Silvia Reuß, DLR, AS, C2A2S2E

Mandatory settings for hybrid RANS/LES computations on the

LEISA high-lift 3-element airfoil

(Preliminary version)

Silvia Reuß, DLR, AS, C2A2S2E

Test case set-up for hybrid RANS/LES

• In general, AoA=6 and SST local transition for all 3 elements

• For partner using SA based DES methods:

AoA =6, and SA local transition on slat and wing, full turb. on flap

Option: AoA=6, and SST transition for all 3 elements

• New run 18% retracted chord length and 128 cells in spanwise direction

According to the mandatory grid (100c farfield distance, ~200000 points per layer): total number of points ~25Mio

• Time step Δt=1e-5

Silvia Reuß, DLR, AS, C2A2S2E

Expected results

• Partners should provide Cd and Cl time history

• Surface data: Cp, Cf (mean and r.m.s.)

• Field data: mean values for velocity <ui>, velocity gradients d<ui>/dxj, pressure <p>, eddy viscosity; correlations of velocity fluctuations <ui’uj’> and r.m.s. pressure <p’-<p>>. Here <> denotes averaging in time and spanwise direction

• Time series of pressure p(.,t) at single probes in the nose region of the main wing element for comparison with KULITE measurement. The positions of the KULITES will be comunicated as soon as they are available

• DLR will check position of PIV windows in experiments. But data postprocessing is independent of this information

Silvia Reuß, DLR, AS, C2A2S2E

Assessment of resolved and modelled part of turbulent shear stress

• Consider relative contribution of modelled to resolved shear stress

Actual DES modus τxz-modelled τxz-resolved

RANS simulation 100% 0%

(D)DES simulation 100% in RANS mode 0% in RANS mode

~50% „grey area“ ~50%

<10% in LES mode > 90% in LES mode

turbresxzturb

odmxzlam

xz

tltotxz wux

w

z

u

x

w

z

u

stressshear

t turbulenresolved

stressshear t turbulenmodelledstressshear laminar