AI SearchAir entrainment from aeration device
Call Number: AIT Thesis no.WA-85-53 Material type:
TextSeries: Asian Institute of Technology. Thesis ; no. WA-85-53Publication details: Bangkok : Asian Institute of Technology, 1985Description: 93 pSubject(s): Online resources: Dissertation note: Thesis (M.Eng.) - Asian Institute of Technology, 1985 Summary: Cavitation erosion at the surface of the hydraulic structure subjected to the high velocity flow is caused by the surface irregularities. A successful and cheap method to prevent the erosion is to supply an amount of air into the flow through an aeration device. An experimental study on the phenomena of the air entrainment from aeration device was carried out in the hydraulic model of two types of device, namely; (i) plane groove type and, (ii) combined groove-deflector type. Air concentration at the chute bottom from the groove type is found too low to protect the surface from cavitation erosion. For the combined type the efficiency is much improved, air concentration found in the flow downstream of the jet impingement shows a typical distribution. A conceptual model was developed from the "Mixing length" theory of the velocity distribution and the free jet assumption to determine the air flow from the device. A linear relationship of the measured air concentration and the air discharge estimated from the model is found. A Model of aeration device with 1:2 scale ratio was constructed according to the Froude law of similarity. The measured air concentration is very low comparing with the prototype result, the model size is considered too small to be used for the purpose of comparison.
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A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Engineering and Technology
Thesis (M.Eng.) - Asian Institute of Technology, 1985
Cavitation erosion at the surface of the hydraulic structure subjected to the high velocity flow is caused by the surface irregularities. A successful and cheap method to prevent the erosion is to supply an amount of air into the flow through an aeration device. An experimental study on the phenomena of the air entrainment from aeration device was carried out in the hydraulic model of two types of device, namely; (i) plane groove type and, (ii) combined groove-deflector type. Air concentration at the chute bottom from the groove type is found too low to protect the surface from cavitation erosion. For the combined type the efficiency is much improved, air concentration found in the flow downstream of the jet impingement shows a typical distribution. A conceptual model was developed from the "Mixing length" theory of the velocity distribution and the free jet assumption to determine the air flow from the device. A linear relationship of the measured air concentration and the air discharge estimated from the model is found. A Model of aeration device with 1:2 scale ratio was constructed according to the Froude law of similarity. The measured air concentration is very low comparing with the prototype result, the model size is considered too small to be used for the purpose of comparison.
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