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Analytical Thermal Boundary Condition for Quasi-Transient Simulation of Internal Flow Experiments
Journal of Thermophysics and Heat Transfer ( IF 2.1 ) Pub Date : 2021-09-06 , DOI: 10.2514/1.t6175
Peter R. Forsyth 1 , David Gillespie 2 , Matthew McGilvray 2
Affiliation  

Transient thermochromic liquid crystal (TLC) experiments can provide high-fidelity spatially resolved heat transfer data for complex geometries, particularly where infrared techniques cannot be applied. One challenge when applying transient methods to internal geometries is the local definition of the driving gas temperature. The transient nature of the streamwise driving gas temperature profile has led to comparisons with steady-state computational fluid dynamics being questioned. This paper explores simulating the temporal behavior of transient TLC experiments directly. A novel technique is developed to account for differences in the gas and solid time scales, where surface temperature is calculated at each spatial location analytically from the surface heat flux, using an impulse response method assuming one dimensional, semi-infinite conduction. Postprocessing of the simulated surface temperature history is performed using the same method as experimentally, allowing for direct comparison. This analytical thermal boundary condition (ATBC) is applied to simulate a transient TLC experiment of a stationary superscaled rib turbulated internal cooling passage in a gas turbine engine. Traditional steady-state simulations were also performed with constant temporal and spatial temperature boundary conditions. Results show that calculations using the new ATBC and traditional steady-state method give very similar Nusselt number distributions and mean values in relation to the experimental data, suggesting the larger discrepancy between simulations and the experiments is not the definition of the driving gas temperature. Analysis of transient variation of Nusselt number indicated brief highly localized maximum variations up to 40%, although this was not found to significantly affect the mean values, and passage-averaged values converged to within 0.5% of the final value within 0.2 s.



中文翻译:

内部流动实验准瞬态模拟的解析热边界条件

瞬态热致变色液晶 (TLC) 实验可以为复杂的几何形状提供高保真空间解析传热数据,尤其是在无法应用红外技术的情况下。将瞬态方法应用于内部几何形状时的一项挑战是驱动气体温度的局部定义。流向驱动气体温度曲线的瞬态特性导致与稳态计算流体动力学的比较受到质疑。本文探讨了直接模拟瞬态 TLC 实验的时间行为。开发了一种新技术来解释气体和固体时间尺度的差异,其中使用假设为一维的脉冲响应方法,从表面热通量分析性地计算每个空间位置的表面温度,半无限导通。模拟表面温度历史的后处理使用与实验相同的方法进行,允许直接比较。该解析热边界条件 (ATBC) 用于模拟燃气涡轮发动机中静止超尺度肋湍流内部冷却通道的瞬态 TLC 实验。传统的稳态模拟也在恒定的时间和空间温度边界条件下进行。结果表明,使用新 ATBC 和传统稳态方法的计算给出了与实验数据非常相似的 Nusselt 数分布和平均值,这表明模拟和实验之间较大的差异不是驱动气体温度的定义。

更新日期:2021-09-06
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