Large-Scale Flow Structures in Shallow Shear Flows behind a splitter plate over Smooth Bed - Archive ouverte HAL Accéder directement au contenu
Proceedings/Recueil Des Communications Année : 2023

Large-Scale Flow Structures in Shallow Shear Flows behind a splitter plate over Smooth Bed

S. Proust
Céline Berni
Vladimir I Nikora

Résumé

Free-surface shallow shear flows behind a vertical splitter plate were studied in a tilted laboratory flume with a rectangular cross-section. The bed and sidewalls, made of glass, were hydraulically smooth. The vertical flow confinement (i.e., flow depth) was modified by changing the total flow rate Q (14, 30, 60, and 120 l s-1). At the flume entrance, for each Q-value, the flow partition from either side of the splitter plate was also varied to cover a wide range of the shear parameter λ = (U2-U1)/(U2+U1), where U1 and U2 are two velocities characterizing the low-speed and high-speed streams, respectively (with λ = 0 to 1.0). The focus of the study was on clarifying the effects on the large-scale flow structures of: (i) vertical flow confinement; (ii) bed-friction; and (iii) λ-parameter. Particular attention was paid to the emergence and development of: quasi-2D KelvinHelmholtz-type Coherent Structures (KHCSs); 3D Large-Scale-Motions (LSMs), e.g., packets of hairpin vortices and associated burst events; and 3D Very-Large-Scale-Motions (VLSMs), which are long meandering streamwise counter-rotating vortices. It was found that in the near-field region, the emergence and lengthscales of the KHCSs were independent of (i) and (ii), but were essentially controlled by (iii). For instance, the KHCSs cannot form if λ <~ 0.3. In the far-field region, the effect of λ decreases while that of bed-friction number S increases. For S > ~ 0.04, KHCSs are fully longitudinally stretched. LSMs/VLSMs development are strongly influenced by splitter effects as well as the magnitude of velocity shear, particularly when λ > 0.3.
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Dates et versions

hal-04347213 , version 1 (15-12-2023)

Identifiants

Citer

S. Proust, Céline Berni, Vladimir I Nikora. Large-Scale Flow Structures in Shallow Shear Flows behind a splitter plate over Smooth Bed. 39th IAHR World Congress, pp.1584-1589, 2023, ⟨10.3850/IAHR-39WC2521716X202262⟩. ⟨hal-04347213⟩
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