Laminar to Turbulent Transition at Unsteady Inflow Conditions: Flight Experiments Under Calm and Moderately Turbulent Conditions

Guissart, Amandine; Nemitz, Timotheus; Tropea, Cameron

doi:10.1007/978-3-030-25253-3_18

Cited by 2 publications

(3 citation statements)

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“…Further investigations reported in [33] confirmed that the discrepancies with LST and wind tunnel results can be explained by a small difference in the investigated airfoil. In conclusion, the phenomena measured in flight and in the wind tunnel exhibit the features typical of the TS-waves driven transition (this is further detailed in [28,33]). The setup is thus appropriate to study the impact of an increase in the inflow turbulence level.…”

Section: Calm Inflow Conditionssupporting

confidence: 56%

“…These two spanwise rows are located at˜ = 0.31 and˜ = 0.34 and they are used to ensure that the studied phenomenon is two-dimensional (verifying that the spanwise distribution of the time averaged standard deviation of the pressure fluctuations is constant). These spanwise rows are also used to compute frequency wavenumber spectra (results not shown here but reported in [33]). In a flush-mounted configuration, the frequency response of the microphones is flat (−3dB flatness in the range [50-6000]Hz), but in the present configuration, the pinhole influences the frequency response.…”

Section: Methodsmentioning

confidence: 99%

“…Then, the transition development is analyzed through disturbance amplification rates and the discrepancies with the results from the linear stability theory are discussed. The data obtained for calm flight conditions are analyzed further in [28,33]. ).…”

Section: Calm Inflow Conditionsmentioning

confidence: 99%

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Small-Scale Atmospheric Turbulence and Its Impact on Laminar-to-Turbulent Transition

et al. 2021

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Using flight measurements conducted between altitudes of 700 m and 3000 m, this work characterizes atmospheric turbulence and investigates the effects of an increase in turbulence level on the laminar-turbulent transition taking place on the pressure side of a laminar airfoil. Flight conditions ranging from calm to moderately turbulent and natural transition driven by Tollmien-Schlichting waves are considered. The inflow conditions are first characterized and reported using single and two-point statistics. Moreover, it is shown how characteristic parameters can be estimated from the turbulence intensity. Then, the sensitivity of the transition location to an increase of turbulence level is investigated. Flight results show a low sensitivity of the transition location to an increase of turbulence level, when the latter is not associated with significant variations of pressure gradient. Similar investigations are also conducted in a wind tunnel where the turbulence level is increased using an active grid and a significant change of the transition location is observed with increasing turbulence level. The differences in the response of the transition to freestream turbulence level in flight and in the wind tunnel is postulated to be attributable to differences in the probability density distributions of the inflow velocity fluctuations.

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Section: Calm Inflow Conditionssupporting

confidence: 56%

Section: Methodsmentioning

confidence: 99%