Experimental Research About Tooth Block Height Effect On Inner Energydissipaters Of Tooth Block

Tooth block is a new-type inner energy dissipaters which is used forpressure pipeline and spillway tunnel. It proposed on the basis of plug dissipater.In the early time our research group has been completed two cases of crosswhich include different tooth block area contraction ratio and different toothblock number in inner energy dissipaters of tooth block through physical modelexperiment. So we got some research results. This article is based on theprevious studies. With more in-depth explorations for inner energy dissipater oftooth block under area contraction ratio and tooth block number in certaincircumstances, the research on tooth block height effect of inner energydissipater of tooth block. In this experiment the tooth block area contractionratio is0.5, tooth block number is4and five different tooth block height（R1=50mm、R2=42.5mm、R3=37.5mm、R4=32.5mm、R5=25mm）, dosome research on inner energy dissipater in different flow. Through combining physical model experiment and theoretical analysis, the pressure characteristicsand energy dissipation characteristics and cavitations characteristics for innerenergy dissipater of tooth block were analyzed, got the following conclusions:(1) The time-averaged pressure distributions along the entire test sectionare basically the same for different tooth block height of inner energy dissipaters.Both time-averaged pressure reduce sharply in the inlet of tooth block all of asudden and reduces to minimize, then the pressure increases gradually, finallythe time-averaged pressure restore stable located far tooth block downstream.Before and after the energy dissipation the scheme R1time-averaged pressuredecreasing amplitude is largest and the scheme R3time-averaged pressuredecreasing amplitude is minimum.(2) Different tooth block height of inner energy dissipaters their flowcoefficient increase with the increase of Reynolds number. But when Re＞1.56×105its influence can be neglected, compared to each scheme the R3flowcapacity is largest and compared to R1the R3flow coefficient increases about8%.(3) Reynolds number has a certain impact on the head loss coefficientwhen it is small, its impact can be neglected when Reynolds number is large fordifferent tooth block height of inner energy dissipaters. The frictional head lossaccounts for about10%of the total head loss. The maximum head loss is R1and the minimum head loss is R3.(4) Its energy dissipation ratio increases as the flow rate increases for different tooth block height of inner energy dissipaters. Within the scope of theexperiment energy dissipation ratio can reach about60%on average. Thescheme R1energy dissipation ratio is best can reach63.84%and scheme R2energy dissipation ratio is57.41%. The scheme R3energy dissipation ratio isworst only can reach51.18%, scheme R4energy dissipation ratio is60.71%andscheme R5energy dissipation ratio is59.80%.(5) The minimum cavitation numbers are within tooth block segment0.2Dposition for different tooth block height of inner energy dissipaters. When thepipe Reynolds number reached3.11×105the minimum cavitation numbers isnegative. Compared with every scheme found that the scheme R1cavitationnumber is minimum and scheme R5cavitation number is maximum. Thesmaller the cavitation number, the more likely happen cavitation phenomenon.(6) Along pipe the fluctuating pressure variation are basically the same fordifferent tooth block height of inner energy dissipaters. Its fluctuating pressuredramatic changes after tooth block segment1.6D position. The scheme R1pressure pulsation is strongest and the scheme R5pressure pulsation is weakestin all schemes when flow is large.(7) Comprehensive analysis of different tooth block height of inner energydissipaters found that scheme R5(tooth block height is25mm) occurs cavitationmost difficult, at the same time its flow capacity and energy dissipation is better,should be the primary choice.