A novel method for automated grid generation of ice shapes for local‐flow analysis

Ogretim, Egemen; Huebsch, Wade W.

doi:10.1002/fld.659

Cited by 6 publications

(10 citation statements)

References 12 publications

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“…The Lagrangian particle tracing in this study is a postprocess that inputs a flowfield solution from the 2-D Navier-Stokes flow solver [8,9]. The advantage of this approach is that the effects of the local flow dynamics in the leading-edge region, such as a separation bubble or unsteady vortex shedding, are revealed.…”

Section: B Droplet-vortex Interactionmentioning

confidence: 99%

“…The surface roughness is introduced through the use of a Prandtl transposition (or shearing transformation) similar to the work of Huebsch and Rothmayer [8]. The numerical scheme is fully implicit finite differencing in 2-D. Further discussion of the solver and the related equations for flowfield calculations are left to [6,8,9], for brevity. Also, the final governing equations (after transformations) for this study are included in the Appendix for interested readers.…”

Section: Governing Equationsmentioning

confidence: 99%

“…The velocities are calculated in the transformed 0 -0 plane (a characteristic of the flow solver [8,9]). The flowfield velocity components are calculated by Eq.…”

Section: Calculation Of the Velocity And Accelerationmentioning

confidence: 99%

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Investigation of Relative Humidity and Induced-Vortex Effects on Aircraft Icing

Ogretim¹,

Huebsch²,

Narramore³

et al. 2007

Journal of Aircraft

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Two new mechanisms for downstream ice growth (i.e., downstream of the primary ice shape) in aircraft icing scenarios were investigated. The first mechanism is local variation of relative humidity with its potential for water deposition due to supersaturation. The second mechanism is induced-vortex effects due to their potential impact on droplet paths. It was shown that for rough surfaces with an extended period of exposure, relative humidity effects can lead to additional growth. The resultant frost is a sandpaperlike roughness that can severely degrade the aerodynamic performance of the wings. It was also shown that the vortices induced by the existing ice-shape features are capable of altering the droplet paths. As a result, impingements occur beyond the limits predicted by the methods in other icing prediction codes.Nomenclature a x , a y = nondimensional acceleration component in the x and y directions a 0 , a 0 = acceleration component in the 0 and 0 directions a = reference value for the nondimensionalization of acceleration C p = pressure coefficient, P P 1 = 1 2 air V 2 1 c = chord length D = diffusivity of water vapor in air, m 2 =s e, e = actual and saturation vapor pressure, respectively, mbar h = height of the roughness element K = thermal conductivity of water, J=m s K L = latent heat of vaporization for water, 2:5 10 6 J=kg LER = leading-edge radius, m LWC, VWC = liquid and vapor water content, respectively, in kilograms of water per cubic meter of air MVD = median volumetric diameter, m N = number of droplets in 1 m 3 of air P = static pressure, Pa (unless otherwise stated) R v = specific gas constant for water vapor, 461 J=kg K RH w , RH ice = relative humidity with respect to liquid water and ice, respectively r = radius of the droplet, m S = cross-sectional area of a sphere, m 2 s d = separation between two neighboring droplets, m T = static temperature, K t = reference value for the nondimensionalization of time V 1 = velocity of the approaching flow v x , v y = nondimensional velocity component in the x and y directions v 0 , v 0 = velocity component in the 0 and 0 directions w = mixing ratio of water vapor and dry air = ratio of the specific heats air , v = density of dry air and water vapor, respectively, kg=m 3 water = density of liquid water, kg=m 3 = stream function

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Section: B Droplet-vortex Interactionmentioning

confidence: 99%

Section: Governing Equationsmentioning

confidence: 99%

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Investigation of Relative Humidity and Induced-Vortex Effects on Aircraft Icing

Ogretim¹,

Huebsch²,

Narramore³

et al. 2007

Journal of Aircraft

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“…The governing flow equations are the stream function-vorticity version of the 2-D incompressible, unsteady Navier-Stokes equations, which are shown below in non-dimensional form. The information related to the flow solver can be found in the relevant references ( [14], [19], and [20]).…”

Section: Governing Equationsmentioning

confidence: 99%

“…This fact and the lack of accuracy in the wake pressure variation point at a pressure gradient related problem for the roughness. The details of the formulation and other information about the code can be found in references [14], [19], and [20].…”

Section: Introductionmentioning

confidence: 99%

Investigation of relative humidity and induced-vortex effects on aircraft icing

Ogretim¹

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Aircraft icing is an area of research that has drawn attention since the early times of powered flight at high altitudes. Since World War II, aircraft icing research has gained a great deal of momentum, and several branches of research have developed as a result. These branches include the experimental, analytical and computational methods. With the advent of high-speed computers, the computational methods are becoming the leading icing research area due to their low cost requirements. However, a significant hindrance is the lack of a complete understanding of the icing phenomena, which leads to discrepancies between the predictions and the experiments. In recent years, there have been efforts to improve this situation by accounting for several mechanisms within the computational models. These mechanisms include the droplet splash and re-impingement, water film dynamics, and different heat transfer mechanisms. In support of enhancing the understanding of the aircraft icing process, this Ph.D. study focuses on the relative humidity effects and the interaction of the induced vortices with the droplets and the surface water. Currently the relative humidity effects are neglected in the icing prediction codes with the assumption that it can at best be a second-order effect. This Ph. D. study looks at the conditions in which the relative humidity effects can pose significant impact on the accreted ice shape. It was seen that the flow around the airfoil suction surfaces and the vortices, which have low-pressure cores, shed from the existing ice shape are highly supersaturated. Therefore, the suction surfaces and the aft regions of the main ice shape are exposed to condensation/deposition due to relative humidity effects. The time scales involved in the relative humidity effects were also investigated by using a numerical droplet growth experiment. In the particular case considered in this study, the required time to re-establish equilibrium, i.e. recover saturation conditions, varied from 12 milliseconds for droplets with 1 micron diameter to 5 seconds for droplets with 20 micron diameter. In an actual flight scenario, the direct impingement region mostly overlaps with the stagnation region, where the local flow is subsaturated. However, the water mass carried by the water droplets is much higher compared to changes that can be triggered by subsaturation. Therefore, it can be concluded that the collection efficiency in the direct impingement region will have negligible change despite the evaporation due to subsaturation. So, the relative humidity can at most be a secondary effect in the direct impingement region. However, exposure to supersaturated air for long periods can lead to localized frost growth beyond the direct impingement region. For a particular case considered in this study, it was found that there is a potential for the growth of extra ice roughness up to 0.4 mm over a 30 minute period. As far as the induced vortex phenomena, no past work has been done, because the ice accretion prediction codes are based ...

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Aircraft ice accretion prediction using neural network and wavelet packet transform

Chang

Leng

et al. 2016

Aircraft Eng & Aerospace Tech

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A novel method for automated grid generation of ice shapes for local‐flow analysis

Cited by 6 publications

References 12 publications

Investigation of Relative Humidity and Induced-Vortex Effects on Aircraft Icing

Investigation of Relative Humidity and Induced-Vortex Effects on Aircraft Icing

Investigation of relative humidity and induced-vortex effects on aircraft icing

Aircraft ice accretion prediction using neural network and wavelet packet transform

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