On the unsteady Reynolds-averaged Navier–Stokes capability of simulating turbulent boundary layers under unsteady adverse pressure gradients

Park, Junshin; Ha, Sangyul; You, Donghyun

doi:10.1063/5.0049509

Cited by 11 publications

(15 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We observed that the turbulence models are more accurate for unsteady calculations than for steady ones. On the other hand, Park et al [7] found much worse agreement between RANS solutions and the DNS than observed here. The reason for these two differences most likely lies in the pressuregradient evolution in time.…”

Section: Resultscontrasting

confidence: 87%

“…The results of Park et al [7] are particularly relevant to the present work. They investigated a turbulent flat-plate boundary-layer under unsteady Adverse Pressure Gradients (APGs) to test the performance of the K−ω and SA turbulence models.…”

Section: Introductionsupporting

confidence: 53%

“…where T is the oscillation period, note that, although this setup is similar to the one examined by Park et al [7], there is a substantial difference. In their case the distribution of V ∞ always resulted in an APG followed by a Favourable Pressure Gradient (FPG), and a recirculation bubble was always present, pulsating in time.…”

Section: Methodsmentioning

confidence: 87%

See 2 more Smart Citations

Evaluation of turbulence models for unsteady separation

MacDougall,

Ambrogi,

Piomelli

2023

Progress in Canadian Mechanical Engineering. Volume 6

View full text Add to dashboard Cite

Unsteady separation is a phenomenon that occurs in many flows due to time-varying adverse pressure gradients and results in increased drag, decreased lift, and loss of efficiency or failure in flow devices. Therefore, it is important to predict and analyze unsteady separation. Turbulence models for the RANS equations are commonly used in the industrial design process due to their low computational cost; however, their performance in predicting steady separations is unsatisfactory, and very few studies investigate unsteady separation. Our goal is to use high-fidelity Large-Eddy Simulation results to evaluate the accuracy of the K − ω, K − ε, and Spalart Almaras turbulence models in unsteady separation. By using an identical grid, numerical scheme and consistent boundary conditions to the LES calculations we are able to isolate modelling errors. All three turbulence models capture the general features of this complex unsteady flow correctly, with only small discrepancies from the LES. Memory effects due to the periodic nature of the unsteadiness have been found to contribute to the model's success.

show abstract

Section: Resultscontrasting

confidence: 87%

Section: Introductionsupporting

confidence: 53%

See 1 more Smart Citation

Evaluation of turbulence models for unsteady separation

MacDougall,

Ambrogi,

Piomelli

2023

Progress in Canadian Mechanical Engineering. Volume 6

View full text Add to dashboard Cite

show abstract

“…In their very recent investigation, Park, Ha & Donghyun (2021) analysed a TBL under unsteady APGs at a reduced frequency with the aim of testing several turbulence models (, where is the turbulent kinetic energy and the turbulent frequency, and Spalart–Allmaras) and provide insights into their accuracy of predicting unsteady separated flows. The APG was periodically varied to obtain dynamic separation and reattachment but the pressure-gradient distribution was always adverse to favourable and the TSB never disappeared.…”

Section: Introductionmentioning

confidence: 99%

Characterization of unsteady separation in a turbulent boundary layer: mean and phase-averaged flow

2022

View full text Add to dashboard Cite

A spatially developing turbulent boundary layer subject to a space- and time-dependent pressure gradient is analysed via large-eddy simulation. The unsteadiness is prescribed by imposing an oscillating suction–blowing velocity profile at the top boundary of the computational domain. The alternating favourable and adverse pressure gradients cause the flow to separate and reattach to the wall periodically. A range of reduced frequencies $k$ was investigated, spanning from a very rapid flutter-like motion to a slow, quasi-steady flapping. The Reynolds number based on the boundary-layer displacement thickness $\delta _o^{*}$ at the inflow plane is $Re_*=1000$ . Both time- and phase-averaged fields are analysed and results are compared with steady conditions. The reduced frequency $k$ has a significant effect on the transient flow-separation process. For high $k$ the separation bubble does not grow as thick as in the corresponding steady case, but the length of the bubble remains comparable; hysteresis is observed in the near-wall region. As $k$ is reduced, a threshold is met at which the separation bubble grows in the wall-normal direction. However, the length of the bubble is significantly reduced again when compared with the steady case. At this frequency, the region of slow-moving fluid generated by the flow reversal is advected downstream, causing a decorrelation between the forcing (the imposed free-stream velocity) and the velocity and pressure downstream of the separation bubble. Moreover, hysteresis effects are shifted away from the wall. At the lowest frequency a quasi-steady solution is approached; however, transient effects are still present in the backflow region.

show abstract

“…However, unfortunately, the RANS-based methods frequently fail to predict highly separated flows, which are dominated by unsteady flow structures with a broad range of scales and, thus, require more complex modeling of the turbulence Reynolds stresses [8]. On the other hand, scale-resolving simulation (SRS) methods, such as large eddy simulation (LES) and hybrid RANS-LES techniques, which are known to be significantly more accurate, are generally deemed to be prohibitively expensive by industrial researchers [9].…”

Section: Introductionmentioning

confidence: 99%

Testing a Generalized Two-Equation Turbulence Model for Computational Aerodynamics of a Mid-Range Aircraft

Rossano,

De Stefano

2023

Applied Sciences

View full text Add to dashboard Cite

The generalized k-ω formulation provides a relatively new flexible eddy-viscosity Reynolds-averaged Navier–Stokes modeling approach to turbulent flow simulation, where free coefficients allow for fine-tuning and optimal adjusting of the turbulence closure procedure. The present study addressed the calibration of this versatile model for the aerodynamic design of an innovative mid-range commercial airplane by carrying out a series of simulations for varying model coefficients. Comparing the different solutions with each other, as well as with reference experimental and higher-fidelity numerical data, the performance of the generalized procedure in predicting the aerodynamic loading on the aircraft model was systematically examined. While drawing particular attention to the high-lift regime, the set of model parameters giving the best results was practically determined.

show abstract

On the unsteady Reynolds-averaged Navier–Stokes capability of simulating turbulent boundary layers under unsteady adverse pressure gradients

Cited by 11 publications

References 38 publications

Evaluation of turbulence models for unsteady separation

Evaluation of turbulence models for unsteady separation

Characterization of unsteady separation in a turbulent boundary layer: mean and phase-averaged flow

Testing a Generalized Two-Equation Turbulence Model for Computational Aerodynamics of a Mid-Range Aircraft

Contact Info

Product

Resources

About