基于非线性动力学的方法研究中庭式建筑空间中自然通风的多解性现象

The application of indoor natural ventilation is beneficial for health of occupant, and can reduce the energy consumption as well as carbon emission of HVAC (Heating, Ventilating and Air Conditioning) equipment. The solution multiplicity of natural ventilation means there exist more than one steady-state flow patterns of natural ventilation under identical indoor heat sources, outdoor wind force and in the same building. If the solution multiplicity exists, the real indoor air quality and thermal environment can be inconsistent with design plan. In the project, zone modelling and nonlinear dynamics are combined to analyze solution multiplicity of natural ventilation in modern widely-used atrium building. Also, the stability of the solution multiplicity is considered and the dynamical effect of initial conditions and perturbations on the solution multiplicity is investigated. Additionally, CFD (Computational Fluid Dynamics) approach based on RANS turbulence model and air modelling experimental method are used to verify the solutin multiplcity of natural ventilation. Furthermore, a new design plan is proposed to control or eliminate the occurrence of solution multiplicity, which can be validated by experimental investigation. Therefore, the design plan can guarantee and ensure the reliablity of natural ventilation in atrium building.

室内自然通风的应用有利于居民的身体健康，同时减少建筑暖通设备的能耗和碳排放。自然通风的多解性是指在确定的建筑空间中，完全相同的热源和风压条件下，存在多个稳态的自然通风的流动模式；若存在多解性，则实际室内空气质量和热环境就与之前的设计不相符。本项目针对当今广泛应用的中庭式建筑空间，采用区域模拟和非线性动力学相结合的方法，研究自然通风的多解性现象；并进一步研究多解的稳定性，以及初始条件和扰动对多解的动力性影响。然后采用以RANS湍流模型为基础的计算流体力学技术和空气模拟的实验方法验证自然通风的多解性现象；最后提出控制或排除多解性现象发生的设计方案，并用实验加以验证。这些设计方案可以为中庭式建筑空间中自然通风的可靠性提供保证和依据。

室内自然通风的应用有利于居民的身体健康，同时减少建筑暖通设备的能耗和碳排放。自然通风的多解性是指在相同的热源、风压条件和建筑空间中，存在多个稳态的自然通风的流动模式；若存在多解性，则实际室内空气质量和热环境与设计不符。针对当今广泛应用的中庭式建筑空间，考虑中庭与一个楼层相连接的建筑模型，楼层与中庭的高度比以及在其中的热源功率比是变化的。分析了稳态和瞬态过程中流经楼层和中庭的空气流率。通过欧拉方法数值计算了从不同初始条件到不同稳态流动模式的瞬态过程，尤其是分析了从“零”初始条件出发空气流率在不同流动模式之间随时间变化的过程。基于非线性动力学的基础知识，分析了多种流动模式的稳定性和分叉点。最后，对于在中庭式建筑空间内由于这两种相互竞争的浮升力所带来的自然通风进行了讨论。