Liquid flow around non-cavitating
and cavitating NACA0015 hydrofoil
-
Introduction
- Definition of the test-cases
- Solver and model requirements
- Required output results
-
Experimental data and reference solution
- References
- Important dates
- Contact
INTRODUCTION
The present benchmark concerns
the simulation of the liquid flow around a NACA0015 hydrofoil.
The first objective is to assess the capability of numerical solvers
for compressible flows to deal with near incompressible flows. Thus,
the first proposed test case, which is mandatory, consists in the simulation
of the liquid flow around the hydrofoil at low angle of attack and in
non-cavitating conditions. In this first test-case, the viscous effects
are not important; thus, solvers of the Euler equations can
be used. The results should be compared with a reference solution
at Mach number equal to zero (numerical solution of a potential flow)
and with experiment results [1]. A second test-case, which is
optional, is also proposed; it consists in the simulation of the same
c as previously, but in cavitating conditions. The aim is to demostrate
the capabilities of the numerical solver to simulate flows in presence
of cavitation, and, in particular, to deal with nearly incompressible
regions together with highly supersonic ones. DEFINITION OF THE TEST-CASES
GEOMETRY
A NACA0015 airfoil is considered. The chord, c, is 0.115m. An analytic expression is available for the NACA0015 profile definition:
The airfoil is symmetric and the x coordinate is the coordinate along the chord, with the origin at the leading edge.
The angle of attack is 4o.
The experimental configuration is shown in Fig.1; the airfoil spans the entire width of the test chamber section, which is equal to 0.7c . Experimental measurements are performed in the symmetry plane.
Fig.1 - Experimental configuration
Thus, the 2D computational configuration
in Fig. 2 can be considered.
Solid wall boundary conditions must be used at the top and bottom sides of the domain. Inlet (farfield) conditions must be sepcified at the left side, while outflow conditions have to be used on the right side.
Solid wall boundary conditions must be used at the top and bottom sides of the domain. Inlet (farfield) conditions must be sepcified at the left side, while outflow conditions have to be used on the right side.
Fig.2 - 2D computational domain
The complete 3D configuration can also be considered,
to account for possible 3D effects. Solid wall boundary conditions
must be specified on the lateral walls.
An example of a 3D unstructured grid ( grid3D.html) is also given.
Contributors are free of using different types of grids.
An example of a 3D unstructured grid ( grid3D.html) is also given.
Contributors are free of using different types of grids.
FLOW CONDITIONS
Test case 1 (mandatory): simulation of non-cavitating flow around a NACA0015 hydrofoil at 4 degrees of incidence.
The inlet experimental conditions are the following:
Tin= 298 o K
Uin=3.11 m/s
pin= 0.59 bar
µin= 0.00089 (N s)/m 2
rhoin=1000 Kg/m3
Min= 0.0021
Test case 2 (optional): simulation of cavitating flow around a NACA0015 hydrofoil at 4 degrees of incidence.
The inlet experimental conditions are the following:
T in = 298 oK
Uin=3.41 m/s
pin= 0.12 bar
µin= 0.00089 (N s)/m2
rhoin=1000 Kg/m3
Min=0.0023
The cavitation number, defined as: s = (p in - psat)/(1/2 rhoin U2 in ), is s=1.52.
SOLVER AND MODEL REQUIREMENTS
Numerical solvers for compressible flows must be used. The computations have to be performed for liquid flows (water) under the conditions specified above. Freedom is left for the choice of the state law: it could be some barotropic law, a stiffened-gas equation, etc ...As stated in the Introduction, for test-case 1 (non-cavitating flow) the viscous effects are not expected to be important; thus an inviscid compressible flow model is recommended.
Conversely, for test-case 2 freedom is left to participants to carry out either viscous or inviscid simulations.
For this latter test-case, the strategy for dealing with cavitation phenomena is not imposed; thus, participants should specify the used model.
REQUIRED OUTPUT RESULTS
The participants should provide the values of the pressure coefficient Cp on the leeward and windward sides of the hydrofoil (on the plane of symmetry for 3D simulations).
The pressure coefficient is defined as follows:
Cp = (p-p in )/(1/2 rho in U 2in )
Iso-contours of pressure and Mach number are also required.
Test case 2 (optional): simulation of non-cavitating flow around a NACA0015 hydrofoil at 4 degrees of incidence.
The participants should provide the values of the pressure coefficient Cp on the leeward and windward sides of the hydrofoil (on the plane of symmetry for 3D simulations) and the location and the extent of the cavitation bubble on the leeward side of the hydrofoil.
Iso-contours of pressure and Mach number are also required.
EXPERIMENTAL DATA AND REFERENCE SOLUTION
Experimental dataTest-case 1: Cp distribution on the hydrofoil ( ASCII format).
Test-case 2: Cp distribution on the hydrofoil ( ASCII format)
The cavitation bubble length is (0.397 - 0.464)c (it oscillates in time).
Potential flow solution (test-case 1)
Cp distribution on the hydrofoil obtained by a 2D potential flow solver with the same blockage factor ( ASCII format, first column: x/c, second column: Cp on both the windward and leeward sides)
Cp distribution on the hydrofoil obtained by a 3D potential flow solution of the whole configuration (ASCII format, first column x/c, second column Cp on the leeward side, third column Cp on the windward side): sections at z/c =0.026, z/c=0.078, z/c=0.12, z/c=0.17, z/c =0.23.
REFERENCES
[1]
Rapposelli E., Cervone A.,
Bramanti C. and d'Agostino L., Thermal cavitation experiments
on a NACA 0015 hydrofoil , Proceedings of FEDSM'03 4TH ASME_JSME
Joint Fluids Engineering Conference, Honolulu, Hawaii, USA, July
6-11, 20 03. (download
in pdf format)
IMPORTANT DATES
April 15th 2004, Intention to partecipate
: send to the organizers a 1 page abstract describing the numerical
approach used to compute the problem solution.
May 28th 2004, Numerical solutions: send the required data to the organizers.
June 21st-25th 2004, Workshop: discussion of the numerical results.
May 28th 2004, Numerical solutions: send the required data to the organizers.
June 21st-25th 2004, Workshop: discussion of the numerical results.
CONTACT
| Maria-Vittoria SALVETTI
Dipartimento di Ingegneria Aerospaziale Universita degli studi di Pisa 56122 Pisa - ITALY fax: (39) 0502217244 email : mv.salvetti@ing.unipi.it |
Francois BEUX Scuola Normale Superiore di Pisa Piazza dei Cavalieri, 7 56126 Pisa - ITALY fax: (39) 050 563513 email: fbeux@sns.it |
Abstracts, mails, etc can be sent to either one of the organisers.
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