Air Entrainment and Air Demand in the Spillway Tunnel at the Jinping-I Dam

Artificial air entrainment has been widely used to avoid cavitation damage in spillways where high-velocity flow occurs, and its performance is very important for spillway safety. In order to evaluate the performance of the aeration system in the spillway tunnel of the Jinping-I Dam, which is the highest arched dam in the world to date, systematic prototype observation was conducted. Ventilation characteristics of the air supply system and aeration-related characteristics of the aeration devices were examined at the prototype scale. The results showed that air flows smoothly in the air intake well and the real effect of air entrainment of the aeration device was desirable. In contrast with results from laboratory tests with a physical model at a scale of 1/30 following the gravity similarity, it was found that air demand in the prototype is much greater, clearly indicating the scale effect. By summing up and analyzing the air demand ratio of the prototype to the model in some projects, the scale effect was found to be ignorable when the model scale was greater than 1/10. In addition, based on a series of prototype data on air demand, a brief evaluation of present calculation methods for air demand was conducted and a new form of calculation method for air demand related to unit width flow rate was established. The present prototype results can be used as a reference for similar engineering design, and to validate and verify numerical simulations as well as model tests.

[1]  James W. Ball.  CAVITATION FROM SURFACE IRREGULARITIES IN HIGH VELOCITY , 1976 .

[2]  Willi H. Hager,et al.  Air Entrainment by Spillway Aerators , 1990 .

[3]  P. A. Lush,et al.  Correlation of Cavitation Erosion and Sound Pressure Level , 1984 .

[4]  Helmut Kobus,et al.  Hydraulics and design of spillway aerators for cavitation prevention in high speed flows , 1988 .

[5]  Zhimin Shi,et al.  Fundamentals and Applications of Slow Light , 2010 .

[6]  Rex A. Elder.  Advances in Hydraulic Engineering Practice: The Last Four Decades and Beyond , 1986 .

[7]  Jian-hua Wu,et al.  On Necessity of Placing an Aerator in the Bottom Discharge Tunnel at the Longtan Hydropower Station , 2006 .

[8]  Willi H. Hager,et al.  Development of Air Concentration on Chute Spillways , 2006 .

[9]  J. F. DOMGIN,et al.  EXPERIMENTAL AND NUMERICAL INVESTIGATION OF GAS STIRRED LADLES , 1999 .

[10]  Xiang Ya-ping.  CAVITATION INCEPTION WITNESSED BY SOUND PRESSURE LEVEL IN MODEL TEST AND PROTOTYPE OBSERVATION , 2004 .

[11]  K. Warren Frizell.  Glen Canyon Dam Spillway Tests Model-Prototype Comparison , 1985 .

[12]  Willi H. Hager,et al.  Closure of “Chute Aerators. I: Air Transport Characteristics , 2010 .

[13]  William L. Haberman,et al.  An Experimental Study of Bubbles Moving in Liquids , 1956 .

[14]  Hubert Chanson.  Flow downstream of an aerator - aerator spacing , 1989 .

[15]  Dong Zhang,et al.  Cavitation Inception Witnessed by Sound Pressure Level both in Model Test and Prototype Observation , 2001 .

[16]  L. D. Lentyaev,et al.  Spillway with nappe aeration , 1973 .

[17]  Jacques Bruschin.  Forced aeration of high velocity flows , 1987 .

[18]  W. S. Hamilton.  Preventing cavitation damage to hydraulic structures , 1983 .

[19]  Ian R. Wood,et al.  Uniform Region of Self‐Aerated Flow , 1983 .

[20]  A. J. Peterka,et al.  The Effect Of Entrained Air On Cavitation Pitting , 1953 .

[21]  Peter Rutschmann,et al.  Aerators on Spillway Chutes: Fundamentals and Applications , 1986 .

[22]  H. T. Falvey,et al.  Cavitation in chutes and spillways , 1990 .

[23]  H. Chanson,et al.  Air-Water Flows in Water Engineering and Hydraulic Structures. Basic Processes and Metrology , 2004 .

[24]  N. L. De S. Pinto.  Designing aerators for high velocity flow , 1989 .

[25]  Lorenz G. Straub,et al.  Experimental Studies Of Air Entrainment In Open Channel Flow , 1953 .

[26]  James A. Kells,et al.  Reduction of cavitation on spillways by induced air entrainment , 1991 .