We have investigated one-dimensional compression waves, produced by heat addition in quiescent and uniform initial conditions, in six different supercritical fluids, each taken in four states ranging from compressible pseudo-liquid fluid to ideal gas. Navier–Stokes simulations of a canonical semi-infinite domain flow problem, spanning five orders of magnitude of heating rate, are also carried out to support the theoretical analysis. Depending on the intensity of the Gaussian-shaped energy source, linear waves or shock waves due to nonlinear wave steepening are observed. A new reference heating rate parameter allows to collapse in the linear regime the whole dataset, together with the existing experimental data, thanks to its absorption of real-fluid effects. Moreover, the scaling strategy illustrates a clear separation between linear and nonlinear regimes for all fluids and conditions, offering motivation for the derivation of a unified fully predictive model for shock intensity. The latter is performed by extending the validity of previously obtained theoretical results in the nonlinear regime to supercritical fluids. Finally, thermal to mechanical power conversion efficiencies are shown to be proportional, in the linear regime, to the fluid’s Grüneisen parameter, which is the highest for compressible pseudo-liquid fluids, and maximum in the nonlinear regime for ideal gases.

中文翻译：

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超临界流体中的热诱导平面冲击波

我们已经研究了一维压缩波，在静止和均匀的初始条件下，在六种不同的超临界流体中通过加热产生，每一种都处于从可压缩伪液体流体到理想气体的四种状态。还进行了规范半无限域流动问题的 Navier-Stokes 模拟，跨越五个数量级的加热速率，以支持理论分析。根据高斯形能量源的强度，观察到线性波或由于非线性波陡峭引起的冲击波。由于吸收了真实流体效应，新的参考加热速率参数允许在线性状态下将整个数据集与现有实验数据一起折叠。而且，缩放策略说明了所有流体和条件的线性和非线性状态之间的明确分离，为推导出冲击强度的统一完全预测模型提供了动力。后者是通过将先前在非线性区域中获得的理论结果的有效性扩展到超临界流体来进行的。最后，热能到机械能的转换效率在线性状态下与流体的 Grüneisen 参数成正比，该参数对于可压缩的伪液体流体是最高的，而在理想气体的非线性状态中是最大的。后者是通过将先前在非线性区域中获得的理论结果的有效性扩展到超临界流体来进行的。最后，热能到机械能的转换效率在线性状态下与流体的 Grüneisen 参数成正比，该参数对于可压缩的伪液体流体是最高的，而在理想气体的非线性状态中是最大的。后者是通过将先前在非线性区域中获得的理论结果的有效性扩展到超临界流体来进行的。最后，热能到机械能的转换效率在线性状态下与流体的 Grüneisen 参数成正比，该参数对于可压缩的伪液体流体是最高的，而在理想气体的非线性状态中是最大的。