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WP1 results: CFD Modelling

Last updated: 8 April

Cavitation causes flow instabilities that hampers the functioning of flow devices, primarily by increasing the noise level, vibration, and, in extreme cases, the devices’ erosion. For controlling the cavitation, an active flow control strategy is deployed by using a wall jet. The experimental details are shown in Fig 1 (for further information, please refer to Timoshevskiy et al. [1]).

We tried to replicate and validate the experimental work of Timoshevskiy et al. [1] using high fidelity MIRACLES code shown in Figure 2 and also using the open source software OpenFOAM (not shown, for further details please refer to Pant et al. [2]).

The quantitative comparison of high fidelity MIRACLES code against the experimental results is shown in Figure 3. We found that for mild (0:7Uin) wall injection, the cavitation phenomena is mitigated.

Open-source software OpenFOAM is used to study the interaction of two Magallanes tidal turbines (shown in Figure 4), and the effect of external pitch on the performance characteristics of these tidal turbines is also studied. The upstream turbine rotates in a clockwise direction while the downstream turbine rotates in an anti-clockwise direction.

Figure 1: Experimental details of active flow control strategy, taken from Timoshevskiy et al. [1]

We found that by tuning the turbines’ external pitch angle, we can achieve the “load-balancing” in terms of power output from both the turbines. We performed six simulations for varying external pitches to understand its effect on the upstream turbine’s performance characteristics.

The summary of the simulations is explained in Table I. In Table I, it is evident that while decreasing the external pitch, the performance coefficients of the upstream turbine decreases, and thus more “undisturbed” flow will be available to the downstream turbine, which will eventually lead to the “load-balancing” of the two turbines.

[1] Mikhail V Timoshevskiy, Ivan I Zapryagaev, Konstantin S Pervunin, Leonid I Maltsev, Dmitriy M Markovich, and Kemal Hanjalić. Manipulating cavitation by a wall jet: Experiments on a 2d hydrofoil. International Journal of Multiphase Flow, 99:312-328, 2018.
[2] Chandra Shekhar Pant, Yann Delorme, and Steven Frankel. Accuracy assessment of rans predictions of active flow control for hydrofoil cavitation. Processes, 8(6):677, 2020.
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