Aerodynamic Design and Validation of a Contraction Profile for Flow Field Improvement and Uncertainty Quantification in a Subsonic Wind Tunnel

Vishwanathan, Vidya; Szőke, Máté; Duetsch-Patel, Julie E.; Gargiulo, Aldo; Fritsch, Daniel J.; Borgoltz, Aurélien; Roy, Christopher J.; Lowe, K. Todd; Devenport, William J.

doi:10.2514/6.2020-2211

Cited by 13 publications

(4 citation statements)

References 15 publications

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“…The flow is tripped in the contraction, 3.54 m upstream of the test section coordinate origin (see Figure 1), such that the measured flow is fully turbulent and free from any transitional effects. Further information regarding the specifics of the wind tunnel facility and experiment configurations can be found in [12][13][14]. The coordinate system is set such that x is streamwise, y is wall-normal, and z is spanwise with corresponding u, v, w velocity components.…”

Section: Experimental Facilities and Methods 21 Facilitymentioning

confidence: 99%

Spatial Resolution Limitations of Particle Image Velocimetry in High Reynolds Number Turbulent Boundary Layers

Vishwanathan

Fritsch

Devenport

et al. 2022

Preprint

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Particle image velocimetry (PIV) has become a standard technique in turbulence experiments for its non-intrusive ability to simultaneously measure multiple points in a flow field. However, inherent volume averaging of the interrogation windows as well as fixed limitations of camera spatial resolution and related hardware set the minimum and maximum scales of structures that can be resolved with this measurement technique. Resolution limitations present themselves as an attenuation of the measured turbulence statistics, seen particularly in the Reynolds wall-normal stress components. This experimental study investigates the impact of hardware-level resolution limitations on the resolved turbulence statistics of PIV measurements made of both rough and smooth wall turbulent boundary layers influenced by external pressure gradients. Velocity fields are measured with PIV using two lens magnifications; one with a baseline lens and one with the addition of a teleconverter lens to view the same flow-field with double magnification (i.e. a finer spatial resolution). A comparison of the turbulence statistics between the rough and smooth wall, components of velocity, and pressure gradient magnitudes are analyzed. The smooth wall turbulence data consistently show a much higher sensitivity to the spatial resolution, particularly for the wall-normal component, due to the smaller eddy length-scales. A fixed camera resolution limits the measured range of scales which affects comparative magnitudes of turbulence for flows with different local Reynolds numbers. The rough wall data measurements show a variable sensitivity to the camera resolution depending on local Reynolds number and streamwise flow history. A statistical convergence study based on the anistropy of turbulence scales is necessary in experimental design for the study of turbulent boundary layers.

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Section: Experimental Facilities and Methods 21 Facilitymentioning

confidence: 99%

Spatial Resolution Limitations of Particle Image Velocimetry in High Reynolds Number Turbulent Boundary Layers

Vishwanathan

Fritsch

Devenport

et al. 2022

Preprint

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“…The SWT is capable of reaching a maximum flow speed of approximately 80 m/s, corresponding to a Reynolds number per meter of 5 × 10 6 . The facility features two interchangeable test sections, one of which has highly modular side walls to facilitate model and instrumentation installation (Duetsch-Patel et al, 2020), as well as an instrumented contraction liner to track the surface static pressure through the contraction (Vishwanathan et al, 2020). Measurements over the BeVERLI Hill were performed in a configuration as depicted in Fig.…”

Section: Stability Wind Tunnelmentioning

confidence: 99%

Structural aspects of the attached turbulent boundary layer flow over a hill

et al. 2023

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Three-dimensional turbulent boundary layers under strong pressure gradients and curvature are the rule in real-world flow applications but are typically not well predicted by turbulence models due to isotropic eddy viscosity or equilibrium assumptions. Validation-quality data in complex 3D flows is necessary for continued efforts to improve simulation accuracy. The BeVERLI (Benchmark Validation Experiments for RANS/LES Investigations) Hill bump model, designed specifically for validation experiments, was tested in the Virginia Tech Stability Wind Tunnel to collect validation experiment data on the three-dimensional (3D) boundary layer flow over a 3D hill. Laser Doppler velocimetry measurements on the bump model were used to study the mean flow and turbulence structure and evaluate the impact of pressure gradient and curvature upon the total shear stress in the boundary layer and evaluate the impact of pressure gradient and curvature upon the total shear stress behavior in the near-wall region. From analysis of the BeVERLI Hill flow, including the boundary layer just upstream of the hill, and comparison with the 3D flow around a wing-body junction of Ölçmen et al (2001), it is shown that none of the stations studied exhibit a constant shear stress region over any significant region of the boundary layer. One station on the hill, located in a region Structural Aspects of the Attached Turbulent Boundary Layer Flow Over a Hill with strong spanwise and streamwise pressure gradients, experiences an apparent return to an equilibrium shear stress for x + 2 < 30 due to significantly increased production of u ′ 1 u ′ 2 and u ′2 2 at this station.

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“…There are other strategies to properly design the contraction curve of a wind tunnel [42]- [44] to reduce the wind tunnel losses and provide a high quality flow at the working section. For the case of low-speed wind tunnels, the contraction curve can be modeled by using polynomials of n − th order typically n = 3, 4, 5, or higher.…”

Section: Contraction Curves In Three-dimensionsmentioning

confidence: 99%

“…[44] showed that contraction curves up to the 5th order without quadratic contribution provide good results at low velocities. There are also techniques concerning cubic spline curves, whose control points are properly set to enhance the the outflow at the end of the contraction section [42].…”

Section: Contraction Curves In Three-dimensionsmentioning

confidence: 99%

Characterization, Design Testing and Numerical Modeling of a Subsonic-Low Speed Wind Tunnel

Lara

Salazar

2022

Ing.

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Context: Wind tunnels are essential devices in the study of flow properties through objects and scaled prototypes. This work presents a numerical study to characterize an existing wind tunnel, proposing modifications with the aim to improve the quality of the flow in the test chamber. Method: Experimental measurements of the inlet velocity and pressure distribution of a wind tunnel are nperformed. These empirical values are used as parameters to define boundary conditions in simulations. The Finite Element Method (FEM) at low speeds is implemented to determine the stream function by using a standard Galerkin method. Polynomial interpolations are employed to modify the contraction section design, and numerical simulations are performed in order to compare the numerical results of the flow for the existing and the modified wind tunnels. Results: Experimental measurements of the flow at the wind tunnel entrance are presented. The velocity field and distribution of thermodynamic variables inside the tunnel are numerically determined. This computations are useful since it is experimentally difficult to make measurements inside the channel. Additionally, numerical calculations of these variables are presented under modifications in the tunnel geometry. Conclusions: A comparison between these simulations show that laminar flow at low velocities can be modeled as incompressible and irrotational fluid under a bidimensional approximation along its longitudinal section. It is observed that modifications in the geometry of the tunnel can improve the flow in the test section of the wind tunnel in the laminar regime.

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Aerodynamic Design and Validation of a Contraction Profile for Flow Field Improvement and Uncertainty Quantification in a Subsonic Wind Tunnel

Cited by 13 publications

References 15 publications

Spatial Resolution Limitations of Particle Image Velocimetry in High Reynolds Number Turbulent Boundary Layers

Spatial Resolution Limitations of Particle Image Velocimetry in High Reynolds Number Turbulent Boundary Layers

Structural aspects of the attached turbulent boundary layer flow over a hill

Characterization, Design Testing and Numerical Modeling of a Subsonic-Low Speed Wind Tunnel

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