A review of scale effects in unsteady aerodynamics

Mabey, D. G.

doi:10.1016/0376-0421(91)90003-m

Cited by 27 publications

(14 citation statements)

References 15 publications

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“…Experiments by Conger and Ramaprian 4 in a water tunnel at Re -5 x 10 4 produced results that agreed very well with tests by Lorber and Carta 5 at Re = (2 -4) x 10 6 . A documentation of the tunnel conditions showed that the free stream turbulence intensity was very high.…”

Section: Introductionsupporting

confidence: 77%

“…On the upper surface, the plateau in both . However, the chordwise extent of the bubble is smaller than that for the 3-inch airfoil at Re = 0.54 x 10 6 . It should be noted that changes in the airfoil boundary layer and thus the airfoil wake, due to the longer bubble in the lower Reynolds number case has effectively limited the viscous/inviscid interaction.…”

Section: Comparison Of Steady Flow Pressure Distributionsmentioning

confidence: 76%

“…This points to the importance of simulating "effective" Reynolds number rather than geometric scale alone in laboratory testing. Mabey 6 points out that in addition to tunnel blockage, differences between flight data and full scale wind tunnel data could appear because of differences in the transition process between the two cases. Transition onset location on the airfoil surface is influenced by the tunnel free stream turbulence level.…”

Section: Introductionmentioning

confidence: 99%

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Reynolds number influence on 2-D compressible dynamic stall

Chandrasekhara

Wilder²,

Carr

1996

34th Aerospace Sciences Meeting and Exhibit

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Reynolds number effects on oscillating airfoil compressible dynamic stall flow have been investigated. The Reynolds number was doubled at constant Mach number by using two (untripped and tripped) NACA 0012 airfoils, one with 3-inch chord and another with 6-inch chord. Pressure distributions documented using point diffraction interferometry(PDI) are compared with each other for Mach numbers of 0.3 and 0.45 at different reduced frequencies. Comparisons with a reference data set at Re = 4 x 10 6 for a Mach number of 0.3 at reduced frequencies of 0.05 and 0.1 showed good agreement for the tripped 6-inch airfoil, thus establishing a minimum model Reynolds number for simulating full-scale results. Reynolds number influence manifests as an increase in the airfoil peak suction pressure coefficient, smaller laminar separation bubble, increase in dynamic stall onset angle, and an increased ability to withstand adverse pressure gradient in the flow. At lower Reynolds numbers, dynamic stall arises from the bursting of the laminar separation bubble at both M = 0.3 and 0.45. At higher effective Reynolds numbers, dynamic stall is induced by large adverse pressure gradient in the flow for M = 0.3 and shock induced dynamic stall onset for at M = 0.45.

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Section: Introductionsupporting

confidence: 77%

Section: Comparison Of Steady Flow Pressure Distributionsmentioning

confidence: 76%

Section: Introductionmentioning

confidence: 99%

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Reynolds number influence on 2-D compressible dynamic stall

Chandrasekhara

Wilder²,

Carr

1996

34th Aerospace Sciences Meeting and Exhibit

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“…Scale effects originate in wind-tunnel tests due to a failure to achieve full-scale Reynolds number and full-scale transition position. 20 In high-incidence model testing, as in dynamic stall studies, the effects appear as a change in the boundary-layer thickness at the separation point due to differences in the transition point location between the high and low Reynolds number flows, as well as a change in the effective Reynolds number due to freestream turbulence. This affects the overall airfoil circulation and, thus, the pressure distribution over the airfoil surfaces.…”

Section: Freestream Ttirbulence and Scale Effects On Resultsmentioning

confidence: 99%

“…Thus, the effects of freestream turbulence are at a minimum here. Mabey 20 notes that failure to fix transition at an appropriate point on the wind tunnel model is probably more serious than failure to reproduce the correct Reynolds number. Hence, the approach followed in the present tests was to fix the transition point to remove the large variability otherwise introduced in the results by the rapid movement of the transition point as the airfoil is oscillated through a large angle-of-attack range.…”

Section: Freestream Ttirbulence and Scale Effects On Resultsmentioning

confidence: 99%

Boundary layer tripping studies of compressible dynamic stall flow

Chandrasekhara

Wilder²,

Carr

1994

Fluid Dynamics Conference

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The challenging task of properly tripping the boundary layer of a leading-edge-stalling airfoil experiencing compressible dynamic stall at Reynolds numbers between 3.6 X 10 s and 8.1 X 10 s has been addressed. Real-time interferometry data of the flow over an oscillating airfoil have been obtained at freestream Mach numbers of 0.3 and 0.45. The airfoil was tripped by separately placing five different trips of varying lengths near the leading edge. The trip heights ranged from 40 to 175 y^m. The resulting flow and airfoil performance were evaluated using the criteria of elimination of the laminar separation bubble that otherwise forms, delay of dynamic stall onset to higher angles of attack, and production of consistently higher suction peaks. Quantitative analysis of the interferograms showed that the laminar separation bubble was still present with the smallest trip and premature dynamic stall occurred with the largest trip. The right trip was determined to be a distributed roughness element extending from 0.5 to 3% chord. Its height was found to compare reasonably with the airfoil boundary-layer thickness at the dynamic stall vortex formation angle of attack, at a location slightly upstream of the vortex origin in the adverse pressure gradient region.

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Techniques for Turbulence Tripping of Boundary Layers in RANS Simulations

Tabatabaei

Vinuesa

Schlatter

2021

Flow Turbulence Combust

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The exact placement of the laminar–turbulent transition has a significant effect on relevant characteristics of the boundary layer and aerodynamics, such as drag, heat transfer and flow separation on e.g. wings and turbine blades. Tripping, which fixes the transition position, has been a valuable aid to wind-tunnel testing during the past 70 years, because it makes the transition independent of the local condition of the free-stream. Tripping helps to obey flow similarity for scaled models and serves as a passive control mechanism. Fundamental fluid-mechanics studies and many engineering developments are based on tripped cases. Therefore, it is essential for computational fluid dynamics (CFD) simulations to replicate the same forced transition, in spite of the advanced improvements in transition modelling. In the last decade, both direct numerical simulation (DNS) and large-eddy simulations (LES) include tripping methods in an effort to avoid the need for modeling the complex mechanisms associated with the natural transition process, which we would like to bring over to Reynolds-averaged Navier–Stokes (RANS) turbulence models. This paper investigates the implementation and performance of such a technique in RANS and specifically in the $$k-\omega$$ k - ω SST model. This study assesses RANS tripping with three alternatives: First, a recent approach of turbulence generation, denoted as turbulence-injection method (kI), is evaluated and investigated through different test cases; second, a predefined transition point is used in a traditional transition model (denoted as IM method); and third a novel formulation combining the two previous methods is proposed, denoted $$\gamma -k$$ γ - k I. The model is compared with DNS, LES and experimental data in a variety of test cases ranging from a turbulent boundary layer on a flat plate to the three-dimensional (3D) flow over a wing section. The desired tripping is achieved at the target location and the simulation results compare very well with the reference results. With the application of the novel model, the challenging transition region can be excluded from a simulation, and consequently more reliable results can be provided.

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A review of scale effects in unsteady aerodynamics

Cited by 27 publications

References 15 publications

Reynolds number influence on 2-D compressible dynamic stall

Reynolds number influence on 2-D compressible dynamic stall

Boundary layer tripping studies of compressible dynamic stall flow

Techniques for Turbulence Tripping of Boundary Layers in RANS Simulations

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