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Flow regimes of submerged rectangular sharp-crested weirs in sand bed channel

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Abstract

Laboratory experiments were conducted out to investigate the regimes of submerged flows over the sharp-crested weirs in sand bed Channel. These kinds of flows were classified as five states such as (I) impinging jet, (II) bed surface flow, (III) surface jump, (IV) surface wave, and (V) surface jet based on the depicted vector plots of the regimes. By increasing the submergence ratio, the impinging jet was developed as a downward jet which was impinged from the weir crest to the downstream. By continue the increasing, flow regime was developed as a bed-surface flow which is supposed that the impinging jet is turned as flow near the bed position instead of having a direct impact with the bed. Additionally, increasing constancy of the submergence ratio causes that the bed-surface regime turned to the surface jump which is accompanied by a hydraulic jump at the water surface. Subcritical condition at downstream of the weir which is provided by raising the tailwater due to constant flow discharge causes that the surface wave regime has vanished at the water surface of the downstream of the weir and some oscillating waves were transferred to downstream. Finally, by considering the maximum range of submergence ratio, the flow regime was changed to the surface jet which was accompanied by a big clockwise vortex at the lower water elevation. The present study classifies these flow regimes based on the velocity components (u, v, w). This approach was chosen by the authors to show the different classification between visual inspection and investigating the velocity direction by ADV. Then, an empirical equation was proposed to show the boundaries of the presented regimes. Also, a dynamic restriction was proposed based on experimental and literate data as a non-eroded status that is due to a submerge ratio, the scour hole is not provided at downstream of sharp-crested weir.

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Data availability

Some or all data, models, or code generated or used during the study are available from the corresponding author by request (data such as head-discharge and ADV measurements).

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Author information

Authors and Affiliations

  1. Department of Civil Engineering, Lakehead University, Thunder Bay, ON, P7B 5E1, Canada

    Saeed Salehi

  2. Department of Agriculture Engineering, Ferdowsi University of Mashhad, Mashhad, Iran

    Saeed Salehi

  3. Faculty of Civil Engineering Department, Shams Institute of Higher Education, Golestan Province, Gonbad, Iran

    Amin Mahmudi Moghadam

  4. Department of Civil Engineering, Ferdowsi University of Mashhad, Mashhad, Iran

    Kazem Esmaili

Authors
  1. Saeed Salehi
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  2. Amin Mahmudi Moghadam
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  3. Kazem Esmaili
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Corresponding author

Correspondence to Amin Mahmudi Moghadam.

List of symbols

List of symbols

d d :

Downstream scour depth (m)

d dm :

Maximum downstream scour depth (m)

d u :

Initial upstream scour depth (m)

d 50 :

Mean diameter of sediment (mm)

g :

Gravitational acceleration (m/s2)

h :

Upstream weir head (m)

h d :

Difference between upstream and downstream water level (m)

H :

Upstream water level (m)

L :

Scour hole length (m)

Q :

Discharge (m3/s)

t :

Tail water (m)

u ave :

Averaged velocity (m/s)

u *c :

Critical shear velocity (m/s)

u c :

Critical threshold velocity (m/s)

x :

Longitudinal direction

y :

Transverse direction

z :

Vertical direction

Z :

Weir height (m)

ρ :

Density of water (kg/m3)

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Salehi, S., Moghadam, A.M. & Esmaili, K. Flow regimes of submerged rectangular sharp-crested weirs in sand bed channel. Sādhanā 48, 6 (2023). https://doi.org/10.1007/s12046-022-02053-4

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  • DOI: https://doi.org/10.1007/s12046-022-02053-4

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