Linearly Sloping Beach

The previously used absorbing beach has been replaced with a linearly sloping beach, to enable investigations into the evolution of broadband spectrum incident waves, as well as the traveling bores which form after wave breaking. The new beach has a slope of 0.04, established in the literature as the maximum value for which realistic wave evolution is observed. The beach is constructed of stainless steel sheets, supported by stainless steel beams, and supported by stainless steel legs which rest on rubber feet that are anchored in place in the tank. Slits have been cut into each section of the beach, into which have been placed clear plastic, allowing PIV measurements to be made at selected locations along the beach. In conjunction with the wave generator, all the different types of breaking waves: spilling, plunging, collapsing, and surging, can be created with this beach.

Wave Gauges

The four capacitive wave gauges mounted on two trolleys have been supplemented with 16 capacitive wave gauges mounted on two new trolleys. The new trolleys allow the wave gauges to be placed within six inches of one another, allowing for clustering near areas of interested. The trolleys also include variable mounting hardware which allows for optimal placement of the gauges on the sloping bottom. Data from the wave gauges is sampled using a 32-channel 16-bit, A/D card from National Instruments. Software is currently being developed which will compute phase speeds and amplitudes for the waves or traveling bores as they move down the tank, allowing for rapid comparisons with the current theories.

Radar

The radar return from the surface signatures is measured using a simple Doppler radar set-up. This set-up consists of an HP 8510C Automatic Network Analyzer (ANA), an HP 8349B microwave amplifier, separate transmit and receive horns, and a low-noise preamplifier for the receive horn. The ANA is used to generate the transmit waveform, as well as to demodulate the received signal. The microwave amplifier and low-noise preamplifier boost the transmit gain and increase the receiver sensitivity respectively.