

Intensity

Tu [%]

Turbulent

viscosity

ratio

[-]

15km 0.19476 0.0000142 12112 216.65 0.169 2 5

Numerical simulation FLUENT

Altitude: 15 km

LATERAL WIND VELOCITY 92 km/h ; VERTICAL VELOCITY 15 km/h

RANS equations; Realizable k- turbulence model with non-equilibrium functions

Working fluid: air; physical properties in function of the altitude

BOUNDARY ZONES: static pressure, static temperature, turbulence parameters, Mach number, flow direction

RELAXATION FACTORS: 0.5 for each DOF ; CONVERGENCE APPROACHES




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Fig.23. Static pressure distribution Fig.24. Velocity flow field distribution

Assymetric pressure distribution around the streamed airships hull, boundary layer

separation and vortex structures, leading to aerodynamic problems, power budget increase, stability

problems and need of strong control. NOT included inertial effects, pressure forces, 6 dof., forces

and moments ...

RESULTS UNIMORE concept

Case without air-jets, 50 m/s velocity of the incoming air-flow.

Altitude 15 km

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TI in zones of separated b.l.

interacting with the incoming flow and

formed vortex structures.

The area of max TI will affect the

working air-jets and lead to worse

aerodynamic behaviour.

Drag coefficient 0.35535

Total force 179 987.73 [N]

Thrust 179 987.73 [N]

Power 8.999 [MW]

Lift coefficient - 0.2679

Total force in vertical direction

-135 702.06[N] !!! Prove - 03.2012. Covilha meeting

NEED ADDITIONAL THRUST

during VERTICAL TAKe-OFF!!!


Case without air-jets, 50 m/s velocity of the incoming air-flow.

Altitude 15 km

Fig.25. Turbulence intensity

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Case without air-jets, dynamic mesh UDF. Altitude 15 km

Incoming air flow 50m/s, imposed 5m/s feeders speed,

Mass and inertia - 28 people on board 2 pilots, 26 passengers

CG motion: (x/y/z) (0.9365/ -0.60576/-0.00311) m

(x y z) (0.006239/-6.035.10-6/-1.0014) deg

(x y x) (0.0004356 /-4.213.10-7/ -0.6991) rad

Drag coefficient 0.3642 Drag force 184 510.804 N Power budget 9.225 W

Fig.26(a,b,c). Static pressure, velocity flow field, turbulence

intensity unsteady T=0.5sec

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Case without air-jets, 50 m/s velocity of the incoming air-

flow. Altitude 15 km

CG motion: (x/y/z) (4.821/ -3.88032/-0.004822) m

(x y z) (0.03346/0.00102/-14.483) deg

(x y x) (0.000403 /-3.55.10-5/ -0.17611 rad

Drag coefficient 0.833 Drag force 468368.804 N (4)

Significant restoring moments, additional forces to maintain the trajectory,

provide additional thrust to overcome the increased drag, .

Fig.27. Static pressure, velocity flow field, turbulence intensity

unsteady T=2.25sec

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Fig. 28. CG motion in X direction Fig. 31. CG position change in Z direction

Maximum angle of rotation (oZ) is -34.473 deg (!!!)

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Fig.30. Drag coeficient values

Drag force: ( 179988 168326 165561 234225.91 245084.76 347823.353 236492.27 622593.25 543417.408 541865.23 609198.59 539035.51 558348.12 544798.92 553347.839 ) [N]

Fig. 31. Power budget changes during one time

period

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Fig.32. Velocity flow field and streamlines

realized around the feeder

Fig.33. Static pressure distribution

RESULTS flight in vertical direction, 5m/s velocity

UNIMORE concept

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Fig.34. Turbulence intencity

Drag coefficient - 0.445

Total force -34023.907 [N]

Thrust -34023.907 [N]

Power 0.17[MW]

Positive lift (!)

RESULTS flight in vertical direction, 5m/s velocity

UNIMORE concept



formed vortex structures with small

intensity

Coupling vortices due to edge

streaming and vortices due to air-jets

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RESULTS previous UNIMORE concept (!!!)

Case without air-jets, 30 m/s velocity for the incoming air-flow.

Altitude 15 km

Fig.35. Static pressure distribution Fig.36. Velocity flow field distribution

Assymetric pressure distribution around the streamed airships hull, boundary layer

separation and vortex structures, leading to aerodynamic problems, power budget increase, stability

problems and need of strong control. NOT included inertial effects, pressure forces, 6 dof....

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Case without air-jets, 30 m/s velocity for the incoming air-flow.

Altitude 15 km

Fig.37. Turbulence intensity



formed vortex structures.

**The area of max TI will affect the

working air-jets and lead to worse

aerodynamic behaviour.

Drag coefficient 0.24569

Total force 150 867.87 [N]

Thrust 150 867.87 [N]

Power 4.526 [MW]

Lift coefficient -0.3427

Total force in vertical direction

- 210 430 [N]

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Case with air-jets, 30 m/s velocity for the incoming air-flow at altitude

15 km. Non-vectorized air-jets case

Air-jets parameters - mass-flow rate ; velocity components X=1 Y=Z=0

Drag coefficient 0.3241 (24%) Thrust 199062 [N] Power budget 5.97

[MW]

Fig.38(a,b). Velocity flow field and turbulence intensity

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15 km

Vectorized air-jets in the case 10 deg

Drag coefficient - 0.2752 Thrust -1680929 [N]

Power budget 5.067[MW]

Fig.39. Velocity flow field in case of

vectorized air-jets.

Coanda effect

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RESULTS UNIMORE concept DYNAMIC MESH

COMPARISON for two cases of T=0.05sec and T=1.0sec (slice Z=0)

Due to the movement and aerodyn. features pressure after the vehicle is decreasing and differences in the pressure flow field around the airship increases, for different time steps. It will tend to move toward the low-pressure zone-

affect on the propulsion system. There is an increase in the max turbulence intensity.

Fig.40(a-f). Static pressure, velocity flow field and turbulence intensity in case of vectorized

air-jets.

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RESULTS DYNAMIC MESH UNIMORE concept

GRAPHIC RESULTS for CG position change along x,y,z axis and

rotation angle

For unsteady calculations were observed periodic changes in both the drag

coefficient and power budget values. Variations in drag values lead to a

strong change in power required for propulsion needs during one time

period.=> design, performance of the airship??? THINK ABOUT ContrS,

ContrDevices, prop system specifics.!!!

Power needed for

propulsion 4.526 [MW] to

5.82 [MW] smaller mass

and inertia

Important calculate the restoring moment!!!

Fig.42

Fig.43

Fig.44

Fig.45

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15 km

Vectorized air-jets at 10 deg, without UDF macro

Power needed for propulsion varies in the range of 5.067 [MW] to 5.49 [MW]

Fig.46(a,b,c). Velocity flow

field and turbulence intensity

in case of vectorised air-jets

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Case with air-jets, 30 m/s velocity incoming air-flow, altitude 15 km

Vectorized air-jets at 10 deg (T=0.05 sec up and down, y const

sections) The zone at the bottom as

previously appeared with high turb.

intensity cause problems for the air-

jets.

As the speed increases, due to

additional movements according

acting moments and 6 dof, air-jets are

also working the pitch- incidence

oscillation mode and the side slip

(yaw angle) shifting mode of the

airship could become more unstable.

This is because of the already

mentioned unstable moment(!), which

could dominate, even over the

stabilizing moment generated by fins

or other stabilizers (last case is

explained in some papers). It is possible for other cases and modes to

become more stable as the speed increases, due to

the increasing of the aerodynamic damping and

some vortex shedding effects, but the last could be

true only for specific shapes

Fig.47a

Fig.47b

Fig.48a

Fig.48b

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RESULTS DYNAMIC MESH UNIMORE concept Case with air-jets, 30 m/s velocity incoming air-flow, altitude 15 km

Vectorized air-jets at 10 deg (tree control sections at the rare part perpendicular to the incoming flow)

Increase a circulation zone around the airship, due to the interaction between the acting air-jets, air stream flow, and the

separated boundary layer. This will cause significant losses in momentum and can involve pressure increase. The pressure

differences are a reason for vortex structures to appear

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Unsteady computations have shown that the stability and related to the prop system

problems (due to inertia, added masses, pressure forces on the vehicles body) lead to CG

additional movement differences, development of vortex structures and the increase of

vortices.

It is also observed that were introduced strong changes in both the drag coefficients

and required power budget.

The change of vorticity during the disturbing movements of the CG lead to

irregularity in pressure distribution around the hull and will introduce stability problems.

Also, a change in vorticity means that there is additional force acting on the body under

study.

The additional vortex structures provoke less aerodynamic performance and stability

problems. The results obtained for this research can be used as a basis for a study on the

frequency of vortex shedding, stability problems and how they exert the propulsion

system performance.

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PROPULSION SYSTEM FOR CRUISER

CRUISERS PROPULSIVE SYSTEM

INITIAL DATA

Altitude 16 km

Air density 0.16647 kg/m3

Velocity v = 28 m/s

Mach number M = 0.6

Local sound speed A = 295.0695 m/s

Disc loading for high-altitude vehicles DL = 300

N/m2

!!!

Table 1. Disc loading (F/A) values for different high-altitude vehicles.

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MAAT Multibody Advanced Airship for Transport Project ID 285602 / FP7-AAT-2011-RTD-1 26.05.2014 26.05.2014

Table 2. Aerodynamic data of cruiser at different angles of attack

Table 3. Aerodynamic data of cruiser at different sideslip angles

Numerical simulations cruiser with 2 feeders (University of Hertfordshire)

Focus on the case without AoA - thrust 202 601 N (min) and on the case with

12 deg AoA - thrust 339 654 N ( 68.14% increase of P)

Drag coefficient

Cd = 0.171;

Drag force

Fd = 172 658.349 N

Power budget

P = 4 834 433.765 W

Drag coefficient

Cd = 0.185;

Drag force

Fd = 290 317.321 N

Power budget

P = 8 128 884.980 W

PROPULSION SYSTEM FOR CRUISER UBI

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FINAL SOLUTION

Number of propellers 40

Diameter of each propeller: 5.552 [m]

RPM = 601.564 [1/min]

Thrust for each propeller: T = 7258 [N]

Efficiency: 0.65 0.70 / as a result of modeling in JBLADE - in function of velocity, advance ratio ./

Minimum power for one propeller (in function of the induced velocity Vind [m/s]) Pmin = 0.342.106 [W]

Maximum power for one propeller (in function of the induced velocity Vind [m/s] and included profile losses)

Pmax = 0.3933.106 [W]

Estimated weight for one propulsion unit: (assumed weight/power

ratio is 0.136 kg/1kW)

is 53.4888 [kg]. For 40 units: 2.14 [tons]


JBLADE results in function of blade design, material Al, ..

Weight for one propulsion unit: 5blades X 418kg = 2090 kg

For 40 units: 83.6 [tons]

In our report 03.2013 around 72 tons (!) with imposed

weight/power ratio 3kg/1kW!!

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Figure 50*. Blades shape comparison for DL 1000 N/m2 (a), and DL 300 N/m2 4 blades (B), five blades (C)

and 6 blades (D), (author -Joao Morgado, Ph.D. student).


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L = 400 m (20 propellers each side)


VECTORIZED THRUST

4 PROPELLERS - MOMENT CONTROL

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PROPULSION SYSTEM FOR FEEDER

Numerical simulations feeder at zero and cruise altitudes (University of Hertfordshire)

Table 4. Aerodynamic data at zero altitude, VTO (author UoH).

Table 5. Aerodynamic data at 15 km altitude, vertical flight (author UoH).

At zero altitude the

maximum drag force Fd = -104

386 N 0degrees.

Minimum drag force

Fd = -14 228 N is realized at

15 km altitude and at angle

of attack 12 degrees.

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Table 6. Aerodynamic data at zero altitude, horizontal flight (author UoH).

Table 7. Aerodynamic data at 15 km altitude, horizontal flight (author UoH).

Maximum drag force Fd = 266 672 N is realized at 15 km altitude and at

angle of attack 12 degrees.

PROPULSION SYSTEM FOR FEEDER UBI

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It is preferable for airships with VTOL and horizontal cruise flight capability to have vectorized thrust. Thrusters

must have high efficiency and possibility to fast change for thrust according to the flight needs. A HAA airship needs to be

light and have an efficient propulsion system that can operate with little or no oxygen. This is important when an airship

operates, in the thin atmosphere, at very high altitudes and for extended periods of time. - > covered by AIR-JETS concept

Fig. 51 Air-jets propulsion concept (a) and main air channels (b) .

Fig. 52. Air-jets working principle.

For higher efficiency, jets must operate at a high mass flow rate and low velocity. The application of higher mass flow

rates, at low speeds, is linked to the dimensions of air inlets, and outlets with large cross sectional area.

Less velocity of air-jets generates insufficient thrust. In order to achieve the required thrust, with less air-jets velocity more air mass is

needed. This fact reflects on the overall concept for distribution of weights, buoyancy and required propulsion needs. In order to

overcome these problems, an additional study for impact of air-jet working parameters (mass flow rate and velocity) on the dimensions

distribution was performed. The research is very helpful in order to arrive to a final solution for dimensions of air-jets channels, their

working parameters,

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Table 8. The impact of air-jets

working parameters on the

dimensions distribution

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Fig. 54. Velocity magnitude and static pressure distribution in a section

along the axis of air-jets outlet area.

Fig.53. Velocity field distribution realized by the working air-jets.

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Vortex structures, which are formed because of the interaction between the two central air-jets and the incoming flow, at the bottom part of airship hull, have higher

vorticity than those raised due to the sideward air-jets. The vorticity change lead to irregularity in pressure distribution around the hull and will introduce stability problems. A

change in vorticity means that there will arise additional force acting on the body under consideration. This analysis helped us to attain power changes due to vortex shedding

effects

(a) (b)

(c) (d)

(e) (f)

Fig. 13(a-f). Streamlines and vortex structures (t=T), obtained due to interaction between the working air-jets and the incoming air flow: section 1-top (a) and bottom side (b), section 2-top (c) and bottom side (d), section 3-top (e) and bottom side (f).

(c) (d)

(e) (f)

Fig. 56(a-f). Streamlines and vortex structures (t=T), obtained due

to interaction between the working air-jets and the incoming air

flow: section 1-top (a) and bottom side (b), section 2-top (c) and

bottom side (d), section 3-top (e) and bottom side (f).

(e) (f)

Fig. 10 (a-f). Streamlines and vortex structures (t=0 s), obtained due to interaction between the working air-jets and the incoming air flow: section 1-top (a) and bottom side (b), section 2-top (c) and bottom side (d), section 3-top (e) and bottom side (f).

(a) (b)

(c) (d)

Fig. 55(a-f). Streamlines and vortex structures (t=0), obtained due to

interaction between the working air-jets and the incoming air flow:

section 1-top (a) and bottom side (b), section 2-top (c) and bottom side

(d), section 3-top (e) and bottom side (f).

(e) (f)

56



Top air-jets: distributed air suppliers !!!

T - to avoid pitching moments!

Bottom air-jets: Zone 2 - for VTO purposes.

Zone 1 - horizontal flight;

control issues

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DEFINE_CG_MOTION

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