Characteristics of Submerged Flow Below Gate With Sill in Non-Prismatic Channels
The characteristics of submerged flow below vertical gate with sill upstream of horizontal diverging channel reach are analyzed based on experimental investigation. The experimental program is conducted in a laboratory flume with 10 cm wide, 31 cm deep and 3.0 m long. A diverging channel reach with fixed length and constant divergence angle is used. Polygonal sills with constant height, constant upstream slope and variable downstream slope are used under the gate. These sills are tested under wide range of similar submerged flow conditions to investigate the effect of sill slope on the flow characteristics. Also, a particular sill is tested under different heights to address the effect of sill height on the flow characteristics. Both the effects of submergence and the under-gate Froude number on the flow below the gate are discussed. Different flow regimes are considered (Supercritical, critical and subcritical flow). It is found that the presence of sill under the gate upstream of diverging channel reach has a remarkable effect on the discharge coefficient of the gate. It is noticed that the submergence ratio and the upstream head ratio are not able to explain the observed variations (or scatter of data) in the discharge coefficients. These variations or scatters are completely explained by the under-gate Froude number and the differential head ratio.
ANALYSIS OF SUBMERGED FLOW UNDER A GATE WITH PRISMATIC SILL
Sluice gates are widely used in irrigation structure, sills under gates has positive effect on flow performance under the gate and reduce its height. An experimental study in a laboratory flume is carried out to study submerged flow passing the opening between the sill and the gate. Four different heights of trapezoidal sill models were used and one without sill, the five groups were ran with four different gate opening. The basic principles of statistical analysis are employed to correlate between the hydraulic and geometric dimensionless parameters with the discharge coefficient. Different relationship models with acceptable significance are suggested. It was found that the some of dimensionless parameters effecting positively on the value of discharge coefficient by increasing its value such as (d/B, Fr, P/Y1, P/d), and other decreasing the value of Cd such as (Yt/d, P/B, H/d, Y1/Y2, P/Y2, P/H). The value of Cd ranges from 0.34 to 0.77, with Standard Error 0.006411. Within the limitations of the present experimental work an equation for prediction the value of the discharge coefficient is suggested with R square is 0.936 and stadard Error of estimate equle to 0.0240235. The actual discharge was checked by the sugested equation which shows a good greement with Adj. R 2 =0.993.
Force on Sill of Forced Jump
The mean force on a continuous sill in a forced hydraulic jump has been measured directly by a transducer for a wide range of experimental conditions. Four sills of heights expressed as multiples of the sluice opening are 1.0, 1.5, 2.0, and 3.0. The Froude number based on the flow at the sluice opening is varied from 3.99 to 9.09. The sills are situated at various distances from the sluice gate. The state of the flow is governed by the depth downstream of the sill. Maximum force is exerted when the supercritical stream impinges directly on the sill. The force reaches an asymptotic value at high submergence and it could be predicted for high sills using an elementary dynamic pressure model. The scale effect due to Froude number of the flow is discussed.