Experimental and computational investigation of transverse gust encounters

Biler, Hulya; Badrya, Camli; Jones, Anya R.

doi:10.2514/6.2018-0571

Cited by 14 publications

(20 citation statements)

References 13 publications

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“…These experiments found that classical analytical models were insufficient for modeling the forces in strong gust encounters that involve separated flows and large angles of attack, especially during the flow's recovery from the gust interaction. Recent work by Biler et al [21] in the same facility found good agreement between experimental and numerical results at a Reynolds number based on the chord length and freestream velocity of Re c 40;000 and confirmed the complexity of such gust encounters. Another classical unsteady problem, the accelerated flat plate, has been investigated by a number of researchers.…”

Section: Introductionmentioning

confidence: 59%

Vortical Gusts: Experimental Generation and Interaction with Wing

Hufstedler

McKeon

2019

AIAA Journal

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We describe the experimental generation of isolated vortical gusts and the interaction between these gusts and a downstream airfoil at a Reynolds number of 20,000. A standard method of generating a vortical gust has been to rapidly pitch an airfoil. A different approach is presented here: heaving a plate across a tunnel and changing direction rapidly to release a vortex. This method is motivated by the desire to limit a test article's exposure to the wake of the gust generator by moving it to the side of the tunnel. Two suites of experiments were performed to characterize the performance of the gust generators and to measure the forces on and flow around the downstream airfoil. The novel mechanism allowed for measurement of the resumption of vortex shedding from the downstream airfoil, which was impossible with the pitching generator. Nomenclature C L = lift coefficient, lift/(dynamic pressure × wing area) c a = airfoil chord length, m c p = plate chord length, m h = plate heave distance, m Re c = Reynolds number with respect to airfoil's chord length S = heaving speed ratio, V heave ∕U T = heaving time ratio, t heave ∕t cp t = time, s t a = normalized plate acceleration time, t accel ∕t cp t accel = plate acceleration time, s t c = chordwise convective time across airfoil, s t cp = chordwise convective time across plate, s t heave = heaving time, s t p = normalized airfoil pitching time, t pitch ∕t c t pitch = generator pitching time, s U = freestream speed, m∕s u = velocity in x direction, m∕s V heave = plate heaving speed, m∕s v = velocity in y direction, m∕s x = streamwise coordinate, m x 0 = streamwise position computed from unwrapping process, m y = cross-stream coordinate with respect to tunnel midline, m y 0 = initial plate distance from midline, m y peak = cross-stream position of maximum displacement of heaving plate, m y plate = cross-stream position of heaving plate, m y upstream = cross-stream position of pitching gust generator, m z = spanwise coordinate, m α = angle of attack of test article, rad (unless otherwise noted) α 1 = initial angle of pitching gust generator, rad (unless otherwise noted) α 2 = final angle of pitching gust generator, rad (unless otherwise noted) α eff = effective angle of attack of heaving gust generator, rad (unless otherwise noted) α upstream = angle of attack of pitching gust generator, rad (unless otherwise noted) Γ v = circulation of shed vortex, m 2 ∕s Γ v;est;heave = estimated circulation of shed vortex from heaving generator, m 2 ∕s Γ v;est;pitch = estimated circulation of shed vortex from pitching generator, m 2 ∕s Γ 2 = vortex identification criterion Δx = streamwise distance between generator and test article, m τ a = normalized time, t∕t c ω z = vorticity measured in x-y plane, s −1

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Section: Introductionmentioning

confidence: 59%

Vortical Gusts: Experimental Generation and Interaction with Wing

Hufstedler

McKeon

2019

AIAA Journal

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“…Both a best fit of a sine squared and Gaussian profile are plotted over the collected data points. The sine squared profile was shown to be a best fit for a similar gust experiment done in a water tow tank [73] [75]. However, for this case, the Gaussian profile is the better match.…”

Section: Conducted Experimentsmentioning

confidence: 84%

“…Using these values for the full power gust, the gust takes about 10.7 convective times to fully actuate. This is a bit slower than previous gust experiments, which typically aim for approximately 6 or fewer convective times [73] [75]. It is still deemed fast enough to be a valid representation of some environmental gusts.…”

Section: Full Power Phased Gust Actuationmentioning

confidence: 93%

“…Initial results from this generator showed good correlation with the desired top-hat shape as well as good correlation to the predicted values from Küssner's function. Biler et al revised the design of the generator created by Perrotta and Jones to create a more controllable and wider gust generator [75]. The updated generator can be seen in Figure 16.…”

mentioning

confidence: 99%

“…The updated generator can be seen in Figure 16. The data collected with the revised generator was compared to results from a computational fluid dynamics (CFD) study by Badrya [75]. Several pump speeds were tested creating various gust velocities; however, the Reynolds number was held constant at 40,000.…”

mentioning

confidence: 99%

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