When modeling complex fluid networks using one-dimensional (1D) approaches, boundary conditions can be imposed using zero-dimensional (0D) models. An application case is the modeling of the entire human circulation using closed-loop models. These models can be considered as a tool to investigate short-term transient and stationary hemodynamic responses to postural changes. The first shortcoming of existing 1D modeling methods in simulating these sudden maneuvers is their inability to deal with rapid variations in flow conditions, as they are limited to the subsonic case. On the other hand, numerical modeling of 0D models representing microvascular beds, venous valves or heart chambers is also currently modeled assuming subsonic flow conditions in 1D connecting vessels, failing when transonic and supersonic flow conditions appear. Therefore, if numerical simulation of sudden maneuvers is a goal in closed-loop models, it is necessary to reformulate the current methodologies used when coupling 0D and 1D models, allowing the correct handling of flow evolution for both subsonic and transonic conditions. This work focuses on the extension of the general methodology for the Junction Riemann Problem (JRP) when coupling 0D and 1D models. As an example of application, the short-term transient response to head-up tilt (HUT) from supine to upright position of a closed-loop model is shown, demonstrating the potential, capability and necessity of the presented numerical models when dealing with sudden maneuvers.

中文翻译：

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血管网络中 0D 和 1D 模型的数值耦合，包括跨音速流动条件。应用于姿势变化的短期瞬态和静态血流动力学模拟

当使用一维 (1D) 方法对复杂流体网络进行建模时，可以使用零维 (0D) 模型施加边界条件。一个应用案例是使用闭环模型对整个人体循环进行建模。这些模型可以被视为研究对姿势变化的短期瞬态和静态血流动力学反应的工具。现有一维建模方法在模拟这些突然机动时的第一个缺点是它们无法处理流动条件的快速变化，因为它们仅限于亚音速情况。另一方面，代表微血管床、静脉瓣膜或心室的 0D 模型的数值建模目前也假设 1D 连接血管中的亚音速流动条件进行建模，但在出现跨音速和超音速流动条件时会失败。因此，如果闭环模型的目标是突然机动的数值模拟，则有必要重新制定耦合 0D 和 1D 模型时使用的当前方法，以便正确处理亚音速和跨音速条件下的流动演化。这项工作的重点是在耦合 0D 和 1D 模型时扩展结黎曼问题 (JRP) 的一般方法。作为应用示例，显示了闭环模型从仰卧到直立位置的平视倾斜 (HUT) 的短期瞬态响应，展示了所提出的数值模型在处理突发情况时的潜力、能力和必要性。演习。