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Airship Drag and lift
Citation preview
Ritu Gavasane
Guide: Prof. Murali Damodaran
INDIAN INSTITUTE OF TECHNOLOGY GANDHINAGARDiscipline of Mechanical Engineering
VGEC Complex, Visat-Gandhinagar HighwayChandkheda, Ahmedabad, GJ 382424
INDIA
24 April 2014
B. Tech Project Presentation
Flow Modeling for High Altitude
Airships with Free and Forced
Transition Modelling
Content Problem statement
Previous work
Motivation behind present work
Computational Setup
Envelope Profile of Airship
Geometry and Computational Domain
Discretized Computational Domain
Physics: Initial and Boundary Conditions
Computational Results
Free Transition
Forced Transition
Validation of CFD Results with those of wind tunnel test
Comparison between free and forced transition
Conclusion
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Problem statement Modelling of high altitude Airship-fully turbulent
conditions
GNV Rao Airship
Modelling of ZHIYUAN-1 Airship transition modelling
Free transition
Forced transition
Validation of CFD results with experimental wind tunnel
test
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Previous work: GNV Rao Airship
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For = 100
Aerodynamic coefficients
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Motivation behind present
work Fully turbulence modelling overpredicts aerodynamic
forces
Transition modelling is absolutely essential for accurate
and near-to-practical results
Hence transition was modelled : ZHIYUAN-1 Airship
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Computational Setup: Envelope Profile of Airship
Hull configuration Fin configuration
NACA 0010 for fin cross section7
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Geometry of Airship
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strips at x/c=0.52 for
forced transition case
(a) Airship geometry for free transition case (b) Airship geometry for forced transition case
Computational Domain
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Velocity Inflow
Freestream
No Slip Boundary
Condition on Hull
surface
Mesh Discretization
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Mesh count :
0.52 millionOverlapping
mesh region
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Physics
Unsteady
Inflow velocity = 60.39
Reynolds number = 2.5106
The free stream turbulence level = 0.1 %
Turbulence modeling, K turbulence model
Transition modelling, -Re- Transition model
Simulations were performed for different angles of
attack () ranging from -300 to 300.
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Governing Equations
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Continuity Equation
Momentum Equation
Integral form of Navier Stokes equation
Computational results
Free transition
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(a) Velocity profile (b) Skin friction coefficient profile
(c) Wall Shear Stress for = 300
Aerodynamic coefficients: Free
transition
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Computational results
Forced transition
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Comparison: Free and Forced transition
Wall Shear stress
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Free transition
At =120
Forced transition
Comparison: Free and Forced transition
Skin friction
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Velocity profile: Treftz plane
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Comparison of Force Coefficients
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Videos: Free transition
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Forced transition
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Discussion All the computationally calculated force coefficients
agree well with the experimental wind tunnel tests.
Drag and Moment coefficients deviated from the
experimental values at lower angles of attack
In case of forced transition, flow separation was
observed at the position of strips on the airship hull.
The CFD results of free and forced transition did not
differ much for the assumed point of transition that was
positioned at x/c=0.52
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Thank You
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