Measurement and modelling of controlled beach groundwater levels under wave action

New laboratory scale experimental data are presented on the forcing of beach groundwater levels by wave run-up. The experimental setup simulates a coastal barrier dividing the ocean from a relatively constant back beach water level, conditions approximating a closed off lagoon system or beach aquifer. The data are critically compared to an advanced numerical model for simulating wave and beach groundwater interaction in the coastal zone, and provide the first experimental verification of such a model. Overall model-data comparisons are good, but some systematic discrepancies are apparent, and reasons for these are discussed.

Dynamics of a transient wave group breaking on a beach

New experimental data are presented on the dynamics of a transient wave group breaking on a beach. The transient group is tracked during shoaling and wave breaking, together with the long waves forced during those processes. High spatial sampling enables novel resolution of the evolution of the wave envelope during breaking and the correlation between the envelope and the long waves. The data show a strong dynamic long wave setup in front of the group in shallow water. The amplitude of the dynamic setup is likely to be a function of beach slope, and larger on steeper beaches.

An experimental study of the jet of a boat propeller

An experimental study of the velocity and concentration (scalar) fields of a propeller is presented. Field and laboratory measurements were undertaken. The former were up to 50 diameters downstream. Important findings were that the mean velocity and scalar fields quickly become Gaussian while further downstream they both become irregular sometimes approaching approximately linear profiles. Propeller turbulence causes rapid mixing giving an initial concentration dilution factor of 1/20,000 after fifty propeller diameters. Some preliminary comparisons with field measurements of an actual boat in a natural waterway are made. Considerably more work is needed to gain a full understanding of the complex problem of propeller mixing.

The effect of xylanase, phytase and lipase supplementation on the performance of broiler chickens fed a diet with a high level of rice bran.

Enzyme products did not have a significant effect (P>0.05) on weekly fed intake and weight gain of birds. But feed intake tended to drop and weight gain tended to increase in response to supplementation of the three enzymes. Weight gain of the birds was increased by 0.6% with lipase, 3.7% with phytase and 2.4% with xylanase. Xylanase had a marked effect (P