Direct Numerical Simulations of K-type transition in a flat-plate boundary layer with supercritical fluids
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| Format: | Preprint |
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2024
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| _version_ | 1866917844097171456 |
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| author | Boldini, Pietro Carlo Bugeat, Benjamin Peeters, Jurriaan W. R. Kloker, Markus Pecnik, Rene |
| author_facet | Boldini, Pietro Carlo Bugeat, Benjamin Peeters, Jurriaan W. R. Kloker, Markus Pecnik, Rene |
| contents | We investigate the controlled K-type breakdown of a flat-plate boundary-layer with highly non-ideal supercritical fluid at a reduced pressure of $p_{r,\infty}=1.10$. Direct numerical simulations are performed at a Mach number of $M_\infty=0.2$ for one subcritical (liquid-like regime) temperature profile and one strongly-stratified transcritical (pseudo-boiling) temperature profile with slightly heated wall. In the subcritical case, the formation of aligned $Λ$-vortices is delayed compared to the reference ideal-gas case of Sayadi et al. (J. Fluid Mech., vol. 724, 2013, pp. 480-509), with steady longitudinal modes dominating the late-transitional stage. When the wall temperature exceeds the pseudo-boiling temperature, streak secondary instabilities lead to the simultaneous development of additional hairpin vortices and near-wall streaky structures near the legs of the primary aligned $Λ$-vortices. Nonetheless, transition to turbulence is not violent and is significantly delayed compared to the subcritical regime. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2411_14286 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Direct Numerical Simulations of K-type transition in a flat-plate boundary layer with supercritical fluids Boldini, Pietro Carlo Bugeat, Benjamin Peeters, Jurriaan W. R. Kloker, Markus Pecnik, Rene Fluid Dynamics We investigate the controlled K-type breakdown of a flat-plate boundary-layer with highly non-ideal supercritical fluid at a reduced pressure of $p_{r,\infty}=1.10$. Direct numerical simulations are performed at a Mach number of $M_\infty=0.2$ for one subcritical (liquid-like regime) temperature profile and one strongly-stratified transcritical (pseudo-boiling) temperature profile with slightly heated wall. In the subcritical case, the formation of aligned $Λ$-vortices is delayed compared to the reference ideal-gas case of Sayadi et al. (J. Fluid Mech., vol. 724, 2013, pp. 480-509), with steady longitudinal modes dominating the late-transitional stage. When the wall temperature exceeds the pseudo-boiling temperature, streak secondary instabilities lead to the simultaneous development of additional hairpin vortices and near-wall streaky structures near the legs of the primary aligned $Λ$-vortices. Nonetheless, transition to turbulence is not violent and is significantly delayed compared to the subcritical regime. |
| title | Direct Numerical Simulations of K-type transition in a flat-plate boundary layer with supercritical fluids |
| topic | Fluid Dynamics |
| url | https://arxiv.org/abs/2411.14286 |