The following picture illustrates how to measure the reflection coefficient.  By plotting the highest and lowest surface elevations for each point, an envelope for the incident and reflected waves is obtained.  The top part represents total reflection which creates a standing wave.  In this case the Hmin value is zero and Kr = Hmax/Hmax = 1 (a maximum).  In the normal case, Kr does not equal one, so measurements must be taken at both the maximum and minimum heights. 

 

 

 

 

 

 

 

 

 

                                                                                                                                                                                                                                (Coastal Engineering Manual, 2004)

 

 

 

 

 

 

 

 

 

Our approach uses two sensors operating in a wave tank.  The tank has a paddle at one end which makes waves at variable frequency and amplitude.  The sensors were placed one at Hmin and one at Hmax for each trial.  We had to move the sensors to several different places to find the Hmin and Hmax locations.  The sensors are calibrated for the depth of the tank and the conversion from the electronic signal into distance. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The wave maker paddle settings as well as the water depth were set at constant values for all trials (amplitude = .4, frequency = .91 hz, depth = 8 in).  On the opposite end of the tank we placed a plywood board to reflect the waves.  For separate trials we tried varying the reflection coefficient by changing the slope of the board, and then running the experiment again using hoarse hair on the surface of the board to increase porosity and surface roughness.