High-speed maglev trains operate at higher speeds than conventional high-speed trains. This has implications on intensified aerodynamic issues, such as the transition between open air running and entering into a tunnel. In this paper, numerical simulation of a maglev train entering a tunnel is carried out using IDDES methods (based on SST k-omega model) to analyze the changing slipstream. The peaks and fluctuations of the slipstream are analyzed, together with the transient wake characteristics and TKE (turbulent kinetic energy) distributions. The influence of train nose length on the slipstream and its associated characteristics inside tunnels is also investigated in this paper. It was found that as the maglev train enters the tunnel, the wake slipstream at measuring points close to tunnel entrance increases significantly then decreases slightly with the increase of distance to tunnel entrance. Overall, the fluctuation and magnitude of slipstream inside tunnel is larger than that on open line, more specifically, the maximum TKE generated inside tunnel is. 7.62% larger than that on the open line at contour X = 3 H behind the train tail. Besides it takes longer time for the slipstream inside tunnel to return to the initial condition. These phenomena could be explained by that the scale of vortex structure formed behind the train tail is larger, the developing distance of the wake vortices in the streamwise direction is longer and the TKE generated is more significant inside tunnel. It was also found that increasing the nose length could effectively decrease the spatial scale and TKE of the wake vortices, which resulted on reducing the peak and pulsation of wake slipstream. Comparing to that of 5.4 m, the peak of the wake slipstream of the maglev trains with the 7.4 m and 9.4 m nose lengths at Y = 0.235 m(0.385) is reduced by approximately 23.7%(58%) and 35.9%(82.2%) on open field, and by about 3.6%(4.7%) and 14%(18.5%) inside tunnel. Besides, the maximum TKE at contour X = 2H/3H/5H behind the train tail decreases about 14.4%/10.7%/11.3% and 51%/31.5%/18% as the nose length increase to 7.4 m and 9.4 m respectively.

中文翻译：

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隧道磁悬浮列车滑流特性数值研究

高速磁悬浮列车的运行速度高于传统高速列车。这对加剧的空气动力学问题有影响，例如露天跑步和进入隧道之间的过渡。本文采用IDDES方法（基于SST k-omega模型）对进入隧道的磁悬浮列车进行数值模拟，分析滑流的变化。分析了滑流的峰值和波动，以及瞬态尾流特性和 TKE（湍流动能）分布。本文还研究了列车机头长度对隧道内滑流及其相关特性的影响。发现随着磁悬浮列车进入隧道，随着距隧道入口距离的增加，靠近隧道入口测点的尾流滑流先显着增加，然后略有下降。总体而言，隧道内滑流的波动幅度和幅度均大于明线，更具体地说，隧道内产生的最大TKE是最大的。比火车尾部后轮廓 X = 3 H 处的空线大 7.62%。此外，隧道内的滑流恢复到初始状态需要更长的时间。可以解释为列车尾部形成的涡结构规模较大，尾涡沿流向发展距离较长，隧道内产生的TKE更为显着。研究还发现，增加机头长度可以有效降低尾流涡的空间尺度和TKE，从而降低尾流滑流的峰值和脉动。与5.4 m相比，机头长度为7.4 m和9.4 m的磁悬浮列车尾流在Y=0.235 m(0.385)处的尾流滑流峰值分别降低了约23.7%(58%)和35.9%(82.2%) ) 在露天场地上，在隧道内分别为 3.6%(4.7%) 和 14%(18.5%)。此外，随着机鼻长度增加到7.4 m和9.4 m，列车尾部后轮廓X = 2H/3H/5H处的最大TKE分别下降约14.4%/10.7%/11.3%和51%/31.5%/18%。Y = 0.235 m(0.385) 处的 4 m 机头长度在开阔场地上减少了约 23.7%(58%) 和 35.9%(82.2%)，在内部减少了约 3.6%(4.7%) 和 14%(18.5%)隧道。此外，随着机鼻长度增加到7.4 m和9.4 m，列车尾部后轮廓X = 2H/3H/5H处的最大TKE分别下降约14.4%/10.7%/11.3%和51%/31.5%/18%。Y = 0.235 m(0.385) 处的 4 m 机头长度在开阔场地上减少了约 23.7%(58%) 和 35.9%(82.2%)，在内部减少了约 3.6%(4.7%) 和 14%(18.5%)隧道。此外，随着机鼻长度增加到7.4 m和9.4 m，列车尾部后轮廓X = 2H/3H/5H处的最大TKE分别下降约14.4%/10.7%/11.3%和51%/31.5%/18%。