IS 6516:1990 is the Indian Standard (BIS) for criteria for design of upstream and downstream transitions in lined canals. This standard provides criteria for the hydraulic design of transitions in lined canals, connecting canal sections of different shapes or sizes. It covers both contracting (upstream) and expanding (downstream) transitions to ensure smooth flow and minimize energy losses.
Provides criteria for the hydraulic design of upstream and downstream transitions in lined canals to ensure smooth flow.
| Parameter | IS Value | International | Source |
|---|---|---|---|
| Head Loss Coefficient (K) for Expanding Transition (Subcritical) | 0.2 (for straight line design) | 0.3 (for well-designed warped transition) to 0.75 (for wedge-type) | USACE EM 1110-2-1601 |
| Head Loss Coefficient (K) for Contracting Transition (Subcritical) | 0.1 (for straight line design) | 0.1 (for well-designed warped transition) to 0.25 (for wedge-type) | USACE EM 1110-2-1601 |
| Recommended Splay Angle (Side Wall) for Upstream Transition (Contraction) | 1 in 3 (approx. 18.4°) | Generally 12.5° to 22.5° | USBR - Design of Small Canal Structures |
| Recommended Splay Angle (Side Wall) for Downstream Transition (Expansion) | 1 in 4 (approx. 14°) | Generally 12.5°. For short transitions, USBR suggests a rule of thumb where Length = 1.5 * (Bed Width₂ - Bed Width₁). | USBR - Design of Small Canal Structures |
| Transition Length Basis (Subcritical) | Based on a fixed splay angle: L = (B₂ - B₁) / (2 * tan α) | Often based on Froude number: L = (W₂ - W₁) / (2 * tan θ), where tan θ ≤ 1/(3*Fr) | USACE EM 1110-2-1601 |
| Bed Profile Shape in Warped Transition | Specifies a reverse parabola with a specific formula for the drop. | Also commonly recommends a reverse parabola or sometimes a simple circular arc. | USBR - Design of Small Canal Structures |