This study focuses on the interaction between the water free surface, the riverbed, and some Darrieus-type hydrokinetic turbines deployed in river flows. As turbines offer a resistance to the flow, they affect the upcoming velocity, which in turn affects their performance. The proximity of the neighboring deformable free surface or rigid bed may also influence their power extraction. In this context, 2D and 3D URANS simulations of a cross-flow (H-Darrieus type) turbine are conducted with free-surface modeling and adapted boundary conditions allowing the capture of the interactions between the turbine and the resource. Different water depth immersions are considered in order to study local proximity effects. It is found, neglecting riverbed friction, that shallow immersion is detrimental to power extraction whereas bed proximity associated with deep immersion is favorable. This observation does not hold when considering a more realistic river with a velocity profile throughout the depth. Direction of rotation in high proximity cases also plays a role. Although the literature suggests a slight increase in power extraction with the Froude number, we find that when interaction with the resource is taken into account, the power extraction is rather independent of the Froude number for deep immersion or slightly decreasing for shallow immersion. Nonetheless, all the variations in power extraction reported in this study remain small compared to the ones associated with blockage effects. Finally, the shallow immersion case simulated in 3D behaves similarly to that simulated in 2D. Switching the orientation of the rotation axis from horizontal to vertical, despite changing the local interaction with the free surface, does not affect significantly the performance of the turbine.

中文翻译：

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河流与部署的错流流体动力涡轮机之间的双向相互作用

本研究侧重于水自由表面、河床和部署在河流中的一些 Darrieus 型流体动力涡轮机之间的相互作用。由于涡轮机对流动产生阻力，它们会影响即将到来的速度，进而影响它们的性能。邻近的可变形自由表面或刚性床的接近度也可能影响它们的功率提取。在这种情况下，交叉流（H-Darrieus 型）涡轮机的 2D 和 3D URANS 模拟是通过自由表面建模和自适应边界条件进行的，允许捕获涡轮机与资源之间的相互作用。为了研究局部邻近效应，考虑了不同的水深浸没。发现，忽略河床摩擦，浅浸入不利于功率提取，而与深浸入相关的床接近度是有利的。当考虑在整个深度具有速度剖面的更现实的河流时，这种观察结果不成立。高度接近情况下的旋转方向也起作用。尽管文献表明弗劳德数的功率提取略有增加，但我们发现，当考虑到与资源的相互作用时，功率提取与深度浸入的弗劳德数相当独立，浅浸入时功率提取略有下降。尽管如此，与与阻塞效应相关的变化相比，本研究中报告的所有功率提取变化仍然很小。最后，在 3D 中模拟的浅浸入情况与在 2D 中模拟的情况类似。