This paper focuses on the flow stability of reverse roll coating flows employed in practical applications to coat thin liquid films on substrates of different materials. Other coating methods are available and various computer programs are purported to predict (for each corresponding method) the set of parameters that permit stable coating conditions. The application of these programs yields so-called coating windows for each particular coating setup. Knowing these coating windows permits coating methods to be applied with preknowledge of the sets of parameters for stable coatings. For reverse roll coating, computer codes for predicting coating windows are scarce or even nonexistent, which was the reason for the present work on the analytical considerations described in this paper. The results obtained formed the basis for a reverse roll coating computer program and its applications. The program is described, and computational results are provided. These are compared with experimental data available in the literature. Good agreement was obtained for high capillary number flows, but there were discrepancies between experimental and computational results for lower capillary numbers. The experimental results for low capillary number flows also appeared less reliable, which triggered the present experimental work. Some experimental results are given for low capillary numbers and these results are also compared with corresponding numerical data. It is suggested that a test section should be built consisting of two rollers and one slot die to study experimentally the stability regions of reverse roll coating flows in a rigorous manner.

中文翻译：

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液膜反向辊涂的涂布窗口的计算

本文着重于在实际应用中用于在不同材料的基材上涂覆薄液膜的反向辊涂流的流动稳定性。还可以使用其他涂覆方法，并且据称各种计算机程序可以预测（对于每种相应方法）允许稳定涂覆条件的参数集。这些程序的应用会为每种特定的涂层设置产生所谓的涂层窗口。知道了这些涂层窗口后，就可以在预先知道用于稳定涂层的参数集的情况下应用涂层方法。对于反向辊涂，预测涂层窗口的计算机代码很少，甚至根本不存在，这就是本文基于分析考虑进行本研究的原因。获得的结果构成了反向辊涂计算机程序及其应用的基础。描述了程序，并提供了计算结果。将这些与文献中提供的实验数据进行比较。高毛细管数流量获得了很好的一致性，但是较低毛细管数的实验结果和计算结果之间存在差异。低毛细管数流量的实验结果似乎也不太可靠，这触发了当前的实验工作。给出了一些低毛细管数的实验结果，并将这些结果与相应的数值数据进行了比较。