The Reynolds number independence (Re independence) criterion of Re > 11,000 is widely adopted to fulfill the dynamic similarity between the urban flow modeling and the down-scale measurements. However, for 2D street canyons with H/W ≥ 1.5, experiments, numerical simulations, and in-situ observations have reported different vortex-flow regimes with similar building configurations but at different scales. This study uses both wind tunnel experiments and numerical simulations to revisit the Re-independent flow regimes and Re independence criteria with an extensive Re range for idealized 2D street canyons with various aspect ratios (H/W = 1.1, 2.4, 3, 4, and 5). We introduced an optimized ratio of relative changes (RRCs) to evaluate the flow regimes’ similarity. The wind tunnel experiment confirms that the cavity flow with H/W = 1.1 meets the Re independence when reference building Re (Re_ref) exceeds 11,000. Simulations validated by the experiment results are conducted to investigate detailed flow regimes and the critical Re (Re_c) range for each aspect ratio. The canyons with H/W = 2.4, 3, and 4 are dominated by a single asymmetric vortex when the Re independence is satisfied, while there are two vertically-stacked counter-rotating vortices in the canyon with H/W = 5. The value range of Re_c increases with aspect ratio from 1.9 × 10⁴–2.6 × 10⁴ (H/W = 2.4) to 1.3 × 10⁵–2.1 × 10⁵ (H/W = 3), and 2.1 × 10⁶–6.4 × 10⁶ (H/W = 4 and 5). Our results indicate that the fully Re-independent flow regimes in deep canyons have fewer vortices than the literature value with down-scale experiments and simulations. The variant Re_c with different aspect ratios suggests the requirement to conduct the Re-independence test for different model configurations.

Re  > 11,000的雷诺数独立性（Reindependent）准则被广泛采用，以实现城市流建模和降尺度测量之间的动态相似性。然而，对于H / W  ≥ 1.5 的2D 街道峡谷，实验、数值模拟和原位观察报告了具有相似建筑配置但规模不同的不同涡流状态。本研究使用风洞实验和数值模拟来重新审视Re独立流态和Re独立标准，以及具有广泛Re范围的理想化 2D 街道峡谷具有各种纵横比 ( H /W  = 1.1、2.4、3、4 和 5）。我们引入了优化的相对变化比率 ( RRC ) 来评估流态的相似性。风洞实验证实，当参考建筑物Re（Re _ref）超过11,000时，H / W  = 1.1的腔流满足Re独立性。进行了实验结果验证的模拟，以研究详细的流态和每个纵横比的临界Re（Re _c）范围。H / W  = 2.4、3 和 4的峡谷在Re满足独立性，而峡谷中有两个垂直叠加的反向旋转涡流，H / W  = 5。Re _c的取值范围随纵横比从 1.9 × 10 ⁴ –2.6 × 10 ⁴ ( H / W  = 2.4) 到 1.3 × 10 ⁵ –2.1 × 10 ⁵ ( H / W  = 3) 和 2.1 × 10 ⁶ –6.4 × 10 ⁶ ( H / W  = 4 和 5)。我们的研究结果表明，全重- 深峡谷中的独立流态具有比缩小规模实验和模拟的文献值更少的涡流。具有不同纵横比的变体Re _c表明需要对不同的模型配置进行重新独立性测试。