Improvement of the eN method for predicting hypersonic boundary-layer transition in case of modal exchange

Tao, Shasha; Su, Caihong; Huang, Zhangfeng

doi:10.1007/s10409-022-22416-x

Cited by 2 publications

(1 citation statement)

References 30 publications

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“…Juliano et al [23] investigated the influence of the noise environment on Hifire-5 elliptic cone transition in the wind tunnel and found that N = 3.5 in the case of noise, and N = 8 in the quiet freestream condition. Su et al [24] improved the e N method while considering the modal transformation; the results show that by neglecting the disturbance decay between the two instability modes, the proposed strategy provides more accurate results than existing strategies. LST method has also been applied to other studies on boundary layer stability.…”

Section: Introductionmentioning

confidence: 99%

The Experiments and Stability Analysis of Hypersonic Boundary Layer Transition on a Flat Plate

Yin,

Jiang,

Liu

et al. 2023

Applied Sciences

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Experimental and linear stability theory (LST) investigation of boundary layer transition on a flat plate was conducted with a flow of Mach number 5. The temperature distributions and second-mode disturbances on the flat plate surface at different unit Reynolds number (Reunit) values were captured by infrared thermography and PCB technology, respectively, which revealed the transition location of the flat-plate boundary layer. The PCB sensors successfully captured the second-mode disturbances within the boundary layer initially at a frequency of about 100 kHz, with a gradually expanding frequency range as the distance travelled downstream increased. The evolution characteristics of the second-mode instabilities were also investigated by LST and obtained for the second mode, ranging from 100 to 250 kHz. The amplitude amplification factor (N-factor) of the second-mode instabilities was calculated by the eN method. The N-factor of the transition location in the wind tunnel experiment predicted by LST is about 0.98 and 1.25 for Reunit = 6.38 × 106 and 8.20 × 106, respectively.

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Section: Introductionmentioning

confidence: 99%

The Experiments and Stability Analysis of Hypersonic Boundary Layer Transition on a Flat Plate

Yin,

Jiang,

Liu

et al. 2023

Applied Sciences

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Large eddy simulation and linear stability analysis of active sway control for wind turbine array wake

Li,

Yang

2024

Physics of Fluids

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The convective instability of wind turbine wakes allows specific upstream forcing to amplify downstream, leading to increased wake meandering and replenishment, thereby providing a theoretical basis for active wake control. In this study, the active sway control—a strategy previously proven to enhance wake recovery at the single wind turbine level—is analyzed at the turbine array level. The similarity and differences between individual turbine wakes and the wake array are analyzed using large eddy simulations and linear stability analysis, considering both uniform and turbulent inflow conditions. For cases with uniform inflow, large eddy simulations reveal significant meandering motion in the wake array induced by active sway control at a motion amplitude of 1% rotor diameter, consistent with previous studies of standalone wind turbine wakes. Nevertheless, the sensitive frequency for the wake array extends down to St = 0.125 below the limit of St > 0.2 for a single wake, and the optimal control frequency for the standalone turbine wake becomes suboptimal for the array. Linear stability analysis reveals the underlying mechanism of this frequency shift as changes in the shear-layer instability due to the overlap of upstream and downstream wakes and is capable to provide fast estimation of optimal control frequencies. When inflow turbulence intensity increases, the gain of active sway control is reduced, underscoring the importance of low-turbulence environment for successfully implementing the active sway control. The reduction in wake response is captured by the linear stability analysis if the base flow accounts for the faster wake expansion caused by inflow turbulence.

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Improvement of the eN method for predicting hypersonic boundary-layer transition in case of modal exchange

Cited by 2 publications

References 30 publications

The Experiments and Stability Analysis of Hypersonic Boundary Layer Transition on a Flat Plate

The Experiments and Stability Analysis of Hypersonic Boundary Layer Transition on a Flat Plate

Large eddy simulation and linear stability analysis of active sway control for wind turbine array wake

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