In order to maintain reasonably close similarity between model and 

 prototype, armor stability models are usually constructed at a scale large enough to 

 avoid significant Reynolds scale effects by ensuring that the flow around the armor 

 remains turbulent. Dai and Kamel (1969) suggested that Re - (gH)^'^D„so /v > 3 x 10" 

 will prevent Reynolds scale effects. Their results were based on large- and small-scale 

 flume tests using regular waves. Van der Meer (1988) stated that the lower limit of 

 Reynolds numbers should be in the range 



Re = V^^"^o ^ 1x10^-4x10" (4.6) 



V 



to prevent Reynolds scale effects. This guidance is presently accepted practice. In the 

 experiment discussed herein, the Reynolds number range is 3.1 x l(f <Re< 4.0 x 10" 

 which satisfies the requirements suggested by both Dai and Kamel and van der Meer. 



4.3 Wave Generation and Measurement in Initial Experiment 

 4.3.1 Wave generation 



Waves were generated based on the Texel, Marsen, and Arsloe (TMA) 

 spectrum (Bouws et al. 1985). The deterministic spectral amplitude and random phase 

 method was used to synthesize the time series that was used to drive the piston-type 

 wave board. Long (1986) describes the computer program used to synthesize the time 

 series. The software creates a variable spectral bandwidth A(i)„ by the method of Goda 

 (1970), which allows closer spectral lines near the peak frequency. For this method, a 



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