Nanowire arrays are promising man-made materials for tuning the spectrum and the magnitude of near-field thermal radiation. Near-field radiative properties of nanowire arrays are often studied using the effective medium theory (EMT). In this paper, we inspect the validity of the Maxwell-Garnett (MG) and Bruggeman (BR) EMTs for predicting near-field thermal emission by quartz and indium tin oxide (ITO) nanowire arrays. The near-field energy density predicted using the EMTs is compared with numerical simulations obtained using the thermal discrete dipole approximation. For quartz nanowire arrays, which support localized surface phonons in the infrared region, neither MG nor BR EMT can accurately predict the spectrum and the magnitude of near-field thermal emission even at distances, z_o, greater than the array pitch, L over π. Based on the performed simulations, the EMT agrees the best with the T-DDA when $1<\frac{L}{z_o}<\pi$. It is also shown that MG EMT is slightly more consistent with numerical simulations than the BR EMT. For the ITO array, which does not support localized surface plasmons in the infrared region, the MG EMT provides an acceptable estimations of near-field thermal radiation. Finally, it is observed that near-field emission can vary by a factor of two in lateral directions which cannot be captured in the EMT.

纳米线阵列是用于调节光谱和近场热辐射强度的有前途的人造材料。经常使用有效介质理论（EMT）研究纳米线阵列的近场辐射特性。在本文中，我们检查了Maxwell-Garnett（MG）和Bruggeman（BR）EMT在预测石英和氧化铟锡（ITO）纳米线阵列的近场热发射中的有效性。将使用EMT预测的近场能量密度与使用热离散偶极子逼近获得的数值模拟进行比较。对于在红外区域支持局部表面声子的石英纳米线阵列，即使在距离z _o处，MG和BR EMT都无法准确预测近场热发射的光谱和强度大于阵列间距L超过π。根据执行的仿真，EMT在以下情况下与T-DDA一致最佳$\mathrm{1个}<\frac{\mathrm{大号}}{{ž}_{Ø}}<\pi$。还表明，MG EMT在数值模拟方面比BR EMT更加一致。对于不支持红外区域中的局部表面等离子体激元的ITO阵列，MG EMT提供了可接受的近场热辐射估计。最后，可以观察到，近场发射在横向方向上的变化幅度是两倍，而在EMT中无法捕获。