Laboratory research on sediment movement due solely to wave motion has 

 previously been concerned with the initiation of motion, transport of material 

 in the form of bed load, and formation of ripple patterns on the bed. Most of 

 these experiments attempted to use monochromatic waves created by a variety 

 of methods including wave paddles, swinging trays in still water, and U-tube 

 oscillatory flow tunnels. There are a number of concerns, however, which 

 limit the usefulness of most of these data, including scale effects, wall and 

 shore reflections, and improper boundary conditions such as the oscillatory 

 flow tubes having no free surface. Other researchers have attempted to char- 

 acterize the geometry of the concentration profiles observed under wave in- 

 ducement, and these studies suffer from some of the same defects. It should 

 also be mentioned that concentration measurements in the past have been made 

 with instruments which are highly invasive of the BBL physics. 



Objectives 



The SUPERTANK Laboratory Data Collection Project was in part con- 

 ceived to give DRP researchers an opportunity to study the processes and 

 effects of sediment motion induced only by waves under controlled laboratory 

 conditions with field-scale waves of known spectral composition. This was 

 achieved by a precisely controlled wave paddle in a large wave channel that 

 could be programmed to account for wave reflections from the beach and 

 seiching. A modified version of ARMS was assembled for use in the wave- 

 channel environment and was included as part of the offshore group, an en- 

 semble of DRP researchers and their instrumentation, studying sediment mo- 

 tion offshore of the wave breaker zone. The primary focus of the OSU de- 

 ployment and data collection system was to compare bed and boundary layer 

 response to monochromatic and equivalent spectral waves. This includes 

 obtaining profiles of the suspended sediment concentration as well as charac- 

 terizing the complex three-dimensional hydrodynamics which effect sediment 

 resuspension. It was also planned that corroborative information would be 

 obtained through cooperation with other members of the offshore group. 



Scope 



There are three main sections to this chapter. The first section is a de- 

 scription of the experiment apparatus including how the devices operate, their 

 locations both in the wave channel and with respect to other instruments in the 

 offshore group, and a review of some unique characteristics of each device. 

 The second section outlines how data were obtained by the OSU instrumenta- 

 tion through a description of the sequence of events of a wave run, the sam- 

 pling regimen, calibration procedures, and electronic processing and filtering 

 before the data were stored. The last section provides a description of the 

 interpretation and analysis of the raw data. This section includes samples of 

 the raw and interpreted data as well as a summary of the pertinent characteris- 

 tics for several comparisons of similar wave runs. The chapter concludes with 



Chapter 9 The Ohio State University Measurements 



153 



