Twenty-Fourth Symposium on Naval Hydrodynamics (2003) / Chapter Skim
Currently Skimming:
Prediction of Vortex Cavitation Inception Using Coupled Spherical and Non-Spherical Models and UnRANS Computations
Prediction of Vortex Cavitation Inception Using Coupled Spherical and Non-Spherical Models and UnRANS Computations
Pages 868-880
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 868... ...
The non-spherical model is embedded in an Unsteady Reynolds-Averaged Navier-Stokes code with appropriate free surface boundary conditions and a moving Chimera grid scheme around the bubble. The effect of non-spherical deformation and bubble/flow interaction on bubble dynamics is illustrated by comparing spherical and non-spherical models.
|
From page 869... ...
Recognizing this fact we apply the spherical model to simulate the bubble capture and then turn on the non-spherical model when the bubble size exceeds a preset limit value to best take advantage of each model. In the current study, our model is applied to predict tip vortex cavitation inception for a canonical problem in which the tip vortex flow is generated by a finite-span elliptic hydrofoil.
|
From page 870... ...
DF_UNCLE is also accompanied by a Baldwin-Lomax algebraic turbulence model to model the Reynolds stresses in Equation (31. 2.2 Spherical Model When one assumes that the bubble remains spherical during its volume variations, the bubble dynamics can be described by the Rayleigh-Plesset equation (Plesset 19481.
|
From page 871... ...
Once the interpolation stencil and interpolation coefficients are determined, the pressure and velocities can be obtained by using Equation (9~. 2.3 Non-Spherical Model To fully account for the interaction between the bubble and the flow filed and for non-spherical deformations, a non-spherical bubble model embedded in the UNRANS computations with appropriate free surface boundary conditions and a moving Chimera grid scheme has been developed by Hsiao and Chahine (2001~.
|
From page 872... ...
Localization of the "hole" points and of the "overlap " points marked as · . 2.3.3 Initial conditions It is important to specify appropriate initial conditions for the unsteady Navier-Stokes computations when the non-spherical model is turn
|
From page 873... ...
This grid generation scheme is selected because the algebraic grid generation technique is suited to create grid clustering and boundary-orthogonal grids at the bubble surface. This is important for resolving the flow field near the bubble surface and for applying appropriate free surface boundary conditions.
|
From page 874... ...
Example computation of bubble dynamics for encountered pressure, bubble radius and emitted acoustic pressure versus time during its capture in the tip vortex of a NACA 16020 foil using the SAP spherical model.
|
From page 875... ...
Comparisons of the bubble radius versus time for the spherical models (the conventional and the SAP model) and the nonspherical model are shown in Figure 8.
|
From page 876... ...
spherical modelenables a more realistic evaluation of the bubble dynamics. Here, the average is obtained using the six polar points at the bubble surface, the solution of our spherical model agrees very well with the nonspherical model as shown in Figure 8.
|
From page 877... ...
4. Conclusions A bubble dynamics model combining a spherical model and a non-spherical model embedded in UnRANS computations was developed to predict cavitation inception in complex flow configurations and was applied here for tip vortex cavitation inception on a finite-span hydrofoil.
|
From page 878... ...
t13] Hsiao, C.-T., Pauley, L.L., "Study of Tip Vortex Cavitation Inception Using Navier-Stokes Computation and Bubble Dynamics model," ASME Journal of Fluid Engineering, Vol.
|
From page 879... ...
1-14. El91 Ligneul, P., Latorre, R., "Study of Nuclei Distribution and Vortex Diffustion Influence on Nuclei Capture by a Tip Vortex and Nuclei Capture Noise," ASME Journal of Fluid Engineering, Vol.
|
From page 880... ...
We then extended it by incorporating a moving Chimera grid scheme to enable the simulation of the dynamics of moving bubbles in a tip vortex flow. The same scheme, of course, can be used to further improve the simulation of sheet cavitation.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.