The Effect of Surface Roughness on Laminar Separated Boundary Layers

Simens, Mark P.; Gungor, Ayse G.

doi:10.1115/gt2013-95810

Cited by 6 publications

(5 citation statements)

References 25 publications

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“…The objective of the present study is to investigate the effect of distributed roughness on subsonic boundary layers typically observed in turbomachines. However, unlike the recent work [32,33,42,43,47] where a flat plate has been subjected to turbine blade loading which triggered flow separation, current simulations are much more fundamental and consider a flat pate in the absence of pressure gradients. In contrast to the simulations of Muppidi and Mahesh [29], the rough surface is specified over the entire length of the flat plate.…”

Section: Turbulent Boundary Layersmentioning

confidence: 99%

Distributed Roughness Effects on Transitional and Turbulent Boundary Layers

Vadlamani

Tucker

Durbin

2017

Flow Turbulence Combust

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A numerical investigation is carried out to study the transition of a subsonic boundary layer on a flat plate with roughness elements distributed over the entire surface. Post-transition, the effect of surface roughness on a spatially developing turbulent boundary layer (TBL) is explored. In the transitional regime, the onset of flow transition predicted by the current simulations is in agreement with the experimentally based correlations proposed in the literature. Transition mechanisms are shown to change significantly with the increasing roughness height. Roughness elements that are inside the boundary layer create an elevated shear layer and alternating high and low speed streaks near the wall. Secondary sinuous instabilities on the streaks destabilize the shear layer promoting transition to turbulence. For the roughness topology considered, it is observed that the instability wavelengths are governed by the streamwise and spanwise spacing between the roughness elements. In contrast, the roughness elements that are higher than the boundary layer create turbulent wakes in their lee. The scale of instability is much shorter and transition occurs due to the shedding from the obstacles. Post-transition, in the spatially developing TBL, the velocity defect profiles for both the smooth and rough walls collapsed when non dimensionalized in the outer units. However, when compared to the smooth wall, deviation in the Reynolds stresses are observable in the outer layer; the deviation being higher for the larger roughness elements.

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Section: Turbulent Boundary Layersmentioning

confidence: 99%

Distributed Roughness Effects on Transitional and Turbulent Boundary Layers

Vadlamani

Tucker

Durbin

2017

Flow Turbulence Combust

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“…Mark P. Simens and Ayse G. Gungor used a flat plate with a strong inverse pressure gradient as the research object to study the effect of roughness on laminar separation bubbles. These numerical experiments indicate that laminar separation and turbulent transition are mainly affected by the type, height, and location of the roughness element (Simens and Gungor 2013). Jongwook Joo et al (Joo et al, 2017).…”

Section: Introductionmentioning

confidence: 77%

Numerical simulation of low reynolds number 2-d rough blade compressor cascade

Wang

et al. 2022

Front. Energy Res.

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In this paper, a double-circular-arc cascade was used as the research object to study the effect of roughness on the compressor cascade under the conditions of different incoming attack angles. The Reynolds number of the cascade is 1.5×105 . The profile of the suction surface is changed to simulate the change in surface roughness. A uniformly distributed 238 control points were selected on the suction surface profile of the smooth blade. The 238 points are increased randomly along with the normal phase of the wall, and a smooth curve connects these points to obtain a rough suction surface profile. In this study, numerical simulation methods were used to calculate the cascade flow field under 5 kinds of attack angles and 6 kinds of suction surface roughness (including smooth surface). In this paper, k−ω SST and large eddy simulation were used for numerical simulation calculation with the model respectively. The calculation results show that the effect of roughness on the flow field of the cascade is different under different angles of attack. When 70<ks+<130 the rough suction surface can increase the lift coefficient of the compressor blade.

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“…The governing equations for two-phase incompressible flows were solved in the commercial program Star-CCM+ by using the finite volume method and a volume of fluid approach [41]. The segregated flow approach was used to solve the equations in which the Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) algorithm was adopted to resolve the pressure-velocity coupling.…”

Section: Numerical Solution Methodsmentioning

confidence: 99%

Numerical Study on Tip Vortex Cavitation Inception on a Foil

Park

Kim

Paik³

et al. 2021

Applied Sciences

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In this paper, the inception of tip vortex cavitation in weak water has been predicted using a numerical simulation, and a new scaling concept with variable exponent has also been suggested for cavitation inception index. The numerical simulations of the cavitating flows over an elliptic planform hydrofoil were performed by using the RANS approach with a Eulerian cavitation model. To ensure the accuracy of the present simulations, the effects of the turbulence model and grid resolution on the tip vortex flows were investigated. The turbulence models behaved differently in the boundary layer of the tip region where the tip vortex is developed, which resulted in different pressure and velocity fields in the vortex region. Furthermore, the Reynolds stress model for the finest grid showed a better agreement with the experimental data. The tip vortex cavitation inception numbers for the foil, predicted by using both wetted and cavitating flow simulation approaches, were compared with the measured cavitation index values, showing a good correlation. The current cavitation scaling study also suggested new empirical relations as a function of the Reynolds number substitutable for the two classic constant scaling exponents. This scaling concept showed how the scaling law changes with the Reynolds number and provided a proper scaling value for any given Reynolds numbers under turbulent flow conditions.

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The Effect of Surface Roughness on Laminar Separated Boundary Layers

Cited by 6 publications

References 25 publications

Distributed Roughness Effects on Transitional and Turbulent Boundary Layers

Distributed Roughness Effects on Transitional and Turbulent Boundary Layers

Numerical simulation of low reynolds number 2-d rough blade compressor cascade

Numerical Study on Tip Vortex Cavitation Inception on a Foil

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