PART VIII: SUMMARY OF RESULTS 



226. Preceding sections of this report describe movable-bed physical model tests designed and 

 conducted primarily to validate a selected set of scaling criteria for use in studying scour at and near 

 coastal structures. A summary of the study results is presented below. 



Summary 



227. A review of proposed movable-bed model scaling criteria applicable to turbulence-dominated 

 regimes supported the criterion of maintaining the same value of the dimensionless sediment fall speed 

 parameter between the model and the prototype situation. Two additional criteria for the selected 

 guidance were that the model should be undistorted and hydrodynamics should be scaled according to the 

 Fronde scaling relationship. These criteria were adopted for testing and verification in this study. A similar 

 sediment transport parameter suggested by Xie (1981) was examined and shown to be quite similar for 

 turbulence-dominated situations. Applicability of the selected model scaling relationships was discussed, 

 noting that most experience with this particular guidance was in 2-D situations. 



228. Prototype-scale experiments conducted in the GroCer Wellenkanal served as the prototype to be 

 reproduced at scale in CERC's 6-ft wave flume. Tests using both regular and irregular wave trains were 

 conducted at a prototype-to-model scale of 7.5:1, and the testing procedures were designed to duplicate 

 those used in the GWK tests. 



229. In the regular wave verification test where the sloping concrete revetment was exposed, a 

 reasonable comparison between the model and the prototype profile evolution was obtained. However, the 

 comparison improved when the model wave height was increcised by about 10 percent over the original 

 scaled value. An explanation for this discovery was given in terms of the difference in Xie's parameter 

 between prototype and model in the offshore region. Increasing the wave height resulted in closer agreement 

 of Xie's parameter between prototype and model, and sediment was moved farther offshore in the model. 

 The resulting increcised erosion of the inshore region adjacent to the exposed sloping revetment gave 

 support to the concept that the offshore bar has a sediment storage capacity for a particular wave climate, 

 and as long as this climate persists, the inshore region will continue to erode until this capacity is met. 



230. Validation of the selected scaling criteria using irregular waves was considered highly successful. 

 The model exhibited profile development that compared very well with the prototype profile development 

 when the revetment was not exposed to wave action. In the irregular wave test, no increase in wave height 

 was required as was done for the regular wave tests using the Xie parameter. Apparently, irregular wave 



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