Flow distribution on a simple separator device for trawling, TREND

Abstract

The authors propose a new bycatch reduction device for trawling with a simply constructed TREND (trawl flow regulative ecological friendly netting device). TREND is a cylinder-shaped netting device with a rectangular-shaped mesh. We examined a selective mechanism from the viewpoint of the flow inside and around TREND. A series of model experiments was conducted and the flow speeds were measured at a flume tank. The ratio of flow speed decreased at points close to the netting and increased slightly at other points in all sections. The angles of tuft at the top netting in the rear area were almost twice the value in the front sections. As the exhaustion of flow and reduction of speed occurred simultaneously, these tendencies were remarkable at higher speed. This flow towards the outside of TREND was considered to be acting as a bycatch reduction device for trawling.