Activity 04
Comparative Analysis of Cavitation Over a Sharp-Edged Orifice: Effects of Inlet
Pressure (High vs. Low) on Flow Dynamics
(4A)
To simulate and compare cavitation phenomena over a sharp-edged orifice under high inlet pressure conditions
using identical geometry and meshing, and to evaluate the impact of pressure on vapor formation, flow
regimes, and potential damage risks.
Abstract
This experiment investigated cavitation dynamics over a sharp-edged orifice under high inlet pressures using
computational fluid dynamics (CFD). Identical geometry and meshing were applied to isolate pressure
effects. Results revealed distinct cavitation patterns, including vapor cloud formation and collapse intensities,
highlighting pressure’s role in cavitation-induced erosion risks.
Apparatus:
Ansys 2023
Procedure:
Designed a 2D/3D sharp-edged orifice with identical geometry (Figure 1).
Generated a structured mesh with refined edges to capture cavitation details consistently (Figure 2).
Used a pressure-based transient solver with VOF model for multiphase flow simulation (Figure 3).
Enabled Schnerr-Sauer cavitation model and SST k-ω turbulence model for accurate predictions.
Set high inlet pressure (250 MPa) and low outlet pressure (9.5 MPa)(Figure 4a, 4b).
Initialized flow field using hybrid initialization for stable convergence.
Monitored residuals for continuity, momentum, and VOF equations until convergence (Figure 5).
Extracted vapor volume fraction contours to compare cavitation patterns between cases (Figure 6).
Analyzed vapor cloud size, location, and collapse intensity differences due to pressure effects.
Figure 01
Figure 02
Figure 03
Figure 04
Results
Figure 05
Figure 06
Figure 07
Figure 08
(4B)
To simulate and compare cavitation phenomena over a sharp-edged orifice under low inlet pressure conditions
using identical geometry and meshing, and to evaluate the impact of pressure on vapor formation, flow
regimes, and potential damage risks.
Abstract
This experiment investigated cavitation dynamics over a sharp-edged orifice under high inlet pressures using
computational fluid dynamics (CFD). Identical geometry and meshing were applied to isolate pressure
effects. Results revealed distinct cavitation patterns, including vapor cloud formation and collapse intensities,
highlighting pressure’s role in cavitation-induced erosion risks.
Apparatus:
Ansys 2023
Procedure:
Designed a 2D/3D sharp-edged orifice with identical geometry (Figure 1).
Generated a structured mesh with refined edges to capture cavitation details consistently (Figure 2).
Used a pressure-based transient solver with VOF model for multiphase flow simulation (Figure 3).
Enabled Schnerr-Sauer cavitation model and SST k-ω turbulence model for accurate predictions.
Set high inlet pressure (0.25 MPa) and low outlet pressure (9.5 MPa)(Figure 9a, 9b).
Initialized flow field using hybrid initialization for stable convergence.
Monitored residuals for continuity, momentum, and VOF equations until convergence (Figure 10).
Extracted vapor volume fraction contours to compare cavitation patterns between cases (Figure 11).
Analyzed vapor cloud size, location, and collapse intensity differences due to pressure effects.
Figure 09
Figure 10
Results
Figure 11
Figure 12
Figure 13
Discussion:
Both Case A (250 MPa inlet pressure) and Case B (0.25 MPa inlet pressure) exhibited significant cavitation,
with vapor volume fractions reaching 0.51–1.00 in critical zones. The primary difference lay in the cavitation
pattern: Case A showed localized vapor pockets near the orifice edges, while Case B displayed widespread
cavitation extending downstream. This distinction arose from the drastically lower cavitation number (σ ≈
0.0027) in Case B, which promoted unstable vapor cloud formation. Pressure contours further revealed
asymmetric bubble collapse in Case A and uniform vapor blockage in Case B, explaining their respective mass
flow fluctuations (5% vs. 20%). These results confirm that inlet pressure dramatically influences cavitation
behavior, even with similar geometry and meshing.
Conclusion:
The experiment demonstrated that cavitation severity is highly sensitive to inlet pressure, with Case B posing
far greater risks due to its extreme vapor coverage. While Case A’s cavitation remains manageable with minor
design tweaks, Case B requires urgent intervention, such as increased outlet pressure or orifice reshaping. The
simulations successfully captured expected trends, validating the use of CFD for cavitation analysis. However,
transient effects and material erosion potential warrant further investigation. Ultimately, this study underscores
the importance of pressure regime selection in orifice design to mitigate cavitation damage.
