We quantify the uncertainty of the momentum coefficient, $$C_{\mu}$$ , for six different experimental approaches. The approaches vary depending on compressibility effects and on the utilized acquisition equipment to measure the product of the mass flow rate with the jet exit velocity. The uncertainty of the directly-measured variables is propagated into the momentum coefficient using the Taylor expansion method to the first order. All relevant random and systematic uncertainties are meticulously quantified and listed. The analysis reveals unacceptably high uncertainty of the momentum coefficient under certain settings. Practical solutions to minimize the sources of uncertainty are then proposed and analyzed. The proposed improvements on the benchmark example of a Coanda actuator with a high aspect ratio slot reduce the uncertainty of $$C_{\mu}$$ significantly but not sufficiently, as it remains at a non-negligible value of $$\approx 11\%$$ for the best scenario. Finally, a list of practical recommendations and guidelines on how to accurately estimate the momentum coefficient experimentally is provided.

中文翻译：

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实验测量的动量系数的不确定性

我们量化了六种不同实验方法的动量系数 $$C_{\mu}$$ 的不确定性。这些方法因可压缩性影响和用于测量质量流量与射流出口速度的乘积而使用的采集设备而异。使用泰勒展开法将直接测量变量的不确定性传播到动量系数中到一阶。所有相关的随机和系统不确定性都经过精心量化和列出。分析揭示了在某些设置下动量系数的高度不确定性。然后提出并分析了最小化不确定性来源的实用解决方案。对具有高纵横比槽的 Coanda 执行器的基准示例的改进建议显着但不充分地降低了 $$C_{\mu}$$ 的不确定性，因为它保持在 $$\approx 11 的不可忽略的值\%$$ 为最佳方案。最后，提供了有关如何通过实验准确估计动量系数的实用建议和指南列表。