TY - JOUR

T1 - Unsteady Cloud Cavitation on a 2D Hydrofoil: Quasi-Periodic Loads and Phase-Averaged Flow Characteristics

AU - Ivashchenko, Elizaveta

AU - Hrebtov, Mikhail

AU - Timoshevskiy, Mikhail

AU - Pervunin, Konstantin

AU - Mullyadzhanov, Rustam

N1 - This research was supported by the Russian Science Foundation (grant No. 19-79-30075-Π). The numerical tools as well as the methods of the automatization of the data acquisition and processing used in the study were developed under a state contract (FWNS-2022-0009) with IT SB RAS.

PY - 2023/10

Y1 - 2023/10

N2 - We perform large-eddy simulations to study a cavitating flow over a two-dimensional hydrofoil section—a scaled-down profile (1:13.26) of guide vanes of a Francis turbine—using the Schnerr–Sauer cavitation model with an adaptive mesh refinement in intensive phase transition flow areas. In the test case, the guide vane is tilted at an angle of attack of (Formula presented.) to the direction of the flow, in which the Reynolds number, based on the hydrofoil chord length, equals (Formula presented.), thus providing a strong adverse pressure gradient along the surface. The calculated time-averaged turbulence characteristics are compared with those measured by particle image velocimetry to verify that the flow is correctly reproduced in numerical simulations using the procedure of conditional averaging proposed and tested in our previous investigation. A re-entrant jet is identified as the primary source of vapor cloud shedding, and a spectral analysis of the cavitating flow over the profile midsection is conducted. Two characteristic frequencies corresponding to the cases, when an attached cavity detaches completely (as a whole) and two partially from the hydrofoil, are found in the flow. The study reveals that the natural frequency of partial cavity shedding is three times higher than that of full detachments. The examined regime exhibits an oscillatory system with two oscillation zones related to cavitation surge instability and unsteady cloud cavitation resulting from the re-entrant jet. Conditional averaging correlates cavitation structures with pressure distributions, forces, and torque on the guide vane. This modeling approach captures the fine details of quasi-periodic cavitation dynamics, providing insights into unsteady sheet/cloud cavitation and offering a method for developing control strategies.

AB - We perform large-eddy simulations to study a cavitating flow over a two-dimensional hydrofoil section—a scaled-down profile (1:13.26) of guide vanes of a Francis turbine—using the Schnerr–Sauer cavitation model with an adaptive mesh refinement in intensive phase transition flow areas. In the test case, the guide vane is tilted at an angle of attack of (Formula presented.) to the direction of the flow, in which the Reynolds number, based on the hydrofoil chord length, equals (Formula presented.), thus providing a strong adverse pressure gradient along the surface. The calculated time-averaged turbulence characteristics are compared with those measured by particle image velocimetry to verify that the flow is correctly reproduced in numerical simulations using the procedure of conditional averaging proposed and tested in our previous investigation. A re-entrant jet is identified as the primary source of vapor cloud shedding, and a spectral analysis of the cavitating flow over the profile midsection is conducted. Two characteristic frequencies corresponding to the cases, when an attached cavity detaches completely (as a whole) and two partially from the hydrofoil, are found in the flow. The study reveals that the natural frequency of partial cavity shedding is three times higher than that of full detachments. The examined regime exhibits an oscillatory system with two oscillation zones related to cavitation surge instability and unsteady cloud cavitation resulting from the re-entrant jet. Conditional averaging correlates cavitation structures with pressure distributions, forces, and torque on the guide vane. This modeling approach captures the fine details of quasi-periodic cavitation dynamics, providing insights into unsteady sheet/cloud cavitation and offering a method for developing control strategies.

KW - LES

KW - cavitation

KW - frequency modulation

KW - hydrofoil

KW - phase averaging

KW - sheet and cloud cavities

UR - https://www.scopus.com/record/display.uri?eid=2-s2.0-85174054003&origin=inward&txGid=aad4326d9d161ea834de669986ee2705

UR - https://www.mendeley.com/catalogue/fadfa3a5-f0e7-35a4-b96a-2643c017e7a2/

U2 - 10.3390/en16196990

DO - 10.3390/en16196990

M3 - Article

VL - 16

JO - Energies

JF - Energies

SN - 1996-1073

IS - 19

M1 - 6990

ER -