Water Resistance Testing

The circular version has slightly greater cross-sectional area, and as the net fills up (and the resistance or pull thus increases), I think this would also result in the greatest ultimate bollard pull. But not by very much over the rectangular version. On the other hand, the rectangular version may be a closer representation of various practical shapes you might be designing toward. Overall, too close to call? You might just go with whichever is easier to fabricate, and hope for a good school of fish to give it the real test!

Thank you.

It would appear to me . . . that shape of the net will have great influence on flow characteristics . . . laminar flow disruptions. Thus . . . the geometry of the net will have great impact on flow characteristics. If flow regimes shift from laminar to turbulent the differential pressure induced by the turbulent flow will produce variations in differential pressures . . . perhaps the reason for the oscillation in the rectangular shape verses the round. Along the surface of the moving membrane, in this case the net, waves will be induced as the pressure wave travels down the net. Therefore, the changing differential becomes significant when shape of net is the critical factor. Ultimately what I am trying to say, is that shape can sway your data. Traveling waves inside of the net ultimately are addiative. My hypothesis is that given the same material of manufacture, that the rectangular shape will show more bollard pull than will the round. If I were doing this test . . . I would build a data base of both shapes and compare the performance curves.

Thank you also.

The idea is still on the board for discussion as to which to go with but we may do both as is suggested, as some involved want more data anyway.

Hi Smitty

Why don't you contact a trawl net manufacturer. Most have software that can model this and give you a theoretical answer. However, I still think your best bet would be to make up the two designs and physically test them.

Brgds

The small little trial project suddenly wound up as a point of contention with several "specilaists".

It will boil down to either dropping the whole thing or making two models.

All that was asked for is a simple way to test the water flow through these 3 nettings.

I am opting for two models and just let that be that.

Thank you.