Near-field radiative heat transfer between irregularly shaped dielectric particles modeled with the discrete system Green's function method
Near-field radiative heat transfer between irregularly shaped dielectric particles modeled with the discrete system Green's function method
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DOI：
10.1103/physrevb.106.195417
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发表时间：
2022-04
影响因子：
3.7
通讯作者：
Lindsay P. Walter;Eric J. Tervo;M. Francoeur
中科院分区：
文献类型：
--
作者：
Lindsay P. Walter;Eric J. Tervo;M. Francoeur
研究了不规则形状SiO2介电颗粒与高斯随机球形貌之间的近场辐射换热问题。采用离散系统格林函数（DSGF）方法对颗粒进行建模，这是一种基于波动电动力学的体积积分数值方法。该方法适用于有限的三维物体，并且所有系统相互作用都是由广义系统格林函数定义的，与热激励无关。通过对2个和3个SiO2球链的解析解的验证，认为DSGF方法适用于不规则形状颗粒之间的NFRHT模型。NFRHT结果表明，在小于颗粒尺寸的真空分离距离下，粒子的几何不规则性导致总电导比类似的完美球体的电导减少，在这种情况下，NFRHT是一种表面现象。当真空分离距离大于颗粒尺寸时，NFRHT成为一个体积过程，不规则形状颗粒之间的总电导收敛于类似的完美球体。然而，光谱分析表明，粒子的不规则性会导致共振在所有分离距离上的阻尼和展宽，从而突出了DSGF方法在近场光谱工程中的重要性。当粒子尺寸大于真空分离距离时，光谱相干性降低是由于随机产生的、扭曲的粒子特征中表面声子-极化子的耦合。对于小于真空分离距离的粒子，共振增宽和阻尼与高斯随机球的复合球谐形态支持的多个局域表面声子模式有关。
Near-field radiative heat transfer (NFRHT) between irregularly shaped dielectric particles made of SiO2 and morphology characterized by Gaussian random spheres is studied. Particles are modeled using the discrete system Green's function (DSGF) approach, which is a volume integral numerical method based on fluctuational electrodynamics. This method is applicable to finite, three-dimensional objects, and all system interactions are defined independent of thermal excitation by a generalized system Green's function. The DSGF method is deemed suitable to model NFRHT between irregularly shaped particles after verification against the analytical solution for chains of two and three SiO2 spheres. The NFRHT results reveal that geometric irregularity in particles leads to a reduction of the total conductance from that of comparable perfect spheres at vacuum separation distances smaller than the particle size, a regime in which NFRHT is a surface phenomenon. At vacuum separation distances larger than the particle size, NFRHT becomes a volumetric process, and the total conductance between irregularly shaped particles converges to that of comparable perfect spheres. Spectral analysis reveals, however, that particle irregularity leads to damping and broadening of resonances at all separation distances, thereby highlighting the importance of the DSGF method for spectral engineering in the near field. The reduced spectral coherence when particle size is larger than the vacuum separation distance is attributed to coupling of surface phonon-polaritons within the randomly generated, distorted particle features. For particle size smaller than the vacuum separation distance, resonance broadening and damping is linked with the multiple localized surface phonon modes supported by the composite spherical harmonic morphologies of the Gaussian random spheres.