The Diagnostic Plot—A Tutorial with a Ten Year Perspective

Alfredsson, P. Henrik; Segalini, Antonio

doi:10.1007/978-3-030-80716-0_17

Cited by 4 publications

(2 citation statements)

References 18 publications

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“…One significant feature of the diagnostic plot is that it does not require knowing the wall position or the friction velocity, therefore ensuring the elimination of any confusion relating to the position of the wall and the velocity related to friction. In their investigation of a smooth-wall turbulent boundary layer subjected to a zero pressure gradient (ZPG) environment [17][18][19][20], it has demonstrated that the turbulent intensity, represented by u rms =U, exhibits a linear decline with U=U ∞ throughout the entire range spanning from the logarithmic to the wake region. Moreover, it can be shown that the linear zone expands as the friction Reynolds number (Reτ) grows.…”

Section: Diagnostic Plotmentioning

confidence: 99%

Wind Tunnel Measurement Techniques

Harun,

Amer Abbas

2024

Boundary Layer Flows - Advances in Experimentation, Modelling and Simulation

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This chapter discusses different measurement techniques of a low-speed wind tunnel designed and built at the Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia (UKM). The fully automated wind tunnel is named Pangkor after an island in Perak, Malaysia. Different measurement techniques are used to understand and validate the flow quality of the turbulent boundary-layer profiles at different locations and directions (wall-normal and spanwise). A hot-wire sensor captures the boundary layer over a smooth, flat surface. These data are then compared with high-quality published data. The flow uniformity shows comparable velocity variations and turbulent intensity. The boundary-layer profiles collapse well in different spanwise locations. Furthermore, the boundary-layer profiles at different Reτ follow the standard boundary-layer profile. Since the wind tunnel is relatively new, the calibration method for the hot-wire anemometry is provided. The approach to spectral analysis is provided using a fast Fourier transform (FFT), revealing the prominence of the energized structure of λx+≈1000 residing in the near-wall, in this analysis, we chose z+≈15. The spectral analysis shows that the compounded effects of small and large-scale do not vary with Reτ. Nonetheless, the outer hump is increasingly visible with increasing Reτ. The proposed measurement technique and findings help validate wind tunnel flow quality and turbulent boundary layer profiles.

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Section: Diagnostic Plotmentioning

confidence: 99%

Wind Tunnel Measurement Techniques

Harun,

Amer Abbas

2024

Boundary Layer Flows - Advances in Experimentation, Modelling and Simulation

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“…It must be noted that the underlying approximation of the wall position from the LDV-PS measurement data remains a source of uncertainty in these considerations. The so-called diagnostic plot (Alfredsson et al, 2021) allows the comparison of turbulent shear flow data without the need to determine the wall position nor the friction velocity. Figure 11 shows such a diagnostic plot for the present investigation, where the ratio of the rms level of streamwise velocity to mean streamwise velocity urms/U is plotted over the ratio of mean streamwise velocity to centerline velocity U/U cl .…”

Section: Evaluation Of the Turbulent Channel Flow Measurementsmentioning

confidence: 99%

Measurements in a turbulent channel flow bymeans of an LDV profile sensor

Pasch

Leister

Gatti

et al. 2023

Preprint

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For the development of flow control techniques in wall-bounded turbulent flows, precise measurements of the flow in the proximity of the wall are essential. A laser Doppler velocity profile-sensor (LDV-PS) allows the combined measurement of tracer particle positions and velocities, which makes it a promising tool for flow measurements with high spatial resolution in flows with high velocity gradients. Therefore, the LDV-PS is employed in measurements of a turbulent channel flow at Reτ = 350. Additionally, LDV-PS measurement and signal-processing accuracies of velocity and location estimations are evaluated for various tracer-object sizes and velocities. On this basis, the turbulent channel flow measurements are evaluated and compared to reference data from direct numerical simulations. Thus, potentials of the LDV-PS are investigated for different regions of the flow, and various data processing routines as well as the experimental practice are discussed from an application perspective.

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Measurements in a Turbulent Channel Flow by Means of an LDV Profile Sensor

Pasch,

Leister,

Gatti

et al. 2023

Flow Turbulence Combust

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Spatially and temporally resolved velocity measurements in wall-bounded turbulent flows remain a challenge. Contrary to classical laser Doppler velocimetry (LDV) measurements, the laser Doppler velocity profile sensor (LDV-PS) allows the combined measurement of tracer particle position and velocity, which makes it a promising tool. To assess its feasibility a commercial LDV-PS is employed in a turbulent channel flow at $$Re_\tau =350$$ R e τ = 350 . Additionally, the measurement and signal-processing accuracies of velocity and location are evaluated for various tracer-object sizes and velocities. On this basis, the turbulent channel flow measurements are evaluated and compared to reference data from direct numerical simulations. Thus, potentials of the LDV-PS are investigated for different regions of the flow and various data processing routines as well as the experimental practice are discussed from an application perspective.

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The Diagnostic Plot—A Tutorial with a Ten Year Perspective

Cited by 4 publications

References 18 publications

Wind Tunnel Measurement Techniques

Wind Tunnel Measurement Techniques

Measurements in a turbulent channel flow bymeans of an LDV profile sensor

Measurements in a Turbulent Channel Flow by Means of an LDV Profile Sensor

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