Approach‐Flow Effects on Downpull of Gates

Thang, Nguyen D.; Naudascher, Eduard

doi:10.1061/(asce)0733-9429(1983)109:11(1521)

Cited by 5 publications

(2 citation statements)

References 13 publications

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“…Nguyen [6] studied the effects of different flow conditions on the high local pressures and the discharge characteristics of the vertical lift gates. The characteristics of the disturbance conditions near the separation point from the bottom of the gate were indicated by using the Doppler laser, and the measurement of the intensity of the nose was shown.…”

Section: Introductionmentioning

confidence: 99%

Variation of Pressure Coefficient Along Bottom of Dam Vertical Lift Gates

Ahmed

2020

J. Inst. Eng. India Ser. A

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The vertical lift gates are exposed to hydrodynamic forces that arise as a result of pressurized flow established by the large-scale effect of the water levels in the dam reservoirs. The most influential forces are those that are applied on the gate vertically upward due to the intensity of the flow under the gate and downward as a result of passage flow above the gate. The difference between these two forces generates a downpull force that is the most important gate stability indicator. In this research, an arbitrary hydraulic model was constructed to investigate the effects of many gate lip shapes with and without extensions on the magnitudes and distribution of bottom pressure coefficient when the values of flow and shaft gap width ratio (b 2 /b l) are constant. The results indicate that the bottom pressure coefficient appears to vary uniformly with gate openings and seem to be influenced effectively by the gate lip geometry. So, for the given value of (b 2 /b l), the top pressure coefficient regarding the downward force will mostly be with uniform changes and hence the downpull coefficient depends on the magnitudes and distribution of bottom pressure coefficient. An attempt by using the correlation coefficient of Statistical Package of Social Sciences was made to determine whether the pressure fluctuation is significantly shown at the bottom pressure distribution curve, which in turn is considered as appropriate indicator for the vibration occurrence. Full range of maximum bottom pressure coefficients in a matrix form is made to assist in design purposes. The results are analyzed and many conclusions are obtained.

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Section: Introductionmentioning

confidence: 99%

Variation of Pressure Coefficient Along Bottom of Dam Vertical Lift Gates

Ahmed

2020

J. Inst. Eng. India Ser. A

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“…It is found that the variation of gate closing speed with range (2.4-3.6 m/min) had less effect on downpull force and its maximum value on closing the moving gate was 74-79% of that on the case of the stationary gate. Many approach flow condition effects on local pressures and the behavior of flow pattern along the bottom surface of intake gates have been studied by Thang and Naudascher, 1983. The study included the use of Doppler laser anemometer and the results showed that the instability instances are indicated near the separation point at the bottom of the gate.…”

Section: Introductionmentioning

confidence: 99%

Effects of Dam Gate Geometry on Pressure Variation Aided by Map Presentation

Ameen

Ahmed

2020

Polytechnic j.

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The dam vertical lift gate is one of the most important operational parts that regulate the high head water flow to power plants as well as satisfying the water needs for projects and areas downstream of the dam. Due to the high water levels in the dam reservoir, the gates are subjected to many hydrostatic and dynamic pressures that affect their performance and stability. Hence, it became necessary to study all parameters that may cause excessive pressures which may lead to reduce the gate performance efficiency or even cause failure. In the current study, the pressure distribution along the bottom surface of various gate lip shapes has been measured and presented as contour maps using Surfer software. The pressure fluctuation was observed to indicate the intensity of flow separation and reattachment which, in turn, causes a vibration that may threaten the stability of the gate or impede its proper functioning. The pressures in this study are expressed as a dimensional coefficient through the integration of pressure measurements at 8 points distributed over the bottom gate surface. The high intensity of pressure attachment indicates the critical condition for hydraulic design.

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