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Temporal mixing layer configuration.

Temporal mixing layer configuration.

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The present article investigates the effects of a BZT (Bethe-Zel'dovich-Thompson) dense gas (FC-70) on the development of turbulent compressible mixing layers at three different convective Mach numbers Mc = 0,1; 1,1 and 2,2. This study extends previous analysis conducted at Mc = 1,1 (Vadrot et al. 2020). Several 3D direct numerical simulation (DNS)...

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... velocity in the upper part of the domain U 1 is set equal to −∆u/2, whereas U 2 is set to ∆u/2. A representation of the computational domain is provided in figure 2. Periodic boundary conditions are imposed in the x and z directions and non-reflective conditions are set in the y directions using the NSCBC model proposed by Poinsot & Lele (1992). ...
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... DG flows, the well-known compressibility-related reduction of the momentum thickness growth rate is almost suppressed by dense gas effects at convective Mach numbers above M c = 1.1. Figure 12 shows the comparison between PG and DG streamwise specific turbulent kinetic energy spectra computed over the centreline. Spectra are normalised by ∆u 2 δ θ (t) in the same way as Pirozzoli et al. (2015) and averaged over the self-similar period. ...
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... are normalised by ∆u 2 δ θ (t) in the same way as Pirozzoli et al. (2015) and averaged over the self-similar period. The longitudinal Taylor microscale λ x is also indicated for each gas in figure 12. Its value is much larger for DG flow consistently with Reynold numbers computed from Taylor microscales given in table 3. The inertial phase is thus significantly reduced for the PG flow. ...
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... a result, the initial sound speed in the computed DG flows is about six times smaller when compared to its initial value for the PG shear layers. Figure 20 shows the normalised momentum growth rate at M c = 2.2 as a function of the normalised sound speed. A rather clear correlation appears between the momentum thickness growth rate and the initial sound speed: the growth rate decreases with increasing sound speed. ...
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... computational parameters corresponding to these simulations are summarized in Table 6 along with the parameters used in the previous study at M c = 1.1. Figure 21 shows temporal evolutions of momentum thickness for the simulations listed in Table 6. DG1 is performed with the same domain lengths and size of initial turbulent structures (relatively to the initial momentum thickness) as in the previous M c = 1.1 study DG0. ...
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... a large decrease of the growth rate is observed for DG2 around τ = 4000; selfsimilarity cannot be reached. Figure 22 displays the time evolution of the integral length scale in the z direction l z for DG2 and DG3 simulations. Around τ = 4000, the integral length scales l z /L z suddenly decreases for DG2 after having reached a value of 0.2. ...

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